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Title: NLTE ANALYSIS OF HIGH-RESOLUTION H -BAND SPECTRA. I. NEUTRAL SILICON

Abstract

We investigated the reliability of our silicon atomic model and the influence of non-local thermodynamical equilibrium (NLTE) on the formation of neutral silicon (Si i) lines in the near-infrared (near-IR) H -band. We derived the differential Si abundances for 13 sample stars with high-resolution H -band spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE), as well as from optical spectra, both under local thermodynamical equilibrium (LTE) and NLTE conditions. We found that the differences between the Si abundances derived from the H -band and from optical lines for the same stars are less than 0.1 dex when the NLTE effects are included, and that NLTE reduces the line-to-line scatter in the H -band spectra for most sample stars. These results suggest that our Si atomic model is appropriate for studying the formation of H -band Si lines. Our calculations show that the NLTE corrections of the Si i H -band lines are negative, i.e., the final Si abundances will be overestimated in LTE. The corrections for strong lines depend on surface gravity, and tend to be larger for giants, reaching ∼−0.2 dex in our sample, and up to ∼−0.4 dex in extreme cases of APOGEE targets. Thus, themore » NLTE effects should be included in deriving silicon abundances from H -band Si i lines, especially for the cases where only strong lines are available.« less

Authors:
; ;  [1];  [2]
  1. Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing 100012 (China)
  2. Apache Point Observatory and New Mexico State University, P.O. Box 59, Sunspot, NM, 88349-0059 (United States)
Publication Date:
OSTI Identifier:
22660904
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 833; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ATOMIC MODELS; CORRECTIONS; ELEMENT ABUNDANCE; GALACTIC EVOLUTION; GRAVITATION; LTE; NEAR INFRARED RADIATION; RELIABILITY; RESOLUTION; SILICON; STARS; SURFACES; VISIBLE SPECTRA

Citation Formats

Zhang, Junbo, Shi, Jianrong, Liu, Chao, Pan, Kaike, and Prieto, Carlos Allende, E-mail: sjr@bao.ac.cn. NLTE ANALYSIS OF HIGH-RESOLUTION H -BAND SPECTRA. I. NEUTRAL SILICON. United States: N. p., 2016. Web. doi:10.3847/1538-4357/833/2/137.
Zhang, Junbo, Shi, Jianrong, Liu, Chao, Pan, Kaike, & Prieto, Carlos Allende, E-mail: sjr@bao.ac.cn. NLTE ANALYSIS OF HIGH-RESOLUTION H -BAND SPECTRA. I. NEUTRAL SILICON. United States. https://doi.org/10.3847/1538-4357/833/2/137
Zhang, Junbo, Shi, Jianrong, Liu, Chao, Pan, Kaike, and Prieto, Carlos Allende, E-mail: sjr@bao.ac.cn. 2016. "NLTE ANALYSIS OF HIGH-RESOLUTION H -BAND SPECTRA. I. NEUTRAL SILICON". United States. https://doi.org/10.3847/1538-4357/833/2/137.
@article{osti_22660904,
title = {NLTE ANALYSIS OF HIGH-RESOLUTION H -BAND SPECTRA. I. NEUTRAL SILICON},
author = {Zhang, Junbo and Shi, Jianrong and Liu, Chao and Pan, Kaike and Prieto, Carlos Allende, E-mail: sjr@bao.ac.cn},
abstractNote = {We investigated the reliability of our silicon atomic model and the influence of non-local thermodynamical equilibrium (NLTE) on the formation of neutral silicon (Si i) lines in the near-infrared (near-IR) H -band. We derived the differential Si abundances for 13 sample stars with high-resolution H -band spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE), as well as from optical spectra, both under local thermodynamical equilibrium (LTE) and NLTE conditions. We found that the differences between the Si abundances derived from the H -band and from optical lines for the same stars are less than 0.1 dex when the NLTE effects are included, and that NLTE reduces the line-to-line scatter in the H -band spectra for most sample stars. These results suggest that our Si atomic model is appropriate for studying the formation of H -band Si lines. Our calculations show that the NLTE corrections of the Si i H -band lines are negative, i.e., the final Si abundances will be overestimated in LTE. The corrections for strong lines depend on surface gravity, and tend to be larger for giants, reaching ∼−0.2 dex in our sample, and up to ∼−0.4 dex in extreme cases of APOGEE targets. Thus, the NLTE effects should be included in deriving silicon abundances from H -band Si i lines, especially for the cases where only strong lines are available.},
doi = {10.3847/1538-4357/833/2/137},
url = {https://www.osti.gov/biblio/22660904}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 833,
place = {United States},
year = {Tue Dec 20 00:00:00 EST 2016},
month = {Tue Dec 20 00:00:00 EST 2016}
}