Gamma-ray flare of high-redshift blazar GB 1508+5714 detected by Fermi/LAT
ATel #15202; A. Gokus (Remeis-Observatory/ECAP & JMU Wuerzburg), M. Kreter (NWU), M. Kadler (JMU Wuerzburg), F. McBride (PSU), S. Buson (JMU Wuerzburg), R. Ojha (NASA), E. Ros (MPIfR), J. Sinapius (DESY), on behalf of the LAT collaboration, M. Boettcher (NWU), J. Hodgson (KASI), J. Wilms (Remeis-Observatory/ECAP)
on 5 Feb 2022; 16:24 UT
Credential Certification: Andrea Gokus (andrea.gokus@fau.de)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar, Quasar
Referred to by ATel #: 15203
We report on the detection of a gamma-ray flare of the source 4FGL J1510.1+5702 (The Fermi-LAT collaboration 2020, ApJS, 247, 33) which is positionally consistent with the high-redshift (z=4.31; Hook et al., 1995, MNRAS, 273, L63) flat-spectrum radio quasar GB 1508+5714 at RA = 15:10:02.920, +57:02:43.367 (J2000; Gaia EDR3), also known as TXS 1508+571.
The source is one of 81 high-z sources for which we monitor their 30-day average detection significance with data from the Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope.
Our detection strategy follows the method described in Kreter et al. 2020, ApJ 903, 128.
Our pipeline signaled a detection of GB 1508+5714 in the energy range from 100 MeV to 300 GeV on February 4. A cross-check LAT analysis confirmed the flare, and found that the flare takes place on shorter-than 30 days time scales. In a five-day interval (January 31 0:00 UTC - February 4 23:59 UTC), the detection significance was ~7 sigma. The five-day average flux of (1.7 +/- 0.4) x 10^-7 ph/cm^2/s (statistical uncertainty only) exceeds the flux reported in the fourth Fermi-LAT catalog (4FGL) by a factor of 25. The corresponding photon index of 2.42 +/- 0.21 is significantly harder than the 10-year average in the 4FGL (2.93 +/- 0.09).
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of GB 1508+5714 will continue. Given that the source is among the most distant blazars detectable at gamma-ray energies, multi-wavelength follow-up observations of the blazar in its current flaring state are highly encouraged.
