SN 2021gno: a calcium-rich transient with double-peaked light curves

Ertini, K.; Folatelli, G.; Martinez, L.; Bersten, M. C.; Anderson, J. P.; Ashall, C.; Baron, E.; Bose, S.; Brown, P. J.; Burns, C.; Derkacy, J. M.; Ferrari, L.; Galbany, L.; Hsiao, E.; Kumar, S.; Lu, J.; Mazzali, P.; Morrell, N.; Orellana, M.; Pessi, P. J.; Phillips, M. M.; Piro, A. L.; Polin, A.; Shahbandeh, M.; Shappee, B. J.; Stritzinger, M.; Suntzeff, N. B.; Tucker, M.; Elias-Rosa, N.; Kuncarayakti, H.; Gutierrez, C. P.; Kozyreva, A.; Mueller-Bravo, T. E.; Chen, T. W.; Hinkle, J. T.; Payne, A., V; Szekely, P.; Szalai, T.; Barna, B.; Koenyves-Toth, R.; Banhidi, D.; Biro, I. B.; Csanyi, I; Kriskovits, L.; Pal, A.; Szabo, Zs; Szakats, R.; Vida, K.; Vinko, J.; Gromadzki, M.; Harvey, L.; Nicholl, M.; Paraskeva, E.; Young, D. R.; Englert, B.
2023
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
DOI
10.1093/mnras/stad2705
We present extensive ultraviolet (UV) and optical photometric and optical spectroscopic follow-up of supernova (SN) 2021gno by the 'Precision Observations of Infant Supernova Explosions' (POISE) project, starting less than 2 d after the explosion. Given its intermediate luminosity, fast photometric evolution, and quick transition to the nebular phase with spectra dominated by [Ca II ] lines, SN 2021gno belongs to the small family of Calcium-rich transients. Moreo v er, it shows double-peaked light curves, a phenomenon shared with only four other Calcium-rich events. The projected distance from the centre of the host galaxy is not as large as other objects in this family. The initial optical light-curve peaks coincide with a very quick decline of the UV flux, indicating a fast initial cooling phase. Through hydrodynamical modelling of the bolometric light curve and line velocity evolution, we found that the observations are compatible with the explosion of a highly stripped massive star with an ejecta mass of 0.8 M-circle dot and a Ni-56 mass of 0.024 M-circle dot. The initial cooling phase (first light-curve peak) is explained by the presence of an extended circumstellar material comprising similar to 10 (-2) M-circle dot with an extension of 1100 R-circle dot. We discuss if hydrogen features are present in both maximum-light and nebular spectra, and their implications in terms of the proposed progenitor scenarios for Calcium-rich transients.