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Fermi and Swift Observations of High Activity in the FSRQ PKS 0502+049

ATel #6425; R. Ojha (NASA/GSFC/UMBC/CRESST), B. Carpenter (CUA/NASA/GSFC), J. Becerra (NASA/GSFC/UMCP/CRESST), F. Krauss (Remeis Observatory & ECAP, FAU Erlangen/Univ. Wuerzburg), D. Gasparini (ASDC/INAF) on behalf of the Fermi LAT Collaboration.
on 28 Aug 2014; 13:22 UT
Credential Certification: Roopesh Ojha (Roopesh.Ojha@gmail.com)

Subjects: Optical, Ultra-Violet, X-ray, Gamma Ray, >GeV, AGN, Black Hole, Blazar, Quasar

Referred to by ATel #: 6457

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed increased gamma-ray flux from a source positionally consistent with the flat spectrum radio quasar PKS 0502+049. Preliminary analysis indicates that on August 22, 23, and 25 the daily averaged flux (E>100MeV) was (0.9+/-0.2), (0.7+/-0.2), and (1.0+/-0.3) x 10^-6 ph cm^-2 s^-1 (statistical uncertainty only) which is up to 34 times its average daily flux from the 2FGL catalog (Nolan et al. 2012 ApJS, 199, 31). This source last flared in 2013 March (ATel#4858).

Two follow-up target of opportunity Swift observations were made on August 23 and August 24 for 2.8 and 2.9 ks, respectively. XRT data were taken in Photon Counting mode. The X-ray spectrum (0.5-10 keV) can be fit by an absorbed power law model with an HI column density set to the Galactic value of 8.76x10^20 cm^-2 (Kalberla et al. 2005, A&A, 440, 775) using the abundances of Wilms et al. (2000, ApJ, 542, 914) and the cross sections of Verner et al. (1996, ApJ, 465, 487). The unabsorbed fluxes were (4.7+-0.8)x10^-12 and (4.8+-0.8)x10^-12 erg cm^-2 s^-1; while the photon indexes were 1.5+-0.2 and 1.5+-0.2, respectively. These fluxes are about 2.5 times that observed during the last high state (2013 March; ATel#4858) and about 7 times that observed during a quiescent state (ATel#4905).

Simultaneous Swift/UVOT observations are shown below. Across all filters the source has brightened between the two epochs with both epochs being much brighter (1 to 1.5 magnitudes) than a U-band observation during the last LAT flare and during a quiescent state (ATel#4905).

Filter   2014-Aug-23   2014-Aug-24
V       16.47+/-0.18   16.20+/-0.06
B       17.00+/-0.11   16.58+/-0.06
U       16.40+/-0.10   15.94+/-0.06
W1     16.62+/-0.11   16.10+/-0.07
M2     16.76+/-0.19   16.40+/-0.07
W2     16.89+/-0.10   16.59+/-0.07

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. This source is being added to the "LAT Monitored Sources" and consequently a preliminary estimation of the daily gamma-ray flux observed by Fermi LAT will be publicly available (link:http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/). We encourage further multifrequency observations of this source. For this source the Fermi LAT contact person is Roopesh Ojha (Roopesh.Ojha@gmail.com).

We would like to thank the Swift Team for making these observations possible, in particular C. J. Mountford as the Swift Observatory Duty Scientist.

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.