Fermi-LAT detection of enhanced gamma-ray activity from the gamma-ray source 4FGL J1706.8+1319
ATel #16201; Denis Bernard (LLR, Ecole Polytechnique & CNRS / IN2P3), on behalf of the Fermi Large Area Telescope Collaboration
on 23 Aug 2023; 14:54 UT
Credential Certification: Denis Bernard (Denis.bernard@in2p3.fr)
Subjects: Gamma Ray, >GeV, Request for Observations, Blazar, Quasar
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed enhanced gamma-ray activity from a source positionally consistent with the gamma-ray source 4FGL J1706.8+1319 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates (J2000) R.A. = 256.72 deg, Decl. = +13.33 deg. 4FGL J1706.8+1319 is associated with the ROSAT source 1RXS J170639.5+13193, and the 1-day transient localization is also consistent with this counterpart.
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on 21 August 2023, with a daily averaged gamma-ray flux (E>100MeV) of (1.1 +/- 0.3) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 90 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL). This is the highest LAT daily flux ever observed for this source. The corresponding photon index is 2.3 +/- 0.2, and is significantly smaller than the 4FGL value of 3.0 +/- 0.2.
The daily-transient detection has best-fit coordinates R.A. = 256.83 deg, Decl. = +13.49 deg (J2000), and a 68% uncertainty radius of 0.19 deg. Within the daily-transient localization is the flat-spectrum radio quasar BZQ J1707+1331, with coordinates R.A. = 256.940155 deg, Decl. = 13.518120 (J2000, Beasley et al., 2002, ApJS, 141, 13) and redshift z = 0.936 (Makarov et al., 2019, ApJ, 873, 132).
On the following day, 22 August 2023, the flux, measured with the same conditions, increased to (1.6 +/- 0.4) X 10^-6 photons cm^-2 s^-1, with a similar index of 2.4 +/- 0.2, with 4FGL J1706.8+1319 and BZQ J1707+1331 within the 99% and the 68% uncertainty radius, respectively.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. This source is being added to the "LAT Monitored Sources" and consequently, a preliminary estimation of the daily gamma-ray flux observed by Fermi-LAT will be publicly available ( http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/ ). We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Denis Bernard (denis.bernard@in2p3.fr).
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.
