Fermi LAT detection of increased gamma-ray activity from the FSRQ PKS 2255-282
ATel #16288; Pfesesani van Zyl (South African Radio Astronomy Observatory, SARAO-HartRAO) and Janeth Valverde (UMBC/ NASA GSFC) on behalf of the Fermi-LAT collaboration
on 13 Oct 2023; 16:32 UT
Credential Certification: Janeth Valverde (valverde@llr.in2p3.fr)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar, Quasar
The Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope, has observed increased gamma-ray flux from a source positionally consistent with the flat spectrum radio quasar (FSRQ) PKS 2255-282, also known as 4FGL J2258.1-2759Â (The Fermi-LAT collaboration 2020, ApJS, 247, 33); R.A.=344.524875 deg, Dec.= -27.972556 deg, (J2000; Lanyi et. al. 2010, AJ, 139, 1695) which has a redshift of 0.92584 (Jones et. al. 2009, MNRAS, 399, 683).Â
Preliminary analysis indicates that the source was in a high state on October 10 and 11, 2023 reaching a daily averaged gamma-ray flux (E>100MeV) of (2.1+/-0.2) x 10^-6 photons/cm^2/s (statistical errors only). This corresponded to a flux increase of a factor of 35 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL) catalog. On October 10, the photon index was reported as 1.7+/-0.1, corresponding to a significantly lower spectrum than the 4FGL value of 2.29+/-0.03. Previous flaring activity on this source was reported in ATels #3948 and #16241.
Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. Further multi-wavelength observations are encouraged. A preliminary light curve for PKS 2255-282 can be accessed via the Fermi-LAT Light-Curve Repository at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/LightCurveRepository/source.html?source_name=4FGL_J2258.1-2759. For this source, the Fermi LAT contact person is Sara Cutini (sara.cutini at pg.infn.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.
