J/MNRAS/540/3523 BLOeM. Physical properties of OB stars (Bestenlehner+, 2025)
Binarity at LOw Metallicity (BLOeM):
Pipeline-determined physical properties of OB stars.
Bestenlehner J.M., Crowther P.A., Bronner V.A., Simon-Diaz S., Lennon D.J.,
Bodensteiner J., Langer N., Marchant P., Sana H., Schneider F.R.N.,
Shenar T.
<Mon. Not. R. Astron. Soc. 540, 3523 (2025)>
=2025MNRAS.540.3523B 2025MNRAS.540.3523B (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Stars, OB ; Rotational velocities ;
Radial velocities ; Optical
Keywords: stars: atmospheres - stars: early-type -
stars: fundamental parameters - stars: massive - stars: rotation
Abstract:
We aim to determine the physical properties of OB stars from the
multi-epoch Binarity at LOw Metallicity (BLOeM) spectroscopic survey
of the Small Magellanic Cloud using the Very Large Telescope/Fibre
Large Array Multi-Element Spectrograph. We apply a pipeline designed
to analyse large spectroscopic samples of OB stars to the co-added,
initial nine epochs of the BLOeM survey, utilizing grids of synthetic
model spectra computed with the stellar atmosphere code fastwind. 69
OB stars are excluded from the analysis owing to disc emission or
significant contamination by secondaries in SB2 binaries. We determine
physical properties of 778 OB stars, including Teff, logg,
logL☉, and ve*sini. There appears to be a bimodality in
ve*sini of single O stars, while ve*sini distributions of OB stars
are strikingly different for single (median 78km/s) and binary (median
200km/s) systems. Inferred temperatures are broadly in agreement with
literature results for stars in common, plus results from a grid-based
automization tool for a subset of O and early B stars, although
uncertainties are larger for surface gravities. Rotational velocities
are broadly in line with an independent tool applied to the same
subset. We recover the anticipated lower mass cut-off at 8M☉
from the survey design using a Bayesian inference method coupled with
SMC metallicity evolutionary models, with median masses of
12.6M☉ (19.8M☉) for B-type (O-type) stars. Spectroscopic
masses exceed evolutionary masses, albeit with large uncertainties in
surface gravities. We also provide an updated catalogue of O stars in
the SMC since half of the 159 BLOeM O stars are newly classified as
O-type stars.
Description:
Table A1: Physical parameters of BLOeM OB stars from Shenar et al.
(2024A&A...690A.289S 2024A&A...690A.289S, Cat. J/A+A/690/A289), excluding systems which
are problematic for spectroscopic analysis. Binarity has been
investigated by Sana et al. (2025NatAs...9.1337S 2025NatAs...9.1337S, Cat.
J/other/NatAs/9.1337) for O stars, Bodensteiner et al.
(2025A&A...698A..38B 2025A&A...698A..38B, Cat. J/A+A/698/A38) for OBe stars, Villasenor et
al. (2025A&A...698A..41V 2025A&A...698A..41V, Cat. J/A+A/698/A41) for early non-supergiant
B stars, Britavskiy et al. (2025A&A...698A..40B 2025A&A...698A..40B, cat. J/A+A/698/A40)
for early supergiant B stars, and Patrick et al. (2025A&A...698A..39P 2025A&A...698A..39P,
cat. J/A+A/698/A39) for cooler supergiants. Evolutionary masses and
ages are from Brott et al. (2011A&A...530A.115B 2011A&A...530A.115B, cat. J/A+A/530/A115)
with the exception of two luminous supergiants involving Hastings et
al. (2021A&A...653A.144H 2021A&A...653A.144H).
Table H1: An updated catalogue of spectroscopically confirmed O stars,
listed in RA order, combining the unpublished compilation from I.D.
