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Previous surveys in a few metal-poor globular clusters (GCs) showed that the determination of abundances for Li and proton-capture elements offers a key tool to address the intracluster pollution scenario. In this Letter, we present Na, O, and Li abundances in a large sample of dwarf stars in the metal-rich GC 47 Tucanae. We found a clear Na–O anticorrelation, in good agreement with what obtained for giant members by Carretta et al. While lithium and oxygen abundances appear to be positively correlated with each other, there is a large scatter, well exceeding observational errors, and no anticorrelation with sodium. These findings suggest that Li depletion, due to mechanisms internal to the stars (which are cooler and more metal-rich than those on the Spite plateau), combines with the usual pollution scenario responsible for the Na–O anticorrelation.

Magnetic reconnection is a process in which field-line connectivity changes in a magnetized plasma. On the solar surface, it often occurs with the cancellation of two magnetic fragments of opposite polarity. Using the 1.6 m New Solar Telescope, we observed the morphology and dynamics of plasma visible in the Hα line, which is associated with a canceling magnetic feature (CMF) in the quiet Sun. The region can be divided into four magnetic domains: two pre-reconnection and two post-reconnection. In one post-reconnection domain, a small cloud erupted, with a plane-of-sky speed of 10 km s⁻¹, while in the other one, brightening began at points and then tiny bright loops appeared and subsequently shrank. These features support the notion that magnetic reconnection taking place in the chromosphere is responsible for CMFs.

We use publicly available XMM-Newton data to systematically compare the hard X-ray photon indices, Γ_2–10 keV, and the iron Kα emission lines of narrow- and broad-line Seyfert 1 (NLS1 and BLS1) galaxies. We compile a flux-limited (f_2–10 keV ⩾ 1 × 10⁻¹² erg s⁻¹ cm⁻²) sample including 114 radio-quiet objects, with the 2–10 keV luminosity ranging from 10⁴¹ to 10⁴⁵ erg s⁻¹. Our main results are: (1) NLS1s and BLS1s show similar luminosity distributions; (2) the weighted means of Γ_2–10 keV of NLS1s, BLS1s, and the total sample are 2.04 ± 0.04, 1.74 ± 0.02, and 1.84 ± 0.02, respectively; a significant anti-correlation between Γ_2–10 keV and FWHMHβ suggests that Γ_2–10 keV > 2.0 may be taken to indicate the X-ray luminous NLS1 type; (3) the 6.4 keV narrow iron Kα lines from NLS1s are generally weaker than that from BLS1s; this would indicate a smaller covering factor of the dusty tori in NLS1s if the line emission originates from the inner boundary region of the dusty torus in an active galactic nucleus; and (4) all the broadened iron Kα lines with intrinsic width σ>0.5 keV correspond to FWHMHβ ⩽4000 km s⁻¹.

We show here a component of the meridional circulation developing at medium–high latitudes (40°–50°) before the new solar cycle starts. Like the torsional oscillation of the zonal flows, this extra circulation seems to precede the onset of magnetic activity at the solar surface and moves slowly toward lower latitudes. However, the behavior of this component differs from that of the torsional oscillation regarding location and convergence toward the equator at the end of the cycle. The observation of this component before the magnetic regions appear at the solar surface has only been possible due to the prolonged solar minimum. The results could settle the discussion as to whether the extra component of the meridional circulation around the activity belts, which has been known for some time, is or is not an effect of material motions around the active regions.

We present Monte Carlo models of open stellar clusters with the purpose of mapping out the behavior of integrated colors with mass and age. Our cluster simulation package allows for stochastic variations in the stellar mass function to evaluate variations in integrated cluster properties. We find that UBVK colors from our simulations are consistent with simple stellar population (SSP) models, provided the cluster mass is large, M_cluster ⩾ 10⁶ M_☉. Below this mass, our simulations show two significant effects. First, the mean value of the distribution of integrated colors moves away from the SSP predictions and is less red, in the first 10⁷ to 10⁸ years in UBV colors, and for all ages in (V − K). Second, the 1σ dispersion of observed colors increases significantly with lower cluster mass. We attribute the former to the reduced number of red luminous stars in most of the lower mass clusters and the latter to the increased stochastic effect of a few of these stars on lower mass clusters. This latter point was always assumed to occur, but we now provide the first public code able to quantify this effect. We are completing a more extensive database of magnitudes and colors as a function of stellar cluster age and mass that will allow the determination of the correlation coefficients among different bands, and improve estimates of cluster age and mass from integrated photometry.

