SN2018fif: The explosion of a large red supergiant discovered in its infancy by the Zwicky Transient Facility

Author(s): Soumagnac, Maayane T; Ganot, Noam; Gal-yam, Avishay; Ofek, Eran O; Yaron, Ofer; Waxman, Eli; Schulze, Steve; Yang, Yi; Rubin, Adam; Cenko, S Bradley; Sollerman, Jesper; Perley, Daniel A; Fremling, Christoffer; Nugent, Peter; Neill, James D; Karamehmetoglu, Emir; Bellm, Eric C; Bruch, Rachel J; Burruss, Rick; Cunningham, Virginia; Dekany, Richard; Golkhou, V Zach; Irani, Ido; Kasliwal, Mansi M; Konidaris, Nicholas P; Kulkarni, Shrinivas R; Kupfer, Thomas; Laher, Russ R; Masci, Frank J; Morag, Jonathan; Riddle, Reed; Rigault, Mickael; Rusholme, Ben; Roestel, Jan van; Zackay, Barak | Abstract: High cadence transient surveys are able to capture supernovae closer to their first light than before. Applying analytical models to such early emission, we can constrain the progenitor stars properties. In this paper, we present observations of SN2018fif (ZTF18abokyfk). The supernova was discovered close to first light and monitored by the Zwicky Transient Facility (ZTF) and the Neil Gehrels Swift Observatory. Early spectroscopic observations suggest that the progenitor of SN2018fif was surrounded by relatively small amounts of circumstellar material (CSM) compared to all previous cases. This particularity, coupled with the high cadence multiple-band coverage, makes it a good candidate to investigate using shock-cooling models. We employ the SOPRANOS code, an implementation of the model by Sapir a Waxman (2017). Compared with previous implementations, SOPRANOS has the advantage of including a careful account of the limited temporal validity domain of the shock-cooling model. We find that the progenitor of SN2018fif was a large red supergiant, with a radius of R=1174_{-81}^{+208} solar radii, and an ejected mass of M=5.6_{-1.0}^{+9.1} solar masses. Our model also gives information on the explosion epoch, the progenitor inner structure, the shock velocity and the extinction. The large radius differs from previously modeled objects, and the difference could be either intrinsic or due to the relatively small amount of CSM around SN2018fif, perhaps making it a "cleaner" candidate for applying shock-cooling analytical models.