Central Bureau for Astronomical Telegrams
CBAT "Transient Object Followup Reports"
TCP J20315286+2740166
TCP J20315286+2740166 2023 11 04.7066* 20 31 52.86 +27 40 16.6 12.4 U Vul 9 0
2023 11 04.7066
The transient was discovered in six images obtained with the NMW wide-field camera (135mm f/2.0 telephoto lens + unfiltered SBIG ST-8300M CCD; http://scan.sai.msu.ru/nmw/ ) operating at the Astroverty astrofarm in Nizhnii Arkhyz, Karachay-Cherkessia, Russia. Preliminary photometry indicates that the transient might have been rising in brightness during 1.5 hours between the discovery and confirmation images: 2023-11-04.7066 UTC CV=12.4 2023-11-04.7677 UTC CV=12.2 typical photometric uncertainty 0.1mag; magnitude zero-point set using V magnitudes of Tycho-2 stars in the field. The transient is not visible in the NMW images obtained the previous night on 2023-11-03.7958 (limiting magnitude CV~14). A known white dwarf candidate Gaia DR2 1857057959447151616 (Gaia DR3 Gmag=20.17; position end figures 52.849s, 17.93', Plx= 2.46 +/-0.57 mas) is located 1.3" (within ~2" uncertainty) from the discovery position. The transient is likely an outburst of a previously unknown dwarf nova. No previous outbursts are found in publicly available ASAS-SN, ATLAS and ZTF data. The plate-solved NMW FITS images and finder charts may be found at http://scan.sai.msu.ru/~kirx/img/TCPJ20315286+2740166/ ---- Stanislav Korotkiy (Astroverty, Ka-Dar), Kirill Sokolovsky (UIUC, SAI MSU), Sergei Ostapenko (Astroverty, Ka-Dar)
2023 11 04.8460
The new NMW images suggest the object continues to brighten: 2023-11-04.8460 UTC CV=11.8 +/-0.1. ---- Stanislav Korotkiy (Astroverty, Ka-Dar), Kirill Sokolovsky (UIUC, SAI MSU), Sergei Ostapenko (Astroverty, Ka-Dar)
2023 11 06.0822
Position end figures 52s.82, 17".1 measured with 0.25m reflector + CCD (T05) at Utah Desert Remote Observatory, USA. J2000, Gaia DR2 positions. Progenitor likely to be Gaia G mag 20.2 star (Gaia DR3 1857057959447151616) located 0.35" from transient measured position. V magnitude approximately 12.0. Andrew Pearce, Nedlands, W. Australia.
2023 11 08.3807
Photometry results were B=12.63, V=12.80, Rc=12.88 and Ic=13.05 with 0.28mSCT + QSI 632ws CCD at TAO-Kamagaya, https://meineko.com/ccd/TCP_J20315286+2740166.jpg Japan. - Seiichiro Kiyota (Kamagaya, Japan)
2023 11 12.788
Andreoli.V ; Ochner.P : Castellani.F, Cazzola.R reports a spectroscopic classification of TCP J20315286+2740166. Low resolution spectra was obteined by 1.22-m tlescope + B&C spectrograph (with dispersion 2.25 Ang/pix) located in Asiago (Italy) on 2023-11-12.788 and with 0.25-m tlescope + Alpy600 spectrograph (with dispersion 4.9 Ang/pix) located in Novezzina (Italy) on 2023-11-12.823, the spectra show emission of Halpha (6562.8 Ang) and [O I] (5577 Ang), absorption of Hbeta, Hdelta, Hgamma, Hepsilon and He I (4471 Ang) and has a blue continuum. Considered d=0.406 kpc from the 3D dust mapping (Green et al 2019) get E(B-V)≈0.00 B,V,R photometry was also collected with 0.4m telescope + Moravian G4 CCD full frame located in Novezzina (Italy) at 2023/11/12.788 with results B=13.961, V=13.466, R= 13.036 , (B-V)0 =0.495 . Gaia DR2 1857057959447151616 is also present in ZTF database at magnitude 17.9 (filter zg) that’s means Δmag ≈ 5 mag (referring to the magnitude of discovery) All this feature are typically of a dwarf nova outburst, we propose to classified TCP J20315286+2740166 (Gaia DR3 1857057959447151616) as a dwarf nova.
