| Issue |
A&A
Volume 668, December 2022
|
|
|---|---|---|
| Article Number | A26 | |
| Number of page(s) | 14 | |
| Section | Stellar structure and evolution | |
| DOI | https://doi.org/10.1051/0004-6361/202244501 | |
| Published online | 29 November 2022 | |
Companions to Kepler giant stars: A long-period eccentric sub-stellar companion to KIC 3526061 and a stellar companion to HD 187878⋆
1
Astronomical Institute, Czech Academy of Sciences, 251 65 Ondřejov, Czech Republic
e-mail: marie.karjalainen@asu.cas.cz
2
Thüringer Landessternwarte Tautenburg, Sternwarte 5, Tautenburg 07778, Germany
3
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
4
Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, Göttingen 37077, Germany
5
Center for Astronomy (ZAH/LSW), Heidelberg University, Königstuhl 12, 69117 Heidelberg, Germany
6
Heidelberg Institute for Theoretical Studies (HITS) gGmbH, Schloss-Wolfsbrunnenweg 35, 69118 Heidelberg, Germany
7
Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D bus 2401, Leuven 3001, Belgium
8
Astronomical Institute, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 18000 Praha 8, Czech Republic
9
Department of Theoretical Physics and Astrophysics, Masaryk University, Kotlářská 2, 61137 Brno, Czech Republic
10
McDonald Observatory and Center for Planetary Systems Habitability, The University of Texas, Austin, Texas, USA
11
Institut d’ Astronomie et d’ Astrophysique, Université Libre de Bruxelles C.P. 226, Boulevard du Triomphe, 1050 Bruxelles, Belgium
Received:
14
July
2022
Accepted:
19
September
2022
Context. Our knowledge of populations and the occurrence of planets orbiting evolved intermediate-mass stars is still incomplete. In 2010 we started a planet search programme among 95 giant stars observed by the Kepler mission to increase the sample of giant stars with planets and with reliable estimates of stellar masses and radii.
Aims. We present the two systems from our planet search programme whose companions we were able to characterise: KIC 3526061 and HD 187878.
Methods. We used precise stellar radial velocity measurements taken with four different echelle spectrographs to derive an orbital solution. We used Gaia astrometric measurements to obtain the inclination of the HD 187878 system and Kepler photometric observations to estimate the stellar mass and radius.
Results. We report the discovery of a sub-stellar companion and a stellar companion around two intermediate-mass red giant branch stars. KIC 3526061 b is most likely a brown dwarf with a minimum mass of 18.15 ± 0.44 MJupiter in a long-period eccentric orbit, with orbital period 3552−135+158 d and orbital eccentricity e = 0.85 ± 0.01. It is the most evolved system found having a sub-stellar companion with such a high eccentricity and wide separation. HD 187878 B has a minimum mass of 78.4 ± 2.0 MJupiter. Combining the spectroscopic orbital parameters with the astrometric proper motion anomaly, we derived an orbital inclination i = 9.8−0.6+0.4 deg, which corresponds to the companion’s mass in the stellar regime of 0.51−0.02+0.04 M⊙.
Conclusions. A sub-stellar companion of KIC 3526061 extends the sample of known red giant branch stars with sub-stellar companions on very eccentric wide orbits, and might provide a probe of the dynamical evolution of such systems over time.
Key words: methods: observational / techniques: radial velocities / techniques: spectroscopic / stars: individual: KIC 3526061 / stars: individual: HD 187878 / brown dwarfs
Full Tables 1 and 2 are only available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/668/A26
© M. Karjalainen et al. 2022
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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