Coronae of an active fast rotator FR Cnc

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 $$\sim$$ 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 $$4.85\times 10^{29}$$ erg $$\hbox {s}^{-1}$$ in the 0.5–2.0 keV energy band.