High state of Mkn 421 in the hard X-rays

RXTE/ASM data revealed an increased activity in the 3-10 keV energy of the TeV gamma-ray loud blazar Mkn 421. Its intensity began to rise in the middle of April 2006, reached a maximum around mid May and decreased since then. Its intensity began to increase again around 10th of June, 2006. This second increase led to the triggering of a target-of-opportunity observation with INTEGRAL. The observation of this blazar by INTEGRAL started on June 14, 2006. The source is detected by both the IBIS/ISGRI imager and the JEM-X X-ray monitor. The flux level during the first two days of observation was ~25 mCrab in both 3-10 keV and 20-40 keV energy bands. From 2006-06-16T07:16 UTC, the fluxes increased to ~50 mCrab within 3 hours in both energy bands, and the source became detected in the 40-80 keV band with a flux of ~25 mCrab. The blazar will be monitored continually by INTEGRAL until July 25. Simultaneous observations with other telescopes and instruments are planned with the Metsahovi Radio Observatory at 37 GHz, with the KVA telescope in La Palma, with the VLBA at NRAO, and with SWIFT. MAGIC will also try to observe this source. Further follow-up observations of this source at all wavelengths are strongly encouraged.