Howarth (priv. comm.) with BLOeM (Shenar et al., 2024A&A...690A.289S 2024A&A...690A.289S,
Cat. J/A+A/690/A289). Coordinates and (G-band) photometry are from
Gaia with the exception of the compact HII regions N81 and N88A. For
N81 we adopt positions and Hubble Space Telescope WFPC2/F547M
photometry from Heydari-Malayeri et al. (1999A&A...344..848H 1999A&A...344..848H), while
for the central ionizing source in N88A (Heydari-Malayeri et al.,
1999A&A...347..841H 1999A&A...347..841H, cat. J/A+A/347/841) we adopt positions and HST
WFPC2/F547M photometry from Testor et al. (2010A&A...510A..95T 2010A&A...510A..95T).
Classifications exclusively from UV spectroscopy are excluded. The
BLOeM sample includes 159/449 O star systems in the SMC, of which 75 -
1/6 of the current total - have been newly spectroscopically
classified as O stars via BLOeM.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 253 847 Physical parameters of BLOeM OB stars
tableh1.dat 130 449 Updated catalogue of spectroscopically
confirmed O stars
refs.dat 72 50 References
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See also:
J/A+A/690/A289 : Binarity at LOw Metallicity (BLOeM). I. (Shenar+, 2024)
J/A+A/698/A38 : BLOeM. Oe and Be stars (Bodensteiner+, 2025)
J/A+A/698/A39 : BLOeM. BAF-type supergiants (Patrick+, 2025)
J/A+A/698/A40 : BLOeM. SMC early B supergiants multiplicity
(Britavskiy+, 2025)
J/A+A/698/A41 : BLOeM. Early B dwarfs and giants at Z=0.2 (Villasenor+, 2025)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- BLOeM BLOeM identifier (N-NNN) (1)
7- 23 A17 --- SpType Spectral type (1)
25- 28 I4 km/s RV Radial velocity
30- 34 F5.1 km/s s_RV ? Radial velocity dispersion
36- 39 F4.1 kK Teff ? Effective temperature
41- 44 F4.1 kK E_Teff ? Error on Teff (upper)
47- 50 F4.1 kK e_Teff ? Error on Teff (lower)
53- 56 F4.2 cm/s2 logg ? log surface gravity
59- 62 F4.2 cm/s2 E_logg ? Error on logg (upper)
65- 68 F4.2 cm/s2 e_logg ? Error on logg (lower)
71- 74 F4.2 cm/s2 loggc ? log surface gravity centrifugal corrected
77- 80 F4.2 cm/s2 E_loggc ? Error on logg_c (upper)
83- 86 F4.2 cm/s2 e_loggc ? Error on logg_c (lower)
88- 92 F5.1 Rsun Rstar ? Stellar radius
95- 98 F4.1 Rsun E_Rstar ? Error on stellar radius (upper)
101-104 F4.1 Rsun e_Rstar ? Error on stellar radius (lower)
107-110 F4.2 [Lsun] logL ? Log stellar luminosity
113-116 F4.2 [Lsun] E_logL ? Error on logL (upper)
119-122 F4.2 [Lsun] e_logL ? Error on logL (lower)
125-128 F4.2 --- Y ? He abundance mass fraction
131-134 F4.2 --- E_Y ? Error on Y (upper)
137-140 F4.2 --- e_Y ? Error on Y (lower)
142-144 I3 km/s vsini ? Projected radial velocity
147-149 I3 km/s E_vsini ? Error on vsini (upper)
153-154 I2 km/s e_vsini ? Error on vsini (lower)
156-160 F5.1 Msun Mspec ? Spectroscopic mass
162-167 F6.1 Msun E_Mspec ? Error on Mspec (upper)
170-174 F5.1 Msun e_Mspec ? Error on Mspec (lower)
176-180 F5.1 Msun Mevol ? Evolutionary mass (2)
183-186 F4.1 Msun E_Mevol ? Error on Mevol (upper)
189-192 F4.1 Msun e_Mevol ? Error on Mevol (lower)
195-198 F4.1 Myr Age ? Stellar age
201-204 F4.1 Myr E_Age ? Error on age (upper)
207-210 F4.1 Myr e_Age ? Error on age (lower)
212-217 F6.3 mag Kmag ? K-band magnitude (3)
219-222 F4.2 mag AV ? Visual extinction
224-253 A30 --- Notes Notes (4)
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Note (1): From Shenar et al. (2024A&A...690A.289S 2024A&A...690A.289S, Cat. J/A+A/690/A289).
