Ferrmi-LAT detection of enhanced gamma-ray activity from the Crab Nebula in May 2019
ATel #12753; C. C. Cheung (NRL), on behalf of the Fermi Large Area Telescope Collaboration
on 13 May 2019; 18:48 UT
Credential Certification: Teddy Cheung (Teddy.Cheung@nrl.navy.mil)
Subjects: Gamma Ray, Transient, Pulsar
Referred to by ATel #: 16387
Preliminary Fermi-LAT analysis indicates enhanced gamma-ray activity from the Crab Nebula beginning on 2019 May 6, when the daily-averaged gamma-ray flux (E>100 MeV) was (3.8 +/- 0.4) x 10^-6 ph cm^-2 s^-1. Its daily flux peaked at (5.2 +/- 0.5) x 10^-6 ph cm^-2 s^-1 on May 11. The peak is 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). All fluxes given are the sums of the pulsar and nebular emission, and with statistical uncertainties only. These are the highest fluxes observed for the Crab since 2018 October (ATel #12095, #12105, #12125, #12148).
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.
