J/ApJ/860/125 Six warm metal-poor stars iron abundances (Roederer+, 2018)
Consistent iron abundances derived from neutral and singly ionized iron lines
in ultraviolet and optical spectra of six warm metal-poor stars.
Roederer I.U., Sneden C., Lawler J.E., Sobeck J.S., Cowan J.J.,
Boesgaard A.M.
<Astrophys. J., 860, 125 (2018)>
=2018ApJ...860..125R 2018ApJ...860..125R
ADC_Keywords: Abundances; Equivalent widths; Stars, metal-deficient;
Spectra, ultraviolet; Optical
Keywords: stars: abundances ; stars: atmospheres ; stars: individual ;
stars: population II
Abstract:
Neutral Fe lines in metal-poor stars yield conflicting abundances
depending on whether and how deviations from local thermodynamic
equilibrium (LTE) are considered. We have collected new
high-resolution and high signal-to-noise ultraviolet (UV) spectra of
three warm dwarf stars with [Fe/H]~-2.9 with the Space Telescope
Imaging Spectrograph on the Hubble Space Telescope. We locate archival
UV spectra for three other warm dwarfs with [Fe/H]~-3.3, -2.2, and
-1.6, supplemented with optical spectra for all six stars. We
calculate stellar parameters using methods that are largely
independent of the spectra, adopting broadband photometry,
color-temperature relations, Gaia parallaxes, and assumed masses. We
use the LTE line analysis code MOOG to derive Fe abundances from
hundreds of FeI and FeII lines with wavelengths from 2290 to 6430Å.
The [Fe/H] ratios derived separately from FeI and FeII lines agree in
all six stars, with [FeII/H]-[FeI/H] ranging from +0.00±0.07 to
-0.12±0.09dex, when strong lines and FeI lines with lower excitation
potential <1.2eV are excluded. This constrains the extent of any
deviations from LTE that may occur within this parameter range. While
our result confirms non-LTE calculations for some warm, metal-poor
dwarfs, it may not be generalizable to more metal-poor dwarfs, where
deviations from LTE are predicted to be larger. We also investigate
trends of systematically lower abundances derived from FeI lines in
the Balmer continuum region (∼3100-3700Å), and we conclude that no
proposed explanation for this effect can fully account for the
observations presently available.
Description:
Our analysis is based on several new sets of UV spectra, supplemented
with new or archival UV and optical spectra.
The new UV spectra were obtained using the Space Telescope Imaging
Spectrograph (STIS) on the Hubble Space Telescope (HST). Three stars
were observed with STIS as part of program GO-14232: BD+03740,
BD-133442, and CD-331173. BD+03740 was observed over the course of
four orbits, or 9556s of integration time, on 2016 February 16 and
March 27. BD-133442 was observed over the course of seven orbits, or
17264s of integration time, on 2016 December 22 and 24. CD-331173 was
observed over the course of nine orbits, or 23355s of integration
time, on 2016 December 31 and 2017 January 01 and 06-08.
Additional spectra are obtained from a variety of online archives,
including the Mikulski Archive for Space Telescopes (MAST), the
European Southern Observatory (ESO) Science Archive Facility, and the
Keck Observatory Archives. These include data collected using the
Ultraviolet and Visual Echelle Spectrograph (UVES) at the Very Large
Telescope (VLT UT2) and the High Resolution Echelle Spectrometer
(HIRES) at the Keck I telescope.
We also make use of spectra obtained using the Robert G. Tull Coude
Spectrograph at the Harlan J. Smith Telescope at McDonald Observatory.
The Tull spectrum of HD 94028 has been described previously by
Roederer+ (2014, J/AJ/147/136). The Tull spectrum of BD+03740 was
obtained on 2016 October 21.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 105 481 Fe line list, equivalent widths, and abundances
table4.dat 65 101 Comparison of Fe equivalent widths and abundances
from STIS -E230M (R∼30000) and -E230H (R∼114000)
spectra
table7.dat 50 7 Stellar parameters
--------------------------------------------------------------------------------
See also:
B/eso : ESO Science Archive Catalog (ESO, 1991-2019)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/311 : Hipparcos, the New Reduction (van Leeuwen, 2007)
J/AJ/120/1841 : Abundances & Kinematics of Halo & Disk Stars (Fulbright 2000)
J/A+A/377/361 : Fe II transition probabilities and loggf (Pickering+, 2001)
J/AJ/124/1144 : Orbits of 171 single-lined spectrosc. binaries (Latham, 2002)
J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)
J/A+A/435/373 : Broadening of Fe II lines by H collisions (Barklem+, 2005)
J/ApJ/681/1524 : Detailed abundances for 28 metal-poor stars (Lai+, 2008)
J/A+A/493/601 : Lithium abundances of halo dwarfs (Hosford+, 2009)
