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Fermi-LAT detection of GeV gamma-ray emission from CRATES J0531-4827

ATEL # 2907; A. Cannon (University College Dublin, NASA/GSFC) and F. D'Ammando (INAF-IASF Palermo) on behalf of the Fermi Large Area Telescope Collaboration
on 5 Oct 2010; 22:46 UT
Password Certification: Filippo D'Ammando (

Subjects: Gamma Ray, >GeV, AGN
Referred to by ATEL #: 2941

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has detected over the time period 25th September - 3rd October, GeV gamma-ray emission from a source positionally consistent with CRATES J0531-4927 (also known as PMN J0531-4827, RA: 05h31m58.61s, Dec: -48d27'35.9", Healey et al. 2007, ApJS, 171, 61). This object is believed to be a blazar, with unknown redshift, not present in the 1FGL catalog (Abdo et al. 2010, ApJS 188, 405).

Preliminary analysis indicates that CRATES J0531-4927 was detected in a flaring state on the 25th September 2010 with a daily flux (E>100MeV) of (1.5+/-0.4) x10^-6 ph cm^-2 s^-1 (errors are statistical only), after brightening over the previous weeks. The source remained very active during the following days, ranging in daily flux (E>100MeV) from (0.8+/-0.3)x10^-6 ph cm^-2 s^-1 to (1.3+/-0.2)x10^-6 ph cm^-2 s^-1, reaching a high daily flux (E>100MeV) of (1.6+/-0.3) x10^-6 ph cm^-2 s^-1 on the 2nd of October.

The Fermi-LAT contact person for this source is Filippo D'Ammando ( Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. In consideration of the ongoing activity of this source we strongly encourage multiwavelength observations, in particular redshift measurements.

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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R. E. Rutledge , Editor
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