AstroNote 2021-75

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DRAFT
2021-02-22 21:52:23
Type: Object/s-Discovery/Classification
adH0cc spectroscopic classification of SN 2021crx, an unusually luminous low-velocity Type II supernova
Authors: G. Csoernyei, S. Taubenberger, C. Vogl, A. Floers, M. G. Cudmani, A. Holas, W. Hillebrandt, S. H. Suyu (MPA Garching), A. Pastorello (INAF Padova), B. Leibundgut, J. Spyromilio (ESO), S. J. Smartt, M. Dobson (QUB), R. Kotak (Turku), R. Bruch, A. Gal-Yam (Weizmann), C. Lemon (Lausanne), S. Blondin (CNRS, LAM)
Source Group: adH0cc
Abstract:
We have obtained an optical spectrum of SN 2021crx, which shows it to be an unusually luminous member of the class of low-velocity Type II supernovae.

The adH0cc programme for an "accurate determination of H0 with core-collapse supernovae" reports the classification of the optical transient SN 2021crx. The target was supplied by the Zwicky Transient Facility ZTF (Kulkarni 2018, 2018ATel11266....1K). The observations were performed on the night of 2021 February 20 with the ESO Very Large Telescope UT1, equipped with the FORS2 spectrograph and grism 300V, covering a wavelength range from 3400 to 9600 Å at a resolution of 10 Å. The classification was done with the help of GELATO (Harutyunyan et al. 2008, 2008A&A...488..383H).

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CatalogNameReported RAReported DECReported Obj-TypeReported RedshiftHost NameHost RedshiftSourcePhaseRemarksTNS RATNS DECTNS Obj-TypeTNS Redshift
TNS2021crx [ZTF21aakigqr]13:21:53.976+08:36:20.34SN II0.066866WISEA J132153.85+083618.50.066866ZTF14dThe presence of strong hydrogen P Cygni features indicates that this object is a Type II supernova. The ZTF light curve suggests that it belongs to the Type IIP subclass and that the phase of the spectrum is about 14 days after the explosion. GELATO finds a good spectroscopic match with the low-energy, low-luminosity type IIP supernova SN 1999br (Pastorello et al. 2004, MNRAS, 347, 74; Lisakov et al. 2018, MNRAS, 473, 3863) at the same phase. We estimate an ejecta velocity of about 3300 km/s from the H-beta and Fe II 5159 Å line. In light of the low expansion velocity, the supernova is exceptionally luminous with an absolute magnitude of about -17.5 in the r band. This is roughly three magnitudes brighter than the spectroscopically similar SN 1999br.13:21:53.976+08:36:20.34SN II0.066866