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arXiv · 1509.04004

Swift detection of the super-swift switch-on of the super-soft phase in nova V745 Sco (2014)

K. L. Page·J. P. Osborne·N. P. M. Kuin·M. Henze·F. M. Walter·A. P. Beardmore·M. F. Bode·M. J. Darnley·L. Delgado·J. J. Drake·M. Hernanz·K. Mukai·T. Nelson·J. -U. Ness·G. J. Schwarz·S. N. Shore·S. Starrfield·C. E. Woodward
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Abstract

V745 Sco is a recurrent nova, with the most recent eruption occurring in February 2014. V745 Sco was first observed by Swift a mere 3.7 hr after the announcement of the optical discovery, with the super-soft X-ray emission being detected around four days later and lasting for only ~two days, making it both the fastest follow-up of a nova by Swift and the earliest switch-on of super-soft emission yet detected. Such an early switch-on time suggests a combination of a very high velocity outflow and low ejected mass and, together with the high effective temperature reached by the super-soft emission, a high mass white dwarf (>1.3 M_sun). The X-ray spectral evolution was followed from an early epoch where shocked emission was evident, through the entirety of the super-soft phase, showing evolving column density, emission lines, absorption edges and thermal continuum temperature. UV grism data were also obtained throughout the super-soft interval, with the spectra showing mainly emission lines from lower ionization transitions and the Balmer continuum in emission. V745 Sco is compared with both V2491 Cyg (another nova with a very short super-soft phase) and M31N 2008-12a (the most rapidly recurring nova yet discovered). The longer recurrence time compared to M31N 2008-12a could be due to a lower mass accretion rate, although inclination of the system may also play a part. Nova V745 Sco (2014) revealed the fastest evolving super-soft source phase yet discovered, providing a detailed and informative dataset for study.

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K. L. Page, J. P. Osborne, N. P. M. Kuin, M. Henze, F. M. Walter, A. P. Beardmore, M. F. Bode, M. J. Darnley, L. Delgado, J. J. Drake, M. Hernanz, K. Mukai, T. Nelson, J. -U. Ness, G. J. Schwarz, S. N. Shore, S. Starrfield, C. E. Woodward. 2015-09-14. Swift detection of the super-swift switch-on of the super-soft phase in nova V745 Sco (2014). https://doi.org/10.1093/mnras%2Fstv2144

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