Table of contents

We have examined the recently detected very high energy (VHE) pulsed radiation from the Crab pulsar. According to the observational evidence, the emission (>25 GeV) peaks at the same phase as the optical spectrum. By considering the cyclotron instability, we show that the pitch angles become non-vanishing, leading to the efficient synchrotron mechanism near the light cylinder surface. We argue that the inverse Compton scattering and the curvature radiation mechanisms do not contribute to the VHE domain detected by MAGIC.

We examine the ability of gravitational lens time delays to reveal complex structure in lens potentials. In a previous paper, we predicted how the time delay between the bright pair of images in a "fold" lens scales with the image separation, for smooth lens potentials. Here we show that the proportionality constant increases with the quadrupole moment of the lens potential, and depends only weakly on the position of the source along the caustic. We use Monte Carlo simulations to determine the range of time delays that can be produced by realistic smooth lens models consisting of isothermal ellipsoid galaxies with tidal shear. We can then identify outliers as "time delay anomalies." We find evidence for anomalies in close image pairs in the cusp lenses RX J1131 − 1231 and B1422+231. The anomalies in RX J1131 − 1231 provide strong evidence for substructure in the lens potential, while at this point the apparent anomalies in B1422+231 mainly indicate that the time delay measurements need to be improved. We also find evidence for time delay anomalies in larger-separation image pairs in the fold lenses, B1608+656 and WFI 2033 − 4723, and the cusp lens RX J0911+0551. We suggest that these anomalies are caused by some combination of substructure and a complex lens environment. Finally, to assist future monitoring campaigns we use our smooth models with shear to predict the time delays for all known four-image lenses.

We present a large robust sample of 1503 reliable and unconfused 70 μm selected sources from the multiwavelength data set of the Cosmic Evolution Survey. Using the Spitzer IRAC and MIPS photometry, we estimate the total infrared (IR) luminosity, L_IR (8–1000 μm), by finding the best-fit template from several different template libraries. The long-wavelength 70 and 160 μm data allow us to obtain a reliable estimate of L_IR, accurate to within 0.2 and 0.05 dex, respectively. The 70 μm data point enables a significant improvement over the luminosity estimates possible with only a 24 μm detection. The full sample spans a wide range in IR luminosity, L_IR ≈ 10⁸–10¹⁴ L_☉, with a median luminosity of 10^11.4 L_☉. We identify a total of 687 luminous, 303 ultraluminous, and 31 hyperluminous infrared galaxies (LIRGs, ULIRGs, and HyLIRGs) over the redshift range 0.01 < z < 3.5 with a median redshift of 0.5. Presented here are the full spectral energy distributions (SEDs) for each of the sources compiled from the extensive multiwavelength data set from the ultraviolet (UV) to the far-infrared. A catalog of the general properties of the sample (including the photometry, redshifts, and L_IR) is included with this paper. We find that the overall shape of the SED and trends with L_IR (e.g., IR color temperatures and optical–IR ratios) are similar to what has been seen in studies of local objects; however, our large sample allows us to see the extreme spread in UV to near-infrared colors spanning nearly 3 orders of magnitude. In addition, using SED fits we find possible evidence for a subset of cooler ultraluminous objects than observed locally. However, until direct observations at longer wavelengths are obtained, the peak of emission and the dust temperature cannot be well constrained. We use these SEDs, along with the deep radio and X-ray coverage of the field, to identify a large sample of candidate active galactic nuclei (AGNs). We find that the fraction of AGNs increases strongly with L_IR, as it does in the local universe, and that nearly 70% of ULIRGs and all HyLIRGs likely host a powerful AGN.

The supermassive ∼4 × 10⁶ M_☉ black hole at the Galactic center is surrounded by a parsec-scale star disk, with several thousands of dynamically relaxed, evolved, late-type CO absorption line stars and a small ∼100 population of luminous O and Wolf–Rayet stars which move in approximately circular Keplerian orbits. These bluish in color massive O and Wolf–Rayet stars are very young with an estimated age of 6 ±  2 Myr. Another small group of roughly 20 young (<10 Myr) blue B stars with the orbital periods as short as 15 years ("S-stars") follow eccentric, randomly oriented orbits well inside the disk stars. A model is proposed to explain the S-stars. Accordingly, the stars formed originally in the parsec-scale disk through Jeans' gravitational fragmentation of gas. The newly formed S-stars then migrated inward to the Galactic center via the torques exerted by Lin–Shu-type spiral density waves on the stars at an inner Lindblad resonance. The model explains both the number of observed S-stars orbiting the Galactic black hole within the nuclear (<0.05 pc) star cluster and the key property of the S-star orbits, namely, their high eccentricities.

The GeV light curve of a pulsar is an important probe to detect acceleration regions in its magnetosphere. Motivated by the recent reports on the observations of pulsars by the Fermi Large Area Telescope, we restudy the two-pole caustic model and revise it to investigate the properties of the light curves in the GeV band. In the revised model, although acceleration gaps can extend from the star surface to the light cylinder along near the last open field lines, the extension of the gaps along the azimuthal direction is limited because of photon–photon pair production process. In such gaps, high-energy photons are emitted uniformly and tangentially to the field lines but cannot be efficiently produced along these field lines where the distances to the null charge surface are larger than ∼0.9 times the distance of the light cylinder, and the effective azimuth extension of the gaps is about 230°. The model is applied to the four pulsars, Vela, PSR J1028-5819, PSR J0205+6449, and PSR J2021+3651, whose light curves obtained with Fermi have been recently released. The model is successful in reproducing the general feature of the light curves for the four pulsars, and the radial distances of the radio pulse for the four pulsars are estimated.

We present high spectral resolution Very Large Telescope observations of the broad absorption line quasar SDSS J0318 − 0600. This high-quality data set allows us to extract accurate ionic column densities and determine an electron number density of n_e = 10^3.3±0.2 cm⁻³ for the main outflow absorption component. The heavily reddened spectrum of SDSS J0318-0600 requires purely silicate dust with a reddening curve characteristic of predominately large grains, from which we estimate the bolometric luminosity. We carry out photoionization modeling to determine the total column density, ionization parameter, and distance of the gas and find that the photoionization models suggest abundances greater than solar. Due to the uncertainty in the location of the dust extinction, we arrive at two viable distances for the main ouflow component from the central source, 6 and 17 kpc, where we consider the 6 kpc location as somewhat more physically plausible. Assuming the canonical global covering of 20% for the outflow and a distance of 6 kpc, our analysis yields a mass flux of 120 M_☉ yr⁻¹ and a kinetic luminosity that is ∼0.1% of the bolometric luminosity of the object. Should the dust be part of the outflow, then these values are ∼4× larger. The large mass flux and kinetic luminosity make this outflow a significant contributor to active galactic nucleus feedback processes.

Fifty observations at frequencies between 1.4 GHz and 43 GHz of the 6.6 day O6.5-7+O5.5-6 binary Cyg OB2 No. 5 using the Very Large Array over 20 years are re-examined. The aim is to determine the location and character of the previously detected variable radio emission. The radio emission from the system consists of a primary component that is associated with the binary, and a non-thermal source (NE), 08 to the NE of the binary that has been ascribed to a wind-collision region (WCR) between the stellar winds of the binary and that of a B-type star (Star D) to the NE. Previous studies have not accounted for the potential contribution of NE to the total radio emission, most especially in observations where the primary and NE sources are not resolved as separate sources. NE shows no evidence of variation in 23 epochs where it is resolved separately from the primary radio component, demonstrating that the variable emission arises in the primary component. Since NE is non-variable, the radio flux from the primary can now be well determined for the first time, most especially in observations that do not resolve both the primary and NE components. The variable radio emission from the primary component has a period of 6.7 ± 0.3 years which is described by a simple model of a non-thermal source orbiting within the stellar wind envelope of the binary. Such a model implies the presence of a third, unresolved stellar companion (Star C) orbiting the 6.6 day binary with a period of 6.7 years and independent of Star D to the NE. The variable non-thermal emission arises from either a WCR between Star C and the binary system, or possibly from Star C directly. The model gives a mass-loss rate of 3.4 × 10⁻⁵ M_☉ yr⁻¹ for Cyg OB2 No. 5, unusually high for an Of supergiant and comparable to that of WR stars, and consistent with an unusually strong He i 1.083 µm emission line, also redolent of WR stars. An examination of radial velocity observations available from the literature suggests reflex motion of the binary due to Star C, for which a mass of 23⁺²²₋₁₄M_☉ is deduced. The natures of NE and Star D are also examined. If NE is a WCR, as suggested by other authors, then the required mass-loss rate is an order of magnitude higher than expected for an early B-type dwarf, and only just consistent with a supergiant. This raises the question of NE as a WCR, but its non-thermal luminosity is consistent with a WCR and a comparison of reddening between Cyg OB2 No. 5 and Star D do not rule out an association, implying Cyg OB2 No. 5 is a quadruple system. Pursuing alternative models for NE, such as an unassociated background source, would require very challenging observations.

We follow the galaxy stellar mass assembly by morphological and spectral type in the COSMOS 2 deg² field. We derive the stellar mass functions and stellar mass densities from z = 2 to z = 0.2 using 196,000 galaxies selected at F_3.6 μm > 1 μJy with accurate photometric redshifts ($\sigma _{(z_{\rm phot}-z_{\rm spec})/(1+z_{\rm spec})}=0.008$ at i⁺ < 22.5). Using a spectral classification, we find that z ∼ 1 is an epoch of transition in the stellar mass assembly of quiescent galaxies. Their stellar mass density increases by 1.1 dex between z = 1.5–2 and z = 0.8–1 (Δt ∼ 2.5 Gyr), but only by 0.3 dex between z = 0.8–1 and z ∼ 0.1 (Δt ∼ 6 Gyr). Then, we add the morphological information and find that 80%–90% of the massive quiescent galaxies $(\log {\cal M} \sim 11)$ have an elliptical morphology at z < 0.8. Therefore, a dominant mechanism links the shutdown of star formation and the acquisition of an elliptical morphology in massive galaxies. Still, a significant fraction of quiescent galaxies present a Spi/Irr morphology at low mass (40%–60% at $\log {\cal M}\sim 9.5$), but this fraction is smaller than predicted by semi-analytical models using a "halo quenching" recipe. We also analyze the evolution of star-forming galaxies and split them into "intermediate activity" and "high activity" galaxies. We find that the most massive "high activity" galaxies end their high star formation rate phase first. Finally, the space density of massive star-forming galaxies becomes lower than the space density of massive elliptical galaxies at z < 1. As a consequence, the rate of "wet mergers" involved in the formation of the most massive ellipticals must decline very rapidly at z < 1, which could explain the observed slow down in the assembly of these quiescent and massive sources.

