J/A+A/678/A172 Multiplicity of massive stars in Sco OB1 (Pauwels+, 2023)
The multiplicity of massive stars in the Scorpius OB1 association through
high-contrast imaging.
Pauwels T., Reggiani M., Sana H., Rainot A., Kratter K.
<Astron. Astrophys. 678, A172 (2023)>
=2023A&A...678A.172P 2023A&A...678A.172P (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Stars, OB ; Photometry, infrared
Keywords: binaries: general - stars: massive - stars: low-mass -
stars: formation - stars: imaging
Abstract:
Despite past efforts, a comprehensive theory of massive star formation
is still lacking. One of the most remarkable properties of massive
stars is that almost all of them are found in binaries or higher-order
multiple systems. Since multiplicity is an important outcome parameter
of a star formation process, observations that cover the full
companion mass ratio and separation regime are essential to constrain
massive star formation theories.
We aim to characterise the multiplicity properties of 20 OB stars (one
of which turned out to be a foreground object) in the active
star-forming region Sco OB1 in the separation range 0.15"-6"
(∼200-9000AU), using high- contrast imaging observations. These
observations enabled us to reach very large magnitude differences and
explore an as of yet uncharted territory of companions around massive
stars.
We used VLT/SPHERE to simultaneously observe with IFS and IRDIS,
obtaining high-contrast imaging observations that cover a field of
view (FoV) of 1.73"x1.73" in YJH bands and 11"x12.5" in K1 and K2
bands, respectively. We extracted low-resolution IFS spectra of
candidate companions within 0.85" and compared them with PHOENIX and
ATLAS9 atmosphere models to obtain an estimate of their fundamental
parameters. Furthermore, we retrieved an estimate of the mass and age
of all sources in the larger IRDIS FoV. The observations reached
contrast magnitudes of ΔK1-13 on average, so we were able to
detect sources at the stellar-substellar boundary.
In total, we detect 789 sources, most of which are likely background
sources. Thirty objects that are estimated to be in the stellar mass
regime have a 20% or lower probability of being spurious associations.
We obtain SPHERE companion fractions of 2.3±0.4 and 4.2±0.8 for O-
and B-type stars, respectively. Splitting the sample between more
massive (>20M☉) and less massive stars (<20M☉), we obtain
companion fractions of 2.3±0.4 and 3.9±0.7, respectively.
Including all previously detected companions, we find a total
multiplicity fraction of 0.89±0.07 for separations in the range of
∼0-12000AU.
With SPHERE, we are probing an unexplored area in the magnitude versus
separation diagram of companions, which is crucial to achieve a
complete overview of the multiplicity properties of massive stars and
ultimately improve our understanding of massive star formation.
Description:
Data derived from SPHERE/IRDIS coronagraphic observations of 19 OB
stars in Sco OB1 and one foreground star (HD152685). The database
contains a total of 789 sources, for which the position and K1 and K2
contrast magnitudes with respect to the central star are listed. In
addition, we provide the spurious association probability which is
used to distinguish likely bound companions from chance projections.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
target.dat 35 20 List of targets
table4.dat 79 789 Characteristics of detected sources
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Byte-by-byte Description of file: target.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Target ID of the central star
13- 14 I2 h RAh Simbad right ascension (J2000)
16- 17 I2 min RAm Simbad right ascension (J2000)
19- 23 F5.2 s RAs Simbad right ascension (J2000)
25 A1 --- DE- Simbad declination sign (J2000)
26- 27 I2 deg DEd Simbad declination (J2000)
29- 30 I2 arcmin DEm Simbad declination (J2000)
32- 35 F4.1 arcsec DEs Simbad declination (J2000)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Target ID of the central star
12- 13 I2 --- SourceID [1/65] ID number of the detected source
15- 19 F5.3 arcsec Sep Projected radial separation of the SourceID
source wrt the Target star
21- 25 F5.3 arcsec e_Sep Uncertainty on the projected radial separation
27- 33 F7.3 deg PA Position angle of the SourceID source
35- 39 F5.3 deg e_PA Uncertainty on the position angle
42- 47 F6.3 mag dmagK1 ? K1 band contrast magnitude of the SourceID
source wrt the Target star
50- 55 F6.3 mag e_dmagK1 ? Uncertainty on the K1 band contrast magnitude
58- 63 F6.3 mag dmagK2 ? K2 band contrast magnitude of the SourceID
source wrt the Target star
66- 71 F6.3 mag e_dmagK2 ? Uncertainty on the K2 band contrast magnitude
75- 79 F5.3 --- Pspur ? Spurious association probability of the
SourceID source
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Acknowledgements:
Tinne Pauwels, tinne.pauwels(at)kuleuven.be
(End) Patricia Vannier [CDS] 14-Aug-2023