Tracking Advanced Planetary Systems (TAPAS) with HARPS-N VII. Elder suns with low-mass companions

Abstract

We present the current status of and new results from our search for exoplanets in a sample of solar-mass, evolved stars observed with the HARPS-N and the 3.6-m Telescopio Nazionale Galileo (TNG), and the High Resolution Spectrograph (HRS) and the 9.2-m Hobby Eberly Telescope (HET). The aim of this project is to detect and characterise planetary-mass companions to solar-mass stars in a sample of 122 targets at various stages of evolution from the main sequence (MS) to the red giant branch (RGB), mostly sub-gaints and giants, selected from the Pennsylvania-Toruń Planet Search (PTPS) sample, and use this sample to study relations between stellar properties, such as metallicity, luminosity, and the planet occurrence rate. This work is based on precise radial velocity (RV) measurements. We have observed the program stars for up to 11 years with the HET/HRS and the TNG/HARPS-N. We present the analysis of RV measurements with the HET/HRS and the TNG/HARPS-N of four solar-mass stars, HD 4760, HD 96992 , BD+02 3313, and TYC 0434-04538-1. We found that: HD 4760 hosts a companion with a minimum mass of 13.9 MJ (a=1.14 au, e=0.23); HD 96992 is a host to a msin i=1.14 MJ companion on a a=1.24 au and e=0.41 orbit, and TYC 0434-04538-1 hosts an msin i=6.1MJ companion on a a=0.66 au and e=0.08$ orbit. In the case of BD+02 3313 we found a correlation between the measured RVs and one of the stellar activity indicators, suggesting that the observed RV variations may originate in either stellar activity or be caused by the presence of an unresolved companion. We also discuss the current status of the project and a statistical analysis of the RV variations in our sample of target stars.

16 pages, 15 figures, accepted by Astronomy and Astrophysics

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