An X-Ray Flare from 47 Cas

Abstract

Using XMM-Newton observations, we investigate properties of a flare from the very active but poorly known stellar system 47 Cas. The luminosity at the peak of the flare is found to be 3.54 × 10³⁰ erg {{s}^-1}, which is ∼2 times higher than that at a quiescent state. The quiescent state corona of 47 Cas can be represented by two temperature plasma: 3.7 and 11.0 MK. The time-resolved X-ray spectroscopy of the flare show the variable nature of the temperature, the emission measure, and the abundance. The maximum temperature during the flare is derived as 72.8 MK. We infer the length of a flaring loop to be 3.3 × 10¹⁰ cm using a hydrodynamic loop model. Using the RGS spectra, the density during the flare is estimated as 4.0 × 10¹⁰ cm^-3. The loop scaling laws are also applied when deriving physical parameters of the flaring plasma.