INTEGRAL observation of flaring activity of Mrk 421
Résumé
During this time the source was observed to be highly variable in both IBIS/ISGRI and JEM-X. Three flares were observed during this observation, respectively on June 16, 17 and 23. The strongest was the last one (detection significance of 30 sigma in both instruments), with maximal fluxes reaching ~92 mCrab in 3-10 keV, ~120 mCrab in 10-20 keV, ~110 mCrab in 20-40 keV and ~80 mCrab in 40-80 keV. A cutoff power law fit to the 3-200 keV spectrum obtained during the first 12 hours of this flare leads to a spectral index of 1.91 +- 0.03 and a cutoff energy of 98+-16 keV (90% confidence level). The flare on June 23 was also observed by the BAT of Swift at the 7.5-sigma level (see Bacodine notice from Swift from 23 June 06, 16:06:34 UT). In the energy interval 15 - 150 keV a flux of ~3.6E-2 photons/(cm² s) [~2.3E-9 erg/(cm² s)] was measured, with a power law spectral index of 1.9 +- 0.4 (90% confidence). Simultaneous ground-based observations were also performed at optical and radio wavelengths. Since the source seems to remain active further observations at all wavelengths are recommended.