Spectroscopic Classification of Astrophysical Transients with the Lick Shane Telescope

ATel #17223; R. Kaur, K. C. Patra, K. W. Davis, R. J. Foley (UCSC)
on 6 Jun 2025; 03:41 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Kishore Patra (kcpatra@ucsc.edu)

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We report the classifications of astrophysical transients from spectroscopic observations with the Kast spectrograph on the Shane telescope obtained on 2025 June 03 UT. The targets were supplied by the Young Supernova Experiment and ATLAS. Targets were identified using the target management platform YSE-PZ (Coulter et al., 2023, PASP, 135, 4501). The classifications were performed with SNID (Blondin & Tonry, 2007, ApJ, 666, 1024).

 
Name         | IAU Name   | RA (J2000)   | Dec (J2000)  |   z   |  Type   | Phase | Notes
 
PS25bze      | AT2025jar  | 15:13:53.76  | +00:17:19.77 | 0.071 | Ia-91bg | +18d  | (1) 
ATLAS25fvu   | AT2025msx  | 11:57:17.69  | +25:11:14.75 | 0.014 | Ic-BL   |  +8d  | (2) 
 

Notes: When the redshift is given to 2 decimal places, it is derived from the SN spectrum. Otherwise, the redshift is determined from the host galaxy. (1) We measure a redshift of 0.0713 from a spectrum of the host galaxy, which differs from the NED-listed redshift that was inferred from a friends-of-friends procedure. The spectrum matches well with SN 1991bg-like SNe Ia at a phase of about 18 days after peak at a redshift of 0.07, consistent with our spectroscopic redshift measurement. We measure a Si II 6355 velocity of -8,100 km/s. (2) The observed spectrum is particularly red, and assuming a typical blue spectrum for a young SN, the color can be attributed to dust reddening of E(B-V) ~ 1.2 mag. The spectrum has broad spectral features consistent with that of a SN Ic-BL soon after peak brightness. The ATLAS light curve is either still rising or at peak, and so we caution that the phase reported is likely biased by ~7 days. Correcting for the derived reddening and a Hubble-flow distance accounting for Virgo inflow and the Great Attractor, we find an absolute magnitude of M_o = -19.0 mag, consistent with a SN Ic-BL before peak brightness.