J/A+A/618/A15 Parameters of EHB stars in ω Cen (Latour+, 2018)
SHOTGLAS. I. The ultimate spectroscopic census of extreme horizontal branch
stars in ω Centauri.
Latour M., Randall S.K., Calamida A., Geier S., Moehler S.
<Astron. Astrophys. 618, A15 (2018)>
=2018A&A...618A..15L 2018A&A...618A..15L (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, horizontal branch ; Stars, subdwarf ;
Radial velocities ; Spectroscopy
Keywords: stars: atmospheres - stars: horizontal branch - subdwarfs -
stars: fundamental parameters - binaries: close -
globular cluster: individual: NGC 5139
Abstract:
The presence of extreme horizontal branch (EHB) and blue hook stars in
some Galactic globular clusters (GGCs) constitutes one of the
remaining mysteries of stellar evolution. While several evolutionary
scenarios have been proposed to explain the characteristics of this
peculiar population of evolved stars, their observational verification
has been limited by the availability of spectroscopic data for a
statistically significant sample of such objects in any single GGC. In
this first paper, we focus on ω Centauri, a peculiar, massive
GGC that hosts multiple stellar populations. We use non-LTE model
atmospheres to derive atmospheric parameters (Teff, log g and
N(He)/N(H)) and spectroscopic masses for 152 EHB stars in the cluster.
We also search for close binaries among these stars based on radial
velocity variations. The majority of our sample consists of sdOB stars
that have roughly solar or super-solar atmospheric helium abundances.
It is these objects that constitute the blue hook at V>18.5mag in
the ω Cen colour-magnitude diagram.
Description:
We analysed new spectra of EHB stars in ω Cen observed with the
FORS and VIMOS instruments and re-analysed additional spectra that
were already published in the literature. We provide atmospheric
parameters for all stars in our sample and estimated spectroscopic
masses, using two different methods, and reddening based on the
atmospheric parameters and magnitudes of the stars. We also provide
radial velocities for all the stars, that are a combination of our
measured values and the literature values when available.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb3.dat 159 152 Spectroscopic sample of EHB stars in ω Cen
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See also:
J/A+A/526/A136 : Hot HB stars in ω Cen (Moehler+, 2011)
J/A+A/547/A109 : Parameters of HB stars in ω Cen (Moni Bidin+, 2012)
J/A+A/589/A1 : Extreme Horizontal Branch stars in ω Cen (Randall+ 2016)
Byte-by-byte Description of file: tableb3.dat
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Bytes Format Units Label Explanations
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1- 7 I7 --- ID Star identification number (1)
9- 18 F10.6 deg RAdeg Right ascension (J2000)
20- 29 F10.6 deg DEdeg Declination (J2000)
31- 35 I5 K Teff [23463/61960] Effective temperature
37- 40 I4 K e_Teff Error on the effective temperature (2)
42- 45 F4.2 [cm/s2] logg [4.75/6.36] Surface gravity in log
47- 50 F4.2 [cm/s2] e_logg Error on the surface gravity (2)
52- 56 F5.2 [Sun] logN(He)/N(H) [-4.09/1.17] Surface helium abundance
58- 61 F4.2 [Sun] e_logN(He)/N(H) Error on surface helium abundance (2)
63- 68 F6.3 mag Umag ? WFI magnitude in U filter (1)
70- 75 F6.3 mag Bmag WFI magnitude in B filter (1)
77- 82 F6.3 mag Vmag WFI magnitude in V filter (1)
84- 89 F6.3 mag Imag WFI magnitude in I filter (1)
91- 96 F6.3 mag F435W ? ACS magnitude in F435W filter (1)
98-103 F6.3 mag F625W ? ACS magnitude in F625W filter (1)
105-107 I3 km/s RV [164/308] Radial velocity
109-110 I2 km/s e_RV ? Error on the radial velocity
112-115 F4.1 km/s s_RV ? Standard deviation on the radial
velocity in cases of radial velocities
averaged from different sources
117-120 F4.2 Msun Mass Spectroscopic mass
122-125 F4.2 Msun e_Mass Error on the spectroscopic mass
127-131 F5.2 mag E(B-V) Estimated color excess
133-136 F4.2 Msun Mbc Spectroscopic mass derived using a
bolometric correction
138-143 I6 --- ID1 ? ID from Moehler et al.
(2011, Cat. J/A+A/526/A136)
145-150 I6 --- ID2 ? ID from Moni Bidin et al.
(2012, Cat. J/A+A/547/A109)
152-159 A8 --- Sample Spectroscopic sample (3)
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Note (1): From Castellani et al. (2007ApJ...663.1021C 2007ApJ...663.1021C; catalog not published).
Note (2): The errors include the correction factor determined in Appendix A.
Note (3): Spectroscopic sample refered as follows :
1 = VIMOS
2 = FORS1.6
3 = FORS2.6
4 = FORS_MB
5 = FLAMES
Vx = The pulsators are indicated with Vx where x is the pulsator number as
in Randal et al. (2016, Cat. J/A+A/589/A1)
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Acknowledgements:
Marilyn Latour, marilyn.latour(at)uni-goettingen.de
(End) Patricia Vannier [CDS] 27-Jun-2018