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Spectroscopic classification of four SNe with the Nordic Optical Telescope

ATel #9610; L. Tomasella (INAF-Padova), N. Elias-Rosa (INAF-Padova), S. Mattila (Turku), P. Lundqvist (Stockholm), M. Stritzinger (Aarhus U), H. Kuncarayakti (MAS, DAS), J. Harmanen (Turku), A. Pastorello (INAF-Padova), S. Benetti (INAF-Padova), E. Cappellaro (INAF-Padova), N. Blagorodnova (Caltech), S. Davis (FSU), S. Dong (KIAA-PKU), M. Fraser (University College Dublin), C. Gall (Aarhus U), D. Harrison (IoA), S. Hodgkin (IoA), E. Y. Hsiao (FSU), P. Jonker (SRON), T. Kangas (Turku), E. Kankare (QUB), Z. Kostrzewa-Rutkowska (Warsaw/SRON), M. Nielsen (Aarhus U), P. Ochner (INAF-Padova), J. L. Prieto (UDP, MAS), T. Reynolds (Turku, NOT), C. Romero-Canizales (PUC, MAS), F. Taddia (OKC), L. Tartaglia (INAF-Padova), G. Terreran (INAF-Padova/QUB), L. Wyrzykowski (Warsaw Observatory)
on 10 Oct 2016; 12:50 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Lina Tomasella (lina.tomasella@oapd.inaf.it)

Subjects: Optical, Supernovae, Transient

The NOT Unbiased Transient Survey (NUTS; ATel #8992) reports spectroscopic classification of: ASASSN-16lg in Ark 530 (Atel# 9601); ASASSN-16ll in IRAS F18594+5429 (Atel# 9602); AT 2016gsd (discovered by Itagaki) and AT 2016ghu (= Gaia16bhj, discovered by the Gaia Photometric Science survey in MCG-01-12-008).

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

 
Survey Name | IAU Name   | Host galaxy     | Discovery (UT) | Discovery mag | Observation (UT) | Redshift | Type       | Phase  | Notes  
ASASSN-16lg | SN 2016gye | Ark 530         | 2016-10-06.20  | 16.2          | 2016-10-09.84    | 0.021    | Ia         | pre-max| (1) 
ASASSN-16ll | SN 2016gyt | IRAS F18594+5429| 2016-09-26.29  | 17.1          | 2016-10-09.85    | 0.026    | II         | young  | (2) 
AT 2016gsd  | SN 2016gsd | anonymous       | 2016-09-29.24  | 17.7          | 2016-10-10.06    | 0.06     | II         | young  | (3) 
Gaia16bhj   | SN 2016ghu | MCG-01-12-008   | 2016-09-15.11  | 17.3          | 2016-10-10.20    | 0.031    | Ia         |~2 weeks| (4) 

(1) The best match is with Type Ia SNe a few days before B-band maximum light. The expansion velocity of the ejecta, as estimated from the position of the minimum of the Si II 635.5 nm line, is about 10400 km/s. The redshift of the host galaxy, z=0.021171, is obtained via NED (d=87.4 Mpc, m-M=34.71).

(2) The spectrum shows narrow emission narrow lines of the host galaxy at z=0.026. After removing the emission lines, a blue continuum emerges with P-Cygni lines of the Balmer series and HeI 587.6 nm. This spectrum is consistent with that of a young Type II SN.

(3) The spectrum shows a blue continuum with shallow Balmer and HeI 587.6 nm lines. There is no evidence for narrow spectral components. This is consistent with a very young Type II SN. The redshift z=0.06 is obtained from the wavelength position of the broad emission features of the SN. With this redshift the absolute magnitude of the SN exceeds mag = -19.5, making this object one the brightest Type-II SN ever discovered.

(4) The best match is with the Type Ia SNe around one-two weeks after B-band maximum light. The redshift of the host galaxy, z=0.031, is obtained 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, and are posted on WISeREP (Yaron & Gal-Yam 2012, PASP, 124, 668). We acknowledge ESA Gaia (http://cosmos.esa.int/gaia), and the DPAC Photometric Science Alerts Team (http://gsaweb.ast.cam.ac.uk/alerts/alertsindex) (Rixon et al, 2014, ATel #6593).