2023/10/22 by Srinivasaragavan, Gokul P., Swain, Vishwajeet, O'Connor, Brendan M. +39
#FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE)
paper · doi:10.48550/arxiv.2310.14397
We report observations of the optical counterpart of the long gamma-ray burst (LGRB) GRB 230812B, and its associated supernova (SN) SN 2023pel. The proximity (z = 0.36) and high energy (E_γ, \rmiso ∼ 1053 erg) make it an important event to study as a probe of the connection between massive star core-collapse and relativistic jet formation. With a phenomenological power-law model for the optical afterglow, we find a late-time flattening consistent with the presence of an associated SN. SN 2023pel has an absolute peak r-band magnitude of Mr = -19.46 ± 0.18 mag (about as bright as SN 1998bw) and evolves on quicker timescales. Using a radioactive heating model, we derive a nickel mass powering the SN of M_\rmNi = 0.38 ± 0.01 \rmM_\odot, and a peak bolometric luminosity of L_\rmbol ∼ 1.3 × 1043 \rmerg \rms-1. We confirm SN 2023pel's classification as a broad-lined Type Ic SN with a spectrum taken 15.5 days after its peak in r band, and derive a photospheric expansion velocity of v_\rmph = 11,300 ± 1,600 \rmkm \rms-1 at that phase. Extrapolating this velocity to the time of maximum light, we derive the ejecta mass M_\rmej = 1.0 ± 0.6 \rmM_\odot and kinetic energy E_\rmKE = 1.3+3.3-1.2 ×1051 \rmerg. We find that GRB 230812B/SN 2023pel has SN properties that are mostly consistent with the overall GRB-SN population. The lack of correlations found in the GRB-SN population between SN brightness and E_γ, \rmiso for their associated GRBs, across a broad range of 7 orders of magnitude, provides further evidence that the central engine powering the relativistic ejecta is not coupled to the SN powering mechanism in GRB-SN systems.