J/A+A/685/A5 TOI-815 light curves and RV sources (Psaridi+, 2024)
Discovery of two warm mini-Neptunes with contrasting densities orbiting the
young K3V star TOI-815.
Psaridi A., Osborn H., Bouchy F., Lendl M., Parc L., Billot N., Broeg C.,
Sousa S.G., Adibekyan V., Attia O., Bonfanti A., Chakraborty H.,
Collins K.A., Davoult J., Delgado-Mena E., Grieves N., Guillot T.,
Heitzmann A., Helled R., Hellier C., Jenkins J.M., Knierim H., Krenn A.,
Lissauer J.J., Luque R., Rapetti D., Santos N.C., Suarez O., Venturini J.,
Wilkin F.P., Wilson T.G., Winn J.N., Ziegler C., Zingales T., Alibert Y.,
Brandeker A., Egger J.A., Gandolfi D., Hooton M.J., Tuson A.,
Ulmer-Moll S., Abe L., Allart R., Alonso R., Anderson D.R.,
Anglada Escude G., Barczy T., Barrado D., Barros S.C.C., Baumjohann W.,
Beck M., Beck T., Benz W., Bonfils X., Borsato L., Bourrier V., Ciardi D.R.,
Collier Cameron A., Charnoz S., Cointepas M., Csizmadia S., Cubillos P.,
Lo Curto G., Davies M.B., Daylan T., Deleuil M., Deline A., Delrez L.,
Demangeon O.D.S., Demory B.-O., Dorn C., Dumusque X., Ehrenreich D.,
Erikson A., Lecavelier des Etangs A., de Miguel Ferreras E.D., Fortier A.,
Fossati L., Frensch Y.G.C., Fridlund M., Gillon M., Guedel M.,
Guenther M.N., Hagelberg J., Helling C., Hoyer S., Isaak K.G., Kiss L.L.,
Lam K., Laskar J., Lavie B., Lovis C., Magrin D., Marafatto L., Maxted P.,
McDermott S., Mekarnia D., Mordasini C., Murgas F., Nascimbeni V.,
Nielsen L.D., Olofsson G., Ottensamer R., Pagano I., Palle E., Peter G.,
Piotto G., Pollacco D., Queloz D., Ragazzoni R., Ramos D., Rando N.,
Rauer H., Reimers C., Ribas I., Seager S., Segransan D., Scandariato G.,
Simon A., Smith A., Stalport M., Steller M., Szabo G., Thomas N.,
Pritchard T.A., Udry S., Corral Van Damme C., Van Grootel V., Villaver E.,
Walter I., Walton N., Watkins C.N., West R.G.
<Astron. Astrophys. 685, A5 (2024)>
=2024A&A...685A...5P 2024A&A...685A...5P (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Radial velocities ;
Photometry ; Optical
Keywords: techniques: photometric - techniques: radial velocities -
planets and satellites: composition -
planets and satellites: detection -
planets and satellites: formation - stars: individual: TOI-815
Abstract:
We present the discovery and characterization of two warm
mini-Neptunes transiting the K3V star TOI-815 in a K-M binary system.
Analysis of the spectra and rotation period reveal it to be a young
star with an age of 200+400-200Myr. TOI-815b has a 11.2-day period
and a radius of 2.94±0.05 R⊕ with transits observed by TESS,
CHEOPS, ASTEP, and LCOGT. The outer planet, TOI-815c, has a radius of
2.62±0.10R⊕, based on observations of three non-consecutive
transits with TESS, while targeted CHEOPS photometry and radial
velocity follow-up with ESPRESSO were required to confirm the 35-day
period. ESPRESSO confirmed the planetary nature of both planets and
measured masses of 7.6±1.5M⊕
(ρP=1.64+0.33-0.31g/cm3) and 23.5±2.4M⊕
(ρP=7.2+1.1-1.0g/cm3) respectively. Thus, the planets have
very different masses, unlike the usual similarity of masses in
compact multi-planet systems. Moreover, our statistical analysis of
mini-Neptunes orbiting FGK stars suggests that weakly irradiated
planets tend to have higher bulk densities compared to those suffering
strong irradiation. This could be ascribed to their cooler
atmospheres, which are more compressed and denser. Internal structure
modeling of TOI-815b suggests it likely has a H-He atmosphere
constituting a few percent of the total planet mass, or higher if the
planet is assumed to have no water. In contrast, the measured mass and
radius of TOI-815c can be explained without invoking any atmosphere,
challenging planetary formation theories.
