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Spectroscopic observation of SN2017dht and ASASSN-17fr by NUTS (NOT Un-biased Transient Survey)

ATel #10344; N. Elias-Rosa, A. Pastorello, G. Terreran, L. Tomasella, S. Benetti, E. Cappellaro, Y. Cai, S. Yang (INAF-OAPd), J. Telting (NOT), on behalf of the NUTS collaboration.
on 3 May 2017; 14:40 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: N. Elias-Rosa (nancy.elias@oapd.inaf.it)

Subjects: Optical, Supernovae, Transient

The Nordic Optical Telescope (NOT) Unbiased Transient Survey (NUTS; ATel #8992) reports the spectroscopic classification of SN2017dht in an anonymous host galaxy, and ASASSN-17fr in IC 4296 (ATel #10339). The candidates were discovered by the ATLAS survey (see Tonry et al. 2011, PASP, 123, 58 and Tonry et al. ATel #8680), and the All Sky Automated Survey for SuperNovae (ASAS-SN, ATEL #8944, #8979).

The observations were performed with the 2.56 m Nordic Optical Telescope equipped with ALFOSC (range 350-950 nm; resolution 1.6 nm FWHM).

Survey Name    | IAU Name   | Discovery (UT)  | Discovery mag | Observation (UT) | Redshift | Type   | Phase      | Notes  
ATLAS17etw     | SN2017dht  | 2017-04-22.38   | 18.8          | 2017-05-02.91    | 0.091    | II-pec | before max | (1)  
ASASSN-17fr    | SN2017dps  | 2017-05-01.28   | 15.4          | 2017-05-02.99    | 0.012    | Ia     | before max | (2)  

(1) High S/N spectrum with a blue continuum and broad Balmer and He I lines with P Cygni profiles. From the minimum of the He I 587.6 nm absorption, a velocity of ~10500 km/s is inferred. The spectrum is consistent with that of a Type II SN a few days after the explosion. We note, however, that the discovery magnitude reported in ATel #10331 indicates this object to be an unusually luminous Type II SN (-19.3). Non-conclusive classifications have been previously reported by ePESSTO (ATel #10331, ATel #10334). The redshift z=0.091 is obtained from the wavelength position of the narrow emission superimposed to the Halpha line.

(2) ASASSN-17fr is a pre-maximum normal Type Ia supernova. SNID gives good matches with normal SN Ia between -5 and -3 days. An expansion velocity of about 13000 km/s from the SiII 635.5 nm absorption was measured. The redshift is obtained from the NED. The redshift of the host galaxy IC 4296 is obtained from Russell et al. 2000 (MNRAS 313, via NED).

Classifications (were performed using the GELATO (Harutyunyan et al. 2008, A&A, 488, 383) and SNID (Blondin and Tonry 2007, ApJ, 666, 1024) tools. Calibrated spectra and additional information can be retrieved in the IAU Transient Name Server.