No random transits in CHEOPS observations of HD 139139^*,**

Author(s)

R. Alonso, S. Hoyer, M. Deleuil, A. E. Simon, M. Beck, W. Benz, H. G. Florén, P. Guterman, L. Borsato, A. Brandeker, D. Gandolfi, T. G. Wilson, T. Zingales, Y. Alibert, G. Anglada, T. Bárczy, D. Barrado Navascues, S. C.C. Barros, W. Baumjohann, T. Beck, N. Billot, X. Bonfils, Ch Broeg, S. Charnoz, A. Collier Cameron, C. Corral van Damme, Sz Csizmadia, P. E. Cubillos, M. B. Davies, A. Deline, L. Delrez, O. D.S. Demangeon, B. O. Demory, D. Ehrenreich, A. Erikson, A. Fortier, L. Fossati, M. Fridlund, M. Gillon, M. Güdel, M. N. Günther, A. Heitzmann, Ch Helling, K. G. Isaak, L. L. Kiss, E. Kopp, K. W.F. Lam, J. Laskar, A. Lecavelier des Étangs, M. Lendl, D. Magrin, P. F.L. Maxted, Ch Mordasini, V. Nascimbeni, G. Olofsson, R. Ottensamer, I. Pagano, E. Pallé, G. Peter, G. Piotto, D. Pollacco, D. Queloz, R. Ragazzoni, N. Rando, H. Rauer, I. Ribas, N. C. Santos, G. Scandariato, D. Ségransan, A. M.S. Smith, S. G. Sousa, M. Stalport, Gy M. Szabó, N. Thomas, S. Udry, B. Ulmer, V. Van Grootel, J. Venturini, F. Verrecchia, N. A. Walton

Abstract

Context. The star HD 139139 (a.k.a. ‘the Random Transiter’) is a star that exhibited enigmatic transit-like features with no apparent periodicity in K2 data. The shallow depth of the events (-200 ppm - equivalent to transiting objects with radii of -1.5 R⊕ in front of a Sun-like star) and their non-periodicity constitute a challenge for the photometric follow-up of this star. Aims. The goal of this study is to confirm with independent measurements the presence of shallow, non-periodic transit-like features on this object. Methods. We performed observations with CHEOPS for a total accumulated time of 12.75 days, distributed in visits of roughly 20 h in two observing campaigns in years 2021 and 2022. The precision of the data is sufficient to detect 150 ppm features with durations longer than 1.5 h. We used the duration and times of the events seen in the K2 curve to estimate how many events should have been detected in our campaigns, under the assumption that their behaviour during the CHEOPS observations would be the same as in the K2 data of 2017. Results. We do not detect events with depths larger than 150 ppm in our data set. If the frequency, depth, and duration of the events were the same as in the K2 campaign, we estimate the probability of having missed all events due to our limited observing window would be 4.8%. Conclusions. We suggest three different scenarios to explain our results: 1) Our observing window was not long enough, and the events were missed with the estimated 4.8% probability. 2) The events recorded in the K2 observations were time critical, and the mechanism producing them was either not active in the 2021 and 2022 campaigns or created shallower events under our detectability level. 3) The enigmatic events in the K2 data are the result of an unidentified and infrequent instrumental noise in the original data set or its data treatment.

Organisation(s)

Department of Astrophysics

External organisation(s)

Institute of Astrophysics of the Canary Islands, University of La Laguna, Aix-Marseille Université, Universität Bern, Université de Genève, Stockholm University, Institute National Des Sciences De L'univers Division Technique, Osservatorio Astronomico, Università degli Studi di Torino, University of St. Andrews, University of Padova, Spanish National Research Council (CSIC), Institute of Space Studies of Catalonia (IEEC), Admatis Ltd., European Space Astronomy Centre (ESA), Universidade do Porto, Österreichische Akademie der Wissenschaften (ÖAW), University of Grenoble Alpes, Université de Paris, Science and Operations Department - Science Division (SCI-SC), Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), INAF-Osservatorio Astrofisico di Torino, Lund University, Université de Liège, Leiden University, Chalmers University of Technology, Technische Universität Graz, Eötvös Loránd University Budapest, Université de recherche Paris Sciences et Lettres, Université Paris VI - Pierre-et-Marie-Curie, Keele University, INAF-Osservatorio Astrofisico di Catania, University of Warwick, Eidgenössische Technische Hochschule Zürich, University of Cambridge, Technische Universität Berlin, Freie Universität Berlin (FU), Isotope Climatology and Environmental Research Centre, Space Science Data Center (SSDC) - Agenzia Spaziale Italiana (ASI), INAF - Osservatorio Astronomico di Roma

Journal

Astronomy and Astrophysics

Volume

680

No. of pages

7

ISSN

0004-6361

Publication date

12-2023

Peer reviewed

Yes

Austrian Fields of Science 2012

103004 Astrophysics, 103003 Astronomy, 103038 Space exploration

Keywords

ASJC Scopus subject areas

Astronomy and Astrophysics, Space and Planetary Science

Portal url

https://ucrisportal.univie.ac.at/en/publications/ba7f7fbf-a2fc-4c82-86ed-6d11f59252ea