J/A+A/559/A101 NGC6656 spectroscopy of 71 blue HB stars (Salgado+, 2013)
Spectroscopy of blue horizontal branch stars in NGC6656 (M22).
Salgado C., Moni Bidin C., Villanova S., Geisler D., Catelan M.
<Astron. Astrophys. 559, A101 (2013)>
=2013A&A...559A.101S 2013A&A...559A.101S
ADC_Keywords: Clusters, globular ; Stars, horizontal branch ; Stars, blue ;
Spectroscopy
Keywords: stars: horizontal branch - stars: atmospheres -
stars: fundamental parameters - stars: abundances -
globular clusters: individual: NGC 6656 (M 22)
Abstract:
Recent investigations revealed very peculiar properties of blue
horizontal branch (HB) stars in ω Centauri, which show
anomalously low surface gravity and mass compared to other clusters
and to theoretical models. ω Centauri, however, is a very
unusual object, hosting a complex mix of multiple stellar populations
with different metallicity and chemical abundances.
We measured the fundamental parameters (temperature, gravity, and
surface helium abundance) of a sample of 71 blue HB stars in M 22,
with the aim of clarifying if the peculiar results found in
ω Cen are unique to this cluster. M 22 also hosts multiple
sub-populations of stars with a spread in metallicity, analogous to
ω Cen.
Description:
Spectroscopically-derived parameters of 71 blue HB stars. The
temperature, gravity, and surface helium abundance were derived
fitting the Balmer and helium lines with synthetic spectra. Reddening
and mass were estimated from these parameters.
Spectra were obtained with the Hydra optical spectrograph mounted on
the Blanco 4.0m telescope. It was used the grating KPGL1, coupled with
the BG39 filter and the 200µ slit plate. The spectra were obtained on
August 27, 2010 and cover the wavelength range of 3700-4900Å with a
spectral resolution of 2.7Å.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 93 71 Spectroscopic parameters of target stars
sp/* . 71 Individual spectra
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See also:
J/ApJ/420/612 : Proper motions + radial velocities in M22 (Peterson+ 1994)
J/A+AS/109/487 : Color-magnitude study of M 22 (Samus+, 1995)
J/PASP/107/32 : uvby-hk photometry in M22 (Anthony-Twarog+ 1995)
J/MNRAS/349/1278 : BVI photometry of M22 (Monaco+, 2004)
J/ApJ/742/37 : Abundances of six RGB stars in M22 (Roederer+, 2011)
J/A+A/541/A15 : Abundances of M22 subgiants (Marino+, 2012)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1 I1 --- Chip Chip number (1)
3- 6 I4 --- ID Identification number (1)
8- 13 F6.3 mag Vmag V magnitude (1)
15- 19 F5.3 mag B-V B-V color index (1)
21- 25 I5 K Teff Effective temperature
27- 30 I4 K e_Teff Error on effective temperature
32- 35 F4.2 [cm/s2] logg Surface gravity
37- 40 F4.2 [cm/s2] e_logg Error on surface gravity
42 A1 --- f_logg [E?] Flag on surface gravity (2)
44- 48 F5.2 [-] lg(He/H) [-4/-0.9] Surface helium abundance
50- 53 F4.2 [-] e_lg(He/H) Error on surface helium abundance
55 A1 --- f_lg(He/H) [E?] Flag on surface helium (2)
57- 61 F5.3 mag E(B-V) Color excess
63- 66 F4.2 Msun Mass Spectroscopic mass
68- 71 F4.2 Msun e_Mass Error on spectroscopic mass
73 A1 --- f_Mass [DE?] Flag on spectroscopic mass (2)
75- 78 I4 km/s RV Radial velocity
80 A1 --- f_RV [DE?] Flag on radial velocity (2)
82 A1 --- Note [F?] Note (2)
84- 93 A10 --- FileName Name of the file with spectrum in
subdirectory sp
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Note (1): from Monaco et al. (2004, Cat. J/MNRAS/349/1278) database,
source designated as Cl* NGC 6656 MPF N-NNNNN, (Chip-ID).
Note (2): Flags as follows:
E = value partially incompatible with cluster membership
D = value incompatible with cluster membership
F = field contaminants excluded from the analysis
? = unknown
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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2- 17 F16.11 0.1nm lambda [3698/5503] Wavelength in Angstroms
19- 31 E13.6 cW/m2/nm Flux Un-normalized flux (erg/cm2/s/Å)
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Acknowledgements:
Carolina Salgado, salgado.carolina(at)gmail.com
(End) Carolina Salgado [UdeC, Chile], Patricia Vannier [CDS] 27-Aug-2013