Problems with exoplanets around sdBV and sdO stars from primary Kepler field

Abstract

The existence of exoplanets around evolved objects is one of the most interesting subjects from the viewpoint of planetary system evolution and its fate. What happens to the exoplanets engulfed in the host star envelope during red giant branch (RGB) phase? Can planets survive this evolutionary stage of the host star? Here, we are showing that at least some of the exoplanetary candidates recently found around a couple of sdBV stars, KIC 5807616 and KIC 10001893, might not be exoplanets after all. One “exoplanetary signal” visible in the light curve FT of KIC 10001893 can be just a frequency combination of stellar pulsation modes, while others are likely artifacts. Similarly, low frequency signals found in KIC 5807616 light curve FT, are beating frequencies of stellar oscillations, rather than resulting from the exoplanetary radiation. We also analyzed frequency and amplitude changes of the signal around 0.256 c/d (∼3.9 day) visible in the light curve FT of the KIC 10449976 sdO star. Our simulations show that it is difficult to reproduce the observed signal frequency variations by the weather changes in the exoplanet atmosphere.

The quest for planets around subdwarfs and white dwarfs fromKeplerspace telescope fields

“…While the vast majority of them have been detected around main sequence stars, the number of detected exoplanets around subdwarfs or white dwarfs (WD) is very low. There have been reports of the discovery of exoplanets around horizontal (Setiawan et al 2010) and extreme-horizontal branch stars, that is, around helium (sdO) stars (Bear & Soker 2014) and type B subdwarf (sdB) stars (Silvotti et al 2007(Silvotti et al , 2014Geier et al 2009;Charpinet et al 2011; see the summary by Heber 2016), but in most cases these planetary candidates were refuted in later papers (Jones & Jenkins 2014;Krzesinski et al 2020;Krzesinski 2015;Blokesz et al 2019). What remains are the two announcements by Silvotti et al (2007) and Geier et al (2009) which, as of yet, have no counterpart papers disputing the existence of the exoplanets.…”