A ToO observation to observe MKN 421 at RA, Dec = 166.1138, 38.2088 (J2000) was approved at 2013-04-12 18:57:00 UTC.
The justification for the ToO is: Mrk 421 is a well-studied, highly variable, nearby blazar. It is one of the brightest TeV sources and has been unusually active since March at TeV energies; The past 48 hours are particularly exceptional in terms of both flux, as well as broad-band coverage due to an intense campaign with NuStar / Swift / MAGIC / VERITAS and others. On 4/12 UTC, VERITAS observed Mkn 421 to be in a >4 Crab flux state for 6 continuous hours, with a peak flux of ~8 Crab. Preliminary reports from MAGIC indicate peak fluxes near 10 Crab & Swift light curves show ~150 cts / s. Intense coverage with MAGIC, VERITAS, Swift and NuStar will continue through the weekend. Given the rapid variations typically observed, strictly simultaneous, continuous LAT coverage is requested, particularly during the TeV windows
The planned duration is 260.00 ks.
The autonomous request threshold during this ToO is LOW.
The ToO observation should begin between 2013-04-12 18:56:59 UTC and 2013-04-19 18:56:59 UTC.
The ToO observation was requested by DR. WYSTAN BENBOW.