J/A+A/658/A69 RVs of B stars in NGC 6231 (Banyard+, 2022)
The observed multiplicity properties of B-type stars in the Galactic
young open cluster NGC 6231.
Banyard G., Sana H., Mahy L., Bodensteiner J., Villasenor J.I., Evans C.J.
<Astron. Astrophys. 658, A69 (2022)>
=2022A&A...658A..69B 2022A&A...658A..69B (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Radial velocities ; Stars, B-type ; Optical
Keywords: binaries: spectroscopic - stars: early-type - stars: massive -
open clusters and associations: individual: NGC 6231
Abstract:
It is well known that massive O stars are frequently (if not always)
found in binary or higher-order multiple systems, but this fact has
been less robustly investigated for the lower mass range of the
massive stars, represented by B-type stars. Obtaining the binary
fraction and orbital parameter distributions of B-type stars is
crucial to understand the impact of multiplicity on the archetypal
progenitor of core-collapse supernovae as well as to properly
investigate formation channels for gravitational wave progenitors.
This work aims to characterise the multiplicity of the B star
population of the young open cluster NGC 6231 through multi-epoch
optical spectroscopy of 80 B-type stars.
We analyse 31 FLAMES/GIRAFFE observations of 80 B-type stars,
monitoring their radial velocities (RVs) and performing a
least-squares spectral analysis (Lomb-Scargle) to search for
periodicity in those stars with statistically significant variability
in their RVs.
We constrained an observed spectroscopic binary fraction of 33±5%
for the B-type stars of NGC 6231, with a first order bias correction
giving a true spectroscopic binary fraction of 52±8%. Out of 27
B-type binary candidates, we obtained orbital solutions for 20
systems: 15 single-lined (SB1) and five double-lined spectroscopic
binaries (SB2s). We present these orbital solutions and the orbital
parameter distributions associated with them.
Our results indicate that Galactic B-type stars are less frequently
found in binary systems than their more massive O-type counterparts,
but their orbital properties generally resemble those of B- and O-type
stars in both the Galaxy and Large Magellanic Cloud.
Description:
Radial velocities of 80 B-type stars across varying levels of RV
variability in the young open galactic cluster NGC 6231 are presented,
with their associated uncertainties.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 57 80 List of studied stars
sb2.dat 50 300 RVs of identified SB2s (5 stars) (table C1)
sb1.dat 50 450 RVs of identified SB1s (15 stars) (table C2)
pnororb.dat 50 210 RVs of RV variable stars with an identified
period but no constrained orbital solution
(7 stars) (table C3)
varnop.dat 50 1395 RVs of RV variable stars without an
identified period (41 stars) (table C4)
nonvar.dat 50 360 RVs of stars identified as stable in RV
(12 stars) (table C5)
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See also:
J/MNRAS/386/447 : RV catalogue of O-type stars in NGC 6231 (Sana+, 2008)
Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 21 A21 --- Object Object name in SIMBAD
23- 24 I2 h RAh Right ascension (J2000)
26- 27 I2 min RAm Right ascension (J2000)
29- 33 F5.2 s RAs Right ascension (J2000)
35 A1 --- DE- Declination sign (J2000)
36- 37 I2 deg DEd Declination (J2000)
39- 40 I2 arcmin DEm Declination (J2000)
42- 45 F4.1 arcsec DEs Declination (J2000)
47- 57 A11 --- FileName Name of the table with RV data
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Byte-by-byte Description of file: sb?.dat sb2.dat n*.dat p*.dat v*.dat
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Bytes Format Units Label Explanations
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1- 21 A21 ---- Object Object name in SIMBAD
23 A1 --- m_Object [1/2] For SB2, 1 for primary, 2 for secondary
25- 32 F8.2 d BJD Baricentric Julian date (BJD-2400000)
34- 42 F9.4 km/s RV ?=- Radial velocity at BJD
44- 50 F7.4 km/s e_RV ?=- Error on RV at BJD
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Acknowledgements:
Gareth Banyard, garethowain.banyard(at)kuleuven.be
(End) Patricia Vannier [CDS] 26-Jan-2022