Spectroscopic classification of some transients at Haute-Provence Observatory: Gaia20fnu (=AT2020abcl), ZTF20actskcf (=AT2020abfa), Gaia20fpd (=AT2020aaun), Atlas20bgpi (=AT2020abqq) and Gaia20fcl (=AT2020aazj)

ATel #14263; M. Dennefeld (IAP-Paris, CNRS & Sorbonne University, C. Adami, D. Russeil & St. Basa (LAM-Marseille), J. Schmitt, J. C. Brunel, Fr. Dolon, Fr. Huppert, A. LeVanSuu & J. P. Troncin (OHP and OSU-Pytheas)
on 11 Dec 2020; 23:57 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Michel Dennefeld (dennefel@iap.fr)

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Observations were made during a test run of the new imaging-spectrograph Mistral mounted at the Cassegrain focus of the 1.93m telescope on Dec. 8 and 9, 2020. The red setting was used, covering the range 599-992 nm with 0.20 nm per pixel and a 2" slit (4 pixels). Classification of the SNe was made with the help of Gelato (Harutyunyan et al. 2008, A&A, 488, 383) but it is to be noted that our spectral range is not optimal for SNe classification and the results are uncertain about the phase, due to the lack of enough reference spectra in this range. The presence of a strong SiII 635.5 nm absorption in Gaia20fnu (AT2020abcl) and ZTF20actskcf (AT2020abfa) shows they are Ia SNe close to maximum light: correcting for a redshift of the host galaxy (from NED) of z=0.03891 and z=0.02865 respectively, we obtain expansion velocities of 10780 and 10080 km/s, supporting the classification. The absence of other absorptions further red, under others OI 777.4 nm or the CaII IR triplet seems to exclude a type Ib/c. Gaia20fpd (AT2020aaun) is a Ia also, but the SiII absorption is weaker, with a recession velocity of only 2930 km/s (after correction for a redshift of z=0.02815), suggesting a phase of about 1-2 weeks after maximum. For Atlas20bgpi (AT2020abqq), we see a weaker SiII absorption also, but no redshift is available for the host and no galaxy features are detected: the best fit from Gelato is with z~0.040 from the SiII line, but for a Ib/c after maximum; the absence of other absorptions further red however plaeds for a Ia also, the SiII velocity being then 8220 km/s with this redshift. Gaia20flc (AT2020aazj) is a galactic star with a red continuum but no absorptions typical of a late type. An unresolved narrow Halpha is seen in emission, as well as a full, slightly broader (FWHM ~ 2.5 nm = 700 km/s) Paschen series in emission, suggesting an expanding enveloppe possibly from a Be type.