The luminosities of short-duration gamma-ray burst (SGRB) host galaxies appear to be anticorrelated with both the isotropic equivalent gamma-ray energy and the gamma-ray luminosity of the explosions, based on a sample of 12 bursts with host galaxy redshifts and photometry. The correlation does depend on the correct identification of the GRB 050509b host, but is otherwise robust. In particular, simple observational selection effects only strengthen the statistical significance of this correlation, from ∼95% to ∼99%. The correlation may indicate that there are two physically distinct groups of SGRBs. If so, it requires that the more luminous class of explosions be associated with the younger class of progenitors. Alternatively, it could be due to a continuous distribution of burst and host properties, in which case it could be used as a crude SGRB distance indicator. As one possible explanation, we find that the effect of binary neutron star masses on inspiral time and energy reservoir produces a correlation of the appropriate sign, but does not automatically reproduce the correlation slope or the full range of SGRB energy scales. If confirmed by larger samples, this correlation will provide a valuable new constraint on SGRB progenitor models.

HD 209458b is an exoplanet found to transit the disk of its parent star. Observations have shown a broad absorption signature about the Lyα stellar line during transit, suggesting the presence of a thick cloud of atomic hydrogen around the "hot Jupiter" HD 209458b. This work expands on an earlier work studying the production of energetic neutral atoms (ENAs) as a result of the interaction between the stellar wind and the exosphere. We present an improved flow model of HD 209458b and use stellar wind values similar to those in our solar system. We find that the ENA production is high enough to explain the observations, and we show that—using expected values for the stellar wind and exosphere—the spatial and velocity distributions of ENAs would give absorption in good agreement with the observations. We also study how the production of ENAs depends on the exospheric parameters and establish an upper limit for the obstacle standoff distance at approximately 4–10 planetary radii. Finally, we compare the results obtained for the obstacle standoff distance with existing exomagnetospheric models and show how the magnetic moment of HD 209458b can be estimated from ENA observations.

On the basis of the recently developed universal decline law of classical novae, we propose prediction formulae for supersoft X-ray on and off times, i.e., t_X-on = (10 ± 1.8)t₃ days and t_X-off = (5.3 ± 1.4)(t₃)^1.5 days for 8 ≲ t₃ ≲ 80 days. Here t₃ is the newly proposed "intrinsic" decay time during which the brightness drops by 3 mag from optical maximum along our universal decline law fitted with observation. We have determined the absolute magnitude of our free–free emission model light curves and derived maximum magnitude versus rate of decline (MMRD) relations. Our theoretical MMRD relations are governed by two parameters, one is the white dwarf (WD) mass and the other is the initial envelope mass at a nova outburst; this second parameter explains the scatter of MMRD points of individual novae. Our theoretical MMRD relations are also in good agreement with the well-known empirical formulae. We also show another empirical relation of M_V(15) ∼ −5.7 ± 0.3 based on the absolute magnitude of our model light curves, i.e., the absolute magnitude at 15 days after optical maximum is almost common among various novae. We analyzed 10 nova light curves, in which a supersoft X-ray phase was detected, and estimated their WD masses. The models best simultaneously reproducing the optical and supersoft X-ray observations are ONeMg WDs with 1.28 ± 0.04 M_☉ (V598 Pup), 1.23 ± 0.05 M_☉ (V382 Vel), 1.15 ± 0.06 M_☉ (V4743 Sgr), 1.13 ± 0.06 M_☉ (V1281 Sco), 1.2 ± 0.05 M_☉ (V597 Pup), 1.06 ± 0.07 M_☉ (V1494 Aql), 1.04 ± 0.07 M_☉ (V2467 Cyg), 1.07 ± 0.07 M_☉ (V5116 Sgr), 1.05 ± 0.05 M_☉ (V574 Pup), and a CO WD with 0.93 ± 0.08 M_☉ (V458 Vul). The newly proposed relationships are consistent with the emergence or decay epoch of the supersoft X-ray phase of these 10 novae. Finally, we discuss the mechanism of shock-origin hard X-ray component in relation to the emergence of companion star from the WD envelope.

We present here the initial results of a new study of massive star yields of Fe-peak elements. We have compiled from the literature a database of carefully determined solar neighborhood stellar abundances of seven iron-peak elements, Ti, V, Cr, Mn, Fe, Co, and Ni, and then plotted [X/Fe] versus [Fe/H] to study the trends as functions of metallicity. Chemical evolution models were then employed to force a fit to the observed trends by adjusting the input massive star metallicity-sensitive yields of Kobayashi et al. Our results suggest that yields of Ti, V, and Co are generally larger as well as anticorrelated with metallicity, in contrast to the Kobayashi et al. predictions. We also find the yields of Cr and Mn to be generally smaller and directly correlated with metallicity compared to the theoretical results. Our results for Ni are consistent with theory, although our model suggests that all Ni yields should be scaled up slightly. The outcome of this exercise is the computation of a set of integrated yields, i.e., stellar yields weighted by a slightly flattened time-independent Salpeter initial mass function and integrated over stellar mass, for each of the above elements at several metallicity points spanned by the broad range of observations. These results are designed to be used as empirical constraints on future iron-peak yield predictions by stellar evolution modelers. Special attention is paid to the interesting behavior of [Cr/Co] with metallicity—these two elements have opposite slopes—as well as the indirect correlation of [Ti/Fe] with [Fe/H]. These particular trends, as well as those exhibited by the inferred integrated yields of all iron-peak elements with metallicity, are discussed in terms of both supernova nucleosynthesis and atomic physics.

The compact binary system in OJ287 is modeled to contain a spinning primary black hole with an accretion disk and a non-spinning secondary black hole. Using post-Newtonian (PN) accurate equations that include 2.5PN accurate non-spinning contributions, the leading-order general relativistic and classical spin–orbit terms, the orbit of the binary black hole in OJ287 is calculated and as expected it depends on the spin of the primary black hole. Using the orbital solution, the specific times when the orbit of the secondary crosses the accretion disk of the primary are evaluated such that the record of observed outbursts from 1913 up to 2007 is reproduced. The timings of the outbursts are quite sensitive to the spin value. In order to reproduce all the known outbursts, including a newly discovered one in 1957, the Kerr parameter of the primary has to be 0.28 ± 0.08. The quadrupole-moment contributions to the equations of motion allow us to constrain the "no-hair" parameter to be 1.0 ±  0.3, where 0.3 is the 1σ error. This supports the "black hole no-hair theorem" within the achievable precision. It should be possible to test the present estimate in 2015 when the next outburst is due. The timing of the 2015 outburst is a strong function of the spin: if the spin is 0.36 of the maximal value allowed in general relativity, the outburst begins in early 2015 November, while the same event starts in the end of January 2016 if the spin is 0.2.

The A5V star Alcor has an M3–M4 dwarf companion, as evidenced by a novel astrometric technique. Imaging spectroscopy combined with adaptive optics coronagraphy allowed for the detection and spectrophotometric characterization of the point source at a contrast of ∼6 J- and H-band magnitudes and separation of 1'' from the primary star. The use of an astrometric pupil plane grid allowed us to determine the projected separations between the companion and the coronagraphically occulted primary star to ⩽3 mas precision at two observation epochs. Our measurements demonstrate common parallactic and proper motion over the course of 103 days, significantly shorter than the period of time needed for most companion confirmations through proper motion measurements alone. This common parallax method is potentially more rigorous than common proper motion, ensuring that the neighboring bodies lie at the same distance, rather than relying on the statistical improbability that two objects in close proximity to each other on the sky move in the same direction. The discovery of a low-mass (∼0.25 M_☉) companion around a bright (V = 4.0 mag), nearby (d= 25 pc) star highlights a region of binary star parameter space that to date has not been fully probed.

We present a universal linear correlation between the stellar mass and surface brightness (SB) of galaxies at 0.3 < z < 3, using a deep K-band-selected catalog in the GOODS-North region. The correlation has a nearly constant slope, independent of redshift and color of galaxies in the rest-z frame. Considering unresolved compact galaxies, the tight correlation gives a lower boundary of SB for a given stellar mass; lower SB galaxies are prohibited over the boundary. The universal slope suggests that the stellar mass in galaxies was built up over their cosmic histories in a similar manner irrelevant to galaxy mass, as opposed to the scenario that massive galaxies mainly accumulated their stellar mass by major merging. In contrast, SB shows a strong dependence on redshift for a given stellar mass. It evolves as ∼(1 + z)^{−2.0∼−0.8}, in addition to dimming as (1 + z)⁴ by the cosmological expansion effect. The brightening depends on galaxy color and stellar mass. The blue population (rest-frame U − V < 0), which is dominated by young and star-forming galaxies, evolves as ∼(1 + z)^−0.8±0.3 in the rest-V band. On the other hand, the red population (U − V>0) and the massive galaxies (M_*>10¹⁰M_☉) show stronger brightening, (1 + z)^−1.5±0.1. By comparison with galaxy evolution models, the phenomena are well understood by the pure luminosity evolution of galaxies out to z ∼ 3.

Apart from the eleven-year solar cycle, another periodicity around 155–160 days was discovered during solar cycle 21 in high-energy solar flares, and its presence in sunspot areas and strong magnetic flux has been also reported. This periodicity has an elusive and enigmatic character, since it usually appears only near the maxima of solar cycles, and seems to be related with a periodic emergence of strong magnetic flux at the solar surface. Therefore, it is probably connected with the tachocline, a thin layer located near the base of the solar convection zone, where a strong dynamo magnetic field is stored. We study the dynamics of Rossby waves in the tachocline in the presence of a toroidal magnetic field and latitudinal differential rotation. Our analysis shows that the magnetic Rossby waves are generally unstable and that the growth rates are sensitive to the magnetic field strength and to the latitudinal differential rotation parameters. Variation of the differential rotation and the magnetic field strength throughout the solar cycle enhance the growth rate of a particular harmonic in the upper part of the tachocline around the maximum of the solar cycle. This harmonic is symmetric with respect to the equator and has a period of 155–160 days. A rapid increase of the wave amplitude could give rise to a magnetic flux emergence leading to observed periodicities in solar activity indicators related to magnetic flux.

In order to reproduce the statistical properties of the observed exoplanets, population synthesis models have shown that the migration of protoplanets should be significantly slowed down, and that processes stalling migration should be at work. Much current theoretical efforts have thus been dedicated to find physical effects that slow down, halt or even reverse migration. Many of these studies rely on the horseshoe drag, whose long-term evolution (saturated or not) is intimately related to the disk viscosity in laminar disk models. We investigate how the horseshoe drag exerted on a low-mass planet is altered by a more realistic treatment of the turbulence in protoplanetary disks. Two-dimensional hydrodynamic simulations are performed with a turbulence model that reproduces the main turbulence properties of three-dimensional magnetohydrodynamic calculations. We find that the horseshoe drag can remain unsaturated on the long term, depending on the turbulence strength. We show that the desaturation of the horseshoe drag by turbulence can be modeled by vortensity diffusion across the time-averaged planet's horseshoe region. At low-turbulence, the running-time-averaged torque is in good agreement with the total torque obtained for an equivalent laminar model, with a similar vortensity diffusion coefficient. At high turbulence, differences arise due to the time evolution of the averaged density profile with turbulence.

