J/A+A/648/A73 Discovery of the directly imaged planet YSES 2b (Bohn+, 2021)
Discovery of a directly imaged planet to the young solar analog YSES 2.
Bohn A.J., Ginski C., Kenworthy M.A., Mamajek E.E., Pecaut M.J.,
Mugrauer M., Vogt N., Adam C., Meshkat T., Reggiani M., Snik F.
<Astron. Astrophys. 648, A73 (2021)>
=2021A&A...648A..73B 2021A&A...648A..73B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, pre-main sequence ; Stars, K-type ;
Stars, double and multiple ; Exoplanets
Keywords: planets and satellites: detection -
planets and satellites: formation -
instrumentation: high angular resolution -
techniques: image processing -
stars: individual: YSES 2 (TYC 8984-2245-1)
Abstract:
To understand the origin and formation pathway of wide-orbit gas giant
planets, it is necessary to expand the limited sample of these
objects. The mass of exoplanets derived with spectrophotometry,
however, varies strongly as a function of the age of the system and
the mass of the primary star. By selecting stars with similar ages and
masses, the Young Suns Exoplanet Survey (YSES) aims to detect and
characterize planetary-mass companions to solar-type host stars in the
Scorpius-Centaurus association.
Our survey is carried out with VLT/SPHERE with short exposure
sequences on the order of 5-min per star per filter. The subtraction
of the stellar point spread function (PSF) is based on reference star
differential imaging (RDI) using the other targets (with similar
colors and magnitudes) in the survey in combination with principal
component analysis. Two astrometric epochs that are separated by more
than one year are used to confirm co-moving companions by proper
motion analysis.
We report the discovery of YSES 2b, a co-moving, planetary-mass
companion to the K1 star YSES 2 (TYC 8984-2245-1, 2MASS
J11275535-6626046). The primary has a Gaia EDR3 distance of 110pc, and
we derive a revised mass of 1.1M☉ and an age of approximately
14Myr. We detect the companion in two observing epochs southwest of
the star at a position angle of 205° and with a separation of
∼1.05", which translates to a minimum physical separation of 115au at
the distance of the system. Photometric measurements in the H and Ks
bands are indicative of a late L spectral type, similar to the
innermost planets around HR 8799. We derive a photometric planet mass
of 6.3+1.6-0.9M{Jup} using AMES-COND and AMES-dusty evolutionary
models; this mass corresponds to a mass ratio of q=(0.5±0.1)% with
the primary. This is the lowest mass ratio of a direct imaging planet
around a solar-type star to date. We discuss potential formation
mechanisms and find that the current position of the planet is
compatible with formation by disk gravitational instability, but its
mass is lower than expected from numerical simulations. Formation via
core accretion must have occurred closer to the star, yet we do not
find evidence that supports the required outward migration, such as
via scattering off another undiscovered companion in the system. We
can exclude additional companions with masses greater than 13M{Jup}
in the full field of view of the detector (0.15"<ρ<5.50"), at 0.5"
we can rule out further objects that are more massive than 6M{Jup},
and for projected separations ρ>2arcsec we are sensitive to
planets with masses as low as 2M{Jup}.
YSES 2b is an ideal target for follow-up observations to further the
understanding of the physical and chemical formation mechanisms of
wide-orbit Jovian planets. The YSES strategy of short snapshot
observations (≤5min) and PSF subtraction based on a large reference
library proves to be extremely efficient and should be considered for
future direct imaging surveys.
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.
Objects:
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RA (2000) DE Designation(s)
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11 27 55.35 -66 26 04.5 YSES 2 = TYC 8984-2245-1
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
bhdetl.dat 34 106 *Contrast limits in H band as presented in Fig. 5
bhmassl.dat 34 106 *Mass limits in H band as presented in Fig. 5
bksdetl.dat 34 106 *Contrast limits in Ks band as presented in Fig. 5
bksmassl.dat 34 106 *Mass limits in Ks band as presented in Fig. 5
list.dat 134 2 List of fits images
fits/* . 2 Individual fits images
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Note on bhdetl.dat: The columns represent different PSF subtraction strategy for
either no subtraction or a subtraction using N principal components.
Note on bhmassl.dat: The columns represent different PSF subtraction strategy
for either no subtraction or a subtraction using N principal components.
Note on bksdetl.dat: The columns represent different PSF subtraction strategy
for either no subtraction or a subtraction using N principal components.
Note on bksmassl.dat: The columns represent different PSF subtraction strategy
for either no subtraction or a subtraction using N principal components.
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Byte-by-byte Description of file: b*detl.dat b*massl.dat
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Bytes Format Units Label Explanations
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1- 4 F4.2 arcsec Sep Projected separation
6- 10 F5.2 mag NoSub H band magnitude contrast without PSF
subtraction
12- 16 F5.2 mag PCA10 ?=- H band magnitude contrast with PSF
subtraction (10 principal components)
18- 22 F5.2 mag PCA20 ?=- H band magnitude contrast with PSF
subtraction (20 principal components)
24- 28 F5.2 mag PCA50 ?=- H band magnitude contrast with PSF
subtraction (50 principal components)
30- 34 F5.2 mag PCA100 ?=- H band magnitude contrast with PSF
subtraction (100 principal components)
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 30 I3 Kibyte size Size of FITS file
32- 41 A10 --- FileName Name of FITS file, in subdirectory fits
43-134 A92 --- Title Title of the FITS file
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Acknowledgements:
Alexander Julian Bohn, bohn(at)strw.leidenuniv.nl
(End) A.J. Bohn [Leiden Obs., The Netherlands], P. Vannier [CDS] 22-Mar-2021