Fermi-LAT detection of enhanced gamma-ray activity from the Crab nebula in October 2018
ATel #12095; C. C. Cheung (NRL), R. Angioni (MPIfR-Bonn), S. Buson (Univ. of Wuerzburg), T. Venters (NASA/GSFC), on behalf of the Fermi Large Area Telescope Collaboration
on 10 Oct 2018; 20:06 UT
Credential Certification: Teddy Cheung (Teddy.Cheung@nrl.navy.mil)
Subjects: Gamma Ray, Transient, Pulsar
Preliminary Fermi LAT analysis reveals enhanced gamma-ray activity from the direction of the Crab Nebula. The daily-averaged gamma-ray fluxes (E>100 MeV) from the direction of the Crab Nebula in the past three days were 5.6 +/- 0.2 (Oct 7), 5.0 +/- 0.4 (Oct 8), and 6.4 +/- 0.5 x 10^-6 ph cm^-2 s^-1 (Oct 9). These are a factor of ~2 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). The flux in the latest 6-hour interval on 2018 October 10 from 00h-04h UT was ~10 x 10^-6 ph cm^-2 s^-1. All fluxes given are the sums of the pulsar and nebular emission, and with statistical uncertainties only.
Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. 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 (https://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/Crab_Pulsar ). 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.