Although recent work in numerical relativity has made tremendous strides in quantifying the gravitational wave luminosity of black hole mergers, very little is known about the electromagnetic luminosity that might occur in immediate conjunction with these events. We show that whenever the heat deposited in the gas near a pair of merging black holes is proportional to its total mass, and the surface density of the gas in the immediate vicinity is greater than the (quite small) amount necessary to make it optically thick, the characteristic scale of the luminosity emitted in direct association with the merger is the Eddington luminosity independent of the gas mass. The duration of the photon signal is proportional to the gas mass, and is generally rather longer than the merger event. At somewhat larger distances, dissipation associated with realigning the gas orbits to the new spin orientation of the black hole can supplement dissipation of the energy gained from orbital adjustment to the mass lost in gravitational radiation; these two heat sources can combine to augment the electromagnetic radiation over longer timescales.

Extinction in galaxies affects their observed properties. In scenarios describing the distribution of dust and stars in individual disk galaxies, the amplitude of the extinction can be modulated by the inclination of the galaxies. In this work, we investigate the inclination dependency in composite spectra of star-forming disk galaxies from the Sloan Digital Sky Survey Data Release 5. In a volume-limited sample within a redshift range 0.065–0.075 and a r-band Petrosian absolute magnitude range −19.5 to −22 mag which exhibits a flat distribution of inclination, the inclined relative to face-on extinction in the stellar continuum is found empirically to increase with inclination in the g, r, and i bands. Within the central 0.5 intrinsic half-light radius of the galaxies, the g-band relative extinction in the stellar continuum for the highly inclined objects (axis ratio b/a = 0.1) is 1.2 mag, agreeing with previous studies. The extinction curve of the disk galaxies is given in the rest-frame wavelengths 3700–8000 Å, identified with major optical emission and absorption lines in diagnostics. The Balmer decrement, Hα/Hβ, remains constant with inclination, suggesting a different kind of dust configuration and/or reddening mechanism in the H ii region from that in the stellar continuum. One factor is shown to be the presence of spatially non-uniform interstellar extinction, presumably caused by clumped dust in the vicinity of the H ii region.

The winds and radiation from massive stars clear out large cavities in the interstellar medium. These bubbles, as they have been called, impact their surrounding molecular clouds and may influence the formation of stars therein. Here we present James Clerk Maxwell Telescope observations of the J = 3–2 line of CO in 43 bubbles identified with Spitzer Space Telescope observations. These spectroscopic data reveal the three-dimensional structure of the bubbles. In particular, we show that the cold gas lies in a ring, not a sphere, around the bubbles indicating that the parent molecular clouds are flattened with a typical thickness of a few parsecs. We also mapped seven bubbles in the J = 4–3 line of HCO⁺ and find that the column densities inferred from the CO and HCO⁺ line intensities are below that necessary for "collect and collapse" models of induced star formation. We hypothesize that the flattened molecular clouds are not greatly compressed by expanding shock fronts, which may hinder the formation of new stars.

We present the results of Spitzer Infrared Spectrograph low-resolution infrared 5–35 μm spectroscopy of 17 nearby ultraluminous infrared galaxies (ULIRGs) at z < 0.2, optically classified as non-Seyferts. The presence of optically elusive, but intrinsically luminous, buried active galactic nuclei (AGNs) is investigated, based on the strengths of polycyclic aromatic hydrocarbon emission and silicate dust absorption features detected in the spectra. The signatures of luminous buried AGNs, whose intrinsic luminosities range up to ∼10¹² L_☉, are found in eight sources. We combine these results with those of our previous research to investigate the energy function of buried AGNs in a complete sample of optically non-Seyfert ULIRGs in the local universe at z < 0.3 (85 sources). We confirm a trend that we previously discovered: that buried AGNs are more common in galaxies with higher infrared luminosities. Because optical Seyferts also show a similar trend, we argue more generally that the energetic importance of AGNs is intrinsically higher in more luminous galaxies, suggesting that the AGN–starburst connections are luminosity dependent. This may be related to the stronger AGN feedback scenario in currently more massive galaxy systems, as a possible origin of the galaxy downsizing phenomenon.

SS73 17 was an innocuous Mira-type symbiotic star until the International Gamma-Ray Astrophysics Laboratory and Swift discovered its bright hard X-ray emission, adding it to the small class of "hard X-ray emitting symbiotics." Suzaku observations in 2006 then showed it emits three bright iron lines as well, with little to no emission in the 0.3–2.0 keV bandpass. We present here follow-up observations with the Chandra High Energy Transmission Grating and Suzaku that confirm the earlier detection of strong emission lines of Fe Kα fluorescence, Fe xxv and Fe xxvi but also show significantly more soft X-ray emission. The high-resolution spectrum also shows emission lines of other highly ionized ions as Si xiv and possibly S xvi. In addition, a re-analysis of the 2006 Suzaku data using the latest calibration shows that the hard (15–50 keV) X-ray emission is brighter than previously thought and remains constant in both the 2006 and 2008 data. The G ratio calculated from the Fe xxv lines shows that these lines are thermal, not photoionized, in origin. With the exception of the hard X-ray emission, the spectra from both epochs can be fit using thermal radiation assuming a differential emission measure based on a cooling-flow model combined with a full and partial absorber. We show that acceptable fits can be obtained for all the data in the 1–10 keV band varying only the partial absorber. Based on the temperature and accretion rate, the thermal emission appears to be arising from the boundary layer between the accreting white dwarf and the accretion disk.

We report the detection of the C iv λλ1548,1551 emission line in the region of the RCW 114 nebula using the FIMS/SPEAR data. The observed C iv line intensity indicates that RCW 114 is much closer to us than WR 90, a Wolf–Rayet star that was thought to be associated with RCW 114 in some of the previous studies. We also found the existence of a small H i bubble centered on WR 90, with a different local standard of rest velocity range from that of the large H i bubble which was identified previously as related to RCW 114. These findings imply that the RCW 114 nebula is likely an old supernova remnant that is not associated with WR 90. Additionally, the global morphologies of the C iv, Hα, and H i emissions show that RCW 114 has evolved in a non-uniform interstellar medium.

Weak-lensing surveys are emerging as an important tool for the construction of "mass-selected" clusters of galaxies. We evaluate both the efficiency and completeness of a weak-lensing selection by combining a dense, complete redshift survey, the Smithsonian Hectospec Lensing Survey (SHELS), with a weak-lensing map from the Deep Lens Survey (DLS). SHELS includes 11,692 redshifts for galaxies with R ⩽ 20.6 in the 4 deg² DLS field; the survey is a solid basis for identifying massive clusters of galaxies with redshift z ≲ 0.55. The range of sensitivity of the redshift survey is similar to the range for the DLS convergence map. Only four of the 12 convergence peaks with signal to noise ⩾3.5 correspond to clusters of galaxies with M ≳ 1.7 × 10¹⁴ M_☉. Four of the eight massive clusters in SHELS are detected in the weak-lensing map yielding a completeness of ∼50%. We examine the seven known extended cluster X-ray sources in the DLS field: three can be detected in the weak-lensing map, three should not be detected without boosting from superposed large-scale structure, and one is mysteriously undetected even though its optical properties suggest that it should produce a detectable lensing signal. Taken together, these results underscore the need for more extensive comparisons among different methods of massive cluster identification.

We revisit the vertical structure of neutrino-dominated accretion flows in spherical coordinates. We stress that the flow should be geometrically thick when advection becomes dominant. In our calculation, the luminosity of neutrino annihilation is enhanced by 1 or 2 orders of magnitude. The empty funnel along the rotation axis can naturally explain the neutrino annihilable ejection.

We present a detailed analysis of the extremely luminous and long-lasting Type IIn supernova (SN) 2006gy using spectra obtained between days 36 and 237 after explosion. We derive the temporal evolution of the effective temperature, radius, blast-wave and SN-ejecta expansion speeds, and bolometric luminosity, as well as the progenitor wind density and total swept-up mass overtaken by the shock. SN 2006gy can be interpreted in the context of shock interaction with a dense circumstellar medium (CSM), but with quite extreme values for the CSM mass of ∼20 M_☉ and SN explosion kinetic energy of at least 5 × 10⁵¹ erg. A key difference between SN 2006gy and other SNe IIn is that, owing to its large amount of swept-up mass, the interaction region remained opaque much longer. At early times, Hα emission-line widths suggest that the photosphere is ahead of the shock, and photons diffuse out through the opaque CSM shell. The pivotal transition to optically thin emission occurs around day 110, when we start to see a decrease in the blackbody radius R_BB and strengthening tracers of the post-shock shell. From the evolution of pre-shock velocities, we deduce that the CSM was ejected by the progenitor star in a ≳10⁴⁹ erg precursor event ∼8 yr before the explosion. The large CSM mass definitively rules out models involving stars with initial masses of ≲10 M_☉. If the pre-SN mass budget also includes the likely SN ejecta mass of 10–20 M_☉ and the distant >10 M_☉ shell inferred from a light echo, then even massive M_ZAMS = 30–40 M_☉ progenitor stars are inadequate. At roughly solar metallicity, substantial mass loss probably occurred during the star's life, so SN 2006gy's progenitor is more consistent with sequential giant luminous blue variable eruptions or pulsational pair-instability ejections in extremely massive stars with initial masses above 100 M_☉. This requires significant revision to current paradigms of massive-star evolution.

We investigate the fraction of starbursts, starburst–active galactic nucleus (AGN) composites, Seyferts, and low-ionization narrow emission-line region galaxies (LINERs) as a function of infrared luminosity (L_IR) and merger progress for ∼500 infrared (IR)-selected galaxies. Using the new optical classifications afforded by the extremely large data set of the Sloan Digital Sky Survey, we find that the fraction of LINERs in IR-selected samples is rare (<5%) compared with other spectral types. The lack of strong IR emission in LINERs is consistent with recent optical studies suggesting that LINERs contain AGN with lower accretion rates than in Seyfert galaxies. Most previously classified IR-luminous LINERs are classified as starburst–AGN composite galaxies in the new scheme. Starburst–AGN composites appear to "bridge" the spectral evolution from starburst to AGN in ULIRGs. The relative strength of the AGN versus starburst activity shows a significant increase at high IR luminosity. In ULIRGs (L_IR > 10¹² L_☉), starburst–AGN composite galaxies dominate at early–intermediate stages of the merger, and AGN galaxies dominate during the final merger stages. Our results are consistent with models for IR-luminous galaxies where mergers of gas-rich spirals fuel both starburst and AGN, and where the AGN becomes increasingly dominant during the final merger stages of the most luminous IR objects.

