Zw 229-15 returning to higher X-ray flux state
ATel #3484; Rick Edelson (University of Maryland, College Park), Richard Mushotzky (University of Maryland, College Park and NASA/GSFC)
on 14 Jul 2011; 14:29 UT
Credential Certification: Rick Edelson (rickedelson@gmail.com)
An earlier telegram (ATel #3458) reported that the narrow-line Seyfert 1 galaxy Zw 229-15 (19h05m25.9s +42d27m40s) exhibited a dramatic decrease in X-ray flux during Swift monitoring, with the count rate dropping from a mean of 0.096 c/s during the ~18 days from May 29 through June 17 to a mean of 0.026 c/s during the ~17 days from June 18 through July 5. (All dates/times UT.) The maximum count rate was 0.172 c/s at 2011 June 2 22:35 and the minimum was 0.005 c/s at June 27 00:23. At a distance of 118 Mpc and a conversion factor based on the average Swift XRT spectrum (column density of 7x10^20 and photon index slope of 1.9) the source had a minimum luminosity of log L(x)<41.5 ergs/cm2/sec in the 0.3-8 keV band.
During the few days, the source flux has returned to near its former level, with a count rate of 0.147 c/s recorded on July 13 17:45. Thus this dramatic fading appears to have ended. See http://www.swift.ac.uk/user_objects/tprods/USERPROD_67.132.100.28_1310642983209/lc/ for a current light curve, but note that this link will only be active through July 20. Daily Swift monitoring is expected to continue for a few more days.
We gratefully acknowledge the assistance of the Swift operations team in responding to the dramatic event by scheduling further monitoring. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester.
Latest Swift XRT light curve (link expires July 20)
