J/AJ/162/296 Gemini/GMOS transmission spectroscopy of WD 1856+534 b (Xu+, 2021)
Gemini/GMOS transmission spectroscopy of the grazing planet candidate
WD1856+534b.
Xu S., Diamond-lowe H., Macdonald R.J., Vanderburg A., Blouin S.,
Dufour P., Gao P., Kreidberg L., Leggett S.K., Mann A.W., Morley C.V.,
Stephens A.W., O'connor C.E., Thao P.C., Lewis N.K.
<Astron. J., 162, 296-296 (2021)>
=2021AJ....162..296X 2021AJ....162..296X (SIMBAD/NED BibCode)
ADC_Keywords: Exoplanets; Stars, white dwarf; Spectra, optical;
Spectra, infrared
Keywords: Exoplanet atmospheres; White dwarf stars; Extrasolar gaseous planets
Brown dwarfs
Abstract:
WD1856+534b is a Jupiter-sized, cool giant planet candidate transiting
the white dwarf WD1856+534. Here, we report an optical transmission
spectrum of WD1856+534b obtained from ten transits using the Gemini
Multi-Object Spectrograph. This system is challenging to observe due
to the faintness of the host star and the short transit duration.
Nevertheless, our phase-folded white light curve reached a precision
of 0.12%. WD1856+534b provides a unique transit configuration compared
to other known exoplanets: the planet is 8x larger than its star and
occults over half of the stellar disk during mid-transit.
Consequently, many standard modeling assumptions do not hold. We
introduce the concept of a "limb darkening corrected, time-averaged
transmission spectrum" and propose that this is more suitable than
(Rp,λ/Rs)2 for comparisons to atmospheric models for
planets with grazing transits. We also present a modified radiative
transfer prescription. Though the transmission spectrum shows no
prominent absorption features, it is sufficiently precise to constrain
the mass of WD1856+534b to be >0.84MJ (to 2σ confidence),
assuming a clear atmosphere and a Jovian composition. High-altitude
cloud decks can allow lower masses. WD1856+534b could have formed
either as a result of common envelope evolution or migration under the
Kozai-Lidov mechanism. Further studies of WD1856+534b, alongside new
dedicated searches for substellar objects around white dwarfs, will
shed further light on the mysteries of post-main-sequence planetary
systems.
Description:
We used the Gemini MultiObject Spectroscopy (GMOS) instrument at the
Gemini North Telescope to observe ten transits of WD1856+534b under
programs GN-2020A-DD-108 and GN-2020B-Q-131 (PI: S.Xu). We used the
R150 grating with a central wavelength of 0.69µm, which has a
spectral resolution of 631 for a 0.5" wide slit.
Objects:
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RA (2000) DE Designation(s) (Period)
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18 57 39.8 +53 30 32.5 WD 1856+534b = NAME WD 1856+534 b (P=1.40793925d)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 61 22 Derived transmission spectrum of WD1856+534b
fig6.jpg 512 2457 WD1856+534b transit and the associated
transmission spectrum
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
J/MNRAS/413/1121 : SDSS post-common envelope bin. X (Rebassa-Mansergas+ 2011)
J/MNRAS/417/1210 : DA-white dwarfs from SDSS and UKIDSS (Girven+, 2011)
J/MNRAS/426/739 : Velocities for seven transiting hot Jupiters (Hellier+, 2012)
J/ApJ/766/3 : Limb-darkening coefficients eclipsing WD* (Gianninas+, 2013)
J/A+A/605/A95 : CH4 & hot methane continuum hybrid line list (Yurchenko+, 2017)
J/AJ/156/18 : APOGEE DR14:Binary comp. of evolved stars (Price-Whelan+, 2018)
J/ApJ/878/63 : Cool WD atmos. models. IV. Spectral evolution (Blouin+, 2019)
J/MNRAS/490/4638 : ExoMol molecular line lists. XXXV. NH3 (Coles+, 2019)
J/other/Nat/576.61 : WDJ0914+1914 X-Shooter spectrum (Gansicke+, 2019)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 5 F5.3 um lambdamin [0.52/0.99] Lower wavelength range
7- 11 F5.3 um lambdamax [0.54/1.1] Upper wavelength range
13- 16 F4.2 --- q1 [0.09/0.24] q1 quadratic limb darkening parameter
18- 21 F4.2 --- e_q1 [0.07/0.2] Uncertainty in q1
23- 26 F4.2 --- q2 [0.04/0.18] q2 quadratic limb darkening parameter
28- 31 F4.2 --- e_q2 [0.08/0.3] Uncertainty in q2
33- 38 F6.4 --- Rp/R* [7.85/7.87] Planet to stellar radii ratio
40- 45 F6.4 --- e_Rp/R* [0.001/0.004] Uncertainty in Rp/R*
47- 52 F6.4 --- sigma [0.32/0.34] Limb darkening corrected
time-averaged transit depth
54- 59 F6.4 --- e_sigma [0.0006/0.002] Uncertainty in sigma
61 A1 --- Flag [e] Data excluded from atmosphere fitting (1)
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Note (1): see discussion in Section 4.1.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 14-Mar-2022