Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ PKS 0805-07
ATel #15676; G. La Mura (LIP, Portugal) on behalf of the Fermi Large Area Telescope Collaboration
on 13 Oct 2022; 20:37 UT
Credential Certification: Giovanni La Mura (glamura@lip.pt)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Quasar
Referred to by ATel #: 15692
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 flat-spectrum radio quasar PKS 0805-07, also known as 4FGL J0808.2-0751 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 122.06473 deg, Decl. = -7.85275 deg (J2000; Johnston et al. 1995, AJ, 110, 880), and redshift z = 1.837 (White et al. 1988, ApJ, 327, 561).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on October 11, 2022, with a daily averaged gamma-ray flux (E>100MeV) of (1.4+/-0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 16 relative to the average flux reported in the third release of the fourth Fermi-LAT catalog (4FGL-DR3, Abdollahi et al. 2022, ApJS, 260, 53). The corresponding photon index is 1.97+/-0.09, and is significantly smaller than the 4FGL-DR3 value of 2.23+/-0.01. The spectral hardening persisted on October 12, 2022, when the source was detected with a flux of (1.2+/-0.2) X 10^-6 photons cm^-2 s^-1 (E>100MeV, statistical uncertainty only) and a spectral index of 1.98+/-0.10. This event represents the second strongest gamma-ray flare observed by LAT from this source after the (1.6+/-0.3) X 10^-6 photons cm^-2 s^-1 flux reported for July 22, 2009 (ATel #2136).
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. This source belongs to the list of daily monitored LAT sources, therefore a preliminary gamma-ray light curve is available at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/PKS_0805-07. Its light curve can also be accessed through the Fermi-LAT Light Curve Repository (LCR) at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/LightCurveRepository/source.html?source_name=4FGL_J0808.2-0751. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Stefano Ciprini (stefano.ciprini[at]ssdc.asi.it).
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.
