J/A+A/692/A83 Transmission spectrum of WASP-69b (Petit dit de la Roche+ 2024)
Detection of faculae in the transit and transmission spectrum of WASP-69b.
Petit dit de la Roche D.J.M., Chakraborty H., Lendl M., Kitzmann D.,
Pietrow A.G.M., Akinsanmi B., Boffin H.M.J., Cubillos P.E., Deline A.,
Ehrenreich D., Fossati L., Sedaghati E.
<Astron. Astrophys. 692, A83 (2024)>
=2024A&A...692A..83P 2024A&A...692A..83P (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Stars, diameters ;
Optical
Keywords: methods: observational - planets and satellites: atmospheres -
stars: activity - planets and satellites: individual: WASP-69b
Abstract:
Transmission spectroscopy is a powerful tool for understanding
exoplanet atmospheres. At optical wavelengths, it makes it possible to
infer the composition and the presence of aerosols in the atmosphere.
However, unocculted stellar activity can result in contamination of
atmospheric transmission spectra by introducing spurious slopes and
molecular signals.
We aim to characterise the atmosphere of the transiting exoplanet
WASP-69b, a hot Jupiter orbiting an active K star, and characterise
the host star's activity levels.
We obtained three nights of spectrophotometric data with the FORS2
instrument on the VLT, covering a wavelength range of 340-1100nm.
These were divided into 10nm binned spectroscopic light curves,
which were fit with a combination of gaussian processes and parametric
models to obtain a transmission spectrum. We performed retrievals on
the full spectrum with combined stellar activity and planet atmosphere
models.
We directly detect a facula in the form of a hot spot crossing event
in one of the transits and indirectly detect unocculted faculae
through an apparently decreasing radius towards the blue end of the
transmission spectrum. We determine a facula temperature of
ΔT=+644+427-263K for the former and a stellar coverage
fraction of around 30% with a temperature of ΔT=+231±72K for
the latter. The planetary atmosphere is best fit with a high-altitude
cloud deck at 1.4mbar that mutes atomic and molecular features. We
find indications of water and ammonia with
logH2O)=-2.01+0.54-0.86 and log(NH3)=-3.4+0.96-5.20
respectively and place 3σ upper limits on TiO (<10-7.65) and K
(<10-7). We see no evidence of Na which we attribute to the presence
of clouds.
Description:
Three files with tables with the wavelengths and planetary radii
(Rp/R*) of the WASP-69b transmission spectrum with errors. Data were
taken in the B, RI and z filters on 08-15-2017, 07-19-2017 and
08-19-2017 respectively.
Objects:
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RA (2000) DE Designation(s)
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21 00 06.19 -05 05 40.0 WASP-69 = TIC 248853232
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table-b.dat 23 27 Planetary radii in the B grism
table-ri.dat 24 34 Planetary radii in the RI grism
table-z.dat 23 33 Planetary radii in the z grism
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Byte-by-byte Description of file: table-b.dat table-ri.dat table-z.dat
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Bytes Format Units Label Explanations
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1- 5 I5 um lambda Wavelength bin center
7- 13 F7.5 --- Rp/R* Observed radius
15- 21 F7.5 --- e_Rp/R* Observed radius error
23- 24 A2 --- Grism Grism
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Acknowledgements:
Dominique Petit dit de la Roche, djmpetit(at)gmail.com
(End) Patricia Vannier [CDS] 29-Oct-2024