DRAFT
2021-02-18 20:44:26
Type: Object/s-Discovery/Classification
Bibcode: 2021TNSAN..71....1P
adH0cc spectroscopic classification of SN 2021ckj, an unusual "Type Icn" supernova
Source Group: adH0cc
Abstract:
We have obtained an optical spectrum of SN 2021ckj, which shows it to be an unusual Type I supernova with narrow carbon and helium lines superimposed on a blue continuum with several broad spectral features.
The adH0cc programme for an "accurate determination of H0 with core-collapse supernovae" reports the classification of the optical transient SN 2021ckj. The target was supplied by the Zwicky Transient Facility ZTF (Kulkarni 2018, 2018ATel11266....1K) and the ATLAS survey (Tonry et al. 2018, 2018PASP..130f4505T). The observations were performed on the night of 2021 February 16 with the ESO Very Large Telescope UT1, equipped with the FORS2 spectrograph and grism 300V, covering a wavelength range from 3400 to 9600 Å at a resolution of 10 Å.
| Catalog | Name | Reported RA | Reported DEC | Reported Obj-Type | Reported Redshift | Host Name | Host Redshift | Source | Phase | Remarks | TNS RA | TNS DEC | TNS Obj-Type | TNS Redshift |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| TNS | 2021ckj [ZTF21aajbgol] | 09:05:51.083 | -08:35:07.57 | SN I | 0.143 | anonymous | 0.143 | ZTF, ATLAS | 10d | The spectrum of SN 2021ckj shows a blue continuum with a blackbody temperature of about 10000 K. The continuum is undulated by several broad (v > 10000 km/s) spectral lines, especially in the restframe range between 3500 and 5500 Å, reminiscent of SLSNe-I. Superimposed on this spectrum, one can find a series of narrow to intermediate-width lines (v = 1000 to 2500 km/s), some of them in emission, others exhibiting P-Cygni profiles. The lines can mostly be attributed to carbon: C III at 4650 Å and 5696 Å, and C II at 4267 Å, 5891 Å, 6580 Å and 7234 Å. He I 5875 Å is also detected. The redshift of the supernova of z = 0.143 has been measured from these narrow lines. A phase of 10d from explosion has been estimated from the combined ZTF and ATLAS light curves. With a rise time of merely a few days and a peak absolute g-band magnitude close to -20, SN 2021ckj is photometrically a fast blue optical transient (FBOT). Spectroscopically, it would be best characterised as a "Type Icn" supernova. Similarities with AT 2021csp (Perley et al., AstroNote 2021-62) should be investigated. | 09:05:51.083 | -08:35:07.56 | SN Icn | 0.143 |
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