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PS1-1000305 an AGN outburst?

ATEL # 2725; A.J. Drake, A.A. Mahabal, S.G. Djorgovski, M.J. Graham, R. Williams (Caltech); J. Prieto (OCIW); M. Catelan (PUC); E. Christensen (Gemini Observatory); E.C. Beshore, S.M. Larson (LPL/UA)
on 8 Jul 2010; 2:25 UT
Password Certification: Andrew J. Drake (ajd@cacr.caltech.edu)

Subjects: Optical, A Comment, AGN

Kankare et al. (2010, ATel#2716) recently reported the discovery of an AGN outburst (PS1-1000305) detected in PS1 taken data on May 19.3 UT. The redshift of the AGN is given by Kankare et al. as z=0.77 with the host galaxy SDSS J152844.16+425722.5. We have extracted the five year archival CSS/CRTS lightcurve at the location of PS1-1000305. The CSS lightcurve is consistent with the long-timescale variability typical for AGN. For example, similar long-timescale variability was recently detected by CRTS in spectroscopically confirmed AGN SDSSJ125956.21+032433.0, (= CSS100405:125956+032434) at redshift z=0.75.

The absolute magnitudes of the host galaxy and AGN outburst are given by Kankare et al. (2010) as -22.1 and -24.0, respectively. The host galaxy magnitude appears relatively consistent with the magnitudes observed by SDSS in images taken on 2002-05-08 and 2003-04-29, but significantly fainter than in recent data. The CSS photometry from May 10th and May 31st 2010 shows no sign of an outburst relative to contemporaneous data. Adopting Kankane et al.'s redshift, we find the AGN+host brightening from Mv~-22.3 (April 2005) to Mv~-23.9 (2009-2010) in CSS data. Combining the CSS photometry with the PS1 the outburst magnitude and the color approximated from the SDSS photometry, we find that, if an outburst event did occur between May 10th and May 31st, the brightness variation was less than half a magnitude.

CRTS will soon make the entire CSS dataset public so that the astronomical community can better assess the nature of transients and other variable sources.


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