Spectroscopic Classification of Astrophysical Transients with the Lick Shane Telescope

ATel #17176; P. Arunachalam, K. W. Davis, K. C. Patra, R. Kaur, R. J. Foley (UCSC)
on 8 May 2025; 20:40 UT
Credential Certification: Prasiddha Arunachalam (parunach@ucsc.edu)

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We report the following classification from spectroscopic observations with the Kast spectrograph on the Shane telescope obtained on 2025 April 21 UT. The targets were supplied by ATLAS and ZTF (through both the ALeRCE and Fritz data streams). The classifications were performed with SNID (Blondin & Tonry, 2007, ApJ, 666, 1024).

 
Name         | IAU Name   | RA (J2000)   | Dec (J2000)  |   z   | Type   | Phase | Notes
 
ZTF24abpqeun | AT2024zxj  | 15:56:57.695 | +19:28:29.50 | 0.11  | II     |  +70  | (1)  
ZTF25aacdjzo | AT2025pb   | 16:23:14.271 | +40:55:20.06 | 0.05  | Ic     |  +10  | (2) 
ATLAS25dpz   | AT2025gxf  | 17:08:43.347 | +33:20:42.13 | 0.055 | Ia-91T |  +4   | (3) 

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) The spectrum of 2024zxj is most consistent with a phase of +70 using SNID; however, the spectrum was taken approximately 135 days after peak. It shows a single emission feature with a broad component with FWHM ~ 8600 km/s, which we assume to be H-alpha at z = 0.11. We note that at a redshift of 0.11, the SN peaked at an absolute magnitude of R < -21 mag. (2) The spectrum is most consistent with those of SNe Ic at +10 days; however, the light curve peaked ~70 days before our observation (around 2025 Feb 10). (3) Using the reported host redshift, we measure a Si II 6355 velocity of -10,200 km/s.