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Fermi LAT detection of increasing gamma-ray activity of blazar PKS 1424-418

ATEL # 2104; F.Longo (INFN Trieste), G.Iafrate (INAF/OA Trieste), E.Hays (NASA GSFC) and M.Marelli (INAF/IASF Milano) on behalf of the Fermi Large Area Telescope Collaboration
on 30 Jun 2009; 22:17 UT
Password Certification: Francesco Longo (

Subjects: Gamma Ray, >GeV, Request for Observations, AGN

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed an increasing gamma-ray flux from a source positionally consistent with PKS 1424-418 at RA=14:27:56.3, Dec=-42:06:19.4 (J2000) (Johnston, K. J., et al. 1995, Astronomical Journal, 110, 880), and redshift z=1.524 (Stickel, M.; Fried, J. W.; Kuehr, H., 1989, Astronomy and Astrophysics Supplement Series, 80, 103).

Preliminary analysis indicates that this source has recently brightened beginning in the week 17-23 June 2009. On 28 June 2009 it reached a relatively high state with a gamma-ray flux (E>100MeV) of (6 +/- 2) x 10-7 ph cm-2 s-1 (statistical errors only) for that day. This is a factor of 10 higher than the average level observed in the first 9 months of all-sky monitoring (Aug 2008 - Apr 2009). The gamma-ray outburst may now be fading, thus we strongly encourage prompt followup observations. This source was previously detected by EGRET as 3EG J1429-4217. Recent optical flaring of the source is reported in ATEL #2103 (Hauser et al.).

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. For this source the Fermi LAT contact person is F.Longo (

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.

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