Fermi-LAT detection of a hard-spectrum gamma-ray flare from the FSRQ OQ 334/B2 1420+32

ATel #12942; R. Angioni (MPIfR-Bonn) on behalf of the Fermi Large Area Telescope Collaboration
on 14 Jul 2019; 20:45 UT
Credential Certification: Roberto Angioni (angioni@mpifr-bonn.mpg.de)

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The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed renewed gamma-ray flaring activity from a source positionally consistent with the flat-spectrum radio quasar OQ 334, also known as B2 1420+32 and 4FGL J1422.3+3223 (The Fermi-LAT Collaboration 2019, arXiv:1902.10045), with coordinates R.A. = 215.62658 deg, Decl. = 32.38623 deg (J2000; Petrov & Taylor 2011 AJ, 142, 89), and redshift z=0.681889 (Hewett & Wild 2010 MNRAS, 405, 2302).

Preliminary analysis indicates that this source was in an elevated gamma-ray emission state during the past three weeks, reaching a peak daily averaged gamma-ray flux (E>100MeV) of (8.9+/-1.1) X 10^-7 photons cm^-2 s^-1 (statistical uncertainty only) on 13 July. The latter corresponds to a flux increase of a factor of about 110 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL). The corresponding photon index is 1.83+/-0.08, and is significantly smaller than the 4FGL value of 2.38+/-0.07. The source showed an even harder spectrum on 25 June, 5 July and 12 July, with a photon index 1.62+/-0.12, 1.65+/-0.16 and 1.60+/-0.10, respectively. The current flux is still somewhat lower than the one observed in December 2018 (see ATel #12277); however, the spectrum on 25 June, 5 July and 12 July was harder. This hard-spectrum state coincided with the detection of several E>10 GeV photons (up to about 26 GeV) with a probability >99% of being produced by the target source, particularly in the past two days. The ongoing activity in gamma-rays has been accompanied by prominent flaring in the NIR (see ATel #12866) and optical (see ATels #12886, #12887, #12914).

Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. This source is included in 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/). Target of opportunity observations with the Neil Gehrels Swift observatory have been triggered. We strongly encourage further multifrequency observations of this source. For this source, the Fermi-LAT contact persons are R. Angioni (angioni@mpifr-bonn.mpg.de) and S. Ciprini (stefano.ciprini@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.