Fermi-LAT detection of renewed gamma-ray activity from the FSRQs B2 0748+33 and PKS 0438-43

ATel #15028; I. Mereu (INFN Perugia) on behalf of the Fermi Large Area Telescope Collaboration
on 10 Nov 2021; 15:41 UT
Credential Certification: Isabella Mereu (mereuisabella@gmail.com)

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The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope, has observed strong gamma-ray emission from a source positionally consistent with the flat-spectrum radio quasar B2 0748+33, also known as 4FGL J0752.2+3313 (The Fermi-LAT Collaboration 2020, ApJS, 247, 33) and from a source positionally consistent with the flat-spectrum radio quasar PKS 0438-43, also known as 4FGL J0440.3-4333 (The Fermi-LAT Collaboration 2020, ApJS, 247, 33). B2 0748+33 has coordinates R.A. = 117.9736383 deg, Decl. = 33.2221719 deg (J2000; Petrov & Taylor 2011 AJ 142, 89) and redshift, z=1.9352 (Schneider et al. 2010 AJ 139, 2360). PKS 0438-43 has coordinates R.A. = 70.0715829 deg, Decl. = -43.5523894 deg (J2000; Johnston et al. 1995 AJ 110, 880) and redshift, z=2.852 (Morton et al. 1978 MNRAS 185, 735).

Preliminary analysis indicates that B2 0748+33 was in an elevated gamma-ray emission state on 2021 November 8, with a daily averaged gamma-ray flux (E>100MeV) of (6+/-2) X 10^-7 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of about 70 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL). The corresponding photon index is 2.9+/-0.4, and is consistent with the 4FGL value of 2.67+/-0.11. This is the second time that the Fermi-LAT Collaboration has announced flaring gamma-ray behavior from B2 0748+33 (see ATel #9590).

Preliminary analysis indicates that PKS 0438-43 was in an elevated gamma-ray emission state on 2021 November 8, with a daily averaged gamma-ray flux (E>100MeV) of (1.0+/-0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of about 160 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL). The corresponding photon index is 2.6+/-0.3, and is consistent with the 4FGL value of 2.76+/-0.16. This is the third time that the Fermi-LAT Collaboration has announced flaring gamma-ray behavior from PKS 0438-43 (see ATel #9854 and ATel #14446). This flaring activity is also detected by Swift in X-rays and reported in ATel #15027.

Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of these sources will continue. B2 0748+33 and PKS 0438-43 are part of the "LAT Monitored Sources" and their light curves are available at the Fermi Science Support Center page (see http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/ ). We encourage multifrequency observations of these sources. For these two sources, the Fermi-LAT contact person is C. C. Cheung (Teddy.Cheung at nrl.navy.mil).

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.