2025/09/30 by Chun Chen, Ning-Chen Sun, Chen, Chun +52 · 1 citation
Physics and Astronomy · Engineering · #Gamma-ray bursts and supernovae #Astronomical and nuclear sciences #CCD and CMOS Imaging Sensors
paper · pdf · doi:10.48550/arxiv.2510.00135
SN 2025coe is a calcium-strong transient located at an extremely large projected offset ∼39.3 kpc from the center of its host, the nearby early-type galaxy NGC 3277 at a distance of ∼25.5 Mpc. In this paper, we present multi-band photometric and spectroscopic observations spanning ∼100 days post-discovery. Its multi-band light curves display multiple distinct peaks: (1) an initial peak at t ≈ 1.6 days attributed to shock cooling emission, (2) a secondary peak of MR, peak ≈ -15.8 mag at t ≈ 10.2 days powered by radioactive decay, and (3) a possible late-time bump at t ≈ 42.8 days likely caused by ejecta-circumstellar material/clump interaction. Spectral evolution of SN 2025coe reveals a fast transition to the nebular phase within 2 months, where it exhibits an exceptionally high [Ca II]/[O I] ratio larger than 6. Modeling of the bolometric light curve suggests an ejecta mass of M\rm ej = 0.29+0.14-0.15 M\odot, a 56Ni mass of M\rm 56Ni = 2.4+0.06-0.05 × 10-2 M\odot, and a progenitor envelope with mass Me = 1.4+6.9-1.2 × 10-3 M\odot and radius Re = 13.5+64.1-11.1 R\odot. The tidal disruption of a hybrid HeCO white dwarf (WD) by a low-mass CO WD provides a natural explanation for the low ejecta mass, the small fraction of 56Ni, and the presence of an extended, low-mass envelope.