Fermi LAT detection of enhanced gamma-ray emission from the Crab Nebula region
ATel #6401; J. Becerra (NASA/GSFC/UMD/CRESST), R. Buehler (DESY), E. Hays (NASA/GSFC), on behalf of the Fermi LAT Collaboration
on 19 Aug 2014; 14:51 UT
Credential Certification: Josefa Becerra Gonzalez (josefa.becerra@nasa.gov)
Subjects: Gamma Ray, >GeV, Transient, Pulsar
Preliminary LAT analysis indicates that the daily-averaged gamma-ray emission (E >100 MeV) from the direction of the Crab Nebula was (7.5+/-0.6) 10^-6 ph cm^-2 s^-1 (statistical errors only) on August 18. This is about a factor of 2.7 greater than the average gamma-ray flux of (2.75+/-0.02) x 10^-6 ph cm^-2 s^-1 reported in the second Fermi LAT catalog (2FGL, Nolan et al. 2012, ApJS, 199, 31). All fluxes given are the sums of the pulsar and nebular emission. This is the highest flux observed since 2013 October (ATel #5485) and the first flare since 2014 March (ATel #5971) . It has been increasing since 2014 August 15.
Fermi will interrupt the currently planned observations and maximize the coverage toward the Crab Nebula for at least 300 ks starting at around 14:30 UT today. This source is one of the "LAT Monitored Sources" and consequently a preliminary estimation of the daily gamma-ray flux observed by Fermi LAT is publicly available (link:http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/ ). We strongly encourage further multifrequency observations of this region. For this source the Fermi LAT contact person is Rolf Buehler (rolf.buehler@desy.de).
The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
