J/A+A/580/A93 VLTS. B stars multiplicity (Dunstall+, 2015)
The VLT-FLAMES Tarantula Survey.
XXII: Multiplicity properties of the B-type stars.
Dunstall P.R., Dufton P.L., Sana H., Evans C.J., Howarth I.D.,
Simon-Diaz S., de Mink S.E., Langer N., Maiz Apellaniz J., Taylor W.D.
<Astron. Astrophys. 580, A93 (2015)>
=2015A&A...580A..93D 2015A&A...580A..93D
ADC_Keywords: Magellanic Clouds ; Stars, B-type ; Binaries, spectroscopic ;
Radial velocities
Keywords: stars: early-type - binaries: spectroscopic -
open clusters and associations: individual: 30 Doradus
Abstract:
We investigate the multiplicity properties of 408 B-type stars
observed in the 30 Doradus region of the Large Magellanic Cloud with
multi-epoch spectroscopy from the VLT-FLAMES Tarantula Survey (VFTS).
We use a cross-correlation method to estimate relative radial
velocities from the helium and metal absorption lines for each of our
targets. Objects with significant radial-velocity variations (and with
an amplitude larger than 16km/s) are classified as spectroscopic
binaries. We find an observed spectroscopic binary fraction (defined
by periods of <103.5d and mass ratios >0.1) for the B-type stars,
fB(obs)=0.25±0.02, which appears constant across the field of
view, except for the two older clusters (Hodge 301 and SL 639). These
two clusters have significantly lower binary fractions of 0.08±0.08
and 0.10±0.09, respectively. Using synthetic populations and a model
of our observed epochs and their potential biases, we constrain the
intrinsic multiplicity properties of the dwarf and giant (i.e.
relatively unevolved) B-type stars in 30 Dor. We obtain a present-day
binary fraction fB(true)=0.58±0.11, with a flat period
distribution. Within the uncertainties, the multiplicity properties of
the B-type stars agree with those for the O stars in 30 Dor from the
VFTS.
Description:
The VFTS spectra were obtained with the Fibre Large Array
Multi-Element Spectrograph (FLAMES) on the Very
Large Telescope (VLT). Classifications for the 438 B-type stars
observed in the VFTS were given by Evans et al. (2015, cat.
J/A+A/574/A13). These are located in the main clusters in the 30 Dor
region (i.e. NGC 2070, NGC 2060, Hodge 301, SL 639) and the
local field population (see Fig. 4 from Evans et al.). All of the
spectra were obtained using the fibre-fed Medusa-Giraffe mode of
FLAMES, so the sample does not include stars in R136, the young
massive cluster at the core of 30 Dor, which is too densely populated
for effective use of the Medusa fibres.
This paper presents a radial-velocity (RV) analysis of the multiple
observations of the B-type stars with the LR02 setting of the Giraffe
spectrograph. The observations spanned 10-12 months for most
targets, with an extended baseline of 22 months for 31 targets, due to
a reobservation for operational reasons. Two or three consecutive
exposures were obtained on any given night, with the longer-term
sampling designed to optimise detection of binaries with periods up to
∼200d, given scheduling constraints.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
stars.dat 44 403 List of studied stars
table2.dat 115 4486 Relative RV estimates for each exposure
table3.dat 47 168 Relative RV estimates for each epoch for stars
with significant nebular contamination
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See also:
J/A+A/530/A108 : VLT-FLAMES Tarantula Survey (Evans+, 2011)
J/A+A/550/A107 : VLTS. RV catalogue of O stars in 30 Doradus (Sana+, 2013)
J/A+A/550/A108 : DIB in VLT-FLAMES Tarantula Survey (van Loon+, 2013)
J/A+A/550/A109 : VLTS: vsini measures (Dufton+ 2013)
J/A+A/558/A134 : VLTS. 30 Dor luminous stars (Doran+, 2013)
J/A+A/560/A29 : O-stars in VLT-FLAMES Tarantula Survey (Ramirez-Agudelo+ 2013)
J/A+A/564/A39 : VLTS. OVz stars in 30 Dor (Sabin-Sanjulian+, 2014)
J/A+A/564/A40 : VFTS. O-type stellar content of 30 Dor (Walborn+, 2014)
J/A+A/564/L7 : VLT-FLAMES Tarantula Survey: VFTS 822 (Kalari+, 2014)
J/A+A/575/A70 : VFTS. B-type supergiants (McEvoy+, 2015)
Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [VFTS]
