A study of the elements copper through uranium in Sirius A: Contributions from STIS and ground-based spectra

Abstract

We determine abundances or upper limits for all of the 55 stable elements from copper to uranium for the A1 Vm star Sirius. The purpose of the study is to assemble the most complete picture of elemental abundances with the hope of revealing the chemical history of the brightest star in the sky, apart from the Sun. We also explore the relationship of this hot metallic-line (Am) star to its cooler congeners, as well as the hotter, weakly- or non-magnetic mercury-manganese (HgMn) stars. Our primary observational material consists of {\em Hubble Space Telescope} ($HST$) spectra taken with the Space Telescope Imaging Spectrograph (STIS) in the ASTRAL project. We have also used archival material from the %\citep/{ayr10}. $COPERNICUS$ satellite, and from the $HST$ Goddard High-Resolution Spectrograph (GHRS), as well as ground-based spectra from Furenlid, Westin, Kurucz, Wahlgren, and their coworkers, ESO spectra from the UVESPOP project, and NARVAL spectra retrieved from PolarBase. Our analysis has been primarily by spectral synthesis, and in this work we have had the great advantage of extensive atomic data unavailable to earlier workers. We find most abundances as well as upper limits range from 10 to 100 times above solar values. We see no indication of the huge abundance excesses of 1000 or more that occur among many chemically peculiar (CP) stars of the upper main sequence. The picture of Sirius as a hot Am star is reinforced.

arXiv commentWith 6 Figures and 4 Tables; accepted for publication in ApJ

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• MESAS: Measuring the Emission of Stellar Atmospheres at Submm/mm wavelengths
• HR 8844: a new transition object between the Am stars and the HgMn stars ?
• The effect of hyperfine splitting on Stark broadening for three blue-green Cu I lines in laser-induced plasma
• A conclusive non-detection of magnetic field in the Am star o Peg with high-precision near-infrared spectroscopy
• The R-Process Alliance: A Nearly Complete R-Process Abundance Template Derived from Ultraviolet Spectroscopy of the R-Process-Enhanced Metal-Poor Star HD 222925