AstroSat detection of long-duration X-ray superflares on EQ Peg
Abstract
We present preliminary results of the study of three large long-duration flares detected on the active M-dwarf binary EQ~Peg using the Soft X-ray Telescope of the AstroSat observatory. The peak X-ray luminosities of the flares in the 0.3--7 keV band are found to be $\sim$4--10~$\times~10^{30}$ erg s$^{-1}$. Spectral analysis indicates that the corona of EQ~Peg has three dominant temperatures, with the first two plasma temperatures remaining constant during all the flares and the post-flare observation at $\sim$3 and $\sim$11~MK. The flare temperature peaked at 56, 40, and 31~MK, which are 2.5, 1.8, and 1.4 times the minimum value. The peak emission measures are found to be 1.16--5.64~$\times~10^{53}$~cm$^{-3}$, whereas the elemental abundances peaked at 0.7--1.2 times the solar abundances. Using quasi-static loop modeling, we estimated the loop lengths for all the flares to be on the order of $10^{11}$~cm. The estimated energies of all three flares are $>10^{33-35}$~erg, which put them in the category of superflare. Our study indicates that all three flares on EQ~Peg are associated with coronal mass ejections (CMEs). We estimated the CME mass and outward velocity of the CME mass are on the order of $10^{19}$~g and $\sim$5800--6500~km~s$^{-1}$, respectively. All three superflares are also found to be the longest duration flares ever observed on EQ~Peg.
- Publication:
-
The 20.5th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun (CS20.5)
- Pub Date:
- March 2021
- DOI:
- 10.5281/zenodo.4750801
- Bibcode:
- 2021csss.confE.332K
- Keywords:
-
- Cool Stars on the main sequence;
- stars: activity;
- stars: coronae;
- stars: flare;
- stars: individual (EQ Peg);
- stars: low-mass;
- stars: magnetic field