Stellar obliquities and magnetic activities of Planet-Hosting Stars and Eclipsing Binaries based on Transit Chord Correlation

TL;DR

This study introduces a new statistical method to determine stellar obliquities and analyze magnetic activity patterns in planet-hosting stars and eclipsing binaries using transit anomaly correlations, with applications to space-based data.

Contribution

The paper presents a less assumption-dependent, automatable method for measuring stellar obliquities from transit anomalies, applied to a diverse sample of stars and binaries.

Findings

Obliquities for ten stars with hot Jupiters were determined.

Kepler-45, an M dwarf, has an obliquity less than 10 degrees.

Eclipsing binaries studied show obliquities consistent with zero.

Abstract

The light curve of an eclipsing system shows anomalies whenever the eclipsing body passes in front of active regions on the eclipsed star. In some cases, the pattern of anomalies can be used to determine the obliquity $\Psi$ of the eclipsed star. Here we present a method for detecting and analyzing these patterns, based on a statistical test for correlations between the anomalies observed in a sequence of eclipses. Compared to previous methods, ours makes fewer assumptions and is easier to automate. We apply it to a sample of 64 stars with transiting planets and 24 eclipsing binaries for which precise space-based data are available, and for which there was either some indication of flux anomalies or a previously reported obliquity measurement. We were able to determine obliquities for ten stars with hot Jupiters. In particular we found $\Psi \lesssim$10$^\circ$ for Kepler-45, which is only the second M dwarf with a measured obliquity. The other 8 cases are G and K stars with low obliquities. Among the eclipsing binaries, we were able to determine obliquities in 8 cases, all of which are consistent with zero. Our results also reveal some common patterns of stellar activity for magnetically active G and K stars, including persistently active longitudes.