Planetary-mass companions to a retired B star BD+37 3172 and a retired F star BD+42 2315
Andrzej Niedzielski, Robert Jaros, Artur Paczuski, Monika Adamów, Aleksander Wolszczan, Eva Villaver, Gracjan Maciejewski, Beata Deka-Szymankiewicz
TL;DR
The study addresses exoplanet detection around intermediate-mass, evolved stars by leveraging long-baseline, high-precision RV data from the PTPS survey obtained with HET/HRS and complemented by HARPS-N data. It applies a hybrid Keplerian fitting approach to archival RV measurements, revealing a planetary-mass companion to BD+37 3172 ($m_2\sin i=10.6\,M_{ m J}$, $P=1887.76$ d, $a=4.65$ AU, $e=0.59$) and another to BD+42 2315 ($m_2\sin i=0.55\,M_{ m J}$, $P=123.05$ d, $a=0.55$ AU, $e=0.73$), along with two preliminary spectroscopic binaries. BD+37 3172 hosts one of the most massive planetary-mass companions known around evolved stars, while BD+42 2315’s signal remains weak and requires more data to confirm, illustrating the challenges of detecting small-amplitude RV signals amid stellar oscillations. The work also reports two preliminary binaries (BD+56 2957 and HD 236555) as part of the archival program. Overall, the paper demonstrates the value of archival RV data in extending baselines for exoplanet detection around higher-mass hosts and informs theories of planet formation and evolution in this regime.
Abstract
Radial velocity searches may lead to detection of exoplanets at large orbital separations only if long-enough time-series of data are available. Therefore publication of precise measurements collected in the past is very valuable even if not successfully completed with a definitive detection. Here we present 309 precise ($σ$RV$\approx$5-7 m s$^{-1}$) multi-epoch radial velocities for 28 stars observed with the Hobby-Eberly Telescope and its High Resolution Spectrograph between 2004 and 2013. Based on the observations gathered we present a low mass companion ($m_{p}\sin{i}$ = 10.6 $M_{J}$ in 1887.76 $\pm$ 0.01 d, 4.65 au orbit with $e$ = 0.59 $\pm$ 0.01) to a K giant BD+37 3172 ($M$=3.75$\pm$ 0.86 M$_{\odot}$), and a planetary mass companion (m$_{p}\sin{i}$=0.55 M$_{J}$ in 123.05$\pm$0.04 day, 0.55 au orbit with e=0.73$\pm$0.03) to a K giant BD+42 2315 ($M$=1.38$\pm$ 0.30 M$_{\odot}$). We also present two preliminary detections of new spectroscopic binaries: BD+56 2957 (K5) and HD 236555 (G5).