Recurring X-ray outbursts in the supernova impostor SN 2010da in NGC 300

B. Binder, B. F. Williams, A. K.H. Kong, T. J. Gaetz, P. P. Plucinsky, E. D. Skillman, A. Dolphin

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24 Scopus citations


We present new observations of the 'supernova impostor' SN 2010da using the Chandra X-ray Observatory and the Hubble Space Telescope. During the initial 2010 outburst, the 0.3-10 keV luminosity was observed by Swift to be ~5 × 1038 erg s-1 and faded by a factor of ~25 in a four month period. Our two new Chandra observations show a factor of ~10 increase in the 0.35-8 keV X-ray luminosity, from~4×1036 to 4×1037 erg s-1 in~6months, and the X-ray spectrum is consistent in both observations with a power-law with a photon index of Γ ~0. We find evidence of X-ray spectral state changes: When SN 2010da is in a high-luminosity state, the X-ray spectrum is harder (Γ ~0) compared to the low-luminosity state (Γ ~ 1.2 ± 0.8). Using our Hubble observations, we fit the colour-magnitude diagram of the coeval stellar population to estimate a time since formation of the SN 2010da progenitor system of ≲5 Myr. Our observations are consistent with SN 2010da being a high-mass X-ray binary (HMXB) composed of a neutron star and a luminous blue variable-like companion, although we cannot rule out the possibility that SN 2010da is an unusually X-ray bright massive star. The ≲5 Myr age is consistent with the theoretically predicted delay time between the formation of a massive binary and the onset of the HMXB phase. It is possible that the initial 2010 outburst marked the beginning of X-ray production in the system, making SN 2010da possibly the first massive progenitor binary ever observed to evolve into an HMXB.

Original languageEnglish (US)
Pages (from-to)1636-1643
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
StatePublished - Apr 1 2016

Bibliographical note

Publisher Copyright:
© 2016 The Authors.


  • Stars: early-type
  • Stars: massive
  • X-rays: binaries X-rays: individual: SN 2010da


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