Fermi-LAT detection of enhanced gamma-ray activity from the FSRQs PKS 0837+012 and PKS 1127-14

ATel #14260; R. Angioni (SSDC/INFN) on behalf of the Fermi Large Area Telescope Collaboration
on 11 Dec 2020; 23:29 UT
Credential Certification: Roberto Angioni (r.angioni90@gmail.com)

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The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed enhanced gamma-ray activity from two sources. The first one is positionally consistent with the flat-spectrum radio quasar PKS 0837+012, also known as 4FGL J0839.8+0105 (The Fermi-LAT Collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 129.956713 deg, Decl. = 1.074093 deg (J2000; Beasley et al. 2002, ApJS, 141, 13), and redshift z=1.123 (Owen et al. 1995, AJ, 109, 14). The second one is positionally consistent with the flat-spectrum radio quasar PKS 1127-14, also known as 4FGL J1129.8-1447 (The Fermi-LAT Collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 172.529385 deg, Decl. = -14.824274 deg (J2000; Johnston et al. 1995, AJ, 110, 880), and redshift z=1.184 (Wilkes 1986, MNRAS, 218, 331).

Preliminary analysis indicates that PKS 0837+012 was in an elevated gamma-ray emission state on 10 December 2020, with a daily averaged gamma-ray flux (E>100MeV) of (5+/-1) X 10^-7 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of about 50 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+/-0.3, and is consistent with the 4FGL value of 2.41+/-0.06.

Preliminary analysis indicates that PKS 1127-14 was in an elevated gamma-ray emission state on 10 December 2020, with a daily averaged gamma-ray flux (E>100MeV) of (1.6+/-0.3) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of about 50 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 2.5+/-0.2, and is consistent with the 4FGL value of 2.72+/-0.05.

Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of these sources will continue. PKS 1127-14 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 these sources. For these sources, the Fermi-LAT contact person is Roberto Angioni (roberto.angioni@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.