We investigate the combined effects of solar energetic particle propagation, parallel and perpendicular to the large-scale magnetic field in the solar wind. Numerical methods employing stochastic differential equations are used incorporating pitch-angle diffusion, focusing, and pitch-angle-dependent diffusion perpendicular to the magnetic field. We compute spatial distributions of ∼100 keV electrons and 4 MeV protons in the inner heliosphere, assuming impulsive injection near the Sun over a limited range of solar longitude and latitude. In addition, spatial distributions and intensity–time profiles for various combinations of the parallel and perpendicular mean free path, with different assumptions for the dependence of λ_⊥ on the radial distance and pitch angle, are investigated. We find that realistic results can be obtained when we assume that the perpendicular mean free path scales in the inner heliosphere with the gyroradius of the particles. Step-like decreases of particle intensities as frequently observed in impulsive events at 1 AU can be reproduced for a ratio of λ_⊥/λ_∥ a few times 10⁻⁵.

We create realistic, full-sky, half-arcminute resolution simulations of the microwave sky matched to the most recent astrophysical observations. The primary purpose of these simulations is to test the data reduction pipeline for the Atacama Cosmology Telescope (ACT) experiment; however, we have widened the frequency coverage beyond the ACT bands and utilized the easily accessible HEALPix map format to make these simulations applicable to other current and near future microwave background experiments. Some of the novel features of these simulations are that the radio and infrared galaxy populations are correlated with the galaxy cluster and group populations, the primordial microwave background is lensed by the dark matter structure in the simulation via a ray-tracing code, the contribution to the thermal and kinetic Sunyaev–Zel'dovich (SZ) signals from galaxy clusters, groups, and the intergalactic medium has been included, and the gas prescription to model the SZ signals has been refined to match the most recent X-ray observations. The cosmology adopted in these simulations is also consistent with the WMAP 5-year parameter measurements. From these simulations we find a slope for the Y₂₀₀–M₂₀₀ relation that is only slightly steeper than self-similar, with an intrinsic scatter in the relation of ∼14%. Regarding the contamination of cluster SZ flux by radio galaxies, we find for 148 GHz (90 GHz) only 3% (4%) of halos have their SZ decrements contaminated at a level of 20% or more. We find the contamination levels higher for infrared galaxies. However, at 90 GHz, less than 20% of clusters with M₂₀₀ > 2.5 × 10¹⁴M_☉ and z < 1.2 have their SZ decrements filled in at a level of 20% or more. At 148 GHz, less than 20% of clusters with M₂₀₀ > 2.5 × 10¹⁴M_☉ and z < 0.8 have their SZ decrements filled in at a level of 50% or larger. Our models also suggest that a population of very high flux infrared galaxies, which are likely lensed sources, contribute most to the SZ contamination of very massive clusters at 90 and 148 GHz. These simulations are publicly available and should serve as a useful tool for microwave surveys to cross-check SZ cluster detection, power spectrum, and cross-correlation analyses.

We re-examine claims for redshift evolution in black hole–bulge scaling relations based on lensed quasars. In particular, we refine the black hole (BH) mass estimates using measurements of Balmer lines from near-infrared spectroscopy obtained with Triplespec at Apache Point Observatory. In support of previous work, we find a large scatter between Balmer and UV line widths, both Mg iiλλ2796, 2803 and C ivλλ1548, 1550. There is tentative evidence that C iii]λ1909, despite being a blend of multiple transitions, may correlate well with Mg ii, although a larger sample is needed for a real calibration. Most importantly, we find no systematic changes in the estimated BH masses for the lensed sample based on Balmer lines, providing additional support to the interpretation that black holes were overly massive compared to their host galaxies at high redshift.

We present Keck/High Resolution Echelle Spectrometer data with model atmosphere analysis of the helium-dominated polluted white dwarf GD 40, in which we measure atmospheric abundances relative to helium of nine elements: H, O, Mg, Si, Ca, Ti, Cr, Mn, and Fe. Apart from hydrogen, whose association with the other contaminants is uncertain, this material most likely accreted from GD 40's circumstellar dust disk whose existence is demonstrated by excess infrared emission. The data are best explained by accretion of rocky planetary material, in which heavy elements are largely contained within oxides, derived from a tidally disrupted minor planet at least the mass of Juno, and probably as massive as Vesta. The relatively low hydrogen abundance sets an upper limit of 10% water by mass in the inferred parent body, and the relatively high abundances of refractory elements, Ca and Ti, may indicate high-temperature processing. While the overall constitution of the parent body is similar to the bulk Earth being over 85% by mass composed of oxygen, magnesium, silicon, and iron, we find n(Si)/n(Mg) = 0.30 ± 0.11, significantly smaller than the ratio near unity for the bulk Earth, chondrites, the Sun, and nearby stars. This result suggests that differentiation occurred within the parent body.

The recent observations of the anomalous cosmic ray (ACR) energy spectrum as Voyager 1 and Voyager 2 crossed the heliospheric termination shock have called into question the conventional shock source of these energetic particles. We suggest that the sectored heliospheric magnetic field, which results from the flapping of the heliospheric current sheet, piles up as it approaches the heliopause, narrowing the current sheets that separate the sectors and triggering the onset of collisionless magnetic reconnection. Particle-in-cell simulations reveal that most of the magnetic energy is released and most of this energy goes into energetic ions with significant but smaller amounts of energy going into electrons. The energy gain of the most energetic ions results from their reflection from the ends of contracting magnetic islands, a first-order Fermi process. The energy gain of the ions in contracting islands increases their parallel (to the magnetic field B) pressure p_∥ until the marginal fire-hose condition is reached, causing magnetic reconnection and associated particle acceleration to shut down. Thus, the feedback of the self-consistent development of the energetic ion pressure on reconnection is a crucial element of any reconnection-based, particle-acceleration model. The model calls into question the strong scattering assumption used to derive the Parker transport equation and therefore the absence of first-order Fermi acceleration in incompressible flows. A simple one-dimensional model for particle energy gain and loss is presented in which the feedback of the energetic particles on the reconnection drive is included. The ACR differential energy spectrum takes the form of a power law with a spectral index slightly above 1.5. The model has the potential to explain several key Voyager observations, including the similarities in the spectra of different ion species.

Furukawa et al. reported the existence of a large mass of molecular gas associated with the super star cluster Westerlund 2 and the surrounding H ii region RCW49, based on a strong morphological correspondence between NANTEN2 ¹²CO(J = 2–1) emission and Spitzer IRAC images of the H ii region. We here present temperature and density distributions in the associated molecular gas at ∼3.5 pc resolution, as derived from a large velocity gradient analysis of the ¹²CO(J = 2–1), ¹²CO(J = 1–0), and ¹³CO(J = 2–1) transitions. The kinetic temperature is as high as ∼60–150 K within a projected distance of ∼5–10 pc from Westerlund 2 and decreases to as low as ∼10 K away from the cluster. The high temperature provides robust verification that the molecular gas is indeed physically associated with the H ii region, supporting Furukawa et al.'s conclusion. The derived temperature is also roughly consistent with theoretical calculations of photodissociation regions (PDRs), while the low spatial resolution of the present study does not warrant a more detailed comparison with PDR models. We suggest that the molecular clouds presented here will serve as an ideal laboratory to test theories on PDRs in future higher resolution studies.

The Infrared Space Observatory (ISO) detected several sharp infrared features around young stars, comets, and evolved stars. These sharp features were identified as Mg-rich crystalline silicates of forsterite and enstatite by comparison with spectra from laboratory data. However, certain infrared emission bands in the observed spectra cannot be identified because they appear at slightly shorter wavelengths than the peaks in forsterite laboratory spectra, where the shapes of forsterite particles are irregular. To solve this problem, we measured infrared spectra of forsterite grains of various shapes (irregular, plate-like with no sharp edges, elliptical, cauliflower, and spherical) in the infrared spectral region between 5 and 100 μm. The spectra depend on particle shape. The spectra of the 11, 19, 23, and 33 μm bands, in particular, are extremely sensitive to particle shape, whereas some peaks such as the 11.9, 49, and 69 μm bands remained almost unchanged despite different particle shapes. This becomes most evident from the spectra of near-spherical particles produced by annealing an originally amorphous silicate sample at temperature from 600 to 1150°C. The spectra of these samples differ strongly from those of other ones, showing peaks at much shorter wavelengths. At a higher annealing temperature of 1200°C, the particle shapes changed drastically from spherical to irregular and the spectra became similar to those of forsterite particles with irregular shapes. Based on ISO data and other observational data, the spectra of outflow sources and disk sources may correspond to differences in forsterite shape, and further some unidentified peaks, such as those at 32.8 or 32.5 μm, may be due to spherical or spherical-like forsterite.

We carry out a model study to determine whether a funnel-type flow geometry in the solar wind source region leads to sufficiently fast hydrogen flow to offset heavy element gravitational settling and can thus explain why solar wind abundances are not much smaller than photospheric abundances. We find that high first ionization potential (FIP) elements are more susceptible to gravitational settling than low-FIP elements, which are pulled up by Coulomb drag from protons, and hence the settling is more sensitive to the charge state of the elements than to their mass. Abundances at the top of the chromosphere, and hence solar wind abundances, can change by many orders of magnitude when the funnel areal expansion factor is changed by a small amount. The observed solar wind neon abundance provides the most severe constraint on the expansion, requiring a total flux tube expansion factor of at least 30–40.

Observational data and theoretical models suggest that the wave spectrum in the solar wind and corona may contain a fast magnetosonic mode component. This paper presents two-dimensional hybrid simulations of the energy cascade among the fast waves in the vicinity of the proton inertial scale. The initial spectrum consists of modes propagating in the positive direction, defined by the mean magnetic field, and is allowed to evolve freely in time. The plasma beta is set to low values typical of the solar corona. The cascade proceeds from lower to higher wavenumbers and mostly in the direction across the magnetic field. The highly oblique fast waves are strongly dissipated on the protons. The resulting proton heating is preferentially perpendicular to the magnetic field. If the wave intensity is constrained by the observed density spectra in the corona, the heating is fast enough to generate the solar wind.

A revision to the flux-transport dynamo model for the solar sunspot cycle is proposed and is demonstrated by using the axisymmetric kinematic simulations. The flux-transport dynamo has succeeded to explain the general cyclic behaviors of the sunspots. It has been known, however, that previous models failed to avoid the strong polar surface field and the strong toroidal field at the base in the high latitude, both of which are not consistent with observations. We propose a new regime of the flux-transport dynamo model by assuming an additional intense diffusivity profile near the surface. The surface poloidal field generated by the α effect is transported down to the base of the convection zone not by the meridional flow but by the surface diffusion mainly in the mid-latitude. With a moderate α quenching, this prevents the concentration of the polar surface field and the amplification of the toroidal field at the high latitude. The condition to obtain the proper magnetic field strength near the pole is η_surf/u₀>2 × 10⁹ cm, where η_surf and u₀ are the surface diffusivity and the meridional flow speed, respectively. We also do some parameter studies to ensure the importance of the surface strong diffusivity. In addition, the dependence of the cycle period on free parameters, the speed of meridional flow and the surface diffusivity, is investigated.

