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Title: On the Iron Abundance Anomaly in K-dwarf and Hyades Stars

Abstract

Using standard 1D-LTE model atmosphere analysis, we provide an in-depth investigation of iron abundance as derived from neutral and singly ionization iron lines (Fe i, ii) in nearby star clusters. Specifically, we replicate the discrepancy regarding Δ[Fe/H], wherein the difference of Fe ii–Fe i increases for stars of the same cluster with decreasing T {sub eff}, reaching an astonishing 1.0 dex at T {sub eff} ∼ 4000 K. Previous studies have investigated this anomaly in the Pleiades and Hyades clusters with no concrete solution. In this analysis, we probe two samples: 63 wide binary field stars where the primary star is of Sun-like temperatures and the secondary is a K-dwarf, ranging from 4231 K ≤ T {sub eff} ≤ 6453 K, and 33 Hyades stars of temperatures 4268 K ≤ T {sub eff} ≤ 6072 K. Previous studies have found discrepancies on the order of 1.0 dex. However, we find that these studies have neglected line-blending effects of certain Fe ii lines, namely λ = (4508.29 Å, 4993.34 Å, 5197.58 Å, 5325.55 Å, 5425.26 Å, 6456.38 Å). When these lines are removed from the line-list, we find Δ[Fe/H] decreases to ∼0.6 dex in the field binaries and ∼0.3 dex inmore » the Hyades. The reason for this remaining trend is investigated by probing NLTE effects, as well as age and activity considerations using Ca ii H+K emission and Li absorption, but these results appear to be small to negligible.« less

Authors:
;  [1];  [2]
  1. McDonald Observatory and Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1402, Austin, TX 78712-1205 (United States)
  2. Tacoma Community College, 6501 South 19th Street, Tacoma, WA 98466-7400 (United States)
Publication Date:
OSTI Identifier:
22663186
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 846; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ABUNDANCE; ATMOSPHERES; CONCRETES; DEPTH; EMISSION; IONIZATION; IRON; MATHEMATICAL SOLUTIONS; STAR CLUSTERS

Citation Formats

Aleo, Patrick D., Sobotka, Alexander C., and Ramírez, Ivan. On the Iron Abundance Anomaly in K-dwarf and Hyades Stars. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA83B6.
Aleo, Patrick D., Sobotka, Alexander C., & Ramírez, Ivan. On the Iron Abundance Anomaly in K-dwarf and Hyades Stars. United States. doi:10.3847/1538-4357/AA83B6.
Aleo, Patrick D., Sobotka, Alexander C., and Ramírez, Ivan. Fri . "On the Iron Abundance Anomaly in K-dwarf and Hyades Stars". United States. doi:10.3847/1538-4357/AA83B6.
@article{osti_22663186,
title = {On the Iron Abundance Anomaly in K-dwarf and Hyades Stars},
author = {Aleo, Patrick D. and Sobotka, Alexander C. and Ramírez, Ivan},
abstractNote = {Using standard 1D-LTE model atmosphere analysis, we provide an in-depth investigation of iron abundance as derived from neutral and singly ionization iron lines (Fe i, ii) in nearby star clusters. Specifically, we replicate the discrepancy regarding Δ[Fe/H], wherein the difference of Fe ii–Fe i increases for stars of the same cluster with decreasing T {sub eff}, reaching an astonishing 1.0 dex at T {sub eff} ∼ 4000 K. Previous studies have investigated this anomaly in the Pleiades and Hyades clusters with no concrete solution. In this analysis, we probe two samples: 63 wide binary field stars where the primary star is of Sun-like temperatures and the secondary is a K-dwarf, ranging from 4231 K ≤ T {sub eff} ≤ 6453 K, and 33 Hyades stars of temperatures 4268 K ≤ T {sub eff} ≤ 6072 K. Previous studies have found discrepancies on the order of 1.0 dex. However, we find that these studies have neglected line-blending effects of certain Fe ii lines, namely λ = (4508.29 Å, 4993.34 Å, 5197.58 Å, 5325.55 Å, 5425.26 Å, 6456.38 Å). When these lines are removed from the line-list, we find Δ[Fe/H] decreases to ∼0.6 dex in the field binaries and ∼0.3 dex in the Hyades. The reason for this remaining trend is investigated by probing NLTE effects, as well as age and activity considerations using Ca ii H+K emission and Li absorption, but these results appear to be small to negligible.},
doi = {10.3847/1538-4357/AA83B6},
journal = {Astrophysical Journal},
number = 1,
volume = 846,
place = {United States},
year = {Fri Sep 01 00:00:00 EDT 2017},
month = {Fri Sep 01 00:00:00 EDT 2017}
}