SOAR spectroscopic follow-up of ASASSN-23hd, a nova in the LMC
ATel #16294; J. Strader, E. Aydi, L. Chomiuk, R. Kyer, R. Urquhart (MSU), K. V. Sokolovsky (U. Illinois UC), K. Z. Stanek, C. S. Kochanek (OSU), B. J. Shappee (U. Hawaii)
on 16 Oct 2023; 16:29 UT
Credential Certification: Elias Aydi (aydielia@msu.edu)
Subjects: Optical, Binary, Cataclysmic Variable, Nova, Star, Transient, Variables
We report on optical spectroscopic follow-up of the optical transient ASASSN-23hd, which was discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN; Shappee et al. 2014, ApJ, 788, 48) on 2023-10-13.9UT at g = 10.37 in the direction of the Large Magellanic Cloud. Spectroscopic follow-up by C. Lidman et al. on 2023-10-15 (TNS Classification Report No. 15779), showed strong emission lines of Balmer, classifying the transient as a classical nova.
On 2023-10-14 and 15 we obtained a low- and medium-resolution spectra of ASASSN-23hd using the Goodman spectrograph (Clemens et al. 2004, SPIE, 5492, 331) on the 4.1m SOAR telescope. The spectra show strong emission lines of H I, He I, N II, and N III. The Balmer lines are characterized by a central emission peak on top of a broad base, whose wings extend up to +\- 6000 km/s in Hbeta and up to +\- 10000 km/s in Halpha. The high-velocities are consistent with the decline time from optical peak by 2 magnitudes in just 2 days, as observed by ASAS-SN sky patrol (Kochanek et al. 2017PASP, 129, 4502): https://asas-sn.osu.edu/sky-patrol/coordinate/b500c1b6-18f6-460a-beea-c078bb7cba20.
The central peak of Hbeta is shifted by +250 km/s, consistent with the radial velocity of the LMC. Assuming a distance of 50 kpc to the nova and Ag = 0.25, we derive a peak absolute magnitude of -8.4 in the g-band, typical for a classical nova. Astrometry performed on the SOAR images confirms that the nova progenitor is likely the Gaia DR3 source ID 4662989888116855808 (G = 20.06). In summary, the optical spectro-photoemtric data of ASASSN-23hd are consistent with an extremely fast LMC nova during the decline from optical peak.
This ATel is based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministerio da Ciencia, Tecnologia, Inovacoes e Comunicacoes do Brasil (MCTIC/LNA), the U.S. National Science Foundation's National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).
