X-ray Eclipse Diagnosis of the Evolving Mass Loss in the Recurrent Nova U Scorpii 2010
Abstract
We report the Suzaku detection of the earliest X-ray eclipse seen in the recurrent nova U Scorpii 2010. A target-of-opportunity observation 15 days after the outburst found a 27+/-5% dimming in the 0.2-1.0 keV energy band at the predicted center of an eclipse. In comparison with the X-ray eclipse depths seen at two later epochs by XMM-Newton, the source region shrank by about 10-20% between days 15 and 35 after the outburst. The X-ray eclipses appear to be deeper than or similar to contemporaneous optical eclipses, suggesting the X-ray and optical source region extents are comparable on day 15. We raise the possibility of the energy dependency in the photon escape regions, and that this would be a result of the supersoft X-ray opacity being higher than the Thomson scattering optical opacity at the photosphere due to bound-free transitions in abundant metals that are not fully ionized. Assuming a spherically symmetric explosion model, we constrain the mass-loss rate as a function of time. For a ratio of actual to Thomson opacity of 10-100 in supersoft X-rays, we find a total ejecta mass of about 10^{-7}-10^{-6} M_{\odot}.
Keywords
Cite
@article{arxiv.1303.5766,
title = {X-ray Eclipse Diagnosis of the Evolving Mass Loss in the Recurrent Nova U Scorpii 2010},
author = {D. Takei and J. J. Drake and M. Tsujimoto and J. -U. Ness and J. P. Osborne and S. Starrfield and S. Kitamoto},
journal= {arXiv preprint arXiv:1303.5766},
year = {2015}
}
Comments
To appear in the Astrophysical Journal Letters; 5 pages, 3 figures