Table of contents

We present precise phase-connected pulse timing solutions for 16 γ-ray-selected pulsars recently discovered using the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope plus one very faint radio pulsar (PSR J1124−5916) that is more effectively timed with the LAT. We describe the analysis techniques including a maximum likelihood method for determining pulse times of arrival from unbinned photon data. A major result of this work is improved position determinations, which are crucial for multiwavelength follow-up. For most of the pulsars, we overlay the timing localizations on X-ray images from Swift and describe the status of X-ray counterpart associations. We report glitches measured in PSRs J0007+7303, J1124−5916, and J1813−1246. We analyze a new 20 ks Chandra ACIS observation of PSR J0633+0632 that reveals an arcminute-scale X-ray nebula extending to the south of the pulsar. We were also able to precisely localize the X-ray point source counterpart to the pulsar and find a spectrum that can be described by an absorbed blackbody or neutron star atmosphere with a hard power-law component. Another Chandra ACIS image of PSR J1732−3131 reveals a faint X-ray point source at a location consistent with the timing position of the pulsar. Finally, we present a compilation of new and archival searches for radio pulsations from each of the γ-ray-selected pulsars as well as a new Parkes radio observation of PSR J1124−5916 to establish the γ-ray to radio phase offset.

We introduce the Galactic Bulge Survey (GBS) and we provide the Chandra source list for the region that has been observed to date. Among the goals of the GBS are constraining the neutron star (NS) equation of state and the black hole (BH) mass distribution via the identification of eclipsing NS and BH low-mass X-ray binaries (LMXBs). The latter goal will, in addition, be obtained by significantly enlarging the number of BH systems for which a BH mass can be derived. Further goals include constraining X-ray binary formation scenarios, in particular the common envelope phase and the occurrence of kicks, via source-type number counts and an investigation of the spatial distribution of X-ray binaries, respectively. The GBS targets two strips of 6° × 1° (12 deg² in total), one above (1° < b < 2°) and one below (−2° < b < −1°) the Galactic plane in the direction of the Galactic center at both X-ray and optical wavelengths. By avoiding the Galactic plane (−1° < b < 1°) we limit the influence of extinction on the X-ray and optical emission but still sample relatively large number densities of sources. The survey is designed such that a large fraction of the X-ray sources can be identified from their optical spectra. The X-ray survey, by design, covers a large area on the sky while the depth is shallow using 2 ks per Chandra  pointing. In this way we maximize the predicted number ratio of (quiescent) LMXBs to cataclysmic variables. The survey is approximately homogeneous in depth to a 0.5–10 keV flux of 7.7 ×  10⁻¹⁴ erg cm⁻² s⁻¹. So far, we have covered about two-thirds (8.3 deg²) of the projected survey area with Chandra  providing over 1200 unique X-ray sources. We discuss the characteristics and the variability of the brightest of these sources.

We present 990 previously unpublished optical linear polarization measurements of quasars, active galactic nuclei, and some stars observed for interstellar polarization. The observations, covering the period 1981–2000, were made with McDonald Observatory's 2.1 m Struve reflector and the Breger photopolarimeter.

We present the Galactic Arecibo L-Band Feed Array H i (GALFA-H i) survey and its first full data release (DR1). GALFA-H i is a high-resolution (∼4'), large-area (13,000 deg²), high spectral resolution (0.18 km s^-1), and wide band (−700 km s⁻¹ < v_LSR < +700 km s^-1) survey of the Galactic interstellar medium in the 21 cm line hyperfine transition of neutral hydrogen conducted at Arecibo Observatory. Typical noise levels are 80 mK rms in an integrated 1 km s^-1 channel. GALFA-H i is a dramatic step forward in high-resolution, large-area Galactic H i surveys, and we compare GALFA-H i to past, present, and future Galactic H i surveys. We describe in detail new techniques we have developed to reduce these data in the presence of fixed pattern noise, gain variation, and inconsistent beam shapes, and we show how we have largely mitigated these effects. We present our first full data release, covering 7520 deg² of sky and representing 3046 hr of integration time, and discuss the details of these data.

