Spectroscopic Classification of Astrophysical Transients with the Lick Shane Telescope

ATel #17250; K. W. Davis, R. J. Foley (UCSC)
on 27 Jun 2025; 01:08 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Ryan Foley (foley@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 26 UT. The targets were supplied by ZTF and ALeRCE (selected from the ZTF data stream). 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
 
ZTF25aastkua | SN2025mhx  | 18:38:38.037 | +62:31:35.97 | 0.04     |  SN Iax | +10d  | (1) 
ZTF18aamfybf | AT2025nrs  | 14:01:33.910 | +24:59:10.37 | 0.07678  |  SN Ia  |  +6d  | (2) 
ZTF25aavoysc | AT2025nzc  | 14:38:51.768 | +10:14:28.26 | 0.05461  |  SN II  |       | (3) 
ZTF25aavpehi | AT2025nzq  | 16:55:41.831 | +53:22:28.12 | 0.050    |  SN Ia  |  -8d  | (4) 
ZTF25aavpdlj | AT2025ode  | 15:54:56.006 | +19:42:41.65 | 0.049    |  SN Ia  |  -6d  | (5) 
 
 

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) SN2025mhx was previously classified as "SN Ia-91T" at z=0.05 by Terwel et al. (2025, TNSCR 2166). With a higher signal-to-noise spectrum and ~2 weeks of evolution, the object shows several spectral lines with absorption velocities more consistent with SNe Iax (~-6000 km/s). We find several matches to SNe Iax, including SN 2002cx, at z=0.04. (2) We subtract the 1-dimensional SDSS spectrum of the host and recover a spectrum with several SN Ia features. We measure a Si II 6355 velocity of -11,400 km/s. (3) The spectrum shows a blue and mostly featureless continuum with a weak broad emission line consistent with H alpha. (4) We measure a Si II 6355 velocity of -12,600 km/s. (5) We measure a Si II 6355 velocity of -16,000 km/s.