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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.
Knigge, C.
Kuulkers, E.
Osborne, Julian Paul
Page, K. L.
Steeghs, D.
Suleimanov, V. F.
Tovmassian, G.
Breedt, E.
Frebel, A.
Garcia-Diaz, M. T.
Hambsch, F.-J.
Jacobson, H.
Parsons, S. G.
Ryu, T.
Sabin, L.
Sjoberg, G.
Miroshnichenko, A. S.
Reichart, D. E.
Haislip, J. B.
Ivarsen, K. M.
LaCluyze, A. P.
Moore, J. P.
First Published: 13-Jan-2017
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.
DOI Link: 10.1093/mnras/stx084
ISSN: 0035-8711
eISSN: 1365-2966
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
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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