Third-nearest WZ Sge-Type dwarf nova candidate ASASSN-14dx classified on the basis of Gaia Data Release 2

• Published in: Publications of the Astronomical Society of Japan Vol. 71; no. 1
• Main Authors: Isogai, Keisuke, Kato, Taichi, Imada, Akira, Ohshima, Tomohito, Kojiguchi, Naoto, Ohnishi, Ryuhei, Hambsch, Franz-Josef, Monard, Berto, Kiyota, Seiichiro, Nishimura, Hideo, Nogami, Daisaku
• Format: Journal Article
• Language: English
• Published: Oxford University Press 01-01-2019
• Subjects: stars: individual (ASASSN-14dx); stars: dwarf novae; accretion, accretion disks; novae, cataclysmic variables
• ISSN: 0004-6264; 2053-051X
• DOI: 10.1093/pasj/psy141

Abstract
ASASSN-14dx showed an extraordinary outburst whose features are a small outburst amplitude (∼2.3 mag) and long duration (>4 yr). Because we found a long observational gap of 123 d before the outburst detection, we propose that the main outburst plateau was missed and that this outburst is just a “fading tail” often seen after the WZ Sge-type super-outbursts. In order to distinguish between WZ Sge and SU UMa-type dwarf novae (DNe), we investigated Gaia Data Release 2 (DR2) statistically. We applied a logistic regression model and succeeded in classifying by using absolute Gaia magnitudes MG and Gaia colors GBP–GRP. Our new classifier also suggests that ASASSN-14dx is the best candidate of a WZ Sge-type DN. We estimated distances from the Earth of known WZ Sge stars by using Gaia DR2 parallaxes. The result indicates that ASASSN-14dx is the third-nearest WZ Sge star (next to WZ Sge and V455 And), and hence the object can show the third-brightest WZ Sge-type super-outburst whose maximum is V = 8–9 mag.