WFST Supernovae in the First Year: III. Systematical Study of the Photometric Behavior of Early-phase Core-collapse Supernovae

TL;DR

This study analyzes seven WFST-detected core-collapse SNe with prominent early shock-cooling emission, using joint analytic modeling of the early cooling phase and later $^{56}$Ni-powered evolution. By fitting bolometric light curves and constraining progenitor properties, the authors infer ejecta masses of about $1.1$–$2.6$ $M_\, ext{odot}$, envelope masses of $0.07$–$0.50$ $M_\odot$, and envelope radii of $60$–$300$ $R_\odot$, with progenitor luminosities near $L oughly10^{4.6}$–$10^{4.9} L_\odot$ corresponding to ZAMS masses of $8$–$20 M_\odot$. The results place these events in a transitional regime between ultra-stripped SNe and normal SESNe, and favor binary evolution as the dominant channel for producing such envelopes. The study demonstrates WFST’s capability for early-time, high-cadence photometry to constrain pre-explosion mass loss and progenitor structure, contributing to our understanding of the binary pathways driving envelope stripping in core-collapse SNe.

Abstract

We investigate the multiband photometric properties of seven supernovae (SNe) showing double-peaked light-curve evolution and prominent shock-cooling emission, observed by the Wide Field Survey Telescope (WFST) during its first year of operation. By jointly employing an analytic early shock-cooling model and the Arnett radioactive-diffusion model, we fit the bolometric light curves and infer ejecta masses in the range $1.1$-$2.6 M_\odot$, consistent with a transitional population between ultra-stripped supernovae (USSNe) and normal stripped-envelope supernovae (SESNe). The envelope masses are estimated to be $M_{\rm env}=0.1$-$0.4 M_\odot$, while the progenitors are constrained to be yellow or blue supergiants (YSGs/BSGs) with radii of $R=120$-$300 R_\odot$. Using empirical relations, we estimate progenitor luminosities of $L=10^{4.6}$-$10^{4.9} L_\odot$, corresponding to zero-age main-sequence (ZAMS) masses of $8$-$20 M_\odot$. Theoretical models suggest that such progenitors are more naturally produced through binary evolution channels, as single-star evolutionary pathways are unable to yield ejecta masses this low.

Figures (8)

• Figure 1: Multiband light curves are presented for the full sample. The $g$-band data are shown in blue, green and purple symbols denote $r$- and $u$-bands, respectively. Triangles indicate $3\sigma$ upper limits. Non-detections separated by $>7$ days from the first detection are omitted.
• Figure 2: Light curves in $r/R$-band absolute magnitude of all SNe. For comparison, light curves of several well-studied SNe are plotted. Gray dashed line marks the phase of primary peak.
• Figure 3: The light-curve decline-rate $\Delta m_{15}$ is plotted against peak brightness. Values correspond to the $r$- or $R$-band. The $R$-band is adopted for SN 1993J, SN 2011fu and SN 2013df. SN 2016gkg, SN 2008ax and SN 2011dh also utilize this band. All other sources rely on $r$-band observations. Comparison samples include SESNe from taddia_carnegie_2018, D23 and D24. WFST-PS240307bh shows a peak brightness and decline rate comparable to Type Ic-BL SNe. Faster declining light curves generally possess lower peak luminosities. This trend associates high $\Delta m_{15}$ values with fainter magnitudes. WFST250522otkg and WFST250617iqnc display the highest decline rates. However, these measurements carry large uncertainties.
• Figure 4: Color evolution of SNe compared to SN 2016gkg, where the $V-R$ color of SN 2016gkg is transformed to $g-r$ using the empirical color-color relation calibrated by jordi_empirical_2006. Solid line with error range coded by colors are color evolution templates from the main peak to 20 days after in rest-frame of type IIb, Ib and Ic SNe introduced in stritzinger_carnegie_2018.
• Figure 5: Left: The bolometric light curves of SNe. Solid lines denote the total best fits from Arnett and P21 model, with dotted lines showing the decomposed components for a representative example. Right: Black body temperature evolution of SNe derived from SuperBol fitting. Shock Cooling models are valid only for data where the $T_{\rm BB}$ is greater than $8120~\mathrm{K}$ or 0.7 eV sapir_uvoptical_2017.