Details

Autor(en) / Beteiligte

• Ezzeddine, Rana
• Frebel, Anna

Titel

Revisiting the Iron Abundance in the Hyper Iron-poor Star HE 1327-2326 with UV COS/HST Data Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under NASA contract NAS 5-26555. These observations are associated with program GO-14151

Ist Teil von

• The Astrophysical journal, 2018-08, Vol.863 (2)

Ort / Verlag

The American Astronomical Society

Erscheinungsjahr

2018

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• We present a new iron abundance analysis of the hyper metal-poor star HE 1327−2326, based on Fe ii lines detected in its UV spectral range for the first time. In a Cosmic Origins Spectrograph (COS) spectrum, five new Fe ii lines could be measured. A Si i line was also detected for the first time. We determine a 1D local thermodynamic equilibrium (LTE) Fe ii abundance of [Fe ii/H] = −5.99 0.25. We also investigate departures from LTE for both Fe i and Fe ii lines. Guided by 3D non-LTE (NLTE) analyses of other well-studied metal-poor stars, we identify potential "residual" 3D effects in HE 1327−2326 arising from the absence of full 3D NLTE Fe calculations. Accordingly, we employ measurements of 10 weak Fe i lines previously detected in an optical spectrum of HE 1327−2326, as no Fe i lines are detectable in our UV spectrum. Following our previous work, we adopt the 1D NLTE Fe i abundance of = −5.20 0.12 for HE 1327−2326. Adopting a value based on the optical Fe i rather than UV lines was heavily informed by our extensive investigation of model atmosphere and radiative transfer effects on different lines across the entire UV-optical wavelength range. An iron abundance of = −5.20 0.12 is only 0.2 dex higher than what was used in previous studies. Accordingly, no previous conclusions regarding the nature of the star are affected.