Spectroscopic classification of AT 2023nzt as a Luminous Red Nova in NGC 0925
ATel #16258; J. Vinko (HUN-REN CSFK Konkoly Observatory) and J. C. Wheeler (UT Austin)
on 27 Sep 2023; 18:03 UT
Credential Certification: Jozsef Vinko (vinko@astro.as.utexas.edu)
Subjects: Optical, Transient
AT 2023nzt was discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey as a faint (m ~ 19.15 mag) transient (ATLAS23pse) in the outskirts of the nearby (redshift ~ 0.00185, D = 9 Mpc) galaxy NGC 0925 on 2023-07-26 (Smith et al. TNS AstroNote 2023-214). The transient was also detected by the Zwicky Transient Facility (ZTF23aatekmu) and Pan-STARRS (PS23gkb) in a few days after discovery.
We started a photometric follow-up of AT 2023nzt with the RC80 robotic telescope at Konkoly Observatory through BVgriz filters. In accordance with ZTF photometry (https://alerce.online/object/ZTF23aatekmu), the transient showed a slowly rising light curve peaking on MJD 60194 (2023-09.27,
3 months after discovery) and a persistent red color (g - r = 0.8 +/- 0.1 mag).
An optical spectrum (R ~ 1500) taken with the Low Resolution Spectrograph 2 (LRS2) on the Hobby-Eberly Telescope at McDonald Observatory on 2023-09-24 revealed the presence of a narrow, unresolved H-alpha emission superimposed on a red continuum. Above 8000 A strong molecular bands start to dominate the spectrum. The overall appearance of the spectrum, as well as the peak absolute magnitude (M_r ~ -11.5 mag) is consistent with a classification of AT 2023nzt as a Luminous Red Nova (LRN), similar to AT 2017jfs at late phases (Pastorello et al. A&A 625, L8, 2019).
We acknowledge the work by the HET observing staff for scheduling and executing the spectroscopic observations.
