Spectroscopic and photometric confirmation of TCP J22135399+3015357 as a WZ Sge-type dwarf nova

ATel #17347; Keisuke Isogai (Kyoto University), Maehara Hiroyuki (NAOJ), Tonny Vanmunster (CBA Belgium Observatory, CBA Extremadura Observatory)
on 22 Aug 2025; 12:28 UT
Credential Certification: Keisuke Isogai (isogai@kusastro.kyoto-u.ac.jp)

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We report on spectral and photometric features seen in the transient TCP J22135399+3015357. We obtained the spectrum by using a fiber-fed integral field spectrograph (KOOLS-IFU; Matsubayashi et al. 2019, Matsubayashi et al. 2025) attached to one of the Nasmyth focuses of the 3.8-m telescope Seimei at Okayama Observatory of Kyoto University. In short, we conclude that this object is a WZ Sge-type dwarf nova.

According to CBAT TCP J22135399+3015357 was discovered by the NMW survey at the Astroverty astrofarm in Russia on 2025-08-19.8461 at CR = 13.6. In the previous night's data, the object was at CV = 14.4(2) on 2025-08-18.8460. According to the SDSS DR16 (Ahumada+, 2020), there is a possible optical counterpart with r = 22.0 and i = 21.6.

We obtained an optical spectrum on 2025-08-21.0609 UT by using KOOLS-IFU. The quick look spectrum shows a blue continuum with the Balmer, He I, and He II emission lines. Around the Hβ emission, we can also see a broad absorption line. We performed time-series photometry. The object has shown double-peaked modulations. The estimated period is 0.0612(12) d. These results suggest that this object is a promising new WZ Sge-type dwarf nova.

Our spectrum