J/AJ/161/70 Radial velocities for WASP-107 with HIRES & CORALIE (Piaulet+, 2021)
WASP-107b's density is even lower: a case study for the physics of planetary gas
envelope accretion and orbital migration.
Piaulet C., Benneke B., Rubenzahl R.A., Howard A.W., Lee E.J., Thorngren D.,
Angus R., Peterson M., Schlieder J.E., Werner M., Kreidberg L., Jaouni T.,
Crossfield I.J.M., Ciardi D.R., Petigura E.A., Livingston J., Dressing C.D.,
Fulton B.J., Beichman C., Christiansen J.L., Gorjian V., Hardegree-
Ullman K.K., Krick J., Sinukoff E.
<Astron. J., 161, 70 (2021)>
=2021AJ....161...70P 2021AJ....161...70P
ADC_Keywords: Exoplanets; Stars, K-type; Radial velocities; Spectra, optical
Keywords: Exoplanet formation ; Planetary structure ; Exoplanet atmospheres
Abstract:
With a mass in the Neptune regime and a radius of Jupiter, WASP-107b
presents a challenge to planet formation theories. Meanwhile, the
planet's low surface gravity and the star's brightness also make it
one of the most favorable targets for atmospheric characterization.
Here, we present the results of an extensive 4yr Keck/HIRES
radial-velocity (RV) follow-up program of the WASP-107 system and
provide a detailed study of the physics governing the accretion of the
gas envelope of WASP-107b. We reveal that WASP-107b's mass is only 1.8
Neptune masses (Mb=30.5±1.7M⊕). The resulting
extraordinarily low density suggests that WASP-107b has a H/He
envelope mass fraction of >85% unless it is substantially inflated.
The corresponding core mass of <4.6M⊕ at 3σ is
significantly lower than what is traditionally assumed to be necessary
to trigger massive gas envelope accretion. We demonstrate that this
large gas-to-core mass ratio most plausibly results from the onset of
accretion at ≳1 au onto a low-opacity, dust-free atmosphere and
subsequent migration to the present-day ab=0.0566±0.0017au. Beyond
WASP-107b, we also detect a second, more massive planet
(Mcsini=0.36±0.04MJ) on a wide eccentric orbit
(ec=0.28±0.07) that may have influenced the orbital migration and
spin-orbit misalignment of WASP-107b. Overall, our new RV observations
and envelope accretion modeling provide crucial insights into the
intriguing nature of WASP-107b and the system's formation history.
Looking ahead, WASP-107b will be a keystone planet to understand the
physics of gas envelope accretion.
Description:
We collected a total of 60 radial-velocity measurements of WASP-107
over 56 nights between 2017 and 2020 using HIRES on the KeckI
telescope. The observations were conducted by the California Planet
Search (CPS; PI: Andrew Howard). The data were acquired using the "C2"
decker, integrating until the exposure meter reached 60000 counts
(signal-to-noise ratio (S/N)∼100/pixel, ∼15minutes).
We supplement our radial-velocity data set with 31 CORALIE
measurements obtained between 2011 and 2014.
Objects:
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RA (2000) DE Designation(s) (Period)
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12 33 32.84 -10 08 46.2 WASP-107 = WASP-107 (P=17d)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 41 91 Radial velocity and activity measurements
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See also:
I/259 : The Tycho-2 Catalogue (Hog+ 2000)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+A/575/A36 : BAGEMASS code (Maxted+, 2015)
J/ApJ/831/64 : Mass-metallicity relation for giant planets (Thorngren+, 2016)
J/ApJ/844/102 : KIC star parallaxes from asteroseismology vs Gaia (Huber+,2017)
J/AJ/153/215 : Photometry and spectroscopy of KELT-11 (Pepper+, 2017)
J/AJ/153/142 : Radial velocities systems hosting sub-Saturns (Petigura+, 2017)
J/ApJ/836/77 : A library of high-S/N optical spectra of FGKM stars (Yee+,2017)
J/ApJ/862/33 : Improved & expanded member. catalog for NGC752 (Agueros+, 2018)
J/AJ/155/165 : Dissipation in exoplanet hosts from tidal spin-up (Penev+,2018)
J/AJ/155/255 : Radial velocity & activity measurements of HAT-P-11 (Yee+,2018)
J/A+A/621/A49 : K2-18 HARPS time-series (Cloutier+, 2019)
J/ApJ/879/49 : Rotation periods for 171 Gaia members of NGC6811 (Curtis+,2019)
J/ApJ/874/L31 : Giant planet bulk & atmosphere metallicities (Thorngren+,2019)
J/AJ/160/90 : Stellar parameters for 13196 Kepler dwarfs (Angus+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 14 F14.6 d BJD [2455651/2459042] Barycentric Julian Date; TDB
16- 21 F6.2 m/s RVel [-29.01/37.27] Barycentric radial velocity
23- 27 F5.2 m/s e_RVel [1.43/13.05] Uncertainty in RVel
29- 33 F5.3 --- SHK [0.66/1.23]? SHK index
35- 39 F5.3 --- e_SHK [0.001]? Uncertainty in SHK
41- 41 I1 --- Tel [1/2] Instrument flag (1)
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Note (1): Instruments as follows:
1 = HIRES (60 occurrences)
2 = CORALIE (CORALIE RVs provided by D. Anderson.) (31 occurrences)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 01-Apr-2021