We present virtual observations of a simulated vortex ring in a galaxy cluster (such as the Virgo Cluster, where such a ring has been observed), using the virtual X-ray observatory software XIM. We derive the expected surface brightness distributions and color maps for a vortex seen at different line-of-sight angles. We present the line profile function ϕ(δν) for the velocity field of a vortex ring as derived from the observations and show that the line core has a frequency dependence of ϕ ∝ (δν/ν₀)⁻² and derive this form of the line profile from the analytic description of the asymptotic behavior of the velocity field of a vortex ring. We discuss further examples of the application of XIM to studies of galaxy clusters and present the capabilities and methodology of the publicly available code XIM.

We report the spectroscopic confirmation of 29 new, 12 plausible, and three previously known quasars behind the central ∼1.5 deg² region of the Small Magellanic Cloud (SMC). These were identified in a single 2df/AAOmega observation on the Anglo-Australian Telescope of 268 candidates selected primarily based on their mid-IR colors, along with a smaller number of optically variable sources in OGLE-II close to known X-ray sources. The low detection efficiency was partly expected from the high surface density of SMC as compared with the Large Magellanic Cloud targets and the faintness of many of them (149 with I>20 mag). The expected number of I < 20 mag quasars in the field is ≃38, and we found 15 (40%). We did not attempt to determine the nature of the remaining sources, although several appear to be new planetary nebulae. The newly discovered active galactic nuclei can be used as reference points for future proper-motion studies, to study absorption in the SMC interstellar medium, and to study the physics of quasar variability with the existing long-term, highly cadenced OGLE light curves.

We describe the Center for Radiative Shock Hydrodynamics (CRASH) code, a block-adaptive-mesh code for multi-material radiation hydrodynamics. The implementation solves the radiation diffusion model with a gray or multi-group method and uses a flux-limited diffusion approximation to recover the free-streaming limit. Electrons and ions are allowed to have different temperatures and we include flux-limited electron heat conduction. The radiation hydrodynamic equations are solved in the Eulerian frame by means of a conservative finite-volume discretization in either one-, two-, or three-dimensional slab geometry or in two-dimensional cylindrical symmetry. An operator-split method is used to solve these equations in three substeps: (1) an explicit step of a shock-capturing hydrodynamic solver; (2) a linear advection of the radiation in frequency-logarithm space; and (3) an implicit solution of the stiff radiation diffusion, heat conduction, and energy exchange. We present a suite of verification test problems to demonstrate the accuracy and performance of the algorithms. The applications are for astrophysics and laboratory astrophysics. The CRASH code is an extension of the Block-Adaptive Tree Solarwind Roe Upwind Scheme (BATS-R-US) code with a new radiation transfer and heat conduction library and equation-of-state and multi-group opacity solvers. Both CRASH and BATS-R-US are part of the publicly available Space Weather Modeling Framework.

The Néel IRAM KIDs Array (NIKA) is a fully integrated measurement system based on kinetic inductance detectors (KIDs) currently being developed for millimeter wave astronomy. The instrument includes dual-band optics allowing simultaneous imaging at 150 GHz and 220 GHz. The imaging sensors consist of two spatially separated arrays of KIDs. The first array, mounted on the 150 GHz branch, is composed of 144 lumped-element KIDs. The second array (220 GHz) consists of 256 antenna-coupled KIDs. Each of the arrays is sensitive to a single polarization; the band splitting is achieved by using a grid polarizer. The optics and sensors are mounted in a custom dilution cryostat, with an operating temperature of ∼70 mK. Electronic readout is realized using frequency multiplexing and a transmission line geometry consisting of a coaxial cable connected in series with the sensor array and a low-noise 4 K amplifier. The dual-band NIKA was successfully tested in 2010 October at the Institute for Millimetric Radio Astronomy (IRAM) 30 m telescope at Pico Veleta, Spain, performing in-line with laboratory predictions. An optical NEP was then calculated to be around 2 × 10⁻¹⁶ W Hz^−1/2 (at 1 Hz) while under a background loading of approximately 4 pW pixel⁻¹. This improvement in comparison with a preliminary run (2009) verifies that NIKA is approaching the target sensitivity for photon-noise limited ground-based detectors. Taking advantage of the larger arrays and increased sensitivity, a number of scientifically relevant faint and extended objects were then imaged including the Galactic Center SgrB2 (FIR1), the radio galaxy Cygnus A, and the NGC1068 Seyfert galaxy. These targets were all observed simultaneously in the 150 GHz and 220 GHz atmospheric windows.

