ASASSN-16eg: New candidate for a long-period WZ Sge-type dwarf nova
/ Authors
Yasuyuki Wakamatsu, K. Isogai, M. Kimura, T. Kato, T. Vanmunster, G. Stone, T. Tordai, M. Richmond, I. Miller, A. Oksanen
and 12 more authors
H. Itoh, H. Akazawa, S. Kiyota, E. Miguel, E. Pavlenko, K. Antonyuk, O. Antonyuk, V. Neustroev, G. Sjoberg, P. Dubovský, R. Pickard, D. Nogami
/ Abstract
We report on our photometric observations of the 2016 superoutburst of ASASSN-16eg. This object showed a WZ Sge-type superoutburst with prominent early superhumps with a period of 0.075478(8) d and a post-superoutburst rebrightening. During the superoutburst plateau, it showed ordinary superhumps with a period of 0.077880(3) d and a period derivative of 10.6(1.1) $\times$ 10$^{-5}$ in stage B. The orbital period ($P_{\rm orb}$), which is almost identical with the period of early superhumps, is exceptionally long for a WZ Sge-type dwarf nova. The mass ratio ($q$ = $M_2/M_1$) estimated from the period of developing (stage A) superhumps is 0.166(2), which is also very large for a WZ Sge-type dwarf nova. This suggests that the 2:1 resonance can be reached in such high-$q$ systems, contrary to our expectation. Such conditions are considered to be achieved if the mass-transfer rate is much lower than those in typical SU UMa-type dwarf novae that have comparable orbital periods to ASASSN-16eg and a resultant accumulation of a large amount of matter on the disk is realized at the onset of an outburst. We examined other candidates of long-period WZ Sge-type dwarf novae for their supercycles, which are considered to reflect the mass-transfer rate, and found that V1251 Cyg and RZ Leo have longer supercycles than those of other WZ Sge-type dwarf novae. This result indicates that these long-period objects including ASASSN-16eg have a low mass-transfer rate in comparison to other WZ Sge-type dwarf novae.
Journal: Publications of the Astronomical Society of Japan
DOI: 10.1093/pasj/psx094