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Fermi-LAT detection of increased gamma-ray activity from the blazar PKS 0727-115

ATEL # 1919; D. Horan (LLR), E. Hays (NASA/GSFC) on behalf of the Fermi Large Area Telescope Collaboration and Mark A. Gurwell (CfA)
on 29 Jan 2009; 9:52 UT
Password Certification: Deirdre Horan (

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

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope (formerly GLAST, launched June 11, 2008), has observed an increasing gamma-ray flux from a source positionally consistent with PKS 0727-115 (RA: 07h30m19.1s, Dec: -11d41m13s, J2000, z=1.59 (Zensus et al. 2002)).

Preliminary analysis indicates that over the past month the source has become, on average, brighter with a gamma-ray flux (E>100MeV) of approximately 5.0+/- 0.8 x 10^-7 photons cm^-2 s^-1 on weekly timescales and occasional day-scale detections at the level of approximately 4.0 +/- 1.0 x 10^-7 photons cm^-2 s^-1. This represents an increase of a factor of 2 with respect to the source flux level in the past months.

PKS 0727-115 is continually being monitored by MOJAVE and, based on these data, it looks like the 15 GHz flux has been steadily increasing since 1995 from about 2 Jy up to the current value of about 7 Jy, making it one of the brightest blazars currently in the radio sky. The Submillimeter Array also shows PKS 0727-115 to be undergoing an increase in the millimeter flux.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. In consideration of the activity of this source we strongly encourage multiwavelength observations, in particular at optical wavelengths due to the dearth of data in this regime. For this source the Fermi LAT contact person is A. Tramacere (e-mail:

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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