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A study of the O/Fe ratio in metal-poor main sequence and subgiant stars is presented using the [OI] 6300A line, the OI 7774A triplet, and a selection of weak FeII lines observed on high-resolution spectra acquired with the VLT UVES…

Astrophysics · Physics 2009-11-07 P. E. Nissen , F. Primas , M. Asplund , D. L. Lambert

We study the spatial distribution of the Fe 6.4 and 6.7 keV lines in the nuclear region of M82 using the Chandra archival data with a total exposure time of 500 ks. The deep exposure provides a significant detection of the Fe 6.4 keV line.…

High Energy Astrophysical Phenomena · Physics 2015-06-17 Jiren Liu , Lijun Gou , Weimin Yuan , Shude Mao

We investigate the impact on Fe abundance determination of including magnetic flux in series of 3D radiation-MHD simulations of solar convection which we used to synthesize spectral intensity profiles corresponding to disc centre. A…

Solar and Stellar Astrophysics · Physics 2015-06-11 D. Fabbian , F. Moreno-Insertis , E. Khomenko , Å. Nordlund

We present the first models allowing one to explore in a consistent way the influence of changes in the alpha-element-to-iron abundance ratio on the high-resolution spectral properties of evolving stellar populations. The models cover the…

Astrophysics · Physics 2008-01-08 P. Coelho , G. Bruzual , S. Charlot , A. Weiss , B. Barbuy , J. Ferguson

We report new branching fractions for 121 UV lines from the low-lying odd-parity levels of Fe II belonging to the z6Do, z6Fo, z6Po, z4Fo, z4Do and z4Po terms of the 3d6(5D)4p configuration. These lines range in wavelength from 2250 - 3280…

Solar and Stellar Astrophysics · Physics 2019-08-21 E. A. Den Hartog , J. E. Lawler , C. Sneden , J. J. Cowan , A. Brukhovesky

It has been occasionally suggested that Fe abundances of K dwarfs derived from Fe I and Fe II lines show considerable discrepancies and oxygen abundances determined from high-excitation O I 7771-5 triplet lines are appreciably overestimated…

Solar and Stellar Astrophysics · Physics 2020-04-08 Yoichi Takeda , Satoshi Honda

We present chemical abundances in a sample of luminous cool stars located within 30 pc of the Galactic Center. Abundances of carbon, nitrogen, oxygen, calcium, and iron were derived from high-resolution infrared spectra in the H- and…

To provide an empirical calibration relation in order to convert Lick indices into abundances for the integrated light of old, simple stellar populations for a large range in the observed [Fe/H] and [alpha/Fe]. This calibration supersedes…

Astrophysics of Galaxies · Physics 2015-05-27 A. Pipino , I. J. Danziger

We use the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope to obtain new high-quality spectra covering the 1900 to 2360 Angstrom wavelength range for two metal-poor stars, HD 108317 and HD 128279. We derive…

We have derived new very accurate abundances of the Fe-group elements Sc through Zn (Z = 21-30) in the bright main-sequence turnoff star HD 84937, based on high-resolution spectra covering the visible and ultraviolet spectral regions. New…

The abundance of oxygen was determined for selected very metal-poor G-K stars (six giants and one turn-off star) based on the high S/N and high-resolution spectra observed with Keck HIRES in the red through near-IR region comprising the…

Astrophysics · Physics 2007-05-23 Y. Takeda , M. Takada-Hidai , S. Sato , W. L. W. Sargent , L. Lu , T. A. Barlow , J. Jugaku

We present an analysis of the subdwarf O star Feige 67 with a fully metal-line blanketed NLTE model atmosphere based on high-resolution Far-UV (912-2000 A) and Near-UV (2000-3400 A) spectra from new ORFEUS II echelle observations and the…

Astrophysics · Physics 2007-05-23 Jochen L. Deetjen

In this paper, we report on the gas-phase abundance of singly-ionized iron (Fe II) for 51 lines of sight, using data from the Far Ultraviolet Spectroscopic Explorer (FUSE). Fe II column densities are derived by measuring the equivalent…

Astrophysics · Physics 2010-11-05 Adam G. Jensen , Theodore P. Snow

A non-LTE analysis of C I lines at 1.068-1.069 micron was carried out for selected 46 halo/disk stars covering a wide metallicity range (-3.7 <[Fe/H]< +0.3), based on the spectral data collected with IRCS+AO188 of the Subaru Telescope, in…

Solar and Stellar Astrophysics · Physics 2015-06-15 Yoichi Takeda , Masahide Takada-Hidai

We have obtained the first high resolution spectra of individual stars in the dwarf irregular galaxy, NGC 6822. The spectra of the two A-type supergiants were obtained at the VLT and Keck Observatories, using UVES and HIRES, respectively. A…

The accurate determination of chemical abundances in stars plays a pivotal role in understanding stellar structure and evolution, nucleosynthesis, and the chemical enrichment history of the Milky Way. Benchmark stars with precise and…

Our ability to model the shapes and strengths of iron lines in the solar spectrum is a critical test of the accuracy of the solar iron abundance, which sets the absolute zero-point of all stellar metallicities. We use an extensive 463-level…

Solar and Stellar Astrophysics · Physics 2017-05-31 K. Lind , A. M. Amarsi , M. Asplund , P. S. Barklem , M. Bautista , M. Bergemann , R. Collet , D. Kiselman , J. Leenaarts , T. M. D. Pereira

Active galactic nuclei (AGN) have Fe II emission from the broad line region (BLR) that differs greatly in strength from object to object. We examine the role of the total and gas-phase iron abundance in determining Fe II strength. Using AGN…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-19 Gregory A. Shields , Randi R. Ludwig , Sarah Salviander

We analyze a sample of 3,944 low-resolution (R ~ 2000) optical spectra from the Sloan Digital Sky Survey (SDSS), focusing on stars with effective temperatures 5800 < Teff < 6300 K, and distances from the Milky Way plane in excess of 5 kpc,…

The following parameters are determined for 63 Galactic supergiants in the solar neighbourhood: effective temperature Teff, surface gravity log g, iron abundance log e(Fe), microturbulent parameter Vt, mass M/Msun, age t and distance d. A…

Solar and Stellar Astrophysics · Physics 2015-05-14 Leonid S. Lyubimkov , David L. Lambert , Sergey I. Rostopchin , Tamara M. Rachkovskaya , Dmitry B. Poklad