Spectroscopic Classification of TCP J20315286+2740166 as a WZ Sge Type Dwarf Nova Outburst
ATel #16323; Jingyuan Zhao, Wenjie Zhou, Xing Gao (Xingming Observatory), Kirill Sokolovsky (UIUC, SAI MSU), Stanislav Korotkiy, Sergei Ostapenko (Astroverty, Ka-Dar)
on 6 Nov 2023; 16:04 UT
Credential Certification: Kirill Sokolovsky (kirx@scan.sai.msu.ru)
Subjects: Optical, Cataclysmic Variable, Transient, Variables
The 12.4 mag optical transient TCP J20315286+2740166 was discovered
using the New Milky Way wide-field camera (135mm f/2.0 telephoto
lens + unfiltered SBIG ST-8300M CCD) on 2023-11-04.7066 UTC and
reported via the CBAT Transient Objects Confirmation Page: http://www.cbat.eps.harvard.edu/unconf/followups/J20315286+2740166.html
Continued photometry with the same camera indicated that
the transient brightness peaked at 11.8 mag on 2023-11-04.8460 and
slightly declined to 12.0 mag by 2023-11-05.6274.
On 2023-11-05.60249 (this is the exposure start time) we obtained
a spectrum of the transient using the Alpy 600 spectrograph mounted
on the 0.6-m f/8 Ritchey-Chretien telescope
at Xingming Observatory. The spectrograph provides a wavelength
coverage of 3730-7400 A. The total exposure time was 120 min.
Our spectrum shows a blue continuum with very weak H_alpha emission
line, and a series of prominent Balmer absorption lines including
H_beta, H_gamma, H_delta, H_epsilon.
There is a known white dwarf candidate Gaia DR2 1857057959447151616
= WD J203152.85+274017.93 (Gentile et al., 2019, 2021) about
0.9 arcsecond away from the position of TCP J20315286+2740166.
It has a 2.46 +/- 0.57 mas parallax according to Gaia DR3,
implying the outburst reached an absolute magnitude
of 3.7 +/- 0.5 mag. The spectral characteristics,
absolute magnitude, and an outburst amplitude of about 8 mag
(above a quiescent level of Gmag=20.17) suggest
TCP J20315286+2740166 is a dwarf nova of the WZ Sge type.
Xingming Observatory spectrum of TCP J20315286+2740166
