Three Red Giants With Substellar-Mass Companions

We present three giant stars from the ongoing Penn State-Toruń Planet Search with the Hobby-Eberly Telescope, which exhibit radial velocity (RV) variations that point to the presence of planetary-mass companions around them. BD+49 828 is a M=1.52+/- 0.22 {{M}_⊙ } K0 giant with a m sin i=1.6_-0.2^+0.4 {{M}_J} minimum mass companion in a = 4.2^+0.32_-0.2 AU (2590⁺³⁰⁰_-180d), e = 0.35^+0.24_-0.10 orbit. HD 95127, a log L/{{L}_⊙ }=2.28+/- 0.38, R=20+/- 9 {{R}_⊙ }, M=1.20+/- 0.22 {{M}_⊙ } K0 giant, has a m sin i = 5.01_-0.44^+0.61 {{M}_J} minimum mass companion in a = 1.28^+0.01_-0.01 AU (482⁺⁵_-5d), e = 0.11^+0.15_-0.06 orbit. Finally, HD 216536 is a M=1.36+/- 0.38 {{M}_⊙ } K0 giant with a msin i=1.47_-0.12^+0.20 {{M}_J} minimum mass companion in a=0.609_-0.002^+0.002 AU (148.6_-0.7^+0.7d), e = 0.38^+0.12_-0.10 orbit. Both HD 95127 b and HD 216536 b in their compact orbits are very close to the engulfment zone and hence prone to ingestion in the near future. BD+49 828 b is among the longest-period planets detected with the RV technique until now and it will remain unaffected by stellar evolution up to a very late stage of its host. We discuss general properties of planetary systems around evolved stars and planet survivability using existing data on exoplanets in more detail.

Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen.