Issue |
A&A
Volume 680, December 2023
|
|
---|---|---|
Article Number | A8 | |
Number of page(s) | 14 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202346840 | |
Published online | 05 December 2023 |
Photometric follow-up of the 20 Myr old multi-planet host star V1298 Tau with CHEOPS and ground-based telescopes★
1
INAF – Osservatorio Astrofisico di Torino,
Via Osservatorio 20,
10025
Pino Torinese, Italy
e-mail: mario.damasso@inaf.it
2
INAF – Osservatorio Astrofisico di Catania,
Via S. Sofia 78,
95123
Catania, Italy
3
INAF – Osservatorio Astronomico di Padova,
Vicolo dell’Osservatorio 5,
35122
Padova, Italy
4
Aix-Marseille Univ., CNRS, CNES, LAM,
Marseille, France
5
Department of Physics, University of Rome “Tor Vergata”,
Via della Ricerca Scientifica 1,
00133
Rome, Italy
6
Max Planck Institute for Astronomy,
Königstuhl 17,
69117
Heidelberg, Germany
7
Gruppo Astrofili Catanesi,
Via Milo 28,
95125
Catania, Italy
8
Stockholm University, Department of Astronomy AlbaNova University Center,
106 91
Stockholm, Sweden
9
INAF – Osservatorio Astronomico di Palermo,
Piazza del Parlamento 1,
90134
Palermo, Italy
10
Instituto de Astrofísica de Canarias (IAC),
Calle Vía Láctea s/n,
38200
La Laguna, Tenerife, Spain
11
Departamento de Astrofísica, Universidad de La Laguna (ULL),
38206
La Laguna, Tenerife, Spain
12
Dipartimento di Fisica e Chimica E. Segré, Università di Palermo,
Via Archirafi 36,
90100
Palermo, Italy
13
Dipartimento di Matematica e Fisica, Università Roma Tre,
Via della Vasca Navale 84,
00146
Roma, Italy
14
Centro de Astrobiología CSIC-INTA,
Carretera de Ajalvir km 4,
28850
Torrejón de Ardoz, Madrid, Spain
Received:
8
May
2023
Accepted:
22
September
2023
Context. The 20 Myr old star V1298 Tau hosts at least four planets. Since its discovery, this system has been a target of intensive photometric and spectroscopic monitoring. To date, the characterisation of its architecture and planets’ fundamental properties has been very challenging.
Aims. The determination of the orbital ephemeris of the outermost planet V1298 Tau e remains an open question. Only two transits have been detected so far by Kepler/K2 and TESS, allowing for a grid of reference periods to be tested with new observations, without excluding the possibility of transit timing variations. Observing a third transit would allow for better constraints to be set on the orbital period and would also help in determining an accurate radius for V1298 Tau e because the previous transits showed different depths.
Methods. We observed V1298 Tau with the CHaracterising ExOPlanet Satellite (CHEOPS) to search for a third transit of planet e within observing windows selected to test three of the shortest predicted orbital periods. We also collected ground-based observations to verify the result found with CHEOPS. We reanalysed Kepler/K2 and TESS light curves to test how the results derived from these data are affected by alternative photometric extraction and detrending methods.
Results. We report the CHEOPS detection of a transit-like signal that could be attributed to V1298 Tau e. If so, that result would imply that the orbital period calculated from fitting a linear ephemeris to the three available transits is close to ~45 days. Results from the ground-based follow-up marginally support this possibility. We found that i) the transit observed by CHEOPS has a longer duration compared to that of the transits observed by Kepler/K2 and TESS; and ii) the transit observed by TESS is >30% deeper than that of Kepler/K2 and CHEOPS, and it is also deeper than the measurement previously reported in the literature, according to our reanalysis.
Conclusions. If the new transit detected by CHEOPS is found to be due to V1298 Tau e, this would imply that the planet experiences TTVs of a few hours, as deduced from three transits, as well as orbital precession, which would explain the longer duration of the transit compared to the Kepler/K2 and TESS signals. Another and a priori less likely possibility is that the newly detected transit belongs to a fifth planet with a longer orbital period than that of V1298 Tau e. Planning further photometric follow-up to search for additional transits is indeed necessary to solve the conundrum, as well as to pin down the radius of V1298 Tau e.
Key words: stars: individual: V1298 Tau / planetary systems / techniques: photometric
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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