Bridging between type IIb and Ib supernovae: SN IIb 2022crv with a very thin Hydrogen envelope

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 a SN~IIb to a SN~Ib; prominent H$\hat{I}\pm$ seen in the pre-maximum phase diminishes toward the post-maximum phase, while He {\sc i} lines show increasing strength. \texttt{SYNAPPS} modeling of the early spectra of SN~2022crv suggests that the absorption feature at 6200\,Ã is explained by a substantial contribution of H$\hat{I}\pm$ together with Si {\sc ii}, as is also supported by the velocity evolution of H$\hat{I}\pm$. The light-curve evolution is consistent with the canonical stripped-envelope supernova subclass but among the slowest. The light curve lacks the initial cooling phase and shows a bright main peak (peak M${}_V$=$-$17.82$\pm$0.17 mag), mostly driven by radioactive decay of ${}^{56}$Ni. The light-curve analysis suggests a thin outer H envelope ($M_{\mathrm{env}}\sim$0.05 M${}_{\odot }$) and a compact progenitor (R${}_{\mathrm{env}}$ $\sim$3 R${}_{\odot }$). An interaction-powered synchrotron self-absorption (SSA) model can reproduce the radio light curves with a mean shock velocity of 0.1c. The mass-loss rate is estimated to be in the range of (1.9$-$2.8) $\times$ 10${}^{-5}$ M${}_{\odot }$ 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.

The paper contains 20 figures and 9 tables. Accepted for publication in The Astrophysical Journal (ApJ)