Short Timescale Coronal Variability in Capella

TL;DR

This study uses high-resolution X-ray imaging to detect short-timescale variability in Capella's coronae, revealing fluctuations indicative of low-density plasma and low-lying loops, advancing understanding of stellar coronal dynamics.

Contribution

It provides the first detailed analysis of Capella's coronal variability at timescales under 50 ks using Chandra data, highlighting the presence of low-level fluctuations.

Findings

Variability detected at timescales < 20 ks.

Fluctuations at 2-7% level over Poisson noise.

Coronae likely consist of low-density plasma and low-lying loops.

Abstract

We analyze 205 ks of imaging data of the active binary, Capella, obtained with the Chandra High Resolution Camera Imager (HRC-I) to determine whether Capella shows any variability at timescales < 50 ks. We find that a clear signal for variability is present for timescales < 20 ks, and that the light curves show evidence for excess fluctuation over that expected from a purely Poisson process. This overdispersion is consistent with variability at the 2-7% level, and suggests that the coronae on the binary components of Capella are composed of low-density plasma and low-lying loops.