Spectroscopic confirmation of TCP J18385851-0351482 as a classical nova
ATel #17292; Alexander Tarasenkov (INASAN/SAI MSU), Andrey Tatarnikov, Alexandr Dodin, Marina Burlak, Natalia Ikonnikova (SAI MSU), Sergey Shugarov (AISAS/SAI MSU), Vladimir Belousov, Stanislav Korotkiy (Astroverty, Ka-Dar), Elias Aydi (TTU), Kirill Sokolovsky (UIUC)
on 19 Jul 2025; 02:13 UT
Credential Certification: Kirill Sokolovsky (kirx@scan.sai.msu.ru)
We report spectroscopic classification of the optical transient
TCP J18385851-0351482 found by the New Milky Way Survey
(Sokolovsky, Korotkiy & Lebedev 2014, ASPC, 490, 395) at
unfiltered magnitude 12 on 2025-07-17.9085 UTC. The transient was
also detected by the Zwicky Transient Facility (Masci et al. 2019,
PASP, 131, 018003) as ZTF25abbsdyb at g=14.41 on 2025-07-17.2329.
The forced photometry with the ASAS-SN Sky Patrol (Shappee et al.
2014, ApJ, 788, 48; Kochanek et al. 2017, PASP, 129, 104502) server
reveals the first significant detection on 2025-07-15.9858
at g=15.8.
TCP J18385851-0351482 was observed on 2025-07-18.846 with
the 2.5 m telescope at the Caucasian Mountain Observatory of
the Sternberg Astronomical Institute (Lomonosov Moscow State
University) using the Transient Double-beam Spectrograph (Potanin
et al. 2020, AstL, 46, 836) covering 3550-5700 A at R~1300 (blue
arm) and 5700-7450 A at R~2400 (red arm). The spectrum displays red
continuum and P Cyg lines, including H_alpha and H_beta.
The peak-to-trough velocity of H_alpha is ~560 km/s.
In addition to the Balmer lines we identify Fe II lines of
the (42), (48), and (49) multiplets. We interpret the spectrum as
that of a classical nova before maximum light affected
by interstellar reddening.
Photometric observations of TCP J18385851-0351482 were obtained
using three telescopes: the 0.6m Zeiss-600 telescope (FLI ML 3041
CCD) at Stara Lesna Observatory of the Astronomical Institute,
Slovak Academy of Sciences; the 0.6m ASA RC600 reflector (Andor
iKon-L CCD) at the Caucasian Mountain Observatory of the Sternberg
Astronomical Institute; and the 0.5m Astrosib RC500 telescope
(ZWO ASI6200MM Pro CMOS) at Kislovodsk observatory of INASAN,
Russian Academy of Sciences, yielding the following
preliminary results:
2025-07-18.8348 V=12.10 B-V=2.36 V-R=1.88 V-I=3.19 SAI
2025-07-18.8764 V=12.09 B-V=2.18 V-R=1.86 V-I=3.33 AISAS
2025-07-18.8776 V=11.94 B-V=2.01 V-R=1.92 V-I=3.40 INASAN
The magnitudes were calibrated using the APASS stars in the field,
but not transformed to the standard system. The new unfiltered
observations with the NMW camera show the nova at the same
brightness as the previous night:
2025-07-18.7704 CV=11.9
2025-07-18.8132 CV=12.0
We also used images from the AISAS, SAI, and INASAN photometric
telescopes to measure the astrometric position of the nova with
respect to Gaia DR3 stars: 18:38:58.47 -03:51:49.4 J2000 which
coincides within 0.1" with the position of ZTF25abbsdyb.
2.5m CMO SAI spectrum of TCP J18385851-0351482