Mon. Not. R. Astron. Soc., 457, 1636-1643 (2016/April-1)
Recurring X-ray outbursts in the supernova impostor SN 2010da in NGC 300.
BINDER B., WILLIAMS B.F., KONG A.K.H., GAETZ T.J., PLUCINSKY P.P., SKILLMAN E.D. and DOLPHIN A.
Abstract (from CDS):
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 x 1038 erg/s 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 x 1036 to 4 x 1037 erg/s in ∼6 months, 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.
© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
stars: early-type - stars: massive - X-rays: binaries X-rays: individual: SN 2010da
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