We present the results of a survey of radio continuum sources near the Galactic plane using the Very Long Baseline Array (VLBA). Our observations are designed to identify compact extragalactic sources of milliarcsecond size that can be used for parallax measurements in the Bar and Spiral Structure Legacy Survey. We selected point sources from the NVSS and CORNISH catalogs with flux densities above 30 mJy and within 15 of known maser targets. Of the 1529 sources observed, 199 were detected. For sources detected on three or more baselines, we determined accurate positions and evaluated their quality as potential calibrators. Most of the 1330 sources that were not detected with the VLBA are probably of extragalactic origin.

The "smoking gun" of small-scale, impulsive events heating the solar corona is expected to be the presence of hot (>5 MK) plasma. Evidence for this has been scarce, but has gradually begun to accumulate due to recent studies designed to constrain the high-temperature part of the emission measure distribution. However, the detected hot component is often weaker than models predict and this is due in part to the common modeling assumption that the ionization balance remains in equilibrium. The launch of the latest generation of space-based observing instrumentation on board Hinode and the Solar Dynamics Observatory (SDO) has brought the matter of the ionization state of the plasma firmly to the forefront. It is timely to consider exactly what emission current instruments would detect when observing a corona heated impulsively on small scales by nanoflares. Only after we understand the full effects of nonequilibrium ionization can we draw meaningful conclusions about the plasma that is (or is not) present. We have therefore performed a series of hydrodynamic simulations for a variety of different nanoflare properties and initial conditions. Our study has led to several key conclusions. (1) Deviations from equilibrium are greatest for short-duration nanoflares at low initial coronal densities. (2) Hot emission lines are the most affected and are suppressed sometimes to the point of being invisible. (3) For the many scenarios we have considered, the emission detected in several of the SDO-AIA channels (131, 193, and 211 Å) would be dominated by warm, overdense, cooling plasma. (4) It is difficult not to create coronal loops that emit strongly at 1.5 MK and in the range 2–6 MK, which are the most commonly observed kind, for a broad range of nanoflare scenarios. (5) The Fe xv (284.16 Å) emission in most of our models is about 10 times brighter than the Ca xvii (192.82 Å) emission, consistent with observations. Our overarching conclusion is that small-scale, impulsive heating inducing a nonequilibrium ionization state leads to predictions for observable quantities that are entirely consistent with what is actually observed.

We present a catalog of photometrically variable stars discovered within two 213 × 213 fields centered on the Cygnus OB2 association (Cyg OB2). There have hitherto been no deep optical variability studies of Cyg OB2, despite it being replete with early-type massive stars, likely due to the high and variable extinction (up to A_V ≈ 20) that permeates much of the region. Here, we provide results of the first variability study with this combination of spatial coverage (∼0.5 deg) and photometric depth (R ∼ 21 mag). We find 121 stars to be variable in both R and I bands, 115 of them newly discovered. Of the 121 variables, we identify 27 eclipsing binaries and eclipsing-binary candidates, 52 pulsating variables, and 20 potential Herbig Ae/Be stars. Confirming both the status and the cluster membership of the Herbig Ae/Be stars would address the uncertainty regarding the age and star formation history of Cyg OB2. We match our catalog to known variables and binaries in the region, Two Micron All Sky Survey near-IR data, and Chandra X-ray observations to find counterparts to new variables in other wavelengths.

