Timing analysis of a unique hard X-ray source, Swift J0042.6+4112, in M31
Abstract
Recent NuSTAR-Swift observations revealed that a single resolved X-ray source, Swift J0042.6+4112, with Lx of a few times 1038 erg/s dominates the hard X-ray emission from the Andromeda galaxy. HST-based stellar population synthesis modeling combined with the 0.5-50 keV spectral shape suggest that this might be an X-ray pulsar with an intermediate (or lower) mass donor. Here we further explore the alternative scenario of a symbiotic or ultracompact X-ray binary, based on long-term variability from Swift observations between 2005 and 2016. We find that the soft (0.3-8.0 keV) X-ray flux varies within a factor of 4 but does not exhibit transient behavior. Its power spectrum suggests a 6.1-day period, which, if interpreted as an orbital period, would not support either the symbiotic or the ultracompact X-ray binary scenario. Finally, we also present the hard X-ray variability of this source deduced from a new NuSTAR observation in 2017.
- Publication:
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AAS/High Energy Astrophysics Division #16
- Pub Date:
- August 2017
- Bibcode:
- 2017HEAD...1610824Y