Fermi-LAT detection of increasing GeV gamma-ray activity from blazars 4C +33.06 and OQ 334

ATel #17854; Stefano Ciprini (INFN Roma Tor Vergata & SSDC ASI) on behalf of the Fermi Large Area Telescope Collaboration
on 23 Jun 2026; 17:56 UT
Credential Certification: Stefano Ciprini (stefano.ciprini@roma2.infn.it)

Tweet

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed enhanced gamma-ray activity from a source positionally consistent with the flat spectrum radio quasar 4C +33.06, also known as B2 0301+33 and 4FGL J0304.5+3349 (Abdollahi et al. 2022, ApJS, 260, 53), with coordinates R.A. = 46.17234 deg, Dec. = 33.81209 deg (J2000; Xu et al., 2019, ApJS, 242, 5), and redshift z=0.68 (Alvarez Crespo et al., 2025, A&A, 694, 46).

Preliminary analysis indicates that 4C +33.06 (B2 0301+33) was in an elevated gamma-ray emission state on June 20, 2026, with a daily averaged gamma-ray flux (E>100MeV) of (0.8+/-0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux of more than 90 times the average flux reported in the fourth data release of the fourth Fermi-LAT source catalog (4FGL-DR4, Ballet et al. 2023, arXiv:2307.12546). The corresponding photon index is 2.0+/-0.2, indicating a harder spectrum than the 4FGL-DR4 value of 2.58 +/- 0.08. This is the second time that the Fermi-LAT Collaboration reports enhanced gamma-ray activity from 4C +33.06 after ATel #17769 and the highest flux, averaged on a 1-day interval, that has been observed from the source.

The Fermi LAT also has observed increasing gamma-ray activity from a source positionally consistent with the flat spectrum radio quasar OQ 334, also known as B2 1420+32, GB2 1420+326, and 4FGL J1422.5+3223 (Abdollahi et al. 2022, ApJS, 260, 53) on June 21, 2026, with radio coordinates R.A. = 215.62657 deg, Dec. = 32.38623 deg (J2000; Petrov & Taylor 2011, AJ, 142, 89), and a redshift z=0.6819 (Hewett & Wild 2010, MNRAS, 405, 2302).

Preliminary analysis indicates that OQ 334 (B2 1420+32) was in an elevated gamma-ray emission state on June 22, 2026, with a daily averaged gamma-ray flux (E>100MeV) of (3.8 +/- 0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux of more than 50 times the average flux reported in 4FGL-DR4 catalog (Ballet et al. 2023, arXiv:2307.12546). The corresponding photon index is 2.0+/-0.1, indicating a slightly harder spectral state than the one corresponding to the 4FGL-DR4 value of 2.24+/-0.01. The peak 6-hour integrated gamma-ray fluxes (E>100 MeV) of (4.2+/-0.5) X 10^-6 photons cm^-2 s^-1, were reached in the intervals 00:00-06:00 UT and 18:00-24:00 UT of June 22. The Fermi-LAT collaboration has previously reported gamma-ray flaring activity positionally consistent with OQ 334 in ATels #17790, #17654, #17504, #16680, #13382, #12942 and #12277.

Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of both 4C +33.06 and OQ 334 will continue. We encourage multifrequency observations of these gamma-ray sources. For 4C +33.06 the Fermi-LAT contact person is Fausto Casaburo (fausto.casaburo[at]inaf.it), for OQ 334 the Fermi-LAT contact persons are Stefano Ciprini (stefano.ciprini[at]roma2.infn.it) and Teddy Cheung (chi.c.cheung2.civ[at]us.navy.mil). Because OQ 334 belongs to the list of LAT daily monitored sources, a preliminary light curve is available at the FSSC Monitored Source List Light Curves page (for OQ 334). The light curves of 4C +33.06 and OQ 334 can also be accessed through the Fermi Light Curve Repository (for 4FGL J0304.5+3349 and for 4FGL J1422.3+3223 respectively).

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.