We draw attention to the transient AT2020tkx (Gaia20ehu), discovered by Gaia on MJD 59106.49 (2020-09-14) at a magnitude of 18.47 (G-Gaia band). AT2020tkx was also detected by ATLAS and ZTF, providing a well sampled rise time. A classification spectrum was obtained from the Liverpool Telescope (Steele et al. 2004) on MJD 59110.84, and a followup LT spectrum on MJD 59113.87.
The spectra show a blue continuum and broad features of Fe II and Si II. Gelato (Harutyunyan et al. 2008) finds a reasonable match with broad-line Ic SNe 2002ap and 2006aj at pre-maximum epochs, for an assumed redshift of 0.01. No redshift of the faint host is available, a diffuse, blue galaxy in the Pan-STARRS 3Pi images with r = 20.
At this redshift, the line velocity inferred from Fe II is ~ 20000-25000 km/sec. The ATLAS light curve appears now to be near maximum, at a magnitude of o = 17.27 +/- 0.04 (on MJD 59114.29), implying an absolute magnitude of M ~ -16.0 (for the assumed redshift) and we observe a rise time of 11 days. This luminosity is unusually low for a broad-line Ic event, and further spectroscopic, photometric and multi-wavelength observations are encouraged. A finder is provided to aid identification.
Catalog | Name | Reported RA | Reported DEC | Reported Obj-Type | Reported Redshift | Host Name | Host Redshift | Remarks | TNS RA | TNS DEC | TNS Obj-Type | TNS Redshift |
---|---|---|---|---|---|---|---|---|---|---|---|---|
TNS | 2020tkx [Gaia20ehu] | 18:40:09.000 | +34:06:59.54 | 18:40:09.000 | +34:06:59.54 | SN Ic-BL |
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