Note (2): From Brott et al. (2011A&A...530A.115B 2011A&A...530A.115B, Cat. J/A+A/530/A115) except
where flagged in Notes.
Note (3): From VMC (Cioni et al., 2011A&A...527A.116C 2011A&A...527A.116C, Cat. II/351) except
where flagged in Notes.
Note (4): Spectroscopic binaries; fitting problems; 2MASS photometry if flagged;
Flagged as likely Post-MS; H2021 evolutionary models Hastings et al.
(2021A&A...653A.144H 2021A&A...653A.144H).
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Byte-by-byte Description of file: tableh1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 h RAh Right Ascension (J2000)
4- 5 I2 min RAm Right Ascension (J2000)
7- 11 F5.2 s RAs Right Ascension (J2000)
14 A1 --- DE- Declination sign (J2000)
15- 16 I2 deg DEd Declination (J2000)
18- 19 I2 arcmin DEm Declination (J2000)
21- 24 F4.1 arcsec DEs Declination (J2000)
27- 31 F5.2 mag Gmag Gaia G-band magnitude (1)
33- 54 A22 --- SpType Literature spectral type
56- 60 A5 --- Ref Literature reference (2)
62- 92 A31 --- Name Name and Common alias (3)
94- 98 A5 --- BLOeM BLOeM identifier (4)
100-104 A5 --- M2002 Massey (2002ApJS..141...81M 2002ApJS..141...81M, Cat. II/236)
SMC identifier
106-130 A25 --- Comment Alternative Spectral type/photometry
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Note (1): Except where noted in Comment.
Note (2): References to literature spectral type in refs.dat.
Note (3): Primary catalogues as follows:
AzV = Azzopardi et al. (1975A&AS...22..285A 1975A&AS...22..285A, Cat. V/13)
[BLK2010] = Bonanos et al. (2010AJ....140..416B 2010AJ....140..416B, cat. J/AJ/140/416)
Cl* NGC 330 ELS = Evans et al. (2006A&A...456..623E 2006A&A...456..623E, cat. J/A+A/456/623)
Cl* NGC 346 MPG = Massey et al. (1989AJ.....98.1305M 1989AJ.....98.1305M, cat. J/AJ/98/1305)
Cl* NGC 346 ELS = Evans et al. (2006A&A...456..623E 2006A&A...456..623E, Cat. J/A+A/546/623)
Lin = Lindsay (1961AJ.....66..169L 1961AJ.....66..169L)
[MA93] = Meyssonnier & Azzopardi (1993A&AS..102..451M 1993A&AS..102..451M,
Cat. J/A+A/102/451)
Sk = Sanduleak (1968AJ.....73..246S 1968AJ.....73..246S, 1969AJ.....74..877S 1969AJ.....74..877S)
[SBV2013] = Sheets et al. (2013ApJ...771..111S 2013ApJ...771..111S, Cat. J/ApJ/771/111)
2dFS = Evans et al. (2004MNRAS.353..601E 2004MNRAS.353..601E, Cat. J/MNRAS/353/601)
Note (4): From Shenar et al. (2024A&A...690A.289S 2024A&A...690A.289S, Cat. J/A+A/690/A289)
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Ref Reference code
7- 25 A19 --- BibCode BibCode
27- 52 A26 --- Aut Author's name
56- 72 A17 --- Com Comments
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Acknowledgements:
Paul Crowther, Paul.crowther(at)sheffield.ac.uk
(End) Paul Crowther [Sheffield univ.], Patricia Vannier [CDS] 03-Dec-2025