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|Title:||The remarkable outburst of the highly evolved post-period-minimum dwarf nova SSS J122221.7−311525|
|Authors:||Neustroev, V. V.|
Marsh, T. R.
Zharikov, S. V.
Osborne, Julian Paul
Page, K. L.
Suleimanov, V. F.
Garcia-Diaz, M. T.
Parsons, S. G.
Miroshnichenko, A. S.
Reichart, D. E.
Haislip, J. B.
Ivarsen, K. M.
LaCluyze, A. P.
Moore, J. P.
|Publisher:||Oxford University Press (OUP)|
|Citation:||Monthly Notices of the Royal Astronomical Society, 2017, 467 (1), pp. 597-618|
|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 near-main-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.|
|Rights:||Copyright © 2017 The Authors. Deposited with reference to the publisher’s open access archiving policy.|
|Appears in Collections:||Published Articles, Dept. of Physics and Astronomy|
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