Exceptional Flare of Mrk 421 at TeV energies
ATel #11184; Adrian Biland (ETH Zurich) for the FACT Collaboration
on 17 Jan 2018; 12:04 UT
Credential Certification: Daniela Dorner (email@example.com)
Subjects: Gamma Ray, >GeV, TeV, VHE, AGN, Blazar
The FACT collaboration reports an enhanced gamma-ray flux at TeV
energies from the high-energy peaked BL Lac type object Mrk 421
(z=0.031). The measurement of last night shows the second highest flux
of the source recorded in six years of monitoring with FACT.
Since December 2017, Mrk 421 has been showing already some activity at
TeV energies, as reported in the ATels #11077 and #11086 by the FACT
and HAWC collaborations.
The source was observed by FACT for a total of 5.5 hours between 1:15
UTC and 7:05 UTC (MJD 58135). At the beginning of the observation, the
source showed a flux of about 6-7 times that of the Crab Nebula (CU) at
TeV energies, then increasing to more than 9 CU. Over the whole
observation, the flux was varying between 3 and 10 CU with a decrease
towards the end of the night and an average flux of roughly 6 CU.
shows the nightly-binned background subtraced light curve since then
the 20-min-binned light curve of last night (MJD 58135).
FACT is regularly monitoring Mrk 421. Currently, observations of the
source are carried out each night from 1:00 UTC to 7:00 UTC, if the
observation conditions permit. The FACT contact person for this source
is Daniela Dorner (firstname.lastname@example.org)
The First G-APD Cherenkov Telescope (FACT) is an Imaging Atmospheric
Cherenkov Telescope with 9.5 sqm mirror area, located in the
Observatorio del Roque de los Muchachos on the Canary Island La Palma.
It is pioneering the usage of semi-conductor photo sensors (SiPM) and
monitoring bright, variable sources with an analysis threshold of 750
GeV. The Collaboration includes ETH Zurich and the Universities of
Dortmund, Geneva and Wuerzburg.