Characterizing Superflares in HR 1099 Using Temporal and Spectral Analysis of XMM-Newton Observations

Abstract

In the present paper, we analyze three energetic X-ray flares from the active RS CVn binary HR 1099 using data obtained from XMM-Newton. The flare duration ranges from 2.8 to 4.1 hr, with e-folding rise and decay times in the range of 27-38 minutes and 1.3-2.4 hr, respectively, indicating rapid rise and slower decay phases. The flare frequency for HR 1099 is one flare per rotation period. Time-resolved spectroscopy reveals peak flare temperatures of 39.44, 35.96, and 32.48 MK, emission measures of 7 × 1053-8 × 1054 cm−3, global abundances of 0.250, 0.299, and 0.362 Z⊙, and peak X-ray luminosities of 1031.21−32.29 erg s−1. The quiescent state is modeled with a three-temperature plasma maintained at 3.02, 6.96, and 12.53 MK. Elemental abundances during quiescent and flaring states exhibit the inverse-first ionization potential (i-FIP) effect. We have conducted a comparative analysis of coronal abundances with previous studies and found evidence supporting the i-FIP effect. The derived flare semi-loop lengths of 6-8.9 × 1010 cm were found to be comparable to the other flares detected on HR 1099; however, they are significantly larger than typical solar flare loops. The estimated flare energies, ranging from 1035.83−37.03 erg, classify these flares as super-flares. The magnetic field strengths of the loops are found to be in the range of 350-450 G. We diagnose the physical conditions of the flaring corona in HR 1099 through the observations of superflares and provide inference on the plasma processes. © 2024. The Author(s). Published by the American Astronomical Society.