Fermi LAT detection of a GeV flare from PKS 2142-75

ATel #2539; Eric Wallace (University of Washington, Seattle), on behalf of the Fermi LAT Collaboration
on 6 Apr 2010; 22:35 UT
Credential Certification: Teddy Cheung (ccheung@milkyway.gsfc.nasa.gov)

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The Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope, has observed an increasing gamma-ray flux from a source positionally consistent with the flat spectrum radio quasar PKS 2142-75 (J2000, RA = 21h47m12.7303s, Dec = -75d36m13.225s, Johnston et al., 1995 AJ, 110, 880; z = 1.139, Jauncey et al., 1978 ApJ, 219, L1). Preliminary analysis indicates that on April 4, the source was in a high state, with a flux (E>100MeV) of (1.1 ± 0.3) × 10-6 ph cm-2 s-1 (statistical uncertainty only). Because the source does not appear in the first Fermi LAT catalog (The Fermi-LAT Collaboration, arXiv:1002.2280), this high flux represents more than an order of magnitude increase over its average flux over the first year of Fermi operations.

Since Fermi operates in all-sky survey mode, regular monitoring of this blazar will continue. The blazar PKS 2142-75 will be one of the "LAT Monitored Sources" (http://fermi.gsfc.nasa.gov/ssc/data/policy/LAT_Monitored_Sources.html), and consequently, a preliminary, uncalibrated estimation of the daily gamma-ray flux observed by Fermi LAT will be publicly available (http://fermi.gsfc.nasa.gov/ssc/data/access/). In light of the ongoing activity of this source, we encourage multiwavelength observations. The Fermi LAT contact person for this source is Eric Wallace (wallacee@uw.edu).

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.