Fermi-LAT detection of record flaring activity from the blazar Ton 599 (4C +29.45)
ATel #15859; Simone Garrappa (Ruhr-University Bochum; DESY, Germany), Janeth Valverde (UMBC/NASA GSFC) on behalf of the Fermi Large Area Telescope Collaboration
on 14 Jan 2023; 20:48 UT
Credential Certification: Simone Garrappa (simone.garrappa@gmail.com)
Subjects: Gamma Ray, Request for Observations, AGN, Blazar
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed renewed gamma-ray activity from a source positionally consistent with the flat spectrum radio quasar Ton 599 (4C +29.45), also known as 4FGL J1159.5+2914 (The Fermi-LAT Collaboration 2022, ApJS, 260, 53), with coordinates RA = 179.8826413 deg, Decl. = 29.2455075 deg, (J2000; Johnston et al. 1995 AJ 110, 880) at z = 0.72449 (Adelman-McCarthy et al. 2008, SDSS6).
Preliminary analysis indicates that this source has been in a persistent, elevated gamma-ray emission state since April 2021 (ATel#14897). On January 10, 2023 the source was observed reaching a daily averaged gamma-ray flux (E>100MeV) of (3.7+/-0.3) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 22 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL). This could be the highest LAT daily flux ever observed for this source. The corresponding photon index is 1.89+/-0.05, indicating a harder spectrum than the 4FGL value of 2.19+/-0.01. Flaring of Ton 599 has recently been reported in gamma rays by AGILE (ATel #15853) and in X-rays by Swift (ATel #15854).
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. Preliminary Fermi-LAT light curves can be accessed via the Monitored Source List at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/Ton_599, and via the Fermi-LAT Light-Curve Repository at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/LightCurveRepository/source.html?source_name=4FGL_J1159.5+2914. We encourage multifrequency observations of this source. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact persons are S. Ciprini (stefano.ciprini@ssdc.asi.it) and D. J. Thompson (David.J.Thompson@nasa.gov).
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.
