Coronal properties of planet-bearing stars

Abstract

Context. Do extrasolar planets affect the activity of their host stars? Indications for chromospheric activity enhancement have been found for a handful of targets, but in the X-ray regime, conclusive observational evidence is still missing. Aims. We want to establish a sound observational basis to confirm or reject major effects of Star-Planet Interactions (SPI) in stellar X-ray emissions. Methods. We therefore conduct a statistical analysis of stellar X-ray activity of all known planet-bearing stars within 30 pc distance for dependencies on planetary parameters such as mass and semimajor axis.Results. In our sample, there are no significant correlations of X-ray luminosity or the activity indicator L X /L bol with planetary parameters which cannot be explained by selection effects. Conclusions. Coronal SPI seems to be a phenomenon which might only manifest itself as a strong effect for a few individual targets, but not to have a major effect on planet-bearing stars in general.

Chromospheric activity of stars with planets

“…Stellar parameters and chromospheric and coronal activity indicators for the sample of stars without planets (Schmitt 1997). small outermost planets, a result corroborating the one obtained by Poppenhaeger et al (2010) for the relationship between X-ray luminosities and planetary parameters. In this context, the Spearman coefficients from the correlation study of log(R HK ) with log( L X L bol ), also displayed in Table 3, show a significant correlation between chromospheric and coronal activity indicators for stars with close-in planets.…”

“…In this context, the Spearman coefficients from the correlation study of log(R HK ) with log( L X L bol ), also displayed in Table 3, show a significant correlation between chromospheric and coronal activity indicators for stars with close-in planets. This correlation indicates that the relations found by Poppenhaeger et al (2010) between the coronal activity indicator and the planetary parameters must be the same as in our analysis of stellar chromospheric activity and the presence of planets around a star.…”

“…In the context of any planet-induced chromospheric activity, one should also expect more evident changes in log(R HK ) for such an aspect. Following the same strategy as used by Poppenhaeger et al (2010) in their analysis of the coronal X-ray emission behavior in stars with planets, we show the distribution of the chromospheric activity indicator log(R HK ) of stars with planets as a function of planetary distance log(1/a pl ) (Fig. 1).…”

“…Table 3 shows the result of such an analysis, with the Spearman's ρ rank correlation for various combinations of stellar quantities and planetary parameters, for two samples. The first is composed of 19 stars with X-ray lumisonity from Kashyap et al (2008), and the second is composed of 13 stars with X-ray luminosities from Poppenhaeger et al (2010). The first interesting aspect of this analysis is a possible anticorrelation between the chromospheric activity indicator and the planetary semi-major axis in stars hosting planets with a pl ≤ 0.20 AU for both samples.…”

Magnetism and activity of planet hosting stars

“…They attempt to correct for sample bias and estimate a planet-induced activity enhancement by a factor of 2. However, Poppenhaeger et al (2010) performed a more careful analysis with a more sensitive set of X-ray data and found no evidence for elevated activity among hosts of hot Jupiters. Scharf (2010) tentatively identified a relation between stellar L X and planet mass for close-in planets (that is not present for more distant planets) in ROSAT All-Sky Survey data.…”