Spectroscopic Classifications of Optical Transients with Keck I/LRIS

ATel #14262; M. R. Siebert, K. Taggart, G. Dimitriadis, S. Tinyanont (UC Santa Cruz), E. Strasburger (UC Berkeley), R. J. Foley (UC Santa Cruz)
on 11 Dec 2020; 23:38 UT
Credential Certification: Samaporn Tinyanont (st@astro.caltech.edu)

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We report the classification of the optical transients from spectroscopic observations with the LRIS spectrograph on the Keck I telescope, made on 2020 Dec 11 UT. The targets were supplied by YSE and ZTF (both self-reported and by ALeRCE). Classifications were performed with SNID (Blondin & Tonry, 2007, ApJ, 666, 1024).

 
Name         | IAU Name | RA (J2000)  | Dec (J2000)  |   z   | Type   | Phase | Notes
 
PS20hie      | 2020tan  | 01:09:44.56 | +00:20:24.93 | 0.079 | IIn    |  +90  | (1) 
ZTF20achaxsk | 2020vdk  | 00:54:18.67 | -14:41:23.48 | 0.074 | II     |  +60  | (2) 
PS20kwu      | 2020zbr  | 03:59:55.55 | -12:14:16.14 | 0.091 | Ia     |  +25  |  
ZTF20acpjfln | 2020zfn  | 21:44:20.19 | +08:37:24.52 | 0.038 | Ia     |  +40  |  
ZTF20acpumut | 2020zjo  | 07:19:53.64 | +37:33:29.08 | 0.082 | Ia     |  +15  | (3) 
PS20kyg      | 2020zmn  | 01:08:03.50 | +01:08:41.46 | 0.019 | LBV    |       | (4) 
PS20lsc      | 2020aavd | 03:57:08.98 | -24:54:06.64 | 0.142 | Ia     |  +20  |  
ZTF20acuzydz | 2020aboh | 09:17:31.76 | +41:59:34.01 | 0.007 | SN     |       | (5) 
PS20lwr      | 2020abvg | 01:11:36.26 | -15:12:52.25 | 0.043 | Ia     |  +20  | 
ZTF20acwilfu | 2020acbc | 04:16:41.25 | -24:50:05.81 | 0.13  | Ia     |  -4   | (6) 
ZTF20acwobku | 2020acct | 09:44:56.06 | +31:05:45.77 | 0.035 | IIn    |  -12  | (7) 
10LYSEnhv    |          | 04:22:26.56 | -25:08:24.51 | 0.154 | Ia-91T |  +0   | (8) 
 

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 an H-alpha FWHM of 1730 km/s. (2) Previously classified as SN on TNS with hot blue continuum and few features. We reclassify as a Type II supernova and measure an H-alpha velocity of -8000 km/s. (3) We measure a Si II velocity of -10,000 km/s. (4) The spectrum is well fit by "SN impostor" (LBV outburst) templates 1999bw and 2001ac, consistent with the peak absolute magnitude of -14 mag. We measure an H-alpha FWHM of 760 km/s. (5) The spectrum is blue and relatively featureless, but there is a broad (FWHM = 4500 km/s) He II emission feature, which may be from the transient or possibly Wolf-Rayet stars in the galaxy. The current absolute magnitude (assuming a distance modulus of 32.2 mag from Tully & Fisher, 1988) of M_V = -15.2 mag, assuming no reddening (despite having a relatively red color of B-V = 0.6 mag). While the current spectrum cannot definitively classify the transient, it is likely to be a supernova if the assumed distance is correct. (6) We measure a Si II velocity of -11,000 km/s. (7) The spectrum is blue and has narrow He I and He II features. He II 4686 has a narrow P-Cygni profile with the absorption blueshifted by -460 km/s, while He I 6678 has a broader absorption feature with a minimum blueshifted by -1300 km/s. There are unresolved H Balmer lines, but it is unclear if they originate from the host galaxy. (8) We measure a Si II velocity of -10,000 km/s.