J/A+A/672/A22 Binarity in fast-rotating O-type stars (Britavskiy+, 2023)
The IACOB project. VIII.
Searching for empirical signatures of binarity in fast-rotating O-type stars.
Britavskiy N., Simon-Diaz S., Holgado G., Burssens S., Maiz-Apellaniz J.,
Eldridge J.J., Naze Y., Panteloni Gonzalez M., Herrero A.
<Astron. Astrophys. 672, A22 (2023)>
=2023A&A...672A..22B 2023A&A...672A..22B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, early-type ; Stars, O ; Rotational velocities ;
Spectroscopy ; Radial velocities ; Optical
Keywords: stars: early-type - stars: rotation - stars: oscillations -
stars: fundamental parameters - techniques: spectroscopic -
binaries: spectroscopic
Abstract:
The empirical distribution of projected rotational velocities (vsini)
in massive O-type stars is characterized by a dominant slow velocity
component and a tail of fast rotators. Binary interaction has been
proposed to play a dominant role in the formation of this tail.
We perform a complete and homogeneous search for empirical signatures
of binarity in a sample of 54 fast-rotating stars with the aim of
evaluating this hypothesis. This working sample has been extracted
from a larger sample of 415 Galactic O-type stars which covers the
full range of vsini values.
We used new and archival multi-epoch spectra in order to detect
spectroscopic binary systems. We complement this information with Gaia
proper motions and TESS photometric data to aid in the identification
of runaway stars and eclipsing binaries, respectively. We also
benefitted from additional published information to provide a more
complete overview of the empirical properties of our working sample of
fast-rotating O-type stars.
The identified fraction of single-lined spectroscopic binary (SB1)
systems and apparently single stars among the fast-rotating sample is
∼18% and ∼70%, respectively. The remaining 12% correspond to four
secure double-line spectroscopic binaries (SB2) with at least one of
the components having a vsini>200km/s (∼8%), along with a small sample
of 2 stars (∼4%) for which the SB2 classification is doubtful: these
could actually be single stars with a remarkable line-profile
variability. When comparing these percentages with those corresponding
to the slow-rotating sample, we find that our sample of fast rotators
is characterised by a slightly larger percentage of SB1 systems (∼18%
vs. ∼13%) and a considerably smaller fraction of clearly detected SB2
systems (8% vs. 33%). Overall, there seems to be a clear deficit of
spectroscopic binaries (SB1+SB2) among fast-rotating O-type stars
(∼26% vs. ∼46%). On the contrary, the fraction of runaway stars is
significantly higher in the fast-rotating domain (∼33-50%) than among
those stars with vsini<200km/s. Lastly, almost 65% of the apparently
single fast-rotating stars are runaways. As a by-product, we
discovered a new over-contact SB2 system (HD 165921) and two
fast-rotating SB1 systems (HD 46485 and HD 152200) Also, we propose HD
94024 and HD 12323 (both SB1 systems with a vsini<200km/s) as
candidates for hosting a quiescent stellar-mass black hole.
Our empirical results seem to be in good agreement with the assumption
that the tail of fast-rotating O-type stars (with vsini>200km/s) is
mostly populated by post-interaction binary products. In particular,
we find that the final statistics of identified spectroscopic binaries
and apparent single stars are in good agreement with newly computed
predictions obtained with the binary population synthesis code BPASS
and earlier estimations obtained in previous studies.
Description:
We present the individual radial velocity measurements for 50 Galactic
fast-rotating stars their peak-to-peak amplitude radial velocity
measurements (see paper).
The individual radial velocity measurements for each available
spectrum per target were determined by using two techniques:
cross-correlation of spectra with each other (RVrel, tableb) and the
absolute radial velocity measurements based on HeI 5876 line profile
fitting. The peak-to-peak radial velocity estimates (RVpp, tablea) is
based on the RVrel measurements.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea.dat 38 50 vsini, peak-to-peak radial velocity measurements,
and final binary status for 50 fast rotators
tableb.dat 94 948 Individual radial velocity measurements for
50 Galactic fast-rotating stars
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See also:
J/A+A/562/A135 : Northern Galactic OB stars vsini (Simon-Diaz+, 2014)
J/A+A/597/A22 : Massive O- and B-type stars velocities (Simon-Diaz+, 2017)
J/A+A/613/A65 : Spectroscopic parameters of O-type stars (Holgado+, 2018)
J/A+A/613/A9 : Extinction towards Galactic O stars (Maiz Apellaniz+, 2018)
J/A+A/638/A157 : O-type stars near ZAMS elusive detection (Holgado+, 2022)
J/A+A/665/A150 : Rotational properties of Galactic O-type stars (Holgado+ 2022)
Byte-by-byte Description of file: tablea.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Target Star name
12- 14 I3 km/s vsini Projected rotational velocity
16- 17 I2 km/s e_vsini Projected rotational velocity error
19- 24 F6.2 km/s RVpp Peak-to-peak radial velocity measurements that
are based on relative radial velocity
measurement (see tableb.dat, RVrel column)
26- 29 F4.1 km/s e_RVpp Peak-to-peak radial velocity measurements
error
31- 38 A8 --- Bin Binary status for each of the stars (1)
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Note (1): Binary status as follows:
LS = likely/apparently single
SB1 = one component spectroscopic binary
LPV/SB1? = line profile variable or one component spectroscopic binary
LPV/SB2? = line profile variable or two-component spectroscopic binary
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Byte-by-byte Description of file: tableb.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Target Star name
13- 56 A44 --- Namesp Name of the spectrum that has been analyzed
58- 72 F15.7 d HJD Heliocentric Julian date of the observations
74- 80 F7.2 km/s RVrel Relative radial velocity of the spectrum
respect to the reference spectrum
(based on the cross-correlation technique).
82- 86 F5.2 km/s e_RVrel ?=- Standard deviation of RVrel measurements
88- 94 F7.2 km/s RV Absolute radial velocity measurements based
on the fitting of HeI 5876 line (1)
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Note (1): the step of radial velocity space during the cross-correlation
fitting process is 0.5 km/s.
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Acknowledgements:
Nikolay Britavskiy, britvavskiy(at)gmail.com
References:
Simon-Diaz & Herrero, Paper I 2014A&A...562A.135S 2014A&A...562A.135S, Cat. J/A+A/562/A135
Simon-Diaz et al., Paper II 2014A&A...570L...6S 2014A&A...570L...6S
Simon-Diaz et al., Paper III 2017A&A...597A..22S 2017A&A...597A..22S, Cat, J/A+A/597/A22
Godart et al., Paper IV 2017A&A...597A..23G 2017A&A...597A..23G
Holgado et al., Paper V 2018A&A...613A..65H 2018A&A...613A..65H, Cat. J/A+A/613/A65
Holgado et al., Paper VI 2020A&A...638A.157H 2020A&A...638A.157H, Cat. J/A+A/638/A157
Holgado et al. Paper VII 2022A&A...665A.150H 2022A&A...665A.150H Cat. J/A+A/665/A150
(End) Patricia Vannier [CDS] 14-Feb-2023