We present an attempt to reconstruct the complete evolutionary path followed by cataclysmic variables (CVs), based on the observed mass–radius relationship of their donor stars. Along the way, we update the semi-empirical CV donor sequence presented previously by one of us, present a comprehensive review of the connection between CV evolution and the secondary stars in these systems, and reexamine most of the commonly used magnetic braking (MB) recipes, finding that even conceptually similar ones can differ greatly in both magnitude and functional form. The great advantage of using donor radii to infer mass-transfer and angular-momentum-loss (AML) rates is that they sample the longest accessible timescales and are most likely to represent the true secular (evolutionary average) rates. We show explicitly that if CVs exhibit long-term mass-transfer-rate fluctuations, as is often assumed, the expected variability timescales are so long that other tracers of the mass-transfer rate—including white dwarf (WD) temperatures—become unreliable. We carefully explore how much of the radius difference between CV donors and models of isolated main-sequence stars may be due to mechanisms other than mass loss. The tidal and rotational deformation of Roche-lobe-filling stars produces ≃ 4.5% radius inflation below the period gap and ≃ 7.9% above. A comparison of stellar models to mass–radius data for non-interacting stars suggests a real offset of ≃ 1.5% for fully convective stars (i.e., donors below the gap) and ≃ 4.9% for partially radiative ones (donors above the gap). We also show that donor bloating due to irradiation is probably smaller than, and at most comparable to, these effects. After calibrating our models to account for these issues, we fit self-consistent evolution sequences to our compilation of donor masses and radii. In the standard model of CV evolution, AMLs below the period gap are assumed to be driven solely by gravitational radiation (GR), while AMLs above the gap are usually described by an MB law first suggested by Rappaport et al. We adopt simple scaled versions of these AML recipes and find that these are able to match the data quite well. The optimal scaling factors turn out to bef_GR = 2.47 ± 0.22 below the gap andf_MB = 0.66 ± 0.05 above (the errors here are purely statistical, and the standard model corresponds tof_GR = f_MB = 1). This revised model describes the mass–radius data significantly better than the standard model. Some of the most important implications and applications of our results are as follows. (1) The revised evolution sequence yields correct locations for the minimum period and the upper edge of the period gap; the standard sequence does not. (2) The observed spectral types of CV donors are compatible with both standard and revised models. (3) A direct comparison of predicted and observed WD temperatures suggests an even higher value forf_GR, but this comparison is sensitive to the assumed mean WD mass and the possible existence of mass-transfer-rate fluctuations. (4) The predicted absolute magnitudes of donor stars in the near-infrared form a lower envelope around the observed absolute magnitudes for systems with parallax distances. This is true for all of our sequences, so any of them can be used to set firm lower limits on (or obtain rough estimates of) the distances toward CVs based only on P_orb and single epoch near-IR measurements. (5) Both standard and revised sequences predict that short-period CVs should be susceptible to dwarf nova (DN) eruptions, consistent with observations. However, both sequences also predict that the fraction of DNe among long-period CVs should decline withP_orb above the period gap. Observations suggest the opposite behavior, and we discuss the possible explanations for this discrepancy. (6) Approximate orbital period distributions constructed from our evolution sequences suggest that the ratio of long-period CVs to short-period, pre-bounce CVs is about 3 × higher for the revised sequence than the standard one. This may resolve a long-standing problem in CV evolution. Tables describing our donor and evolution sequences are provided in electronically readable form.

The Large Area Telescope (LAT) aboard the FermiGamma-ray Space Telescope provides an unprecedented opportunity to study gamma-ray blazars. To capitalize on this opportunity, beginning in late 2007, about a year before the start of LAT science operations, we began a large-scale, fast-cadence 15 GHz radio monitoring program with the 40 m telescope at the Owens Valley Radio Observatory. This program began with the 1158 northern (δ > −20°) sources from the Candidate Gamma-ray Blazar Survey and now encompasses over 1500 sources, each observed twice per week with about 4 mJy (minimum) and 3% (typical) uncertainty. Here, we describe this monitoring program and our methods, and present radio light curves from the first two years (2008 and 2009). As a first application, we combine these data with a novel measure of light curve variability amplitude, the intrinsic modulation index, through a likelihood analysis to examine the variability properties of subpopulations of our sample. We demonstrate that, with high significance (6σ), gamma-ray-loud blazars detected by the LAT during its first 11 months of operation vary with almost a factor of two greater amplitude than do the gamma-ray-quiet blazars in our sample. We also find a significant (3σ) difference between variability amplitude in BL Lacertae objects and flat-spectrum radio quasars (FSRQs), with the former exhibiting larger variability amplitudes. Finally, low-redshift (z < 1) FSRQs are found to vary more strongly than high-redshift FSRQs, with 3σ significance. These findings represent an important step toward understanding why some blazars emit gamma-rays while others, with apparently similar properties, remain silent.

