J/A+A/598/A54 Line list (Hansen+, 2017)
Something borrowed, something blue: The nature of blue metal-poor stars inferred
from their colours and chemical abundances.
Hansen C.J., Jofre P., Koch A., McWilliam A., Sneden C.S.
<Astron. Astrophys. 598, A54 (2017)>
=2017A&A...598A..54H 2017A&A...598A..54H (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: stars: abundances - stars: blue stragglers - binaries: general -
stars: fundamental parameters - stars: Population II - galaxies: halos
Abstract:
Blue metal-poor stars (BMPs) are main sequence stars that appear bluer
and more luminous than normal turnoff stars. They were originally
singled out by using B-V and U-B colour cuts. Early studies
found that a larger fraction of field BMPs stars were binaries
compared to normal halo stars. Thus, BMP stars are ideal field blue
straggler candidates for investigating internal stellar evolution
processes and binary interaction. In particular, the presence or
depletion in lithium in their spectra is a powerful indicator of their
origin. They are either old, halo blue stragglers experiencing
internal mixing processes or mass transfer (Li-depletion), or
intermediate-age, single stars of possibly extragalactic origin
(2.2dex halo plateau Li). However, we note that internal mixing
processes can lead to an increased level of Li. Hence, this study
combines photometry and spectroscopy to unveil the origin of various
BMP stars. We first show how to separate binaries from young blue
stars using photometry, metallicity and lithium. Using a sample of
80 BMP stars (T>6300K), we find that 97% of the BMP binaries have
(V-Ks)0<1.08±0.03, while BMP stars that are not binaries lie above
this cut in two thirds of the cases. This cut can help classify stars
that lack radial velocities from follow-up observations. We then trace
the origin of two BMP stars from the photometric sample by conducting
a full chemical analysis using new high-resolution and high
signal-to-noise spectra. Based on their radial velocities, Li, α
and s- and r-process abundances we show that BPS CS22874-042 is a
single star (A(Li)=2.38±0.10dex) while with A(Li)=2.23±0.07dex
CD-48 2445 is a binary, contrary to earlier findings. Our analysis
emphasises that field blue stragglers can be segregated from single
metal-poor stars, using (V-Ks) colours with a fraction of single
stars polluting the binary sample, but not vice versa. These two
groups can only be properly separated by using information from
stellar spectra, illustrating the need for accurate and precise
stellar parameters and high-resolution, high-S/N spectra in order to
fully understand and classify this intriguing class of stars. Our
high-resolution spectrum analysis confirms the findings from the
colour cuts and shows that CS 22874-042 is single, while CD -48 2445
is most likely a binary. Moreover, the stellar abundances show that
both stars formed in situ; CS 22874-042 carry traces of massive star
enrichment and CD -48 2445 shows indications of AGB mass transfer
mixed with gases ejected possibly from neutron star mergers.
Description:
Line list used in our analysis.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 34 466 Line list
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See also:
J/ApJ/667/1267 : CrI transition probabilities (Sobeck+, 2007)
J/ApJS/214/26 : Line lists for CN isotopes transitions (Sneden+, 2014)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 8 F8.3 0.1nm lambda Wavelength
11- 14 F4.1 --- Species Atomic number (element.ionisation state)
17- 22 F6.3 [-] loggf Oscillator strength
25- 29 F5.3 eV Ex Excitation potential
32- 34 A3 --- Ref Reference (1)
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Note (1): References as follows:
WIE = Wiese et al. (1996, Atomic transition probabilities
of carbon, nitrogen, and oxygen : a critical data compilation)
SNE = Sneden et al. (2014, Cat. J/ApJS/214/26)
LAW = Lawler et al. (2001ApJ...556..452L 2001ApJ...556..452L, 2001ApJ...563.1075L 2001ApJ...563.1075L)
SOB = Sobeck et al. (2007, Cat. J/ApJ/667/1267)
YAN = Yan et al. (1998, Phys. Rev. A, 57, 1652)
GAL = Gallagher et al. (2012A&A...538A.118G 2012A&A...538A.118G)
BER = Bergemann et al. (2012MNRAS.427...27B 2012MNRAS.427...27B)
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Acknowledgements:
Camilla Juul Hansen, camillajuul(at)gmail.com
(End) Patricia Vannier [CDS] 30-Jan-2017