Modern population synthesis models estimate that 50% of the rest-frame K-band light is produced by thermally pulsing asymptotic giant branch (TP-AGB) stars during the first Gyr of a stellar population, with a substantial fraction continuing to be produced by the TP-AGB over a Hubble time. Between 0.2 and 1.5 Gyr, intermediate-mass stars evolve into TP-AGB C stars which, due to significant amounts of circumstellar dust, emit half their energy in the mid-IR. We combine these results using published mid-IR colors of Galactic TP-AGB M and C stars to construct simple models for exploring the contribution of the TP-AGB to 24 μm data as a function of stellar population age. We compare these empirical models with an ensemble of galaxies in the Chandra Deep Field South from z = 0 to z = 2, and with high-quality imaging in M81. Within the uncertainties, the TP-AGB appears responsible for a substantial fraction of the mid-IR luminosities of galaxies from z = 0 to z = 2, the maximum redshift to which we can test our hypothesis, while, at the same time, our models reproduce much of the detailed structure observed in mid-IR imaging of M81. The mid-IR is a good diagnostic of star formation over timescales of ∼1.5 Gyr, but this implies that ongoing star formation rates at z = 1 may be overestimated by factors of ∼1.5–6, depending on the nature of star formation events. Our results, if confirmed through subsequent work, have strong implications for the star formation rate density of the universe and the growth of stellar mass over time.

We report on the discovery of a luminous blue variable (LBV) lying ≈7 pc in projection from the Quintuplet cluster. This source, which we call LBV G0.120 − 0.048, was selected for spectroscopy owing to its detection as a strong source of Paschen-α (Pα) excess in a recent narrowband imaging survey of the Galactic center region with the Hubble Space Telescope/Near-Infrared Camera and Multi-Object Spectrometer. The K-band spectrum is similar to that of the Pistol Star and other known LBVs. The new LBV was previously cataloged as a photometric variable star, exhibiting brightness fluctuations of up to ≈1 mag between 1994 and 1997, with significant variability also occurring on month-to-month timescales. The luminosity of LBV G0.120 − 0.048, as derived from Two-Micron All Sky Survey photometry, is approximately equivalent to that of the Pistol Star. However, the time-averaged brightness of LBV G0.120 − 0.048 between 1994 and 1997 exceeded that of the Pistol Star; LBV G0.120 − 0.048 also suffers more extinction, which suggests that it was intrinsically more luminous in the infrared than the Pistol Star between 1994 and 1997. Pα images reveal a thin circular nebula centered on LBV G0.120 − 0.048 with a physical radius of ≈0.8 pc. We suggest that this nebula is a shell of ejected material launched from a discrete eruption that occurred between 5000 and 10,000 years ago. Because of the very short amount of time that evolved massive stars spend in the LBV phase, and the close proximity of LBV G0.120 − 0.048 to the Quintuplet cluster, we suggest that this object might be coeval with the cluster, and may have once resided within it.

Several active galactic nuclei (AGNs) with multiple sets of emission lines (ELs) separated by over 2000 km s^-1 have been observed recently. These have been interpreted as being due to massive black hole (MBH) recoil following a black hole merger, MBH binaries, or chance superpositions of AGNs in galaxy clusters. Moreover, a number of double-peaked AGNs with velocity offsets of ∼a few 10² km s^-1 have also been detected and interpreted as being due to the internal kinematics of the narrow-line regions or MBH binary systems. Here we re-examine the superposition model. Using the Millennium Run, we estimate the total number of detectable AGN pairs, and we set very conservative lower limits on the AGN superpositions as a function of the EL offset. We show that AGN pairs with high velocity line separations up to ∼2000 km s^-1 are very likely to be chance superpositions of two AGNs in clusters of galaxies for reasonable assumptions about the relative fraction of AGNs. No superimposed AGN pairs are predicted for velocity offsets in excess of ∼3000 km s^-1, as the required AGN fractions would violate observational constraints. The high velocity AGN pair numbers predicted here are competitive with those predicted from the models relying on MBH recoil or MBH binaries. However, the model fails to account for the largest EL velocity offsets that require the presence of MBH binaries.