We have carried out a near-infrared, narrowband imaging survey of the Crab Nebula, in the H₂ 2.12 μm and Brγ 2.17 μm lines, using the Spartan Infrared camera on the SOAR Telescope. Over a 28 × 51 area that encompasses about 2/3 of the full visible extent of the Crab, we detect 55 knots that emit strongly in the H₂ line. We catalog the observed properties of these knots. We show that they are in or next to the filaments that are seen in optical-passband emission lines. Comparison to Hubble Space Telescope [S ii] and [O iii] images shows that the H₂ knots are strongly associated with compact regions of low-ionization gas. We also find evidence of many additional, fainter H₂ features, both discrete knots and long streamers following gas that emits strongly in [S ii]. A pixel-by-pixel analysis shows that about 6% of the Crab's projected surface area has significant H₂ emission that correlates with [S ii] emission. We measured radial velocities of the [S ii] λ6716 emission lines from 47 of the cataloged knots and find that most are on the far (receding) side of the nebula. We also detect Brγ emission. It is right at the limit of our survey, and our Brγ filter cuts off part of the expected velocity range. But clearly the Brγ emission has a quite different morphology than the H₂ knots, following the long linear filaments that are seen in Hα and in [O iii] optical emission lines.

The morphology of selected groups of sources in the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) survey and catalog is examined. Sources in the FIRST catalog (2003 April release, 811,117 entries) were sorted into singles, doubles, triples, and groups of higher-count membership based on a proximity criteria. The 7106 groups with four or more components were examined individually for bent types including, but not limited to, wide-angle tail and narrow-angle tail types. In the process of this examination, ring, double–double, X-shaped, hybrid morphology, giant radio sources, and the herein described W-shaped and tri-axial morphology systems were also identified. For the convenience of the reader separate tables for distinctive types were generated. A few curiosities were found. For the 16,950 three-component groups and 74,788 two-component groups, catalogs with probability estimates for bent classification, as determined by pattern recognition techniques, are presented.

The Green Bank Telescope (GBT) H ii Region Discovery Survey has doubled the number of known H ii regions in the Galactic zone 343° ⩽ ℓ ⩽ 67° with | b | ⩽ 1°. We detected 603 discrete hydrogen radio recombination line (RRL) components at 9 GHz (3 cm) from 448 targets. Our targets were selected based on spatially coincident mid-infrared and 20 cm radio continuum emission. Such sources are almost invariably H ii regions; we detected hydrogen RRL emission from 95% of our target sample. The sensitivity of the GBT and the power of its spectrometer together made this survey possible. Here, we provide a catalog of the measured properties of the RRL and continuum emission from the survey nebulae. The derived survey completeness limit, 180 mJy at 9 GHz, is sufficient to detect all H ii regions ionized by single O-stars to a distance of 12 kpc. These recently discovered nebulae share the same distribution on the sky as does the previously known census of Galactic H ii regions. On average, however, the new nebulae have fainter continuum fluxes, smaller continuum angular sizes, fainter RRL intensities, and smaller RRL line widths. Though small in angular size, many of our new nebulae show little spatial correlation with tracers associated with extremely young H ii regions, implying that our sample spans a range of evolutionary states. We discovered 34 first quadrant negative-velocity H ii regions, which lie at extreme distances from the Sun and appear to be part of the Outer Arm. We found RRL emission from 208 Spitzer GLIMPSE 8.0 μm "bubble" sources, 65 of which have been cataloged previously. It thus appears that nearly all GLIMPSE bubbles are H ii regions and that ∼50% of all Galactic H ii regions have a bubble morphology at 8.0 μm.

The graduated cylindrical shell (GCS) model developed by Thernisien et al. has been used with the goal of studying the three-dimensional morphology, position, and kinematics of coronal mass ejections observed by coronagraphs. These studies focused more on the results rather than the details of the model itself. As more researchers begin to use the model, it becomes necessary to provide a deeper discussion on how it is derived, which is the purpose of this paper. The model is built using the following features and constraints: (1) the legs are conical, (2) the front is pseudo-circular, (3) the cross section is circular, and (4) it expands in a self-similar way. We derive the equation of the model from these constraints. We also show that the ice-cream cone model is a limit of the GCS when the two legs overlap completely. Finally, we provide formulae for the calculation of various geometrical dimensions, such as angular width and aspect ratio, as well as the pseudo-code that is used for its computer implementation.