We study the growth of massive galaxies from z = 2 to the present using data from the NOAO/Yale NEWFIRM Medium Band Survey. The sample is selected at a constant number density of n = 2 × 10⁻⁴ Mpc⁻³, so that galaxies at different epochs can be compared in a meaningful way. We show that the stellar mass of galaxies at this number density has increased by a factor of ≈2 since z = 2, following the relation log M_n(z) = 11.45 − 0.15z. In order to determine at what physical radii this mass growth occurred, we construct very deep stacked rest-frame R-band images of galaxies with masses near M_n(z), at redshifts 〈z〉 = 0.6, 1.1, 1.6, and 2.0. These image stacks of typically 70–80 galaxies enable us to characterize the stellar distribution to surface brightness limits of ∼28.5 mag arcsec⁻². We find that massive galaxies gradually built up their outer regions over the past 10 Gyr. The mass within a radius of r = 5 kpc is nearly constant with redshift, whereas the mass at 5 kpc < r < 75 kpc has increased by a factor of ∼4 since z = 2. Parameterizing the surface brightness profiles, we find that the effective radius and Sersic n parameter evolve as r_e ∝ (1 + z)^−1.3 and n ∝ (1 + z)^−1.0, respectively. The data demonstrate that massive galaxies have grown mostly inside-out, assembling their extended stellar halos around compact, dense cores with possibly exponential radial density distributions. Comparing the observed mass evolution to the average star formation rates of the galaxies we find that the growth is likely dominated by mergers, as in situ star formation can only account for ∼20% of the mass buildup from z = 2 to z = 0. A direct consequence of these results is that massive galaxies do not evolve in a self-similar way: their structural profiles change as a function of redshift, complicating analyses which (often implicitly) assume self-similarity. The main uncertainties in this study are possible redshift-dependent systematic errors in the total stellar masses and the conversion from light-weighted to mass-weighted radial profiles.

We have carried out long-term (14 years) V and R photometric monitoring of 12 carbon-rich proto-planetary nebulae. The light and color curves display variability in all of them. The light curves are complex and suggest multiple periods, changing periods, and/or changing amplitudes, which are attributed to pulsation. A dominant period has been determined for each and found to be in the range of ∼150 days for the coolest (G8) to 35–40 days for the warmest (F3). A clear, linear inverse relationship has been found in the sample between the pulsation period and the effective temperature and also an inverse relationship between the amplitude of light variation and the effective temperature. These are consistent with the expectation for a pulsating post-asymptotic giant branch (post-AGB) star evolving toward higher temperature at constant luminosity. The published spectral energy distributions and mid-infrared images show these objects to have cool (200 K), detached dust shells and published models imply that intensive mass loss ended 400–2000 years ago. The detection of periods as long as 150 days in these requires a revision in the published post-AGB evolution models that couple the pulsation period to the mass loss rate and that assume that intensive mass loss ended when the pulsation period had decreased to 100 days. This revision will have the effect of extending the timescale for the early phases of post-AGB evolution. It appears that real time evolution in the pulsation periods of individual objects may be detectable on the timescale of two or three decades.

We present the rest-frame optical galaxy merger fraction between 0.2 < z < 1.2, as a function of stellar mass and optical luminosity, as observed by the Canada–France–Hawaii Telescope Legacy Deep Survey (CFHTLS-Deep). We developed a new classification scheme to identify major galaxy–galaxy mergers based on the presence of tidal tails and bridges. These morphological features are signposts of recent and ongoing merger activity. Through the visual classification of all galaxies, down to i_vega ⩽ 22.2 (≈27,000 galaxies) over 2 square degrees, we have compiled the CFHTLS-Deep Catalog of Interacting Galaxies, with ≈ 1600 merging galaxies. We find the merger fraction to be 4.3% ± 0.3% at z ∼ 0.3 and 19.0% ± 2.5% at z ∼ 1, implying evolution of the merger fraction going as (1 + z)^m, with m = 2.25 ± 0.24. This result is inconsistent with a mild or non-evolving (m < 1.5) scenario at a ≳4σ level of confidence. A mild trend, where by massive galaxies with M_*>10^10.7 M_☉ are undergoing fewer mergers than less massive systems (M_* ∼ 10¹⁰ M_☉), consistent with the expectations of galaxy assembly downsizing is observed. Our results also show that interacting galaxies have on average SFRs double that found in non-interacting field galaxies. We conclude that (1) the optical galaxy merger fraction does evolve with redshift, (2) the merger fraction depends mildly on stellar mass, with lower mass galaxies having higher merger fractions at z < 1, and (3) star formation is triggered at all phases of a merger, with larger enhancements at later stages, consistent with N-body simulations.

We present a kinematic analysis of the globular cluster (GC) system in the giant elliptical galaxy (gE) NGC 4636 in the Virgo cluster. Using the photometric and spectroscopic database of 238 GCs (108 blue GCs and 130 red GCs) at the galactocentric radius 039 < R < 1543, we have investigated the kinematics of the GC system. The NGC 4636 GC system shows weak overall rotation, which is dominated by the red GCs. However, both the blue GCs and red GCs show some rotation in the inner region at R < 43 (=2.9R_eff = 18.5 kpc). The velocity dispersion for all the GCs is derived to be σ_p = 225⁺¹²₋₉ km s⁻¹. The velocity dispersion for the blue GCs (σ_p = 251⁺¹⁸₋₁₂ km s⁻¹) is slightly larger than that for the red GCs (σ_p = 205⁺¹¹₋₁₃ km s⁻¹). The velocity dispersions for the blue GCs about the mean velocity and about the best-fit rotation curve have a significant variation depending on the galactocentric radius. Comparison of observed stellar and GC velocity dispersion profiles (VDPs) with the VDPs calculated from the stellar mass profile shows that the mass-to-light ratio should increase as the galactocentric distance increases, indicating the existence of an extended dark matter halo. From the comparison of the observed GC VDPs and the VDPs calculated for the X-ray mass profiles in the literature, we find that the orbit of the GC system is tangential, and that the orbit of the red GCs is slightly more tangential than that of the blue GCs. We compare the GC kinematics of NGC 4636 with those of other six gEs, finding that the kinematic properties of the GCs are diverse among gEs. We find several correlations between the kinematics of the GCs and the global parameters of their host galaxies. We discuss the implication of the results for the formation models of the GC system in gEs, and suggest a mixture scenario for the origin of the GCs in gEs.

We perform axisymmetric relativistic magnetohydrodynamic simulations to investigate the acceleration and collimation of jets and outflows from disks around compact objects. Newtonian gravity is added to the relativistic treatment in order to establish the physical boundary condition of an underlying accretion disk in centrifugal and pressure equilibrium. The fiducial disk surface (respectively a slow disk wind) is prescribed as boundary condition for the outflow. We apply this technique for the first time in the context of relativistic jets. The strength of this approach is that it allows us to run a parameter study in order to investigate how the accretion disk conditions govern the outflow formation. Substantial effort has been made to implement a current-free, numerical outflow boundary condition in order to avoid artificial collimation present in the standard outflow conditions. Our simulations using the PLUTO code run for 500 inner disk rotations and on a physical grid size of 100 × 200 inner disk radii. The simulations evolve from an initial state in hydrostatic equilibrium and an initially force-free magnetic field configuration. Two options for the initial field geometries are applied—an hourglass-shaped potential magnetic field and a split monopole field. Most of our parameter runs evolve into a steady state solution which can be further analyzed concerning the physical mechanism at work. In general, we obtain collimated beams of mildly relativistic speed with Lorentz factors up to 6 and mass-weighted half-opening angles of 3–7 deg. The split-monopole initial setup usually results in less collimated outflows. The light surface of the outflow magnetosphere tends to align vertically—implying three relativistically distinct regimes in the flow—an inner subrelativistic domain close to the jet axis, a (rather narrow) relativistic jet and a surrounding subrelativistic outflow launched from the outer disk surface—similar to the spine-sheath structure currently discussed for asymptotic jet propagation and stability. The outer subrelativistic disk-wind is a promising candidate for the X-ray absorption winds that are observed in many radio-quiet active galactic nuclei. The hot winds under investigation acquire only low Lorentz factors due to the rather high plasma-β we have applied in order to provide an initial force-balance in the disk corona. When we increase the outflow Poynting flux by injecting an additional disk toroidal field into the outflow, the jet velocities achieved are higher. These flows gain super-magnetosonic speed and remain Poynting flux dominated.

Radiative diffusion damps acoustic modes at large comoving wavenumber (k) before decoupling ("Silk damping"). In a simple WKB analysis, neglecting moments of the temperature distribution beyond the quadrupole (the tight-coupling limit), damping appears in the acoustic mode as a term of order $ik^2\dot{\tau }^{-1}$, where $\dot{\tau }$ is the scattering rate per unit conformal time. Although the Jeans instability is stabilized on scales smaller than the adiabatic Jeans length, I show that the medium is linearly unstable to first order in $\dot{\tau }^{-1}$ to a slow diffusive mode. At large comoving wavenumber, the characteristic growth rate becomes independent of spatial scale and constant: (t_KH a)⁻¹ ≈ (128πG/9κ_Tc)(ρ_m/ρ_b), where a is the scale factor, ρ_m and ρ_b are the matter and baryon energy density, respectively, and κ_T is the Thomson opacity. This is the characteristic timescale for a fluid parcel to radiate away its total thermal energy content at the Eddington limit, analogous to the Kelvin–Helmholz (KH) timescale for a radiation pressure-dominated massive star or the Salpeter timescale for black hole growth. Although this mode grows at all times prior to decoupling and on scales smaller than roughly the horizon, the growth time is long, about 100 times the age of the universe at decoupling. Thus, it modifies the density and temperature perturbations on small scales only at the percent level. The physics of this mode in the tight-coupling limit is already accounted for in the popular codes CMBFAST and CAMB, but is typically neglected in analytic studies of the growth of primordial perturbations. The goal of this work is to clarify the physics of this diffusive instability in the epoch before decoupling, and to emphasize that the universe is formally unstable on scales below the horizon, even in the limit of very large $\dot{\tau }$. Analogous instabilities that might operate at yet earlier epochs are also mentioned.

We present a multifrequency radio investigation of the Crab-like pulsar wind nebula (PWN) G54.1+0.3 using the Very Large Array. The high resolution of the observations reveals that G54.1+0.3 has a complex radio structure which includes filamentary and loop-like structures that are magnetized, a diffuse extent similar to the associated diffuse X-ray emission. But the radio and X-ray structures in the central region differ strikingly, indicating that they trace very different forms of particle injection from the pulsar and/or particle acceleration in the nebula. No spectral index gradient is detected in the radio emission across the PWN, whereas the X-ray emission softens outward in the nebula. The extensive radio polarization allows us to image in detail the intrinsic magnetic field, which is well-ordered and reveals that a number of loop-like filaments are strongly magnetized. In addition, we determine that there are both radial and toroidal components to the magnetic field structure of the PWN. Strong mid-infrared (IR) emission detected in Spitzer Space Telescope data is closely correlated with the radio emission arising from the southern edge of G54.1+0.3. In particular, the distributions of radio and X-ray emission compared with the mid-IR emission suggest that the PWN may be interacting with this interstellar cloud. This may be the first PWN where we are directly detecting its interplay with an interstellar cloud that has survived the impact of the supernova explosion associated with the pulsar's progenitor.

