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Fermi and Swift observation of a GeV/X-ray/UV flare from PKS 2233-148

ATEL # 2589; K. V. Sokolovsky (MPIfR/ASC Lebedev), D. Donato (NASA/GSFC), F. K. Schinzel (MPIfR) on behalf of the Fermi Large Area Telescope Collaboration; and Y. Y. Kovalev (ASC Lebedev/MPIfR)
on 29 Apr 2010; 19:11 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Frank Schinzel (

Subjects: Radio, Ultra-Violet, X-ray, 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 the BL Lac type object PKS 2233-148 (R.A.= 22:36:34.08716, Dec.= -14:33:22.1897, J2000; Petrov et al. 2008, AJ, 136, 580).

Preliminary analysis indicates that the source on 2010-04-23 was in a high state with a gamma-ray flux (E>100MeV) of (0.7 +/-0.3) x 10^-6 ph/cm^2/sec (statistical only). It was previously detected by LAT at daily timescale on 2010-04-19. The current flux is more than 13 times higher than the first 11 month average (1FGL J2236.4-1432, Abdo et al. 2010, arXiv:1002.2280). The average weekly flux (2010-04-21/28) was (0.6 +/-0.1) x 10^-6 ph/cm^2/sec. The weekly lightcurve shows an increasing trend in the gamma-ray flux starting about six weeks ago.

Swift observed PKS 2233-148 on 2010-04-27 revealing a high X-ray and UV flux state compared to archival data from 2009-09-28, confirming identification of the flaring gamma-ray source with PKS 2233-148.
Swift results:
JD XRT_flux Gamma W2
2455102.44 2.4 +/-0.6 1.5 +/-0.6 18.09 +/-0.04
2455313.88 9.8 +/-1.0 1.6 +/-0.1 16.91 +/-0.02
"XRT_flux" is the 0.3-10 keV flux x10^-12 ergs/cm^2/s, "Gamma" is the X-ray photon index, "W2" is the W2 band magnitude. The Galactic N_HI= 0.347 x10^21 cm^-2 (Kalberla et al. 2005, A&A, 440, 775) was assumed for the X-ray spectrum modeling.

Multi-frequency (5-43 GHz) VLBA observations have been triggered (Fermi GI Cycle-2 program 21087), four experiments will be conducted during the next four months. Simultaneous Swift coverage will be requested. Fermi will provide continuing regular gamma-ray monitoring of this source. We strongly encourage multi-wavelength observations. For this source the Fermi LAT contact person is K. Sokolovsky (ksokolov at

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.

We thank the Swift team for their rapid scheduling of these observations.

RATAN-600 1-22 GHz radio spectrum of the source in 1997-2006

MOJAVE page of the source

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R. E. Rutledge , Editor
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