Continued spin-up of the NGC300 ULX-1, supernova impostor SN2010da

ATel #11228; S. A. Grebenev, I. A. Mereminskiy (Space Research Institute, Moscow)
on 25 Jan 2018; 16:43 UT
Credential Certification: Ilya Mereminskiy (i.a.mereminskiy@gmail.com)

Tweet

Following detection of pulsations with 31.6 s period in Supergiant HMXB, associated with impostor-SN2010da (ATel#11158) we used recent Swift-XRT observation (ObsId:00049834015) performed on 24 Jan 2018 (initiated after ATel#11174, see also ATel#11179 for correct period determination) in order to monitor long-term period evolution.
Source is clearly seen, with 0.3-10 keV unabsorbed flux of 4x10^-12 erg cm^-2 s^-1, which correspond to luminosity of 2x10³⁸ erg s^-1. Using barycentered events we found a significant signal, corresponding to 20.06 s period, matching with one predicted in ATel#11179. Therefore NGC300 ULX-1 continues to spin-up with mean rate of -3.3x10^-7 s s^-1 over ~400 days from first period detection. Using period measured by Swift-XRT on 22 Apr 2017 we calculated spin-up rate of -2.7x10^-7 s s^-1 over 278 days, which is two times lower than measured during brighter phase with L_X ~ 3x10³⁹ erg s^-1 (ATel#11158).
We are very grateful to the Swift team for a rapid scheduling of our observations. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester.