Coronae of an active fast rotator FR Cnc

TL;DR

This study provides the first detailed X-ray and optical analysis of the active fast-rotating star FR Cnc, revealing its coronal properties, rotational modulation, and surface activity correlations over 30 years.

Contribution

It offers the first comprehensive X-ray spectral and temporal analysis of FR Cnc, highlighting its coronal plasma characteristics and surface activity behavior.

Findings

X-ray spectra fit a two-temperature plasma model with 0.34 and 1.1 keV.

X-ray light curve shows ~17% rotational modulation.

X-ray luminosity remains stable over 30 years at ~4.85x10^{29} erg/s.

Abstract

We present the first detailed X-ray study and simultaneous optical observations of the active fast rotating star FR Cnc. The X-ray spectra are found to be explained by two-temperature plasma model with temperature of cool and hot components of 0.34 and 1.1 keV, respectively. The X-ray light curve in the 0.5 -- 2.0 keV energy band is found to be rotationally modulated with the degree of rotational modulation of ~17%. We have also found that the X-ray light curve is anti-correlated with the optical light and colour curves in the sense that maximum X-ray light corresponds to minimum optical light and cooler region on the surface of FR Cnc. The X-ray luminosity of FR Cnc is found to be almost consistent in the last 30 years with an average value of 4.85x10^{29} erg/s in the 0.5 -- 2.0 keV energy band.