J/A+A/646/A157 HD 108236 CHEOPS light curves (Bonfanti+, 2021)
CHEOPS observations of the HD 108236 planetary system:
a fifth planet, improved ephemerides, and planetary radii.
Bonfanti A., Delrez L., Hooton M.J., Wilson T.G., Fossati L., Alibert Y.,
Hoyer S., Mustill A.J., Osborn H.P., Adibekyan V., Gandolfi D., Salmon S.,
Sousa S.G., Tuson A., Van Grootel V., Cabrera J., Nascimbeni V.,
Maxted P.F.L., Barros S.C.C., Billot N., Bonfils X., Borsato L., Broeg C.,
Davies M.B., Deleuil M., Demangeon O.D.S., Fridlund M., Lacedelli G.,
Lendl M., Persson C., Santos N.C., Scandariato G., Szabo Gy.M.,
Collier Cameron A., Udry S., Benz W., Beck M., Ehrenreich D., Fortier A.,
Isaak K.G., Queloz D., Alonso R., Asquier J., Bandy T., Barczy T.,
Barrado D., Barragan O., Baumjohann W., Beck T., Bekkelien A., Bergomi M.,
Brandeker A., Busch M-D., Cessa V., Charnoz S., Chazelas B.,
Corral Van Damme C., Demory B.-O., Erikson A., Farinato J., Futyan D.,
Garcia Munoz A., Gillon M., Guedel M., Guterman P., Hasiba J., Heng K.,
Hernandez E., Kiss L., Kuntzer T., Laskar J., Lecavalier des Etangs A.,
Lovis C., Magrin D., Malvasio L., Marafatto L., Michaelis H., Munari M.,
Olofsson G., Ottacher H., Ottensamer R., Pagano I., Palle E., Peter G.,
Piazza D., Piotto G., Pollacco D., Ragazzoni R., Rando N., Ratti F.,
Rauer H., Ribas I., Rieder M., Rohlfs R., Safa F., Salatti M.,
Segransan D., Simon A.E., Smith A.M.S., Sordet M., Steller M., Thomas N.,
Tschentscher M., Van Eylen V., Viotto V., Walter I., Walton N.A., Wildi F.,
Wolter D.
<Astron. Astrophys. 646, A157 (2021)>
=2021A&A...646A.157B 2021A&A...646A.157B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Photometry
Keywords: ephemerides - planets and satellites: detection -
planets and satellites: fundamental parameters -
stars: fundamental parameters
Abstract:
The detection of a super-Earth and three mini-Neptunes transiting the
bright (V=9.2mag) star HD108236 (also known as TOI-1233) was
recently reported on the basis of TESS and ground-based light curves.
We perform a first characterisation of the HD108236 planetary system
through high-precision CHEOPS photometry and improve the transit
ephemerides and system parameters.
We characterise the host star through spectroscopic analysis and
derive the radius with the infrared flux method.We constrain the
stellar mass and age by combining the results obtained from two sets
of stellar evolutionary tracks. We analyse the available TESS light
curves and one CHEOPS transit light curve for each known planet in the
system.
We find that HD108236 is a Sun-like star with
R*=0.877±0.008R☉, M*=0.869+0.0500.048M☉, and an age
of 6.7+4.05.1Gyr. We report the serendipitous detection of an
additional planet, HD108236 f, in one of the CHEOPS light curves. For
this planet, the combined analysis of the TESS and CHEOPS light curves
leads to a tentative orbital period of about 29.5days. From the light
curve analysis, we obtain radii of 1.615±0.051, 2.071±0.052,
2.539+0.0620.065, 3.083±0.052, and
2.017+0.052+0.057R⊕_ for planets HD108236 b to HD108236 f,
respectively. These values are in agreement with previous TESS-based
estimates, but with an improved precision of about a factor of two. We
perform a stability analysis of the system, concluding that the
planetary orbits most likely have eccentricities smaller than 0.1. We
also employ a planetary atmospheric evolution framework to constrain
the masses of the five planets, concluding that HD108236 b and
HD108236 c should have an Earth-like density, while the outer planets
should host a low mean molecular weight envelope.
The detection of the fifth planet makes HD108236 the third system
brighter than V=10mag to host more than four transiting planets.
The longer time span enables us to significantly improve the orbital
ephemerides such that the uncertainty on the transit times will be of
the order of minutes for the years to come. A comparison of the
results obtained from the TESS and CHEOPS light curves indicates that
for a V∼9mag solar-like star and a transit signal of 500ppm, one
CHEOPS transit light curve ensures the same level of photometric
precision as eight TESS transits combined, although this conclusion
depends on the length and position of the gaps in the light curve.
Description:
Three observation runs, or visits, of HD108236 were obtained with
CHEOPS. The first visit, of 18.33h duration, was obtained during the
IOC phase using exposure times of 42s. The other two visits, with a
total duration 18.63h and 17.04h, were obtained during routine
operations of the satellite using exposure times of 49s.
Objects:
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RA (2000) DE Designation(s)
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12 26 17.89 -51 21 46.2 HD 108236 = HIC 60689
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 169 3 List of fits files
fits/* . 3 Individual fits files
fig7.dat 74 788 *Detrended CHEOPS LC containing the transits of
HD 108236 c and HD 108236 e
fig8.dat 74 701 *Detrended CHEOPS LC containing the transits of
HD 108236 d
fig9.dat 74 610 *Detrended CHEOPS LC containing the transits of
HD 108236 b and HD 108236 f
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Note on fig7.dat: first visit, file key CHPR300046TG000101_V0102
Note on fig8.dat: second visit, file key CHPR100031TG015401_V0102
Note on fig9.dat: third visit, file key CHPR100031TG015702_V0102
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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 observations
24- 42 A19 "datime" Obs.date Observation date
44- 46 I3 Kibyte size Size of FITS file
48-127 A80 --- FileName Name of FITS file, in subdirectory fits
129-169 A41 --- Title Title of the FITS file
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Byte-by-byte Description of file: fig7.dat fig8.dat fig9.dat
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Bytes Format Units Label Explanations
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1- 24 E24.18 d Time Time of observation (JD)
26- 49 E24.18 --- Flux Detrended flux
51- 74 E24.18 --- e_Flux Error on flux
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Acknowledgements:
Andrea Bonfanti, Andrea.Bonfanti(at)oeaw.ac.at
History:
19-Feb-2021: on-line version
24-Mar-2021: fig7, fig8 and fig9 added
(End) Patricia Vannier [CDS] 08-Jan-2021