6- 8 I3 --- VFTS [1/891] VFTS star number
11- 12 I2 h RAh Right ascension (J2000)
14- 15 I2 min RAm Right ascension (J2000)
17- 21 F5.2 s RAs Right ascension (J2000)
23 A1 --- DE- Declination sign (J2000)
24- 25 I2 deg DEd Declination (J2000)
27- 28 I2 arcmin DEm Declination (J2000)
30- 33 F4.1 arcsec DEs Declination (J2000)
36- 37 I2 --- Nobs [4/16] Number of observations
39- 44 A6 --- File Table with RV data ("table2" or "table3")
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- VFTS [1/891] VFTS star number
5 A1 --- T [*] Template spectrum for relative RV estimates
7 A1 --- --- [(]
8 A1 --- S [BVS] Status: Binary, Variable or Single
9 A1 --- --- [)]
11- 19 F9.3 d MJD [54748/55460] Modified Julian date of exposure
21- 27 F7.2 km/s Si4553 ? Relative RV estimate for SiIII line at 4553Å
29- 35 F7.2 km/s O4080 ? Relative RV estimate for OII lines near 4080Å
37- 43 F7.2 km/s O4317 ? Relative RV estimate for OII doublet
near 4317Å
45- 51 F7.2 km/s O4414 ? Relative RV estimate for OII doublet
near 4414Å
53- 59 F7.2 km/s He4026 ? Relative RV estimate for HeI line at 4026Å
61- 67 F7.2 km/s He4471 ? Relative RV estimate for HeI line at 4471Å
69- 75 F7.2 km/s He4009 ? Relative RV estimate for HeI line at 4009Å
77- 83 F7.2 km/s He4144 ? Relative RV estimate for HeI line at 4144Å
85- 91 F7.2 km/s He4388 ? Relative RV estimate for HeI line at 4388Å
93- 99 F7.2 km/s He4121 ? Relative RV estimate for HeI line at 4121Å
101-107 F7.2 km/s He4438 ? Relative RV estimate for HeI line at 4438Å
109-115 F7.2 km/s He4169 ? Relative RV estimate for HeI line at 4169Å
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- VFTS [1/891] Star number
5 A1 --- T [*] Template spectrum for relative RV estimates
7 A1 --- --- [(]
8 A1 --- S [BVS] Status: Binary, Variable or Single
9 A1 --- --- [)]
11- 15 I5 d MJD [54767/55459] Modified Julian date of epoch
17- 23 F7.2 km/s He4388 ? Relative RV estimate for He I line at 4388Å
25- 31 F7.2 km/s He4144 ? Relative RV estimate for He I line at 4144Å
33- 39 F7.2 km/s He4026 ? Relative RV estimate for He I line at 4026Å
41- 47 F7.2 km/s He4471 ? Relative RV estimate for He I line at 4471Å
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Acknowledgements:
Philip Dufton, P.Dufton(at)qub.ac.uk
Chirs Evans, chris.evans(at)stfc.ac.uk
References:
Evans et al., Paper I 2011A&A...530A.108E 2011A&A...530A.108E, Cat. J/A+A/530/108
Taylor et al., Paper II 2011A&A...530L..10T 2011A&A...530L..10T
Bestenlehner et al., Paper III 2011A&A...530L..14B 2011A&A...530L..14B
Bressert et al., Paper IV 2012A&A...542A..49B 2012A&A...542A..49B
Dunstall et al., Paper V 2012A&A...542A..50D 2012A&A...542A..50D
Henault-Brunet et al., Paper VI 2012A&A...545L...1H 2012A&A...545L...1H
Henault-Brunet et al., Paper VII 2012A&A...546A..73H 2012A&A...546A..73H
Sana et al., Paper VIII 2013A&A...550A.107S 2013A&A...550A.107S, Cat. J/A+A/550/A107
van Loon et al., Paper IX 2013A&A...550A.108V 2013A&A...550A.108V, Cat. J/A+A/550/A108
Dufton et al., Paper X 2013A&A...550A.109D 2013A&A...550A.109D, Cat. J/A+A/550/A109
Doran et al., Paper XI 2013A&A...558A.134D 2013A&A...558A.134D, Cat. J/A+A/558/A134
Ramirez-Agudelo et al., Paper XII 2013A&A...560A..29R 2013A&A...560A..29R, Cat. J/A+A/560/A29
Sabin-Sanjulian et al., Paper XIII 2014A&A...564A..39S 2014A&A...564A..39S, Cat. J/A+A/564/A39
Walborn et al., Paper XIV 2014A&A...564A..40W 2014A&A...564A..40W, Cat. J/A+A/564/A40
Kalari et al., Paper XV 2014A&A...564L...7K 2014A&A...564L...7K, Cat. J/A+A/564/L7
Maiz Apellaniz et al., Paper XVI 2014A&A...564A..63M 2014A&A...564A..63M
Bestenlehner et al., Paper XVII 2014A&A...570A..38B 2014A&A...570A..38B
Evans et al., Paper XVIII 2015A&A...574A..13E 2015A&A...574A..13E
McEvoy et al., Paper XIX 2015A&A...575A..70M 2015A&A...575A..70M, Cat. J/A+A/575/A70
Clark et al., Paper XX 2015A&A...579A.131C 2015A&A...579A.131C
Ramirez-Agudelo et al., Paper XXI 2015A&A...580A..92R 2015A&A...580A..92R
Howarth et al., Paper XXIII 2015A&A...582A..73H 2015A&A...582A..73H
(End) P. Dufton [Queens Univ. of Belfast], P. Vannier [CDS] 29-May-2015