J/A+A/513/A35 : Abundances of Galactic red giants (Alves-Brito+, 2010)
J/A+A/512/A54 : Teff and Fbol from Infrared Flux Method (Casagrande+, 2010)
J/ApJ/743/140 : Abundances (Be,α) in metal-poor stars (Boesgaard+, 2011)
J/A+A/530/A138 : Geneva-Copenhagen survey re-analysis (Casagrande+, 2011)
J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)
J/ApJ/778/56 : Hamburg/ESO Survey extremely metal-poor stars (Cohen+, 2013)
J/ApJ/773/33 : Chemical data of the metal-poor subgiant BD+44493 (Ito+, 2013)
J/ApJS/208/27 : Sun and HD 84937 TiII log(gf) and abundances (Wood+, 2013)
J/ApJS/215/23 : FeI radiative lifetimes (Den Hartog+, 2014)
J/A+A/564/A133 : Gaia FGK benchmark stars: metallicity (Jofre+, 2014)
J/ApJS/215/20 : Vanadium log(gf) and transition probabilities (Lawler+, 2014)
J/AJ/148/81 : APASS BVgri photometry of RAVE stars. I. Data (Munari+, 2014)
J/AJ/147/136 : Stars of very low metal abundance. VI. (Roederer+, 2014)
J/MNRAS/441/3127 : FeI oscillator strengths for Gaia-ESO (Ruffoni+, 2014)
J/ApJS/214/18 : VII log(gf) values, and V abundance in HD 84937 (Wood+ 2014)
J/ApJS/211/20 : NiI transition probability measurements (Wood+, 2014)
J/ApJS/220/13 : Co I transition probabilities (Lawler+, 2015)
J/A+A/580/A23 : Stroemgren-Crawford uvbyβ photometry cat. (Paunzen, 2015)
J/ApJS/216/1 : New FeI level energies from stellar spectra (Peterson+, 2015)
J/A+A/582/A74 : WISE J072543.88-235119.7 line abundances (Spite+, 2015)
J/ApJ/817/53 : Fe-group elemental abundances in HD84937 (Sneden+, 2016)
J/ApJ/847/142 : Ultra-metal-poor stars LTE & NLTE abund. (Ezzeddine+, 2017)
J/ApJS/229/23 : New FeI level energies. II. (Peterson+, 2017)
J/A+A/608/A46 : Constraining cosmic scatter (Reggiani+, 2017)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Ion Species (FeI or FeII)
6- 12 F7.2 0.1nm lambda [2297.7/6430.9] Wavelength
in Angstroms
14- 17 F4.2 eV ExPot [0/4.8] Excitation potential in eV
19- 23 F5.2 --- log(gf) [-5/0.6] Log of degeneracy times
oscillator strength
25- 29 F5.1 0.1pm EW(BD+03_740) [1/105.4]? Equivalent with
in milli Angstroms for BD+03 740
31- 35 F5.1 0.1pm EW(BD-13_3442) [1.3/102.2]? Equivalent with
in milli Angstroms for BD-13 3442
37- 40 F4.1 0.1pm EW(CD-33_1173) [1.3/99.3]? Equivalent with
in milli Angstroms for CD-33 1173
42- 45 F4.1 0.1pm EW(G64-12) [1.8/99]? Equivalent with
in milli Angstroms for G64-12
47- 51 F5.1 0.1pm EW(HD19445) [1/128.2]? Equivalent with
in milli Angstroms for HD19445
53- 57 F5.1 0.1pm EW(HD84937) [1/132.3]? Equivalent with
in milli Angstroms for HD84937
59- 63 F5.1 0.1pm EW(HD94028) [2.7/139.1]? Equivalent with
in milli Angstroms for HD94028
65- 69 F5.3 [-] loge(BD+03_740) [4/5]? Log epsilon abundance
for BD+03 740
71- 75 F5.3 [-] loge(BD-13_3442) [4/5.1]? Log epsilon abundance
for BD-133442
77- 81 F5.3 [-] loge(CD-33_1173) [4/5]? Log epsilon abundance
for CD-331173
83- 87 F5.3 [-] loge(G64-12) [3.7/4.7]? Log epsilon abundance
for G64-12
89- 93 F5.3 [-] loge(HD19445) [5/5.8]? Log epsilon abundance
for HD19445
95- 99 F5.3 [-] loge(HD84937) [4.9/5.6]? Log epsilon abundance
for HD84937
101-105 F5.3 [-] loge(HD94028) [5.5/6.3]? Log epsilon abundance
for HD94028
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Star (HD84937 or HD94028)
9- 12 A4 --- Ion Species (FeI or FeII)
14- 20 F7.2 0.1nm lambda [2297.7/3100.7] Wavelength in Angstroms
22- 25 F4.2 eV ExPot [0/4] Excitation potential in eV
27- 31 F5.2 --- log(gf) [-3.1/0.5] Log of degeneracy times
oscillator strength
33- 37 F5.1 0.1pm EW(E230M) [12.6/143] Equivalent width
in milli Angstroms measured from
E230M spectrum
39- 43 F5.1 0.1pm EW(E230H) [10.8/143.3] Equivalent width
in milli Angstroms measured from
E230H spectrum
45- 49 F5.3 [-] loge(E230M_EW) [4.5/6.3] Log epsilon abundance derived
from EW measured from E230M spectrum
51- 55 F5.3 [-] loge(E230H_EW) [4.3/6.3] Log epsilon abundance derived
from EW measured from E230H spectrum
57- 60 F4.2 [-] loge(E230M_s) [5/6.2] Log epsilon abundance derived
from synthesis of E230M spectrum
62- 65 F4.2 [-] loge(E230H_s) [4.9/6.3] Log epsilon abundance derived
from synthesis of E230H spectrum
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Star name
12 A1 --- f_Name a: Rederived; see Section 6.1
14- 17 I4 K Teff [6055/6625] Effective temperature
19- 21 I3 K e_Teff [73/137] log of surface gravity
23- 26 F4.2 [cm/s2] logg [3.9/4.5] log of surface gravity
28- 31 F4.2 [cm/s2] e_logg [0.1/0.3] logg uncertainty
33- 36 F4.2 km/s Vt [1.1/1.7] Microturbulent velocity
38- 40 F3.1 km/s e_Vt [0.2] Vt uncertainty
42- 46 F5.2 [-] [M/H] [-3.3/-1.6] Metallicity
48- 50 F3.1 [-] e_[M/H] [0.1] [M/H] uncertainty
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 05-Jul-2019