Emission spectra of the B²Σ⁺–X²Σ⁺ transition of ¹³C¹⁴N have been observed at high resolution using the Fourier transform spectrometer associated with the McMath–Pierce Solar Telescope of the National Solar Observatory. The spectra have been measured in the 21000–30000 cm⁻¹ region and a total of 52 vibrational bands involving vibrational levels up to v = 15 of the ground and excited states have been rotationally analyzed to provide a much improved set of spectroscopic constants. An experimental line list and calculated term values are provided. The results of the present analysis should prove useful in the identification of additional ¹³C¹⁴N lines in comets and cool stars, and will help in the determination of the ¹²C/¹³C abundance ratio.

The goal of the present work is to produce transition probabilities with very low uncertainties for a selected set of multiplets of Mn i and Mn ii. Multiplets are chosen based upon their suitability for stellar abundance analysis. We report on new radiative lifetime measurements for 22 levels of Mn i from the e⁸D, z⁶P, z⁶D, z⁴F, e⁸S, and e⁶S terms and six levels of Mn ii from the z⁵P and z⁷P terms using time-resolved laser-induced fluorescence on a slow atom/ion beam. New branching fractions for transitions from these levels, measured using a Fourier-transform spectrometer, are reported. When combined, these measurements yield transition probabilities for 47 transitions of Mn i and 15 transitions of Mn ii. Comparisons are made to data from the literature and to Russell–Saunders (LS) theory. In keeping with the goal of producing a set of transition probabilities with the highest possible accuracy and precision, we recommend a weighted mean result incorporating our measurements on Mn i and ii as well as independent measurements or calculations that we view as reliable and of a quality similar to ours. In a forthcoming paper, these Mn i/ii transition probability data will be utilized to derive the Mn abundance in stars with spectra from both space-based and ground-based facilities over a 4000 Å wavelength range. With the employment of a local thermodynamic equilibrium line transfer code, the Mn i/ii ionization balance will be determined for stars of different evolutionary states.

We study the neutral hydrogen properties of a sample of 20 bulgeless disk galaxies (Sd–Sdm Hubble types), an interesting class that can be used to constrain galaxy formation and evolution, especially the role of mergers versus internal processes. Our sample is composed of nearby (within 32 Mpc), moderately inclined galaxies that bracket the circular velocity of 120 km s⁻¹, which has been found to be associated with a transition in dust scale heights in edge-on, late-type disks. Here, we present H i channel maps, line profiles, and integrated intensity maps. We also derive kinematic parameters, including the circular velocity, from rotation curve analyses and calculate the integrated H i flux and H i mass for each galaxy in the sample. Three of the 20 galaxies in our sample have kinematically distinct outer components with major axes that differ by 30°–90° from the main disk. These distinct outer components may be due to a recent interaction, which would be somewhat surprising because the disks do not contain bulges. We will use the data products and derived properties in subsequent investigations into star formation and secular evolution in bulgeless disks with circular velocities above and below 120 km s⁻¹.

The first release of the Chandra Source Catalog (CSC) contains ∼95,000 X-ray sources in a total area of 0.75% of the entire sky, using data from ∼3900 separate ACIS observations of a multitude of different types of X-ray sources. In order to maximize the scientific benefit of such a large, heterogeneous data set, careful characterization of the statistical properties of the catalog, i.e., completeness, sensitivity, false source rate, and accuracy of source properties, is required. Characterization efforts of other large Chandra catalogs, such as the ChaMP Point Source Catalog or the 2 Mega-second Deep Field Surveys, while informative, cannot serve this purpose, since the CSC analysis procedures are significantly different and the range of allowable data is much less restrictive. We describe here the characterization process for the CSC. This process includes both a comparison of real CSC results with those of other, deeper Chandra catalogs of the same targets and extensive simulations of blank-sky and point-source populations.

We present new radial velocities (RVs), improved pulsation periods, and reference epochs of 11 field RR Lyrae ab-type variables: AS Vir, BS Aps, CD Vel, DT Hya, RV Oct, TY Gru, UV Oct, V1645 Sgr, WY Ant, XZ Aps, and Z Mic. This study is based on high-resolution spectra obtained with the echelle spectrograph of the 2.5 m du Pont telescope at Las Campanas Observatory. We obtained ∼200 spectra per star (i.e., a total of ∼2300 spectra), distributed more or less uniformly throughout their pulsation cycles. RV curves and photometric light curves phased to our new ephemerides are presented for all program stars. In a subsequent paper, we will use these spectra to derive stellar atmospheric parameters and chemical compositions throughout the pulsational cycles, based purely on spectroscopic constraints.

