High Optical Polarization Detected in PKS 1441+25

ATel #7417; Paul S. Smith (Steward Observatory, University of Arizona), Demet Tutar Ozdarcan (Steward Observatory & Ege University)
on 20 Apr 2015; 16:01 UT
Credential Certification: Paul S. Smith (psmith@as.arizona.edu)

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An optical observation of the z=0.939 quasar PKS 1441+25 (RA=14h43m56.89s DEC=+25d01m44.5s) was obtained on UTC 2015 April 20 using the SPOL spectropolarimeter at the 1.54m Kuiper Telescope on Mt. Bigelow, Arizona. This observation was prompted by ATEL #7416, which reported the detection by MAGIC of very high energy (VHE) emission from this object within the past few days. The object was found to be highly polarized, with P = 37.7% (0.1%) at a position angle of 107.6 deg (0.1 deg) during a 16-minute observation centered at 11:00:59 UT. The linear polarization reported is derived from the median Stokes values found in a 5000-7000 Angstrom bandpass of the spectrum. Measurement uncertainties are given in parentheses and are based on photon statistics. The polarization is constant with wavelength from 4000-8000 Angstroms and the flux spectrum appears to be featureless. Rapid-cadence flux and polarization monitoring of PKS 1441+25 are encouraged while it remains in an active state (see also e.g., ATEL #6923 and #7402).