Spectroscopic Classifications of Optical Transients with Keck II/KCWI
ATel #17793; Jenna Karcheski, Kishore C. Patra, Ryan J. Foley (UCSC)
on 11 May 2026; 10:35 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Kishore Patra (kcpatra@ucsc.edu)
Subjects: Optical, Supernovae, Transient
We report the following classifications of optical transients from spectroscopic observations with the Keck Cosmic Web Imager (KCWI) Integral Field Spectrograph. The targets were supplied by the Legacy Survey of Space and Time (LSST) via the ANTARES alerts broker (Matheson et al., 2021, AJ, 161, 107). Observations were made on 2026 May 7 UT. Classifications were performed with SNID (Blondin & Tonry, 2007, ApJ, 666, 1024).
Name | IAU Name | RA (J2000) | Dec (J2000) | z | Type | Phase | Notes
LSST-AP-DO-170257199649521669 | AT2026kfw | 09:56:52.77 | +01:49:59.20 | 0.21 | SN Ia | +7 d |(1)
LSST-AP-DO-170230797176406143 | AT2026jkr | 10:04:17.29 | +03:25:22.88 | 0.35 | SN Ic-BL | +3 d |
LSST-AP-DO-170226393328648251 | AT2026ikn | 09:59:46.48 | +03:46:48.85 | 0.298 | SN Ia | +15 d |(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 Si II 6355 velocity of -12,500 km/s.
(2) Redshift was determined using emission lines from the host galaxy. The spectrum is highly contaminated by galaxy light. SNID template fitting was performed after subtracting a host-galaxy template spectrum. The best-fit match was SN 2005hf at +15 days past peak brightness.
We thank the Vera C. Rubin Observatory leadership and staff, and especially thank the Prompt Processing team (Findeisen et al., arXiv:2603.19541), for publicly releasing these discoveries.