We explore explosions of massive stars, which are triggered via the quark–hadron phase transition during the early post-bounce phase of core-collapse supernovae. We construct a quark equation of state, based on the bag model for strange quark matter. The transition between the hadronic and the quark phases is constructed applying Gibbs conditions. The resulting quark–hadron hybrid equations of state are used in core-collapse supernova simulations, based on general relativistic radiation hydrodynamics and three-flavor Boltzmann neutrino transport in spherical symmetry. The formation of a mixed phase reduces the adiabatic index, which induces the gravitational collapse of the central protoneutron star (PNS). The collapse halts in the pure quark phase, where the adiabatic index increases. A strong accretion shock forms, which propagates toward the PNS surface. Due to the density decrease of several orders of magnitude, the accretion shock turns into a dynamic shock with matter outflow. This moment defines the onset of the explosion in supernova models that allow for a quark–hadron phase transition, where otherwise no explosions could be obtained. The shock propagation across the neutrinospheres releases a burst of neutrinos. This serves as a strong observable identification for the structural reconfiguration of the stellar core. The ejected matter expands on a short timescale and remains neutron-rich. These conditions might be suitable for the production of heavy elements via the r-process. The neutron-rich material is followed by proton-rich neutrino-driven ejecta in the later cooling phase of the PNS where the νp-process might occur.

A photometric catalog, developed for the calibration of the Deep Ecliptic Survey, is presented. The catalog contains 213,272 unique sources that were measured in V and R filters and transformed to the Johnson–Cousins systems using the Landolt standard catalog. All of the sources lie within 6° of the ecliptic and cover all longitudes except for the densest stellar regions nearest the galactic center. Seventeen percent of the sources in the catalog are derived from three or more nights of observation. The catalog contains sources as faint as R ∼19 but the largest fraction fall in the R ∼15–16 (V ∼16–17) mag range. All magnitude bins down to R = 19 have a significant fraction of objects with uncertainties ⩽0.1 mag.

The Atacama Cosmology Telescope was designed to measure small-scale anisotropies in the cosmic microwave background and detect galaxy clusters through the Sunyaev–Zel'dovich effect. The instrument is located on Cerro Toco in the Atacama Desert, at an altitude of 5190 m. A 6 m off-axis Gregorian telescope feeds a new type of cryogenic receiver, the Millimeter Bolometer Array Camera. The receiver features three 1000-element arrays of transition-edge sensor bolometers for observations at 148 GHz, 218 GHz, and 277 GHz. Each detector array is fed by free space millimeter-wave optics. Each frequency band has a field of view of approximately 22' × 26'. The telescope was commissioned in 2007 and has completed its third year of operations. We discuss the major components of the telescope, camera, and related systems, and summarize the instrument performance.

We present Mg ii-based black hole (BH) mass estimates for 27,602 quasars with rest-frame UV spectra available in the Sloan Digital Sky Survey Data Release Three. This estimation is possible due to the existence of an empirical correlation between the radius of the broad-line region (BLR) and the continuum luminosity at 3000 Å. We regenerate this correlation by applying our measurement method to UV spectra of low-redshift quasars in the Hubble Space Telescope/International Ultraviolet Explorer databases which have corresponding reverberation mapping estimates of the Hβ BLR's radius. Our mass estimation method uses the line dispersion rather than the full width at half-maximum of the low-ionization Mg ii emission line. We measure Mg ii line dispersions for quasars whose spectra have been reconstructed using the most significant eigenspectra produced through Principal Component Analysis. We have tested the reliability of using reconstructed spectra in BH mass estimation using a Monte Carlo simulation and by comparing the results from original and reconstructed Data Release Three spectra. We show that using reconstructed spectra not only makes bias-free mass estimation possible for quasars with low spectroscopic signal-to-noise ratio, but also reduces the intrinsic scatter of the distribution of the BH masses to lower than 0.15 dex.

