Spectroscopic classification of AT2020upt in M 33 and re-classification of SN 2020uem as a Type IIn-pec SN

ATel #14189; A. Reguitti (UNAB, INAF-OAPd), A. Pastorello, S. Benetti, N. Elias-Rosa (INAF-OAPd), C. Balcon (ISSP)
on 17 Nov 2020; 17:03 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Andrea Pastorello (andrea.pastorello@oapd.inaf.it)

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In the framework of the Asiago Transient Classification Program (Tomasella et al. 2014, AN, 335, 841) we report the spectroscopic classification of AT2020upt (ZTF20aceeeuz; Nordin et al. 2020, TNSTR 3001) in the Triangulum galaxy M 33, and SN 2020uem (ATLAS20bbsz; Tonry et al. 2020, TNSTR 2930) in the galaxy WISEA J082423.32-032918.6. The candidates were provided by the Zwicky Transient Factory (ZTF; Bellm et al. 2019, Graham et al. 2019) and the ATLAS survey (Tonry et al. 2018, PASP, 130, 4505), respectively.

The observations were performed with the Asiago 1.82 m Copernico Telescope equipped with AFOSC (range 340-820 nm; resolution 2.3 nm) on 2020-11-16.91 UT (AT 2020upt) and 2020-11-17.18 UT (SN 2020uem).

 
IAU Name   |  Survey name  | Redshift | Discovery (UT) |   Discovery mag   |   Type     |  Phase   | Notes 
AT 2020upt |  ZTF20aceeeuz | -0.0001  | 2020-09-26.45  | 20.77 (g-ZTF)     | Fe II nova |  +50 d   | (1) 
SN 2020uem |  ATLAS20bbsz  |  0.041   | 2020-09-22.60  | 16.49 (ATLAS-cyan)|   IIn-pec  | 2 months | (2) 

(1) The spectrum is that of a Fe Nova, with strong and unresolved Balmer emission lines, visible up to H-epsilon. We detect emission lines of the Fe II multiplet 42. A prominent O I 777.4 nm line is also identified. The redshift is determined from the center of Halpha in the spectrum of the transient, and is consistent with that of M33 (z=-0.0006) reported by De Vaucouleurs et al. 1991, RC3, 9.

(2) The low signal-to-noise spectrum shows a prominent Halpha in emission as in Type II SNe, consistently with that seen in the P60/SEDM classification spectrum (Dahiwale et al. 2020, TNSCR, 3122). Gelato (Harutyunyan et al. 2008, A&A, 488, 383) returns fair matches with spectra of the peculiar type IIn SN 2005gj (Prieto et al 2007, arXiv:0706.4088) about two months after maximum. The redshift is determined from the Halpha line in the spectrum of the supernova, and is consistent with the one (z=0.045) reported by Dahiwale et al. 2020. No redshift is available for the host galaxy.