Fermi LAT detection of GeV gamma-ray activity from FR-I radio galaxy SBS 1343+537 and the FSRQ TXS 0946+181
ATel #16671; Stefano Ciprini (INFN Roma Tor Vergata & SSDC ASI), Fausto Casaburo (INFN Roma Tor Vergata & SSDC ASI), Federica Giacchino (INFN Roma Tor Vergata & SSDC ASI), C. C. Cheung (Naval Research Laboratory), on behalf of the Fermi Large Area Telescope Collaboration.
on 25 Jun 2024; 20:32 UT
Credential Certification: Stefano Ciprini (stefano.ciprini@ssdc.asi.it)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar, Quasar
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed enhanced gamma-ray activity from the FR-I radio galaxy SBS 1343+537, also known as RX J1345.7+5332, TXS 1344+537, and 4FGL J1346.5+5330 in the 14-year fourth Fermi-LAT catalog (4FGL) Data Release 4 (4FGL-DR4; Ballet et al. 2024, arXiv:2307.12546), with coordinates R.A. = 206.438980 deg, Dec = +53.547858 deg (J2000; Petrov & Taylor 2011, AJ, 142, 89). The redshift of SBS 1343+537 is z=0.1356 (SDSS16, Ahumada et al. 2020, ApJS, 249, 3). This FR-I radio galaxy is composed of a compact radio core, two-sided S-shaped precessing kpc-scale radio jets, and diffuse FR-I-like morphology also S-shaped and lobes, and showing also some blazar-like behavior (Pajdosz-Smierciak et al. 2022, MNRAS, 514, 2122).
Preliminary analysis indicates that SBS 1343+537 was in an elevated gamma-ray emission state on June 23, 2024 reaching a daily averaged gamma-ray flux (E>100MeV) of (2.4+/-0.9) X 10^-7 photons cm^-2 s^-1 (statistical uncertainties only) corresponding to a flux increase of a factor of about 30 with respect to the average flux reported in the 4FGL-DR4. The corresponding photon spectral index is 2.3+/-0.3, harder than the 4FGL-DR4 value of 2.678+/-0.081. This is the first time that the Fermi LAT Collaboration has reported enhanced gamma-ray activity from the radio galaxy SBS 1343+537.
The Fermi LAT also has observed enhanced gamma-ray activity from a source positionally consistent with the flat spectrum radio quasar TXS 0946+181, also known as MG1 J094941+1752, GB6 J0949+1752 and 4FGL J0949.2+1749 in the 4FGL-DR4 Catalog, with coordinates R.A. = 147.415678 deg, Dec = +17.880391 deg (J2000; Petrov & Taylor 2011, AJ, 142, 89). The redshift of TXS 0946+181 is z=0.693 (Schneider et al. 2010, AJ, 139, 2360).
Preliminary analysis indicates that TXS 0946+181 was in an elevated gamma-ray emission state on June 20, 2024, with a daily averaged gamma-ray flux (E>100MeV) of (2.2+/-1.0) X 10^-7 photons cm^-2 s^-1 (statistical uncertainties only), corresponding to a flux increase of a factor of about 30 with respect to the average flux reported in the 4FGL-DR4 Catalog. The corresponding photon index is 1.9+/-0.2, considerably harder than the 4FGL value of 2.504+/-0.107. This is the first time that the Fermi LAT Collaboration has reported enhanced gamma-ray activity from TXS 0946+181.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of both SBS 1343+537 and TXS 0946+181 will continue. We encourage multifrequency observations of these gamma-ray sources. For these sources, the Fermi-LAT contact persons are F. Casaburo (fausto.casaburo[at]roma2.infn.it), F. Giacchino (federica.giacchino[at]roma2.infn.it) , S. Ciprini (stefano.ciprini[at]roma2.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