We employ numerical simulations and simple analytical estimates to argue that dark matter substructures orbiting in the inner regions of the Galaxy can be efficiently destroyed by disk shocking, a dynamical process known to affect globular star clusters. We carry out a set of fiducial high-resolution collisionless simulations in which we adiabatically grow a disk, allowing us to examine the impact of the disk on the substructure abundance. We also track the orbits of dark matter satellites in high-resolution Aquarius simulations and analytically estimate the cumulative halo and disk-shocking effect. Our calculations indicate that the presence of a disk with only 10% of the total Milky Way mass can significantly alter the mass function of substructures in the inner parts of halos. This has important implications especially for the relatively small number of satellites seen within ∼30 kpc of the Milky Way center, where disk shocking is expected to reduce the substructure abundance by a factor of 2 at 10⁹ M_☉ and a factor of 3 at 10⁷ M_☉. The most massive subhalos with 10¹⁰ M_☉ survive even in the presence of the disk. This suggests that there is no inner missing satellite problem and calls into question whether these substructures can produce transient features in disks, like multi-armed spiral patterns. Also, the depletion of dark matter substructures through shocking on the baryonic structures of the disk and central bulge may aggravate the problem to fully account for the observed flux anomalies in gravitational lens systems, and significantly reduces the dark matter annihilation signal expected from nearby substructures in the inner halo.

Magnetic-field generation by a relativistic ion beam propagating through an electron–ion plasma along a homogeneous magnetic field is investigated with 2.5D high-resolution particle-in-cell (PIC) simulations. The studies test predictions of a strong amplification of short-wavelength modes of magnetic turbulence upstream of nonrelativistic and relativistic parallel shocks associated with supernova remnants (SNRs), jets of active galactic nuclei, and gamma-ray bursts. We find a good agreement in the properties of the turbulence observed in our simulations compared with the dispersion relation calculated for linear waves with arbitrary orientation of ${\vec{k}}$. Depending on the parameters, the back-reaction on the ion beam leads to filamentation of the ambient plasma and the beam, which in turn influences the properties of the magnetic turbulence. For mildly and ultrarelativistic beams, the instability saturates at field amplitudes a few times larger than the homogeneous magnetic field strength. This result matches our recent studies of nonrelativistically drifting, hot cosmic-ray particles upstream of SNR shocks which indicated only a moderate magnetic-field amplification by nonresonant instabilities. We also demonstrate that the aperiodic turbulence generated by the beam can provide efficient particle scattering with a rate compatible with Bohm diffusion. Representing the ion beam as a constant external current, i.e., excluding a back-reaction of the magnetic turbulence on the beam, we observe nonresonant parallel modes with wavelength and growth rate as predicted by analytic calculations. In this unrealistic setup, the magnetic field is amplified to amplitudes far exceeding the homogeneous field, as observed in recent magnetohydrodynamic and PIC simulations.

We report Al–Mg, Ca, and Ti isotopic data in 16 silicon carbide grains and four silicon nitride grains from the Qingzhen enstatite chondrite. Previous C, N, and Si isotopic measurements had identified these grains as type X grains, believed to have an origin in Type II supernovae (SNe). The grains analyzed include both subtypes X1 and X2. Twelve SiC and three Si₃N₄ grains show evidence for initial ²⁶Al, and eight SiC grains evidence for ⁴⁴Ti; 11 SiC grains have ⁴⁹Ti excesses, possibly indicating the initial presence of ⁴⁹V. A correlation with subtype is shown for ⁴⁴Ti: X2 grains that have the highest inferred ⁴⁴Ti/⁴⁸Ti ratios. A weaker correlation exists for N ratios: X2 grains with ¹²C/¹³C > 300 have higher ¹⁴N/¹⁵N ratios than X1 grains. We compare our data and data from previous reports with the SN models by Rauscher et al. The SN models can explain the C and N isotopic ratios fairly well if material from the ¹⁵N-rich spike in the He/N zone of the 25 M_☉ SN model is used. They also can explain the ⁴⁴Ti/⁴⁸Ti ratios of the X1 and X2 grains. For the latter, substantial contributions from the inner Ni core are required. They indicate that not for all grains the ⁴⁹Ti excesses can be attributed to decay of ⁴⁹V and material from the He/C zone, where ⁴⁹Ti is produced by neutron capture, is needed. The SN models, however, fail in explaining the Si isotopic ratios of most of the grains in a satisfactory fashion and the distinction between X1 and X2 grains. They also fail in explaining the observed correlation between the ²⁶Al/²⁷Al ratios and ¹²C/¹³C (and ¹⁴N/¹⁵N) ratios.

We numerically construct models of spherically symmetric relativistic stellar clusters with anisotropic distribution functions. Newtonian solutions obtained in Paper I are generalized as isotropic Maxwellian ones with energy cutoff in their distribution function. We consider distributions with different levels of anisotropy and discuss some general characteristics of the models.

We have carried out high-precision photometry on a large number of archival Hubble Space Telescope images of the Galactic globular cluster NGC 6752, to search for signs of multiple stellar populations. We find a broadened main sequence (MS) and demonstrate that this broadening cannot be attributed either to binaries or to photometric errors. There is also some indication of an MS split. No significant spread could be found along the sub-giant branch, however. Ground-based photometry reveals that in the U versus (U − B) color–magnitude diagram the red-giant branch (RGB) exhibits a clear color spread, which we have been able to correlate with variations in Na and O abundances. In particular, the Na-rich, O-poor stars identified by Carretta et al. define a sequence on the red side of the RGB, while Na-poor, O-rich stars populate a bluer, more dispersed portion of the RGB.

We determine an absolute calibration of the initial mass function (IMF) of early-type galaxies, by studying a sample of 56 gravitational lenses identified by the Sloan Lenses ACS Survey. Under the assumption of standard Navarro, Frenk, and White dark matter halos, a combination of lensing, dynamical, and stellar population synthesis models is used to disentangle the stellar and dark matter contribution for each lens. We define an "IMF mismatch" parameter α≡M^LD_*,Ein/M^SPS_*,Ein as the ratio of stellar mass inferred by a joint lensing and dynamical model (M^LD_*,Ein) to the current stellar mass inferred from stellar populations synthesis models (M^SPS_*,Ein). We find that a Salpeter IMF provides stellar masses in agreement with those inferred by lensing and dynamical models (〈log α〉 = −0.00 ± 0.03 ± 0.02), while a Chabrier IMF underestimates them (〈log α〉 = 0.25 ± 0.03 ± 0.02). A tentative trend is found, in the sense that α appears to increase with galaxy velocity dispersion. Taken at face value, this result would imply a non-universal IMF, perhaps dependent on metallicity, age, or abundance ratios of the stellar populations. Alternatively, the observed trend may imply non-universal dark matter halos with inner density slope increasing with velocity dispersion. While the degeneracy between the two interpretations cannot be broken without additional information, the data imply that massive early-type galaxies cannot have both a universal IMF and universal dark matter halos.

Galaxies moving through the intracluster medium (ICM) of a cluster of galaxies can lose gas via ram pressure stripping. This stripped gas forms a tail behind the galaxy which is potentially observable. In this paper, we carry out hydrodynamical simulations of a galaxy undergoing stripping with a focus on the gas properties in the wake and their observational signatures. We include radiative cooling in an adaptive hydrocode in order to investigate the impact of a clumpy, multi-phase interstellar medium. We find that including cooling results in a very different morphology for the gas in the tail, with a much wider range of temperatures and densities. The tail is significantly narrower in runs with radiative cooling, in agreement with observed wakes. In addition, we make detailed predictions of H i, Hα, and X-ray emission for the wake, showing that we generally expect detectable H i and Hα signatures, but no observable X-ray emission (at least for our chosen ram pressure strength and ICM conditions). We find that the relative strength of the Hα diagnostic depends somewhat on our adopted minimum temperature floor (below which we set cooling to zero to mimic physics processes not included in the simulation).

We show that the gas giant exoplanet HD 189733b is less oblate than Saturn, based on Spitzer Space Telescope photometry of seven transits. The observable manifestations of oblateness would have been slight anomalies during the ingress and egress phases, as well as variations in the transit depth due to spin precession. Our nondetection of these effects gives the first empirical constraints on the shape of an exoplanet. The results are consistent with the theoretical expectation that the planetary rotation period and orbital period are synchronized, in which case the oblateness would be an order of magnitude smaller than our upper limits. Conversely, if HD 189733b is assumed to be in a synchronous, zero-obliquity state, then the data give an upper bound on the quadrupole moment of the planet (J₂ < 0.068 with 95% confidence) that is too weak to constrain the interior structure of the planet. An Appendix describes a fast algorithm for computing the transit light curve of an oblate planet, which was necessary for our analysis.

We investigate conditions for and consequences of spallation in radio-quiet Seyfert galaxies. The work is motivated by the recent discovery of significant line emission at 5.44 keV in Suzaku data from NGC 4051. The energy of the new line suggests an identification as Cr i Kα emission; however, the line is much stronger than would be expected from material with cosmic abundances, leading to a suggestion of enhancement owing to nuclear spallation of Fe by low-energy cosmic rays from the active nucleus. We find that the highest abundance enhancements are likely to take place in gas out of the plane of the accretion disk and that timescales for spallation could be as short as a few years. The suggestion of a strong nuclear flux of cosmic rays in a radio-quiet active Seyfert galaxy is of particular interest in light of the recent suggestion from Pierre Auger Observatory data that ultra-high-energy cosmic rays may originate in such sources.

The relative importance of different initiation mechanisms for coronal mass ejections (CMEs) on the Sun is uncertain. One possible mechanism is the loss of equilibrium of coronal magnetic flux ropes formed gradually by large-scale surface motions. In this paper, the locations of flux rope ejections in a recently developed quasi-static global evolution model are compared with observed CME source locations over a 4.5 month period in 1999. Using extreme ultraviolet data, the low-coronal source locations are determined unambiguously for 98 out of 330 CMEs. An alternative method of determining the source locations using recorded Hα events was found to be too inaccurate. Despite the incomplete observations, positive correlation (with coefficient up to 0.49) is found between the distributions of observed and simulated ejections, but only when binned into periods of 1 month or longer. This binning timescale corresponds to the time interval at which magnetogram data are assimilated into the coronal simulations, and the correlation arises primarily from the large-scale surface magnetic field distribution; only a weak dependence is found on the magnetic helicity imparted to the emerging active regions. The simulations are limited in two main ways: they produce fewer ejections, and they do not reproduce the strong clustering of observed CME sources into active regions. Due to this clustering, the horizontal gradient of radial photospheric magnetic field is better correlated with the observed CME source distribution (coefficient 0.67). Our results suggest that while the gradual formation of magnetic flux ropes over weeks can account for many observed CMEs, especially at higher latitudes, there exists a second class of CMEs (at least half) for which dynamic active region flux emergence on shorter timescales must be the dominant factor. Improving our understanding of CME initiation in future will require both more comprehensive observations of CME source regions and more detailed magnetic field simulations.

