J/A+A/550/A107 RV catalogue of O stars in 30 Doradus (Sana+, 2013)
The VLT-FLAMES Tarantula Survey.
VIII. Multiplicity properties of the O-type star population.
Sana H., de Koter A., de Mink S.E., Dunstall P.R., Evans C.J.,
Henault-Brunet V., Maiz Apellaniz J., Ramirez-Agudelo O.H., Taylor W.D.,
Walborn N.R., Clark J.S., Crowther P.A., Herrero A., Gieles M., Langer N.,
Lennon D.J., Vink J.S.
<Astron. Astrophys. 550, A107 (2013)>
=2013A&A...550A.107S 2013A&A...550A.107S
ADC_Keywords: Magellanic Clouds ; Stars, O ; Binaries, spectroscopic ;
Radial velocities
Keywords: stars: early-type - stars: massive - binaries: spectroscopic -
open clusters and associations: individual: 30 Dor -
binaries: close - Magellanic Clouds
Abstract:
The Tarantula Nebula in the Large Magellanic Cloud is our closest view
of a starburst region and is the ideal environment to investigate
important questions regarding the formation, evolution and final fate
of the most massive stars.
We analyze the multiplicity properties of the massive O-type star
population observed through multi-epoch spectroscopy in the framework
of the VLT-FLAMES Tarantula Survey. With 360 O-type stars, this is the
largest homogeneous sample of massive stars analyzed to date.
We use multi-epoch spectroscopy and variability analysis to identify
spectroscopic binaries. We also use a Monte-Carlo method to correct
for observational biases. By modelling simultaneously the observed
binary fraction, the distributions of the amplitudes of the radial
velocity variations and the distribution of the time scales of these
variations, we derive the intrinsic current binary fraction and period
and mass-ratio distributions.
We observe a spectroscopic binary fraction of 0.35±0.03, which
corresponds to the fraction of objects displaying statistically
significant radial velocity variations with an amplitude of at least
20km/s . We compute the intrinsic binary fraction to be 0.51±0.04.
We adopt power-laws to describe the intrinsic period and mass-ratio
distributions: f(log10P/d)~(log10 P/d)pi (with log10P/d in the
range 0.15-3.5) and f(q)∼qkappa with 0.1<q=M2/M1< 1.0. The power-law
indexes that best reproduce the observed quantities are
pi=-0.45±0.30 and kappa=-1.0±0.4. The period distribution that we
obtain thus favours shorter period systems compared to an Opik law
(pi=0). The mass ratio distribution is slightly skewed towards low
mass ratio systems but remains incompatible with a random sampling of
a classical mass function (kappa=-2.35). The binary fraction seems
mostly uniform across the field of view and independent of the
spectral types and luminosity classes. The binary fraction in the
outer region of the field of view (r>7.8 , i.e. ∼117pc) and among the
O9.7 I/II objects are however significantly lower than expected from
statistical fluctuations. The observed and intrinsic binary fractions
are also lower for the faintest objects in our sample (Ks>15.5mag),
which results from observational effects and the fact that our O star
sample is not magnitude-limited but is defined by a spectral-type
cutoff. We also conclude that magnitude-limited investigations are
biased towards larger binary fractions.
Using the multiplicity properties of the O stars in the Tarantula
region and simple evolutionary considerations, we estimate that over
50% of the current O star population will exchange mass with its
companion within a binary system. This shows that binary interaction
is greatly affecting the evolution and fate of massive stars, and must
be taken into account to correctly interpret unresolved populations of
massive stars.
Description:
Radial velocity (RV) measurements and multiplicity status of 332
O-type stars observed at multi-epochs as part as the VLT-FLAMES
Tarantula Survey.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 20 332 List of lines used for RV measurements
table2.dat 26 2136 RV data base
table3.dat 39 332 Multiplicity status
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See also:
J/A+A/530/A108 : VLT-FLAMES Tarantula Survey (Evans+, 2011)
J/A+A/550/A108 : DIB in VLT-FLAMES Tarantula Survey (van Loon+, 2013)
J/A+A/550/A109 : vsini in VLT-FLAMES Tarantula Survey (Dufton+, 2013)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- VFTS [14/892] VLT-FLAMES Tarantula Survey identifier
6 A1 --- 4026 [x-] HeI+II 4026 line used (6)
8 A1 --- 4200 [x-] HeII 4200 line used (6)
10 A1 --- 4387 [x-] HeI 4387 line used (6)
12 A1 --- 4471 [x-] HeI 4471 line used (6)
14 A1 --- 4541 [x-] HeII 4541 line used (6)
16 A1 --- 4686 [x-] HeII 4686 line used (6)
18 A1 --- 4713 [x-] HeI 4713 line used (6)
20 A1 --- 4922 [x-] HeI 4922 line used (6)
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Note (6): An 'x' indicates that the line has been used in the RV measurement
procedure. An '-' indicates that it has not been used.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- VFTS [14/892] VLT-FLAMES Tarantula Survey identifier
6- 14 F9.3 d HJD Heliocentric Julian date (HJD-2400000)
16- 20 F5.1 km/s RV Radial velocity (RV)
22- 26 F5.1 km/s e_RV 1σ uncertainty on RV
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- VFTS [14/892] VLT-FLAMES Tarantula Survey identifier
6- 12 F7.2 --- sigVar ?=-999.0 Significance of the RV variability (1)
14- 19 F6.1 km/s dRV ?=-999.0 Amplitude of the RV variations (2)
21 A1 --- LPV [y:-] Line profile variations (3)
23- 27 A5 --- Morph Morphological comments (3)(4)
29- 39 A11 --- HST Multiplicity in HST images (3)(5)
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Note (1): sigVat (σdetect) is defined by Eq.1, (variation relative
to σ); a confidence threshold of 4.0 was adopted. A dummy value
of -999.0 indicate that no variability test could be performed.
Note (2): The amplitude (ΔRV) is only given if the criteria of Eq.4
are met; otherwise dummy value of -999.0 is given.
Note (3): A semicolon (:) indicate uncertain diagnostic.
Note (4): Morphological comments as follows:
AMPL = Variable line amplitude
ASYM = Asymmetric profile
FWHM = Variable full width at half-maximum
SB2 = Double-line profile
Note (5): Multiplicity in HST images code as follows:
DBL = Double source
TRPL = Triple source
MULT = Multiple source
NO DATA = Not covered in the consulted HST images
RoC = Risk of Contamination by a nearby relatively bright source
RoC-### = Risk of Contamination by VFTS ###
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Acknowledgements:
Hugues Sana, H.Sana(at)uva.nl
References:
Evans et al., Paper I 2011A&A...530A.108E 2011A&A...530A.108E, Cat. J/A+A/530/A108
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...542A..49B 2012A&A...542A..49B
Henault-Brunet et al., Paper VII 2012A&A...546A..73H 2012A&A...546A..73H
van Loon et al., Paper IX 2012A&A...550A.108V 2012A&A...550A.108V, Cat. J/A+A/550/A108
Dufton et al., Paper X 2012A&A...550A.109D 2012A&A...550A.109D, Cat. J/A+A/550/A109
(End) Hugues Sana [UvA, The Netherlands], Patricia Vannier [CDS] 04-Feb-2013