Description:
The TOI-815 system (TIC 102840239) was observed in TESS Sector 9 (2018
December 12 to 2019 January 06) in 30-min cadence and Sectors 36 (2021
March 07 to 2021 April 01) and 63 (2023 March 10 to 2023 April 06) in
20-s cadence. In Sectors 9 and 36, the target was imaged on CCD 2 of
camera 2, and in Sector 63, on CCD 1 of camera 2.
TOI-815 was jointly observed by two programs within the CHEOPS
guaranteed time observation (GTO): one targeting improved radius
precision for multi-planet systems detected by NASA TESS (CHESS;
PR0031) and the other targeted on confirming the orbital periods of
long-period candidates found by TESS (DUOS; PR0048). The observations
had an exposure time of 60s, typical duration of 5-7 orbits
(8.2-11.4h), and achieved efficiencies between 51 and 73% (e.g.,
due to Earth occultations, Earth's stray light contamination and
South Atlantic Anomaly crossings). We observed TOI-815 with ASTEP on
2021 April 04 but could only rule out an ingress of TOI-815b that was,
at the time, predicted to occur at BJD 2459309.02.
We observed an intended full transit window of TOI-815b on 2021
February 18 in Pan-STARRS z-short band using the LCOGT 1.0m network
node at South Africa Astronomical Observatory (SAAO).
We acquired 34 high-resolution spectroscopic observations of TOI-815
using ESPRESSO on the 8.2m Very Large Telescope (VLT) located in
Paranal, Chile. The observations were carried out between 2021 April
04 and 2022 December 04 as part of the observing programs
105.20P7.001, 109.23DX.001 and 110.2481.001 (PI: Bouchy), dedicated to
the characterization of warm mini-Neptune transiting exoplanets.
TOI-815 was also observed by the Wide Angle Search for Planets (WASP)
Transit survey in multiple years between 2006 and 2014, with the
observing season in each year spanning ∼120 nights. A total of 86000
photometric data points was obtained using 200mm, f/1.8 Canon lenses
until 2012 and 85mm f/1.2 Canon lenses after that. TOI-815 is by far
the brightest star in the extraction aperture.
Objects:
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RA (2000) DE Designation(s)
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10 23 29.25 -43 50 05.8 TOI-815 = TYC 7721-1451-1
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
lcs1.dat 38 123699 TESS photometry
lcs2.dat 139 3659 CHEOPS photometry
lcs3.dat 66 1236 LCOGT & ASTEP photometry
lcs4.dat 40 47050 WASP photometry
rvs.dat 93 28 ESPRESSO radial velocities
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Byte-by-byte Description of file: lcs1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Inst Instrument
6- 18 F13.5 d BJD Time (BJD)
20- 26 F7.5 --- Flux Flux
28- 34 F7.5 --- e_Flux Flux uncertainty
36- 38 A3 --- Sector TESS Sector
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Byte-by-byte Description of file: lcs2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Inst Instrument
8- 21 F14.6 d BJD Time (BJD)
23- 30 F8.6 --- Flux Flux
32- 39 F8.6 --- e_Flux Flux uncertainty
41- 50 F10.6 --- phi Roll angle
52- 62 F11.6 --- bg Background
64- 73 F10.6 --- centX X-centroid
75- 84 F10.6 --- centY Y-centroid
86- 95 F10.6 --- deltaT Temperature change
97-105 F9.6 --- Xoff X-offset
107-115 F9.6 --- Yoff Y-offset
117-139 A23 --- FileKey File key
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Byte-by-byte Description of file: lcs3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Inst Instrument
7- 20 F14.6 d BJD Time (BJD)
22- 29 F8.6 --- Flux Flux
31- 38 F8.6 --- e_Flux Flux uncertainty
40- 54 F15.6 --- Tot-cts ? Total counts
56- 66 F11.6 --- Ycen ? Y centroid
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Byte-by-byte Description of file: lcs4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Inst Instrument
6- 21 F16.8 d BJD Time (BJD)
23- 31 F9.6 --- Flux Flux
33- 40 F8.6 --- e_Flux Flux uncertainty
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Byte-by-byte Description of file: rvs.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Inst Instrument
10- 22 F13.5 d BJD Time (BJD)
24- 34 F11.5 m/s RV Radial velocity
36- 42 F7.5 m/s e_RV Radial velocity uncertainty
44- 53 F10.5 m/s FWHM FWHM
55- 61 F7.5 m/s e_FWHM FWHM uncertainty
63- 71 F9.5 --- BIS-Span Bisector span
73- 79 F7.5 --- e_BIS-Span Bisector span uncertainty
81- 88 F8.5 --- RHK RHK activity index
90- 93 F4.2 --- e_RHK RHK activity index uncertainty
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Acknowledgements:
Angelica Psaridi, angeliki.psaridi(at)unige.ch
(End) Patricia Vannier [CDS] 30-Jan-2024