The remarkable outburst of the highly-evolved post period-minimum dwarf nova SSS J122221.7−311525
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Author(s)
Neustroev, V. V.
Marsh, T. R.
Zharikov, S. V.
Knigge, C.
Kuulkers, E.
Osborne, J. P.
Page, K. L.
Steeghs, D.
Suleimanov, V. F.
Tovmassian, G.
Date Issued
May 2017
Journal
Monthly Notices of the Royal Astronomical Society
Publisher
Oxford University Press (OUP)
Citation
Neustroev, V. V. et al. “The Remarkable Outburst of the Highly-Evolved Post Period-Minimum Dwarf Nova SSS J122221.7−311525.” Monthly Notices of the Royal Astronomical Society (January 2017): stx084 © 2017 The Authors
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Author's final manuscript
Abstract
We report extensive 3-yr multiwavelength observations of the WZ Sge-type dwarf nova SSS J122221.7-311525 during its unusual double superoutburst, the following decline and in quiescence. The second segment of the superoutburst had a long duration of 33 d and a very gentle decline with a rate of 0.02 mag d-1, and it displayed an extended post-outburst decline lasting at least 500 d. Simultaneously with the start of the rapid fading from the superoutburst plateau, the system showed the appearance of a strong near-infrared excess resulting in very red colours, which reached extreme values (B - I ≃ 1.4) about 20 d later. The colours then became bluer again, but it took at least 250 d to acquire a stable level. Superhumps were clearly visible in the light curve from our very first time-resolved observations until at least 420 d after the rapid fading from the superoutburst. The spectroscopic and photometric data revealed an orbital period of 109.80 min and a fractional superhump period excess ≲0.8 per cent, indicating a very low mass ratio q ≲ 0.045. With such a small mass ratio the donor mass should be below the hydrogen-burning minimum mass limit. The observed infrared flux in quiescence is indeed much lower than is expected from a cataclysmic variable with a nearmain- sequence donor star. This strongly suggests a brown-dwarf-like nature for the donor and that SSS J122221.7-311525 has already evolved away from the period minimum towards longer periods, with the donor now extremely dim. Keywords: binaries: close; stars: evolution; stars: individual: SSS J122221.7−311525; novae; cataclysmic variables
MIT Department
Massachusetts Institute of Technology. Department of Physics
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
https://doi.org/10.1093/MNRAS/STX084
