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 (email@example.com)
Subjects: Optical, Ultra-Violet, X-ray, Gamma Ray, >GeV, Blazar
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.