Tracking Advanced Planetary Systems (TAPAS) with HARPS-N

V. A Massive Jupiter orbiting the very-low-metallicity giant star BD+03 2562 and a possible planet around HD 103485^⋆,⋆⋆

¹ Departamento de Física Teórica, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
e-mail: Eva.Villaver@uam.es
² Toruń Centre for Astronomy, Faculty of Physics, Astronomy and Applied Informatics, Nicolaus Copernicus University in Toruń, Grudziadzka 5, 87-100 Toruń, Poland
e-mail: Andrzej.Niedzielski@umk.pl
³ Department of Astronomy and Astrophysics, Center for Exoplanets and Habitable Worlds, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802, USA
⁴ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
⁵ Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
⁶ National Center for Supercomputing Applications, University of Illinois, Urbana-Champaign, 1205 W Clark St, MC-257, Urbana, IL 61801, USA
⁷ McDonald Observatory and Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1402, Austin, TX, 78712-1206, USA
⁸ INAF–Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy

Received: 20 January 2017
Accepted: 31 May 2017

Abstract

Context. Evolved stars with planets are crucial to understanding the dependency of the planet formation mechanism on the mass and metallicity of the parent star and to studying star-planet interactions.

Aims. We present two evolved stars (HD 103485 and BD+03 2562) from the Tracking Advanced PlAnetary Systems (TAPAS) with HARPS-N project devoted to RV precision measurements of identified candidates within the PennState – Toruń Centre for Astronomy Planet Search.

Methods. The paper is based on precise radial velocity (RV) measurements. For HD 103485 we collected 57 epochs over 3317 days with the Hobby-Eberly Telescope (HET) and its high-resolution spectrograph and 18 ultra-precise HARPS-N data over 919 days. For BD+03 2562 we collected 46 epochs of HET data over 3380 days and 19 epochs of HARPS-N data over 919 days.

Results. We present the analysis of the data and the search for correlations between the RV signal and stellar activity, stellar rotation, and photometric variability. Based on the available data, we interpret the RV variations measured in both stars as Keplerian motion. Both stars have masses close to Solar (1.11 M_⊙ HD 103485 and 1.14 M_⊙ BD+03 2562), very low metallicities ([Fe/H] = − 0.50 and − 0.71 for HD 103485 and BD+03 2562), and both have Jupiter planetary mass companions (m₂sini = 7 and 6.4 M_J for HD 103485 and BD+03 2562 resp.) in close to terrestrial orbits (1.4 au HD 103485 and 1.3 au BD+03 2562) with moderate eccentricities (e = 0.34 and 0.2 for HD 103485 and BD+03 2562). However, we cannot totally rule-out the possibility that the signal in the case of HD 103485 is due to rotational modulation of active regions.

Conclusions. Based on the current data, we conclude that BD+03 2562 has a bona fide planetary companion while for HD 103485 we cannot totally exclude the possibility that the best explanation for the RV signal modulations is not the existence of a planet but stellar activity. If the interpretation remains that both stars have planetary companions, they represent systems orbiting very evolved stars with very low metallicities, a challenge to the conditions required for the formation of massive giant gas planets.