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Fermi LAT detection of renewed gamma-ray activity from the FSRQ PKS 2255-282

ATel #16241; Sara Cutini (INFN Perugia) and Chiara Bartolini (Università di Trento, Università di Bari, INFN Bari) on behalf of Fermi-LAT collaboration
on 12 Sep 2023; 18:40 UT
Credential Certification: Isabella Mereu (mereuisabella@gmail.com)

Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar

Referred to by ATel #: 16288

The Large Area Telescope (LAT) onboard of Fermi Gamma-ray Space Telescope, has observed increasing gamma-ray flux from a source positionally consistent with the flat spectrum radio quasar PKS 2255-282, also known as 4FGL J2258.1-2759, (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 0.925840 (Jones et. al. 2009; MNRAS, 399, 683). A strong gamma-ray flare from this source was also detected by EGRET in 1997 (Macomb et. al. 1999, ApJ, 513, 652).

Preliminary analysis indicates that the source was in a high state on 2023 September 10 with a daily averaged gamma-ray flux (E>100MeV) of 1.5+/-0.2 x 10^-6 photons/cm^2/s, which represents an increase of a factor of 26 with respect to the flux in the 4FGL catalog, with a power law index of 2.3+/-0.1 (statistical errors only). On 2023 September 11 the daily flux increased to 2.2+/-0.2 x 10^-6 photons/cm^2/s (E>100MeV, statistical uncertainty only). This is the highest daily flux so far observed by Fermi-LAT from this source; previous flaring activity was reported in the ATel #3948.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. Further multi-wavelength observations are encouraged. For this source, the Fermi-LAT contact person is Sara Cutini (sara.cutini@pg.infn.it). The light curve of this source can be obtained from 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

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.