Spectroscopic and photometric observations show that many globular clusters host multiple stellar populations, challenging the common paradigm that globular clusters are "simple stellar populations" composed of stars of uniform age and chemical composition. The chemical abundances of second-generation (SG) stars constrain the sources of gas out of which these stars must have formed, indicating that the gas must contain matter processed through the high-temperature CNO cycle. First-generation massive asymptotic giant branch (AGB) stars have been proposed as the source of this gas. In a previous study, by means of hydrodynamical and N-body simulations, we have shown that the AGB ejecta collect in a cooling flow in the cluster core, where the gas reaches high densities, ultimately forming a centrally concentrated subsystem of SG stars. In this Letter, we show that the high gas density can also lead to significant accretion onto a pre-existing seed black hole. We show that gas accretion can increase the black hole mass by up to a factor of 100. The details of the gas dynamics are important in determining the actual black hole growth. Assuming a near-universal seed black hole mass and small cluster-to-cluster variations in the duration of the SG formation phase, the outcome of our scenario is one in which the present intermediate-mass black hole (IMBH) mass may have only a weak dependence on the current cluster properties. The scenario presented provides a natural mechanism for the formation of an IMBH at the cluster center during the SG star formation phase.

We report on the discovery of a molecular cavity in the Norma near arm in the general direction of Westerlund 1 (Wd1), but not associated with it. The cavity has a mean radial velocity of −91.5 km s⁻¹, which differs by as much as ∼40 km s⁻¹ from the mean radial velocity of the Wd1 stars. The cavity is surrounded by a fragmented molecular shell of an outer diameter of about 100 pc and 10⁶M_☉, which is expanding at velocities of 6 to 8 km s⁻¹. The amount of kinetic energy involved in the expanding shell is ∼10⁵¹ erg. Inside this cavity, the atomic H i gas surface density is also the lowest. Structure of the extended Very High Energetic γ-ray emission, recently reported by the H.E.S.S. collaboration, coincides with the cavity. The observed morphology suggests that the inner wall of the molecular shell is the zone of the γ-ray emission, and not the dense gas surrounding massive stars of Wd1 as had been speculated by the H.E.S.S. collaboration. A likely candidate responsible for creating the observed cavity and the γ-ray emission is the pulsar PSR J1648 − 4611.

We have observed the J = 3 − 2 transition of N₂H⁺ and N₂D⁺ to investigate the trend of deuterium fractionation with evolutionary stage in three selected regions in the infrared dark cloud (IRDC) G28.34+0.06 with the Submillimeter Telescope and the Submillimeter Array. A comprehensible enhancement of roughly 3 orders of magnitude in deuterium fractionation over the local interstellar D/H ratio is observed in all sources. In particular, our sample of massive star-forming cores in G28.34+0.06 shows a moderate decreasing trend over a factor of 3 in the N(N₂D⁺)/N(N₂H⁺) ratio with evolutionary stage, a behavior resembling that previously found in low-mass protostellar cores. This suggests a possible extension for the use of the N(N₂D⁺)/N(N₂H⁺) ratio as an evolutionary tracer to high-mass protostellar candidates. In the most evolved core, MM1, the N₂H⁺(3-2) emission appears to avoid the warm region traced by dust continuum emission and emission of ¹³CO sublimated from grain mantles, indicating an instant release of gas-phase CO. The majority of the N₂H⁺ and N₂D⁺ emission is associated with extended structures larger than 8'' (∼0.2 pc).

Light curves are calculated for an off-axis observer due to the scattering of primary radiation by extended baryonic material. The unusually long duration and the chromaticity of the light curves above several KeV of XRF 060218 can be explained as a result of the acceleration of the baryonic scattering material by the primary radiation. The observed light curves by our model and detailed fits to the data are presented. The model predicts that ∼ 4 × 10⁴⁸ erg are put into accelerated, mildly relativistic baryons by the radiation pressure at large radii from the central engine. It is suggested that the emission below 3 KeV, which lies below the Amati relation, is a baryon contaminated fireball.

