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Solar Abundances (solar + abundance)
Selected AbstractsEarly-type stars observed in the ESO UVES Paranal Observatory Project , I. Interstellar Na i UV, Ti ii and Ca ii K observations,MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006I. Hunter ABSTRACT We present an analysis of interstellar Na i (,air= 3302.37 and 3302.98 Å), Ti ii(,air= 3383.76 Å) and Ca ii K (,air= 3933.66 Å) absorption features for 74 sightlines towards O- and B-type stars in the Galactic disc. The data were obtained from the Ultraviolet and Visual Echelle Spectrograph Paranal Observatory Project, at a spectral resolution of 3.75 km s,1 and with mean signal-to-noise ratios per pixel of 260, 300 and 430 for the Na i, Ti ii and Ca ii observations, respectively. Interstellar features were detected in all but one of the Ti ii sightlines and all of the Ca ii sightlines. The dependence of the column density of these three species with distance, height relative to the Galactic plane, H i column density, reddening and depletion relative to the solar abundance has been investigated. We also examine the accuracy of using the Na i column density as an indicator of that for H i. In general, we find similar strong correlations for both Ti and Ca, and weaker correlations for Na. Our results confirm the general belief that Ti and Ca occur in the same regions of the interstellar medium (ISM) and also that the Ti ii/Ca ii ratio is constant over all parameters. We hence conclude that the absorption properties of Ti and Ca are essentially constant under the general ISM conditions of the Galactic disc. [source] Constraining the star formation histories of spiral bulgesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2000R. N. Proctor Stellar populations in spiral bulges are investigated using the Lick system of spectral indices. Long-slit spectroscopic observations of line strengths and kinematics made along the minor axes of four spiral bulges are reported. Comparisons are made between central line strengths in spiral bulges and those in other morphological types [elliptical, spheroidal (Sph) and S0]. The bulges investigated are found to have central line strengths comparable to those of single stellar populations of approximately solar abundance or above. Negative radial gradients are observed in line strengths, similar to those exhibited by elliptical galaxies. The bulge data are also consistent with correlations between Mg2, Mg2 gradient and central velocity dispersion observed in elliptical galaxies. In contrast to elliptical galaxies, central line strengths lie within the loci defining the range of ,Fe, and Mg2 achieved by Worthey's solar abundance ratio, single stellar populations (SSPs). The implication of solar abundance ratios indicates significant differences in the star formation histories of spiral bulges and elliptical galaxies. A ,single zone with infall' model of galactic chemical evolution, using Worthey's SSPs, is used to constrain the possible star formation histories of our sample. We show that the ,Fe,, Mg2 and H, line strengths observed in these bulges cannot be reproduced using primordial collapse models of formation but can be reproduced by models with extended infall of gas and star formation (2,17 Gyr) in the region modelled. One galaxy (NGC 5689) shows a central population with a luminosity-weighted average age of ,5 Gyr, supporting the idea of extended star formation. Kinematic substructure, possibly associated with a central spike in metallicity, is observed at the centre of the Sa galaxy NGC 3623. [source] The warm absorber of the type 1 Seyfert galaxy H1419+480MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2003X. Barcons ABSTRACT The bright type 1 Seyfert galaxy H1419+480 (z, 0.072), whose X-ray colours from earlier HEAO-1 and ROSAT missions suggested a complex X-ray spectrum, has been observed with XMM,Newton. The EPIC spectrum above 2 keV is well fitted by a power law with photon index ,= 1.84 ± 0.01 and an Fe K, line of equivalent width ,250 eV. At softer energies, a decrement with respect to this model extending from 0.5 to 1 keV is clearly detected. After trying a number of models, we find that the best fit corresponds to O vii absorption at the emission redshift, plus a 2, detection of O viii absorption. A photoionized gas model fit yields log ,, 1.15,1.30 (, in erg cm s,1) with NH, 5 × 1021 cm,2 for solar abundances. We find that the ionized absorber was weaker or absent in an earlier ROSAT observation. An International Ultraviolet Explorer spectrum of this source obtained two decades before shows a variable (within a year) C iv absorber outflowing with a velocity ,1800 km s,1. We show that both X-ray and ultraviolet absorptions are consistent with arising in the same gas, with varying ionization. [source] Elemental abundance analyses with Coudé Echelle spectrograms from the TÜB,TAK National Observatory of Turkey: I. The HgMn stars 11 Per, HR 2801, and , Cnc,ASTRONOMISCHE NACHRICHTEN, Issue 8 2010S.J. Adelman Abstract Using coadded spectrograms taken with the Coudé Echelle Spectrograph (CES) of the 1.50-m Russian-Turkish Telescope of the TÜB,TAK National Observatory (TUG) near Antalya in Turkey, elemental abundance analyses of three HgMn stars 11 Per, HR 2801, and , Cnc were performed. Comparisons are made with spectra obtained with the long camera of the Dominion Astrophysical Observatory (DAO) coudé spectrograph and its SITe4 CCD. The CES equivalent widths are about 12% larger than that for the DAO long camera. Our first results from TUG data/spectra show that all three stars exhibit the Hg II ,3984 line and somewhat diverse abundance patterns. 11 Per tends to have underabundant light elements with underabundant and overabundant Fe-peak elements. HR 2801 has mostly underabundant elements, with a few elements having solar abundances while N and Mn are overabundant. The coolest star , Cnc has light elements having mostly solar abundances, overabundant iron group abundances, and very overabundant SrYZr and Ba. Comparisons with the abundance patterns of other HgMn stars show that they have a wide diversity of abundance patterns (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Chandra ACIS Imaging Spectroscopy of Sgr A EastASTRONOMISCHE NACHRICHTEN, Issue S1 2003Y. Maeda Abstract We report on the X-ray emission from the shell-like, non-thermal radio source Sgr A East located in the inner few parsecs of the Galaxy based on observations made with the ACIS detector on board the Chandra X-ray Observatory. The X-ray emission from Sgr A East is concentrated within the central ,2 pc of the larger radio shell. The spectrum shows strong K, lines from highly ionized ions of S, Ar, Ca, and Fe. A simple isothermal plasma model gives electron temperature ,2 keV, absorption column ,1 × 1023 H cm,2, luminosity ,8 × 1034 ergs s,1 in the 2,10 keV band, and gas mass ,2,½ M, with a filling factor ,. The plasma appears to be rich in heavy elements, over-abundant by roughly a factor of four with respect to solar abundances. Accompanied with filamentary or blob-like structures, the plasma shows a spatial gradient of elemental abundance: the spatial distribution of iron is more compact than that of the lighter elements. These Chandra results strongly support the long-standing hypothesis that Sgr A East is a supernova remnant (SNR). Since Sgr A East surrounds Sgr A* in projection, it is possible that the dust ridge compressed by the forward shock of Sgr A East hit Sgr A* in the past, and the passage of the ridge may have supplied material to accrete onto the black hole in the past, and may have removed material from the black hole vicinity, leading to its present quiescent state. [source] | ||||||||||