4U 2206+54 is a high-mass X-ray binary which has been suspected to contain a neutron star accreting from the wind of its companion, BD +53° 2790. Reig et al. have recently detected 5560 s period pulsations in both Rossi X-ray Timing Explorer (RXTE) and International Gamma-ray Astrophysics Laboratory observations which they conclude are due to the spin of the neutron star. We present observations made with Suzaku which are contemporaneous with their RXTE observation of this source. We find strong pulsations at a period of 5554 ± 9 s in agreement with their results. We also present a reanalysis of BeppoSAX observations of 4U 2206+54 made in 1998, in which we find strong pulsations at a period of 5420 ± 28 s, revealing a spin-down trend in this long-period accreting pulsar. Analysis of these data suggests that the neutron star in this system is an accretion-powered magnetar.

We present our Spitzer-Infrared Spectrometer (IRS) spectroscopic survey from 10 μm to 37 μm of the Seyfert galaxies of the 12 μm Galaxy Sample, collected in a high-resolution mode (R ∼ 600). The new spectra of 61 galaxies, together with the data we already published, give us a total of 91 12 μm Seyfert galaxies observed, out of 112. We discuss the mid-IR emission lines and features of the Seyfert galaxies, using an improved active galactic nucleus (AGN) classification scheme: instead of adopting the usual classes of Seyfert 1's and Seyfert 2's, we use the spectropolarimetric data from the literature to divide the objects into categories "AGN 1" and "AGN 2," where AGN 1's include all broad-line objects, including the Seyfert 2's showing hidden broad lines in polarized light. The remaining category, AGN 2's, contains only Seyferts with no detectable broad lines in either direct or polarized spectroscopy. We present various mid-IR observables, such as ionization-sensitive and density-sensitive line ratios, the polycyclic aromatic hydrocarbon (PAH) 11.25 μm feature and the H₂ S(1) rotational line equivalent widths (EWs), the (60–25 μm) spectral index, and the source extendedness at 19 μm, to characterize similarities and differences in the AGN populations, in terms of AGN dominance versus star formation dominance. We find that the mid-IR emission properties characterize all the AGN 1's objects as a single family, with strongly AGN-dominated spectra. In contrast, the AGN 2's can be divided into two groups, the first one with properties similar to the AGN 1's except without detected broad lines, and the second with properties similar to the non-Seyfert galaxies, such as LINERs or starburst galaxies. We computed a semianalytical model to estimate the AGN and the starburst contributions to the mid-IR galaxy emission at 19 μm. For 59 galaxies with appropriate data, we can separate the 19 μm emission into AGN and starburst components using the measured mid-IR spectral features. We use these to quantify the brightness thresholds that an AGN must meet to satisfy our classifications: AGN 1's have an AGN contribution ⩾73% and AGN 2 ⩾ 45% of their total emission at 19 μm. The detection of [Ne v] lines turns out to be an almost perfect signature of energy production by an AGN. Only four (∼7.5%) of 55 AGN 1's and two (10%) out of 20 AGN 2's do not have [Ne v] 14.3 μm down to a flux limit of ∼4 × 10⁻¹⁵ erg s⁻¹ cm⁻². We present mean spectra of the various AGN categories. Passing from AGN-dominated to starburst-dominated objects, the continuum steepens, especially at wavelengths shorter than 20 μm, while the PAH feature increases in its EW and the high ionization lines decrease. We estimate H₂ mass and excitation temperature through the measurement of the S(1) rotational line of this molecule. Finally, we derive the first local luminosity functions for the brightest mid-IR lines and the PAH feature at 11.25 μm. No statistical difference is apparent in the space densities for Seyfert 1's and 2's of a given line luminosity, or for the new classes of AGN 1's and 2's. We use the correlation between [Ne v] line and nonstellar IR continuum luminosity to derive the global output of accretion-powered galactic nuclei in the local universe.

Stellar irradiation and particle forcing strongly affect the immediate environment of extrasolar giant planets orbiting near their parent stars. However, it is not clear how the energy is deposited over the planetary atmosphere, nor how the momentum and energy spaces of the different species that populate the system are modified. Here, we use far-ultraviolet emission spectra from HD209458 in the wavelength range (1180–1710) Å to bring new insight to the composition and energetic processes in play in the gas nebula around the transiting planetary companion. In that frame, we consider up-to-date atmospheric models of the giant exoplanet where we implement non-thermal line broadening to simulate the impact on the transit absorption of superthermal atoms (H i, O i, and C ii) populating the upper layers of the nebula. Our sensitivity study shows that for all existing models, a significant line broadening is required for O i and probably for C ii lines in order to fit the observed transit absorptions. In that frame, we show that O i and C ii are preferentially heated compared to the background gas with effective temperatures as large as T_O i/T_B ∼ 10 for O i and T_C ii/T_B ∼ 5 for C ii. By contrast, the situation is much less clear for H i because several models could fit the Lyα observations including either thermal H i in an atmosphere that has a dayside vertical column [H i] ∼ 1.05 × 10²¹ cm⁻², or a less extended thermal atmosphere but with hot H i atoms populating the upper layers of the nebula. If the energetic H i atoms are either of stellar origin or populations lost from the planet and energized in the outer layers of the nebula, our finding is that most models should converge toward one hot population that has an H i vertical column in the range [H i]_hot  ∼ (2–4) × 10¹³ cm⁻² and an effective temperature in the range T_H i ∼ (1–1.3) × 10⁶ K, but with a bulk velocity that should be rather slow.

Fundamental modes supported by a thin magnetic flux tube embedded in the solar atmosphere are typically classified as longitudinal, transverse, and torsional waves. If the tube is isothermal, then the propagation of longitudinal and transverse tube waves is restricted to frequencies that are higher than the corresponding global cutoff frequency for each wave. However, no such global cutoff frequency exists for torsional tube waves, which means that a thin and isothermal flux tube supports torsional tube waves of any frequency. In this paper, we consider a thin and non-isothermal magnetic flux tube and demonstrate that temperature gradients inside this tube are responsible for the origin of a cutoff frequency for torsional tube waves. The cutoff frequency is used to determine conditions for the wave propagation in the solar atmosphere, and the obtained results are compared to the recent observational data that support the existence of torsional tube waves in the Sun.

Classical Be stars are known to occasionally transition from having a gaseous circumstellar disk ("Be phase") to a state in which all observational evidence for the presence of these disks disappears ("normal B-star phase"). We present one of the most comprehensive spectropolarimetric views to date of such a transition for two Be stars, π Aquarii and 60 Cygni.The disk-loss episode of 60 Cyg was characterized by a generally monotonic decrease in emission strength over a timescale of ∼1000 days from the maximum V-band polarization to the minimum Hα equivalent width, consistent with the viscous timescale of the disk, assuming α∼0.14. π Aqr's disk loss was episodic in nature and occurred over a timescale of ∼2440 days. An observed time lag between the behavior of the polarization and Hα in both stars indicates the disk clearing proceeded in an "inside-out" manner. We determine the position angle of the intrinsic polarization to be 1667 ± 01 for π Aqr and 1077 ± 04 for 60 Cyg, and model the wavelength dependence of the observed polarization during the quiescent diskless phase of each star to determine the interstellar polarization along the line of sight. Minor outbursts observed during the quiescent phase of each star shared similar lifetimes as those previously reported for μ Cen, suggesting that the outbursts represent the injection and subsequent viscous dissipation of individual blobs of material into the inner circumstellar environments of these stars. We also observe deviations from the mean intrinsic polarization position angle during polarization outbursts in each star, indicating deviations from axisymmetry. We propose that these deviations might be indicative of the injection (and subsequent circularization) of new blobs into the inner disk, either in the plane of the bulk of the disk material or in a slightly inclined (non-coplanar) orbit.

We investigate the locations of the satellites of relatively isolated host galaxies in the Sloan Digital Sky Survey and the Millennium Run simulation. Provided we use two distinct prescriptions to embed luminous galaxies within the simulated dark matter halos (ellipticals share the shapes of their halos, while disks have angular momenta that are aligned with the net angular momenta of their halos), we find a fair agreement between observation and theory. Averaged over scales r_p ⩽ 500 kpc, the satellites of red, high-mass hosts with low star formation rates are found preferentially near the major axes of their hosts. In contrast, the satellites of blue, low-mass hosts with low star formation rates show little to no anisotropy when averaged over the same scale. The difference between the locations of the satellites of red and blue hosts cannot be explained by the effects of interlopers in the data. Instead, it is caused primarily by marked differences in the dependence of the mean satellite location, 〈ϕ〉, on the projected distance at which the satellites are found. We also find that the locations of red, high-mass satellites with low star formation rates show considerably more anisotropy than do the locations of blue, low-mass satellites with high star formation rates. There are two contributors to this result. First, the blue satellites have only recently arrived within their hosts' halos, while the red satellites arrived in the far distant past. Second, the sample of blue satellites is heavily contaminated by interlopers, which suppresses the measured anisotropy compared to the intrinsic anisotropy.

We investigate hypernova (hyper-energetic supernova) and gamma-ray burst (GRB) remnants in our Galaxy as TeV gamma-ray sources, particularly in the role of potential TeV unidentified sources, which have no clear counterpart at other wavelengths. We show that the observed bright sources in the TeV sky could be dominated by GRB/hypernova remnants, even though they are fewer than supernova remnants (SNRs). If this is the case, TeV SNRs are more extended (and more numerous) than deduced from current observations. In keeping with their role as cosmic ray accelerators, we discuss hadronic gamma-ray emission from π⁰ decay, from β decay followed by inverse Compton emission, and propose a third novel process of TeV gamma-ray emission arising from the decay of accelerated radioactive isotopes such as ⁵⁶Co entrained by relativistic or semi-relativistic jets in GRBs/hypernovae. We discuss the relevant observational signatures which could discriminate between these three mechanisms.

