Enhanced gamma-ray activity from the Crab nebula
ATel #8519; R. Buehler (DESY) and S. Ciprini (ASDC Rome and INFN Perugia, Italy) on behalf of the Fermi LAT Collaboration
on 9 Jan 2016; 03:35 UT
Credential Certification: Elizabeth Hays (elizabeth.a.hays@nasa.gov)
Subjects: Gamma Ray, Transient, Pulsar
Preliminary LAT analysis indicates enhanced gamma-ray activity from the Crab nebula. The daily-averaged gamma-ray emission (E>100 MeV) from the direction of the Crab Nebula has surpassed 4.0 x 10^-6 ph cm^-2 s^-1 five times in the last 12 days. The daily flux measured on January 7th was (4.7 +/- 0.5) x 10^-6 ph cm^-2 s^-1 (statistical uncertainty only). This is about a factor of 1.7 greater than the average gamma-ray flux of (2.71 +/- 0.02) x 10^-6 ph cm^-2 s^-1 reported in the third Fermi-LAT source catalog (Acero et al. 2015, ApJS, 218, 23). All fluxes given are the sums of the pulsar and nebular emission. This is the highest flux observed for the Crab since 2014 August (ATel #6401).
Fermi will interrupt the currently planned observations and maximize the coverage toward the Crab nebula for at least 250 ks. 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.
