Central Bureau for Astronomical Telegrams

CBAT "Transient Object Followup Reports"

TCP J02472889+6758170

TCP J02472889+6758170   2025 05 25.9796*  02 47 28.89 +67 58 17.0  13.0 U             Cas       9 0

2025 05 25.9796

The transient was found in images obtained with the second NMW camera (135mm f/2.0 telephoto lens + unfiltered STL-11000M CCD) on 2025-05-25.9796 UTC at CV=13.0. The plate-solved FITS images are available at http://scan.sai.msu.ru/~kirx/img/TCPJ02472889+6758170/ The transient coincides with the known variable star Gaia DR3 517539710877791488, which has a magnitude range of 17.93-18.18 G and a period of 0.0182338d according to its AAVSO VSX record: https://www.aavso.org/vsx/index.php?view=detail.top&oid=2841325 The star is listed as a white dwarf by Gentile Fusillo et al. (2019, MNRAS, 482, 4570) and Vincent et al. (2024, A&A, 682, A5). Finally, the transient AT 2010mg (Thevenot et al., 2021, TNS Astronomical Transient Report No. 98120), retrospectively identified in the AllWISE Multiepoch Photometry Table at IRSA, coincides with the newly discovered transient. The available information suggests that the object might be a previously unrecognized outbursting AM CVn type binary. ---- Kirill Sokolovsky, Stanislav Korotkiy (Astroverty, Ka-Dar) for the NMW team

2025 05 26.833

Vagnozzi A., Andreoli V., and Ochner P. report the classification of TCP J02472889+6758170. A low-resolution spectrum was obtained on 2025-05-26.833 UT using the 0.5-m telescope equipped with a self-built MARK III spectrograph (resolution: 2.6 Å/pixel), located at S.Lucia di Stroncone (observatory MPC 589), Italy. The spectrum shows a blue continuum with Balmer lines. Notably, Hα (6562.8 Å) is absent, filled up by the disk emission, while the other Balmer lines are broad and appear in absorption. The FWHM of Hβ (4860 Å) is approximately 2000 km/s. These spectral characteristics are consistent with those of a cataclysmic variable (CV). We therefore propose that TCP J02472889+6758170 is a cataclysmic variable.

2025 05 27.6744

follow-up :It appears to be a super hump, B,V,Rc amplitudes are . . were about 0.1 mag, mag is, B= +11.10, V= +11.16, Rc= +11.10, with 0.36m FLI 1001E 30 sec, Nayoro Hokkaido, Japan obs by, Yasuo Sano, http://sn1997ef.web.fc2.com/sn/nova/cas_tcpj_202505.html