Low-resolution spectroscopy of the long-orbital period dwarf nova candidate ASASSN-19rx

ATel #13010; Keisuke Isogai, Taichi Kato, Naoto Kojiguchi, Daisaku Nogami, Masaaki Otsuka, Masayuki Yamanaka (Kyoto University)
on 9 Aug 2019; 08:43 UT
Credential Certification: Keisuke Isogai (isogai@kusastro.kyoto-u.ac.jp)

Tweet

ASASSN-19rx was discovered on 2019-07-21.02 UT by the All-Sky Automated Survey for Supernovae (ASAS-SN; Shappee et al. 2014, Kochanek et al. 2017). Although the ASAS-SN website indicated that this object shows an "unusual slow stellar outburst", we confirmed that its spectrum is a characteristic of a dwarf nova outburst.

The archive data of the ASAS-SN Sky Patrol shows a long (~2 months) and small (~1 mag) outburst in 2015. In addition, the Gaia color and absolute magnitude are respectively redder and brighter than those of ordinary dwarf novae. Thus, it is proposed that this object is a candidate for a long-orbital period dwarf nova such as V630 Cas or BD Pav. (vsnet-alert 23415). Furthermore, we have found that the object is eclipsing and identified the period of ~2.5 d (vsnet-alert 23460). Thus this object is likely to be a kind of such rare objects.

We report on an optical low-resolution spectrum of ASASSN-19rx. The data was obtained on 2019-07-30.77 UT by fiber-fed integral field spectrograph (KOOLS-IFU; Matsubayashi et al. 2019) mounted on the 3.8-m telescope Seimei at Okayama Observatory of Kyoto University. The obtained spectrum shows the Balmer, HeI, HeII and CIII/NIII emission lines. The emission lines are shifted by +100--200 km/s. It is remarkable that the HeII 4688 is very strong whereas HeI lines are relatively weak. Such features are also observed in some other long-orbital period dwarf novae (Kimura et al. 2018). Although this system should have an accretion disk, all emission lines have single peaked profiles. We are planning to observe the line-profile variations through the orbital period and outburst cycle. Observations at other wavelengths are encouraged.