# Starspots in contact and semi-detached binary systems

## TL;DR

This study analyzes starspots in eclipsing binary stars, revealing differences in properties between types and suggesting different formation mechanisms like mass transfer and magnetic activity.

## Contribution

It provides a comprehensive statistical analysis of starspots in contact and semi-detached binaries, highlighting differences between A- and W-type systems and their formation processes.

## Key findings

- Cool spots in W-type binaries resemble sunspots and dynamo-generated spots.
- Hot spot properties differ between A- and W-type binaries.
- Hot-spot size correlates with star temperature, orbital period, mass ratio, and fill-out factor.

## Abstract

We investigated the statistical properties of both cool and hot starspots in eclipsing binary stars. The starspot and binary parameters for contact and semi-detached systems were collected from literature, which were determined on the basis of synthetic light-curve analysis. We examined associations between these parameters. As a result, the cool spots in W-type binaries show properties similar to those of sunspots and starspots generated by dynamos, which differs from those of the cool spots in A-type binaries. The properties of hot spots also differ between the W- and A-type samples. From the physical properties of A- and W-type binaries, we infer that mass transfer is a dominant process for forming the hot spots in A-type binaries; and both mass transfer and magnetic activity can contribute to the formation of the hot spots in W-type binaries. Our results also indicate that the hot-spot size in the A-type sample is correlated with the temperature of spotted stars, orbital period, mass ratio, and fill-out factor.