NuSTAR timing of NGC 300 ULX-1 / Supernova Impostor SN2010da

ATel #11282; Matteo Bachetti (INAF-OACagliari), Brian W. Grefenstette (Caltech), Dominic J. Walton (Cambridge), Felix Fuerst (ESAC), Marianne Heida (Caltech), Jaime A. Kennea (PSU), Ryan Lau (Caltech)
on 9 Feb 2018; 23:21 UT
Credential Certification: Matteo Bachetti (bachetti@oa-cagliari.inaf.it)

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NuSTAR observed NGC 300 on UT 2018-01-31T01:23:50 -- 2018-02-01T06:39:02. We used the cleaned event files provided by HEASARC, ran barycorr to refer the times to the Solar System Barycenter, and filtered a region of 30" around the transient source. We used HENDRICS (github.com/stingraysoftware/HENDRICS) to perform a pulsation search. We calculated the periodogram, and detected a peak at ~0.05 Hz. We refined the analysis running a Z^2 search (Buccheri et al. 2003) around this frequency, and found a peak incompatible with a constant frequency (using the criterion of Leahy et al. 1987). We searched over frequency and frequency derivative, and we measured a strong spin up compatible with the general spin up trend of the source (ATEL #11158, ATEL #11174, ATEL #11179, ATEL #11229). We calculated the pulse TOAs using Stingray (github.com/stingraysoftware/Stingray) and refined the timing solution using PINT (https://github.com/nanograv/PINT) and TEMPO2 (http://www.atnf.csiro.au/research/pulsar/tempo2/), obtaining consistent results. Below we quote, for each parameter, the higher uncertainty value obtained between the two fits. The timing solution is PEPOCH MJD 58149.058221232100000 F0 0.05006052(42) x 10^-7 Hz F1 4.38(24) x 10^-12 Hz / s which corresponds to P0 = 19.9758(2) s P1 = -1.75(9) x 10^-7 s/s We do not find significant evidence for an orbital modulation.