Optical Activity of the Flaring Gamma-ray Blazar PKS 1441+25

ATel #6923; Tapio Pursimo (Nordic Optical Telescope) and Roopesh Ojha (ORAU/NASA/GSFC)
on 15 Jan 2015; 01:34 UT
Credential Certification: Roopesh Ojha (Roopesh.Ojha@gmail.com)

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We report optical photometry of the high redshift z= 0.939 (Shaw et al. 2012, ApJ, 748, 49), flat spectrum radio quasar PKS 1441+25 obtained with the 2.56m Nordic Optical Telescope in La Palma. Observations were made with the griz filters on Jan 12, 2015. The data were reduced using standard iraf routines/procedures, de-biasing and flat field correction. Photometry used iraf apphot, and seven nearby SDSS field stars were used to estimate the photometric zero point.

The results are:
Filter   Magnitude
g'      18.52+-0.03
r'       18.15±0.03
i'       17.81±0.03
z'      17.89±0.04
where the AB magnitude system is used and the errors are the standard deviation of the sigma clipped zero point plus the expected 2% accuracy for a random SDSS field.

As a comparison, the SDSS griz -magnitudes of this object are:
Filter   Magnitude
g'      19.73
r'       19.38
i'       19.17
z'      18.96

Thus, PKS 1441+25 is currently more than 1 magnitude brighter than the SDSS-survey magnitudes. This optical activity coincides with its reported period of gamma-ray activity (ATel#6878).

Further multi-wavelength observations of this source are encouraged. We will continue to monitor this source and report future developments using this and other platforms.