We present Spitzer Space Telescope IRAC and MIPS observations of a 0.85 deg² field including the Corona Australis (CrA) star-forming region. At a distance of 130 pc, CrA is one of the closest regions known to be actively forming stars, particularly within its embedded association, the Coronet. Using the Spitzer data, we identify 51 young stellar objects (YSOs) in CrA which include sources in the well-studied Coronet cluster as well as sources distributed throughout the molecular cloud. Twelve of the YSOs discussed are new candidates, one of which is located in the Coronet. Known YSOs retrieved from the literature are also added to the list, and a total of 116 candidate YSOs in CrA are compiled. Based on these YSO candidates, the star formation rate is computed to be 12 M_☉ Myr⁻¹, similar to that of the Lupus clouds. A clustering analysis was also performed, finding that the main cluster core, consisting of 68 members, is elongated (having an aspect ratio of 2.36), with a circular radius of 0.59 pc and mean surface density of 150 pc⁻². In addition, we analyze outflows and jets in CrA by means of new CO and H₂ data. We present 1.3 mm interferometric continuum observations made with the Submillimeter Array (SMA) covering R CrA, IRS 5, IRS 7, and IRAS 18595-3712 (IRAS 32). We also present multi-epoch H₂ maps and detect jets and outflows, study their proper motions, and identify exciting sources. The Spitzer and ISAAC/VLT observations of IRAS 32 show a bipolar precessing jet, which drives a CO(2–1) outflow detected in the SMA observations. There is also clear evidence for a parsec-scale precessing outflow, which is east–west oriented and originates in the SMA 2 region and likely driven by SMA 2 or IRS 7A.

We report multi-frequency Very Large Array observations of three massive star formation regions (MSFRs) containing radio continuum components that were identified as broad radio recombination line (RRL) sources and hypercompact (HC) H ii region candidates in our previous H92α and H76α study: G10.96+0.01 (component W), G28.20−0.04 (N), and G34.26+0.15 (B). An additional HC H ii region candidate, G45.07+0.13, known to have broad H66α and H76α lines, small size, high electron density, and emission measure, was also included. We observed with high spatial resolution (09–23) the H53α, H66α, H76α, and H92α RRLs and the radio continuum at the corresponding wavelengths (0.7–3.6 cm). The motivation for these observations was to obtain RRLs over a range of principal quantum states to look for signatures of pressure broadening and macroscopic velocity structure. We find that pressure broadening contributes significantly to the linewidths, but it is not the sole cause of the broad lines. We compare radio continuum and dust emission distributions and find a good correspondence. We also discuss maser emission and multi-wavelength observations reported in the literature for these MSFRs.

We present a compilation of properties of the 105,783 quasars in the Sloan Digital Sky Survey Data Release 7 (DR7) quasar catalog. In this product, we compile continuum and emission line measurements around the Hα, Hβ, Mg ii, and C iv regions, as well as other quantities such as radio properties, and flags indicating broad absorption line quasars, disk emitters, etc. We also compile virial black hole mass estimates based on various calibrations. For the fiducial virial mass estimates we use the Vestergaard & Peterson (VP06) calibrations for Hβ and C iv, and our own calibration for Mg ii which matches the VP06 Hβ masses on average. We describe the construction of this catalog and discuss its limitations. The catalog and its future updates will be made publicly available online.

As emphasized by previous studies, proper treatment of the density fluctuation on the fundamental scale of a cosmological simulation volume—the "DC mode"—is critical for accurate modeling of spatial correlations on scales ≳ 10% of simulation box size. We provide further illustration of the effects of the DC mode on the abundance of halos in small boxes and show that it is straightforward to incorporate this mode in cosmological codes that use the "supercomoving" variables. The equations governing evolution of dark matter and baryons recast with these variables are particularly simple and include the expansion factor, and hence the effect of the DC mode, explicitly only in the Poisson equation.

In this paper, a new hydrodynamical code for the numerical simulation of the collision of the gas components of galaxies is described. The code is based on the Fluids-in-Cells method with the Godunov-type scheme at the Eulerian stage. Also, the velocity correction is employed at the Lagrangian stage and energy imbalance is minimized. The performance of the code is shown by the simulation of the collision of gas components of two similar disk galaxies in the course of the central collision of the galaxies in the polar direction. As a result of the numerical simulations within the model, we succeeded in determining the main scenarios of the collision of galaxies. At low velocities, both galaxies and their gas components coalesce. At high velocities, the massive stellar components of galaxies dissipate almost freely, leaving their gaseous components slowed down and heated by the collision. If the common gas component of the colliding galaxies cools down to the virial temperature, a new galaxy is formed from the two. With the high collision velocity, the gas component has no time to cool and therefore the gas dissipates in the intergalactic medium.