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Optical, X-, Gamma-ray flare of the FSRQ PKS 1441+25

ATel #7402; Luigi Pacciani (INAF-IAPS)
on 16 Apr 2015; 12:08 UT
Credential Certification: Luigi Pacciani (luigi.pacciani@iaps.inaf.it)

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

Referred to by ATel #: 7416, 7417, 7429, 7433

We detected a gamma-ray flare from the FSRQ PKS 1441+25 (z=0.939), triggering on FERMI-LAT data at E > 10 GeV with TS ~44, from 2015-03-21 to 2015-04-15, following the prescription of Pacciani et al. 2014, ApJ, 790, 45. The gamma-ray flux was (38+/-3)E-8 ph cm^-2 s^-1, photon index 1.93+/-0.07, TS ~ 760 (E>0.1 GeV), to be compared with the catalog flux of 1.3E-8 ph cm^-2 s^-1 reported in the 3rd Fermi-LAT point-source catalog. The FERMI-LAT revealed gamma-ray emission up to 33 GeV. The source has been detected in high gamma-ray state also on January 2015 (ATEL#6878). The Swift Follow-up revealed the source in high state in optical and X-ray. The preliminary Swift-UVOT photometry on 2015-04-15 is:

V = 16.79 +/- 0.06

B = 17.01 +/- 0.03

U = 16.21 +/- 0.02

UVW1 = 16.36 +/- 0.03

UVM2 > 18.4

UVW2 = 16.59 +/- 0.03 which is ~4 times brighter then the optical flux on 2015 January 5th and 28th (swift obsid 00040618005, 00040618003, see also ATEL#6895, ATEL#6923). Magnitudes are in the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) and have not been corrected for Galactic extinction. We verified the optical photometry using SDSS J144357.93+250051.0 as a reference. The simultaneous Swift-XRT observation gives a counting rate of 0.109+/-0.006 cps (to be compared with 0.045+/-0.004 cps of the brightest state on 28th January 2015, Swift obsid 00040618005) and an unabsorbed flux of (5.3+/-0.5)E-12 erg cm^-2 s^-1 (0.3-10 keV). We encourage further multi-wavelength observations. We thank the Swift team and Swift Observatory Duty Scientist for rapidly scheduling our observations.