J/A+A/635/A73 Multiplicity study of transiting exoplanet hosts. I. (Bohn+, 2020)
A multiplicity study of transiting exoplanet host stars.
I. High-contrast imaging with VLT/SPHERE .
Bohn A.J., Southworth, J., Ginski, C., Kenworthy M.A., Maxted P.F.L.,
Evans D.F.
<Astron. Astrophys. 635, A73 (2020)>
=2020A&A...635A..73B 2020A&A...635A..73B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets
Keywords: planets and satellites: dynamical evolution and stability -
planets and satellites: formation - planetary systems -
binaries: visual - techniques: high angular resolution
Abstract:
Many main-sequence stars are part of multiple systems. The effect of
stellar multiplicity on planet formation and migration, however, is
poorly understood.
We study the multiplicity of stars hosting known transiting
extra-solar planets to test competing theories on the formation
mechanisms of hot Jupiters.
We observed 45 exoplanet host stars using the infrared dual imaging
spectrograph (IRDIS) of the Spectro-Polarimetric High-Contrast
Exoplanet Research (SPHERE) instrument at the Very Large Telescope
(VLT) to search for potential companions. For each identified
candidate companion we determined the probability that it is
gravitationally bound to its host by performing common proper motion
checks and modelling of synthetic stellar populations around the host.
In addition, we derived contrast limits as a function of angular
separation to set upper limits on further companions in these systems.
We converted the derived contrast into mass thresholds using
AMES-Cond, AMES-Dusty, and BT-Settl models.
We detected new candidate companions around K2-38, WASP-72, WASP-80,
WASP-87, WASP-88, WASP-108, WASP-118, WASP-120, WASP-122, WASP123,
WASP-130, WASP-131, and WASP-137. The closest candidates were detected
at separations of 0.124"±0.007" and 0.189"±0.003" around WASP-108
and WASP-131; the measured K-band contrasts indicate that these are
stellar companions of 0.35±0.02M☉ and
0.62+0.05-0.04M☉, respectively. Including the re-detection
and confirmation of previously known companions in 13 other systems,
we derived a multiplicity fraction of 55.4+5.9-9.4%. For the
representative sub-sample of 40 hot Jupiter host stars among our
targets, the derived multiplicity rate is 54.8+6.3-9.9%. Our data
do not confirm any trend that systems with eccentric planetary
companions are preferably part of multiple systems. On average, we
reached a magnitude contrast of 8.5±0.9,mag at an angular separation
of 0.5". This allows us to exclude additional stellar companions with
masses higher than 0.08M☉ for almost all observed systems;
around the closest and youngest systems, this sensitivity is achieved
at physical separations as small as 10au.
Our study shows that SPHERE is an ideal instrument for detecting and
characterising close companions to exoplanetary host stars.Although
the second data release of the Gaia mission also provides useful
constraints for some of the systems, the achieved sensitivity provided
by the current data release of this mission is not good enough to
measure parallaxes and proper motions for all detected candidates. For
14 identified companion candidates further astrometric epochs are
required to confirm their common proper motion at 5σ
significance.
Description:
Fits images corresponding to the imagery presented in the paper. The
data are obtained with VLT/SPHERE/IRDIS. The data reduction is
performed with version 0.8.1 of PynPoint. Furthermore, the achieved
contrast performance that is presented in the paper is included in
this catalogue. This is valuable data, when combining several of these
surveys for companions to transiting exoplanet host stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 95 23 List of studied stars
table2.dat 101 29 Astrometry, photometry, background probability
and derived masses and effective temperatures
of identified candidate companions
det-lim.dat 46 4815 Contrast limits of our data reduction for
all targets
fits/* . 23 Individual fits images
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See also:
J/MNRAS/492/431 : A planetary-mass companion to a solar-type star (Bohn+, 2020)
Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Star Star name
10- 11 I2 h RAh Right Ascension (J2000)
13- 14 I2 min RAm Right Ascension (J2000)
16- 20 F5.2 s RAs Right Ascension (J2000)
21 A1 --- DE- Declination sign (J2000)
22- 23 I2 deg DEd Declination (J2000)
25- 26 I2 arcmin DEm Declination (J2000)
28- 31 F4.1 arcsec DEs Declination (J2000)
33- 35 I3 --- Nx Number of pixels along X-axis
37- 39 I3 --- Ny Number of pixels along Y-axis
41- 44 I4 Kibyte size Size of FITS file
46- 63 A18 --- FileName Name of FITS file, in subdirectory fits
65- 95 A31 --- Title Title of the FITS file
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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1- 8 A8 --- Star Host star name around which the companion
was detected
10 I1 --- CCID ID of the companion candidate
12- 21 A10 "date" Date Date of the observation
23- 27 F5.3 arcsec Sep Separation of the CC
29- 33 F5.3 arcsec e_Sep Uncertainty of CC separation
35- 39 F5.1 deg PA Position angle of the CC
41- 45 F5.1 deg e_PA Uncertainty of the CC PA
47- 51 F5.2 mag Kmag K band magnitude of the host star,
corrected for contribution of the CCs
53- 56 F4.2 mag DeltaK Magnitude difference between primary and CC
58- 61 F4.2 mag e_DeltaK Uncertainty in magnitude difference between
primary and CC
63 A1 --- Status [ABC] Status of the CC (1)
65- 71 F7.5 --- pbg Probability that CC is background object
73- 76 F4.2 Msun Mass ? Mass of the CC (2)
78- 81 F4.2 Msun B_Mass ? Upper threshold for CC mass
83- 86 F4.2 Msun b_Mass ? Lower threshold for CC mass
88- 91 I4 K Teff ? Effective temperature of the CC (2)
93- 96 I4 K B_Teff ? Upper threshold for CC temperature
98-101 I4 K b_Teff ? Lower threshold for CC temperature
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Note (1): Status of the CC as follows:
C = companion
B = background
A = ambiguous
Note (2): No mass and Teff are provided for background objects.
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Byte-by-byte Description of file: det-lim.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Star Star name
10- 13 F4.2 arcsec Sep Projected separation
15- 19 F5.2 mag DeltaKs Magnitude contrast Ks band
21- 25 F5.2 mag e_DeltaKs Uncertainty of magnitude contrast Ks band
27- 32 F6.2 Mjup Masslimit Average mass limit
34- 39 F6.2 Mjup E_Masslimit Upper mass limit
41- 46 F6.2 Mjup e_Masslimit Lower mass limit
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Acknowledgements:
Alexander Julian Bohn, bohn(at)strw.leidenuniv.nl
(End) A. Bohn [Leiden Obs., The Netherlands], P. Vannier [CDS] 13-Feb-2020