Bridging between Type IIb and Ib Supernovae: SN IIb 2022crv with a Very Thin Hydrogen Envelope
Anjasha Gangopadhyay, Keiichi Maeda, Avinash Singh, A. J. Nayana, Tatsuya Nakaoka, Koji S. Kawabata, Kenta Taguchi, Mridweeka Singh, P. Chandra, S. D. Ryder, Raya Dastidar, M. Yamanaka, Miho Kawabata, R. Z. E. Alsaberi, Naveen Dukiya, Rishabh Singh Teja, Bhavya Ailawadhi, Anirban Dutta, D. K. Sahu, Takashi J. Moriya, Kuntal Misra, Masaomi Tanaka, Roger A. Chevalier, Nozomu Tominaga, Kohki Uno, Ryo Imazawa, Taisei Hamada, Tomoya Hori, Keisuke Isogai
Abstract
Abstract We present optical, near-infrared, and radio observations of supernova (SN) SN IIb 2022crv. We show that it retained a very thin H envelope and transitioned from an SN IIb to an SN Ib; prominent H α seen in the pre-maximum phase diminishes toward the post-maximum phase, while He i lines show increasing strength. SYNAPPS modeling of the early spectra of SN 2022crv suggests that the absorption feature at 6200 Å is explained by a substantial contribution of H α together with Si ii , as is also supported by the velocity evolution of H α . The light-curve evolution is consistent with the canonical stripped-envelope SN subclass but among the slowest. The light curve lacks the initial cooling phase and shows a bright main peak (peak M V = −17.82 ± 0.17 mag), mostly driven by radioactive decay of 56 Ni. The light-curve analysis suggests a thin outer H envelope ( M env ∼ 0.05 M ⊙ ) and a compact progenitor ( R env ∼ 3 R ⊙ ). An interaction-powered synchrotron self-absorption model can reproduce the radio light curves with a mean shock velocity of 0.1 c . The mass-loss rate is estimated to be in the range of (1.9−2.8) × 10 −5 M ⊙ yr −1 for an assumed wind velocity of 1000 km s −1 , which is on the high end in comparison with other compact SNe IIb/Ib. SN 2022crv fills a previously unoccupied parameter space of a very compact progenitor, representing a beautiful continuity between the compact and extended progenitor scenario of SNe IIb/Ib.