We present optical spectra of SN 2007gr, SN 2007rz, SN 2007uy, SN 2008ax, and SN 2008bo obtained in the nebular phase when line profiles can lead to information about the velocity distribution of the exploded cores. We compare these to 13 other published spectra of stripped-envelope core-collapse supernovae (Type IIb, Ib, and Ic) to investigate properties of their double-peaked [O i] λλ6300, 6364 emission. These 18 supernovae are divided into two empirical line profile types: (1) profiles showing two conspicuous emission peaks nearly symmetrically centered on either side of 6300 Å and spaced ≈64 Å apart, close to the wavelength separation between the [O i] λλ6300, 6364 doublet lines, and (2) profiles showing asymmetric [O i] line profiles consisting of a pronounced emission peak near 6300 Å plus one or more blueshifted emission peaks. Examination of these emission profiles, as well as comparison with profiles in the lines of [O i] λ5577, O i λ7774, and Mg i] λ4571, leads us to conclude that neither type of [O i] double-peaked profile is necessarily the signature of emission from front and rear faces of ejecta arranged in a toroidal disk or elongated shell geometry as previously suggested. We propose possible alternative interpretations of double-peaked emission for each profile type, test their feasibility with simple line-fitting models, and discuss their strengths and weaknesses. The underlying cause of the observed predominance of blueshifted emission peaks is unclear, but may be due to internal scattering or dust obscuration of emission from far side ejecta.

Hypervelocity stars (HVSs) escaping away from the Galactic halo are dynamical products of interactions of stars with the massive black hole(s) (MBH) in the Galactic Center (GC). They are mainly B-type stars with their progenitors unknown. OB stars are also populated in the GC, with many being hosted in a clockwise-rotating young stellar (CWS) disk within half a parsec from the MBH and their formation remaining puzzles. In this paper, we demonstrate that HVSs can well memorize the injecting directions of their progenitors using both analytical arguments and numerical simulations, i.e., the ejecting direction of an HVS is almost anti-parallel to the injecting direction of its progenitor. Therefore, the spatial distribution of HVSs maps the spatial distribution of the parent population of their progenitors directly. We also find that almost all the discovered HVSs are spatially consistent with being located on two thin disk planes. The orientation of one plane is consistent with that of the (inner) CWS disk, which suggests that most of the HVSs originate from the CWS disk or a previously existed disk-like stellar structure with an orientation similar to it. The rest of HVSs may be correlated with the plane of the northern arm of the mini-spiral in the GC or the plane defined by the outer warped part of the CWS disk. Our results not only support the GC origin of HVSs but also imply that the central disk (or the disk structure with a similar orientation) should persist or be frequently rejuvenated over the past 200 Myr, which adds a new challenge to the stellar disk formation and provides insights to the longstanding problem of gas fueling into MBHs.

The Na i D₁ line in the solar spectrum is sometimes attributed to the solar chromosphere. We study its formation in quiet-Sun network and internetwork. We first present high-resolution profile-resolved images taken in this line with the imaging spectrometer Interferometric Bidimensional Spectrometer at the Dunn Solar Telescope and compare these to simultaneous chromospheric images taken in Ca ii 8542 Å and Hα. We then model Na i D₁ formation by performing three-dimensional (3D) non-local thermodynamic equilibrium profile synthesis for a snapshot from a 3D radiation-magnetohydrodynamics simulation. We find that most Na i D₁ brightness is not chromospheric but samples the magnetic concentrations that make up the quiet-Sun network in the photosphere, well below the height where they merge into chromospheric canopies, with aureoles from 3D resonance scattering. The line core is sensitive to magneto-acoustic shocks in and near magnetic concentrations, where shocks occur deeper than elsewhere, and may provide evidence of heating deep within magnetic concentrations.

We present results of optical spectroscopic observations of the mass donor star in SS 433 with Subaru and Gemini, with an aim to best constrain the mass of the compact object. Subaru/Faint Object Camera and Spectrograph observations were performed on four nights of 2007 October 6–8 and 10, covering the orbital phase of ϕ = 0.96 − 0.26. We first calculate the cross-correlation function (CCF) of these spectra with that of the reference star HD 9233 in the wavelength range of 4740–4840 Å. This region is selected to avoid "strong" absorption lines accompanied with contaminating emission components, which most probably originate from the surroundings of the donor star, such as the wind and gas stream. The same analysis is applied to archive data of Gemini/GMOS taken at ϕ = 0.84 − 0.30 by Hillwig & Gies. From the Subaru and Gemini CCF results, the amplitude of the radial velocity curve of the donor star is determined to be 58.3 ± 3.8 km s⁻¹ with a systemic velocity of 59.2 ± 2.5 km s⁻¹. Together with the radial velocity curve of the compact object, we derive the mass of the donor star and compact object to be M_O = 12.4 ± 1.9 M_☉ and M_X = 4.3 ± 0.6 M_☉, respectively. We conclude, however, that these values should be taken as upper limits. From the analysis of the averaged absorption line profiles of strong lines (mostly ions) and weak lines (mostly neutrals) observed with Subaru, we find evidence for heating effects from the compact object. Using a simple model, we find that the true radial velocity amplitude of the donor star could be as low as 40 ± 5 km s⁻¹ in order to produce the observed absorption-line profiles. Taking into account the heating of the donor star may lower the derived masses to M_O = 10.4^+2.3_−1.9M_☉ and M_X = 2.5^+0.7_−0.6M_☉. Our final constraint, 1.9 M_☉ ⩽M_X⩽ 4.9 M_☉, indicates that the compact object in SS 433 is most likely a low mass black hole, although the possibility of a massive neutron star cannot be firmly excluded.

We present X-ray proper-motion measurements of the forward shock and reverse-shocked ejecta in Tycho's supernova remnant, based on three sets of archival Chandra data taken in 2000, 2003, and 2007. We find that the proper motion of the edge of the remnant (i.e., the forward shock and protruding ejecta knots) varies from 020 yr⁻¹ (expansion index m = 0.33, where R = t^m) to 040 yr⁻¹ (m = 0.65) with azimuthal angle in 2000–2007 measurements, and 014 yr⁻¹ (m = 0.26) to 040 yr⁻¹ (m = 0.65) in 2003–2007 measurements. The azimuthal variation of the proper motion and the average expansion index of ∼0.5 are consistent with those derived from radio observations. We also find proper motion and expansion index of the reverse-shocked ejecta to be 021–031 yr⁻¹ and 0.43–0.64, respectively. From a comparison of the measured m-value with Type Ia supernova evolutionary models, we find a pre-shock ambient density around the remnant of ≲0.2 cm⁻³.

We compute models of the transmission spectra of planets HD 209458b, HD 189733b, and generic hot Jupiters. We examine the effects of temperature, surface gravity, and metallicity for the generic planets as a guide to understanding transmission spectra in general. We find that carbon dioxide absorption at 4.4 and 15 μm is prominent at high metallicity, and is a clear metallicity indicator. For HD 209458b and HD 189733b, we compute spectra for both one-dimensional and three-dimensional model atmospheres and examine the differences between them. The differences are usually small, but can be large if atmospheric temperatures are near important chemical abundance boundaries. The calculations for the three-dimensional atmospheres, and their comparison with data, serve as constraints on these dynamical models that complement the secondary eclipse and light curve data sets. For HD 209458b, even if TiO and VO gases are abundant on the dayside, their abundances can be considerably reduced on the cooler planetary limb. However, given the predicted limb temperatures and TiO abundances, the model's optical opacity is too high. For HD 189733b we find a good match with some infrared data sets and constrain the altitude of a postulated haze layer. For this planet, substantial differences can exist between the transmission spectra of the leading and trailing hemispheres, which are an excellent probe of carbon chemistry. In thermochemical equilibrium, the cooler leading hemisphere is methane-dominated, and the hotter trailing hemisphere is CO-dominated, but these differences may be eliminated by non-equilibrium chemistry due to vertical mixing. It may be possible to constrain the carbon chemistry of this planet, and its spatial variation, with James Webb Space Telescope.

We complied the optical, X-ray, and γ-ray data for 54 Fermi blazars and studied the relationship between the broadband spectral index α_ox and α_xγ, as well as the relationship between the intrinsic composite spectral indices α_xox and α_γxγ for this sample. The relationship between α_xox and α_γxγ reveals that flat spectrum radio quasars and low-energy peaked BL Lacertae follow a continuous trend, which is consistent with previous results, whereas high-energy peaked BL Lacertae follow a separate distinct trend. Even so, a unified scheme is also revealed from α_xox–α_γxγ diagram when all three subclasses of blazars are considered.

We consider a recently discovered class of instabilities, driven by cosmic ray streaming, in a variety of environments. We show that although these instabilities have been discussed primarily in the context of supernova-driven interstellar shocks, they can also operate in the intergalactic medium and in galaxies with weak magnetic fields, where, as a strong source of helical magnetic fluctuations, they could contribute to the overall evolution of the magnetic field. Within the Milky Way, these instabilities are strongest in warm ionized gas and appear to be weak in hot, low density gas unless the injection efficiency of cosmic rays is very high.

We discuss the extent to which photometric measurements alone can be used to identify Type Ia supernovae (SNIa) and to determine the redshift and other parameters of interest for cosmological studies. We fit the light curve data of the type expected from a survey such as the one planned with the Large Synoptic Survey Telescope (LSST) and also remove the contamination from the core-collapse SNe to SNIa samples. We generate 1000 SNIa mock flux data for each of the LSST filters based on existing design parameters, then use a Markov Chain Monte Carlo analysis to fit the redshift, apparent magnitude, stretch factor, and the phase of the SNIa. We find that the model fitting works adequately well when the true SNe redshift is below 0.5, while at z < 0.2 the accuracy of the photometric data is almost comparable with spectroscopic measurements of the same sample. We discuss the contamination of Type Ib/c (SNIb/c) and Type II supernova (SNII) on the SNIa data set. We find that it is easy to distinguish the SNII through the large χ² mismatch when fitting to photometric data with Ia light curves. This is not the case for SNIb/c. We implement a statistical method based on the Bayesian estimation in order to statistically reduce the contamination from SNIb/c for cosmological parameter measurements from the whole SNe sample. The proposed statistical method also evaluates the fraction of the SNIa in the total SNe data set, which provides a valuable guide to establish the degree of contamination.

At the heavy ion storage ring CRYRING in Stockholm, Sweden, we have investigated the dissociative recombination of DCOOD⁺₂ at low relative kinetic energies, from ∼1 meV to 1 eV. The thermal rate coefficient has been found to follow the expression k(T) = 8.43 × 10⁻⁷ (T/300)^−0.78 cm³ s⁻¹ for electron temperatures, T, ranging from ∼10 to ∼1000 K. The branching fractions of the reaction have been studied at ∼2 meV relative kinetic energy. It has been found that ∼87% of the reactions involve breaking a bond between heavy atoms. In only 13% of the reactions do the heavy atoms remain in the same product fragment. This puts limits on the gas-phase production of formic acid, observed in both molecular clouds and cometary comae. Using the experimental results in chemical models of the dark cloud, TMC-1, and using the latest release of the UMIST Database for Astrochemistry improves the agreement with observations for the abundance of formic acid. Our results also strengthen the assumption that formic acid is a component of cometary ices.