Swift observations of SN 2025coe, a potential Ca-rich SN Ib
ATel #17138; T. S. Hu, S. Ketchum, V. Tananko, D. Byun, X. Xiang, J. M. Miller (University of Michigan)
on 7 Apr 2025; 20:50 UT
Credential Certification: Jon Miller (jonmm@umich.edu)
Subjects: Optical, Ultra-Violet, Supernovae, Transient
We report on recent Swift UVOT observations of SN 2025coe, recently classified as a potential Ca-rich SN Ib (Andrews et al. 2025). This class of supernovae is notable for particularly rapid increases and decreases to and from peak flux levels, and for spectra that are dominated by Ca at late times. It is possible that double-white dwarf binaries, or white dwarf plus neutron star binaries, are the progenitors of Ca-rich SN Ib.
We analyzed a set of 9 UVOT observations, spanning MJD 60732-60751. In the W2 filter, the measured flux density on MJD 60732 is F_nu = 5.9 +/- 0.2 E-15 erg/cm2/s/A, falling to F_nu = 0.96 +/- 0.05 E-15 two days later on MJD 60734. The UVOT M2 filter has the smallest red leak, and in this band the flux density falls from F_nu = 4.9 +/- 0.2 E-15 erg/cm2/s/A to F_nu = 0.8 +/- 0.1 E-15 erg/cm2/s/A over the same two days. Apart from the V band, which shows a relatively steady flux at all times, the other UVOT bands show similarly sharp declines, and all bands appear to reach a quasi-steady flux level by 60742, just 10 days after the initial UVOT exposure.
Further photometry and spectroscopy are encouraged at all wavelengths.
References:
Andrews, M., et al., 2025, TNSCR 1033
