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Classification of ASASSN-18dl as a type Ia supernova

ATel #11353; P. Pessi (Inst. de Astrofisica, La Plata), J. Quirola (PUC, Santiago), G. Navarro (UNAB, Santiago), M. Dennefeld (IAC), L. Ferrero (OAC, Cordoba), E. Sani (ESO), L. Schmidtobreick (ESO)
on 25 Feb 2018; 08:04 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Linda Schmidtobreick (lschmidt@eso.org)

Subjects: Optical, Supernovae

We report the classification of the supernova candidate ASASSN-18dl which was discovered as a V~17.6mag transient by the All Sky Automated Survey for SuperNovae (ASAS-SN, Shappee et al. 2014) on 2018-02-21.25 UT. The discovery is reported in ATel #11343 (Stone et al. 2018). A 600s exposure was obtained on 2018-02-25 at 03:26 UT with EFOSC2 and Grism 13 (3985-9315, 18A resolution) mounted on the ESO New Technology Telescope at La Silla. Using SNID (Blondin & Tonry, 2007) we classify the transient as a SNe Ia similar to 2006cf at an age of 2d and an approximate redshift of z=0.033 consistent with the suspected host galaxy 2MASX J10023148+1343409 as given by NASA/IPAC Extragalactic Database (NED). GELATO (Harutyunyan et al., 2008) confirms the SN 1a classification matching 1999ac. Using the redshift z=0.033537 of the host galaxy to correct the SiII 635.5nm absorption line, we determine the expansion velocity as ~10630 km/s. The observation and analysis were performed by students of the ESO/NEON observing school taking place in La Silla right now.