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Swift Follow-up of Giant Optical/NIR Flare of the Blazar NVSS J141922-083830

ATel #7184; Bryce Carpenter (CUA/NASA/GSFC), Josefa Becerra (NASA/GSFC/UMCP), Roopesh Ojha (NASA/GSFC/UMBC), Tapio Pursimo (Nordic Optical Telescope)
on 7 Mar 2015; 00:04 UT
Credential Certification: Roopesh Ojha (Roopesh.Ojha@gmail.com)

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

Following the giant optical (ATel#7133) and NIR (ATel#7168) flares observed in the blazar NVSS J141922-083830 (which is positionally coincident with the gamma ray source 2FGL J1419.4-0835), a Swift target of opportunity observation was performed on 2015 March 3 revealing an X-ray flare.

Swift/XRT data were taken in Photon Counting mode for 2 ksec. 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 3.76x10^20 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 observed flux was (2.0+-0.8)x10^-12 erg cm^-2 s^-1 with a photon index of 1.2+-0.4. This is almost a five-fold increase compared to a 1.2 ks observation on 2014 September 9 when it was barely detected with flux (4.2^{+4.0}_{-2.1})E-13 erg cm^-2 s^-1 and a photon index of 2.0+/-0.9.

The UVOT observed in the W2 filter on both 2015 March 3 and 2014 September 9 and the observed magnitudes were 16.27+/-0.06 and 17.7+/-0.13 mag (Vega system), respectively. This represents an increase by a factor of about 3.7.

We note that this source was detected on a daily timescale by Fermi-LAT during the week Feb 9-15 with flux below 1X10^-6 photons cm^2 s^-1 (http://fermisky.blogspot.com/2015_02_01_archive.html).

We would like to thank the Swift Team for making these observations possible, in particular D. Malesani as the Swift Observatory Duty Scientist. Further multiwavelength observations are encouraged. We will report future results on this and other platforms.