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WiFeS+FIRE classification of ASASSN-14lw as a young SN Ia

ATel #6832; Michael Childress (ANU), Tiara Diamond (FSU), Richard Scalzo (ANU), Carlos Contreras(LCO), Brad Tucker (ANU / UC Berkeley), Mark M. Phillips (LCO), Fang Yuan (ANU), Eric Y. Hsiao (Aarhus U.), Bonnie Zhang (ANU), Ashley Ruiter (ANU), Ivo Seitenzahl (ANU), Brian Schmidt (ANU)
on 17 Dec 2014; 00:43 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Michael Childress (mjc@mso.anu.edu.au)

Subjects: Optical, Supernovae

The Australian National University supernova group reports spectroscopic classification of ASASSN-14lw with an optical spectrum (3500-9800 AA) obtained on 2014 Dec 16 UT with the Wide Field Spectrograph (WiFeS - Dopita et al., 2007, ApSS, 310, 255) on the ANU 2.3m telescope at Siding Spring Observatory. Classification with SNID (Blondin & Tonry, 2007, ApJ, 666, 1024) shows matches to a number of young SN Ia spectra ranging from -4 to -9 days, many of which are luminous SN1991T-like SNe. The Si 6355 feature shows a possible blue wing from high velocity features (HVFs), and the Si 5972 line is very weak relative to Si 6355, indicating high stretch (slow decline rate). The SN is apparently hostless, and no narrow emission features from a host are evident despite the 100 km/s resolution of WiFeS. SNID suggests the SN redshift is about 0.016, and assuming this redshift the Si 6355 absorption minimum corresponds to a velocity of 9500 km/s. For this redshift the Ca H/K line shows a velocity of 18,400 km/s, consistent with being dominated by HVFs. These facts, along with a very blue continuum, indicate a relatively young age for the SN.

Carnegie Supernova Project (CSP) reports on the spectroscopic classification of ASASSN-14lw using a near-infrared spectrogram (range 800-2500 nm) obtained on Dec. 14.08 UT with the FoldedPort Infrared Echellette (FIRE) spectrograph on the 6.5-m Magellan Baade Telescope at Las Campanas Observatory. The near-infrared spectrum shows several weak features of intermediate-mass ions, such as Mg II and Si III. It resembles the pre-maximum spectra of several type Ia supernovae, including SN 2002cr at a week before maximum (Marion et al. 2009, AJ, 138, 727) and SN 2011fe also at a week before maximum (Hsiao et al. 2013, ApJ, 766, 72). The approximate supernova redshift is z=0.015. Because of the weakness of the spectral features in the near-infrared, we waited for the following confirmation in the optical before reporting the classification.

 Name                  | RA (J2000)   | Dec (J2000)  | Disc. Date | Disc Mag  | Disc. Source  | SNID z | Type   |  Phase | Match SN 
ASASSN-14lw | 01:06:49.17 | -46:58:59.1 | 20141212 | 16.5 | ASAS-SN | 0.016 | Ia | -4 | SN 2007S