The oldest solids formed in the solar system, calcium–aluminum inclusions, are ¹⁶O-enriched compared to chondrules, asteroids, Earth, and Mars. Based on the preliminary measurements of the solar wind by Genesis, the Sun also appears to be ¹⁶O-enriched. This distribution of oxygen isotopes in the solar system cannot be reconciled via conventional mass-dependent isotopic fractionation processes and instead require the existence and/or production of distinct ¹⁶O-enriched and ¹⁶O-depleted reservoirs in the early solar system. The origin of these distinct reservoirs is unknown, although several mechanisms have been proposed to date including the following: (1) the injection of pure ¹⁶O by a supernova into the protoplanetary disk or parent molecular cloud, (2) self-shielding of CO in the parent molecular cloud or protoplanetary disk, (3) symmetry-dependent chemical fractionation processes in the protoplanetary disk, and (4) Galactic chemical evolution. While some of these proposals have been ruled out, the validity of others is still open. Here I propose that the ¹⁶O-enriched and ¹⁶O-depleted reservoirs present in the early solar system originated in the parent molecular cloud via the heterogeneous chemical processes that form H₂O, a significant oxygen reservoir, on the surface of interstellar (IS) dust grains in dense molecular clouds, the astrophysical setting where star formation is observed to occur. As a consequence, this model predicts that molecular cloud H₂O and possibly other IS solids inherited from the molecular cloud were depleted in ¹⁶O compared to the bulk gas-phase O present, thus providing distinct ¹⁶O reservoirs at the earliest stages of planetary formation.

Stereo data collected by the HiRes experiment over a six-year period are examined for large-scale anisotropy related to the inhomogeneous distribution of matter in the nearby universe. We consider the generic case of small cosmic-ray deflections and a large number of sources tracing the matter distribution. In this matter tracer model the expected cosmic-ray flux depends essentially on a single free parameter, the typical deflection angle θ_s. We find that the HiRes data with threshold energies of 40 EeV and 57 EeV are incompatible with the matter tracer model at a 95% confidence level unless θ_s > 10° and are compatible with an isotropic flux. The data set above 10 EeV is compatible with both the matter tracer model and an isotropic flux.

UV spectra of the bright sungrazing comet C-2003K7 detected at 2.37 R_☉ above the Sun surface by the Ultraviolet Coronagraph Spectrometer (UVCS) during the daily synoptic scan show bright lines of H i Lyα, Si iii λ 1206, and C iii λ 977. The derived outgassing rate is an order of magnitude larger than those of the other sungrazers observed by UVCS. Analysis of the spectra suggests that the comet broke apart into smaller pieces before it reached the UVCS slit. The observations provide lower and upper limits to the values of the Si iii/C iii ratio, in the range 8–22. The ratio indicates a larger abundance of silicates in the cometary dust as compared to organic refractory materials.

The Perseus galaxy cluster is known to present multiple and misaligned pairs of cavities seen in X-rays, as well as twisted kiloparsec-scale jets at radio wavelengths; both morphologies suggest that the active galactic nucleus (AGN) jet is subject to precession. In this work, we performed three-dimensional hydrodynamical simulations of the interaction between a precessing AGN jet and the warm intracluster medium plasma, whose dynamics are coupled to a Navarro–Frenk–White dark matter gravitational potential. The AGN jet inflates cavities that become buoyantly unstable and rise up out of the cluster core. We found that under certain circumstances precession can originate multiple pairs of bubbles. For the physical conditions in the Perseus cluster, multiple pairs of bubbles are obtained for a jet precession opening angle >40° acting for at least three precession periods, reproducing both radio and X-ray maps well. Based on such conditions, assuming that the Bardeen–Peterson effect is dominant, we studied the evolution of the precession opening angle of this system. We were able to constrain the ratio between the accretion disk and the black hole angular momenta as 0.7–1.4. We were also able to constrain the present precession angle to 30°–40°, as well as the approximate age of the inflated bubbles to 100–150 Myr.