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Near-infrared spectroscopy of the young SN Ia in NGC4424

ATel #4119; E. Y. Hsiao, M. M Phillips, N. Morrell, C. Contreras (Las Campanas Observatory), G. H. Marion (Harvard, CfA), B. F. Madore, W. L. Freedman, C. R. Burns (Carnegie Observatories), L. Sturch (Boston University) on behalf of the Carnegie Supernova Project
on 19 May 2012; 15:05 UT
Credential Certification: Eric Hsiao (hsiao@lco.cl)

Subjects: Infra-Red, Supernovae

We report a near-infrared (NIR) spectrum obtained of the young SN Ia recently discovered in NGC 4424, PSN J12271283+0925132 (ATel #4115). The spectrum was acquired using the FIRE spectrometer on the 6.5-m Magellan I telescope on May 18.5 UT. We compare the spectrum to the SpeX spectrum of SN 2011fe (ATel #3599), the earliest NIR spectrum ever obtained for a SN Ia, at 2.6 days past the time of explosion. The line strengths are noticeably weaker than that of SN 2011fe, indicating that PSN J12271283+0925132 may be a slow decliner. Placed at the rest frame of NGC 4424, the minimum of the Mg II line at 1.0927 micron was measured at ~-15,500 km/s. This velocity is significantly higher in magnitude than the -13,500 km/s reported for SN 2011fe (ATel #3599); it is likely the highest velocity ever reported for this feature. This confirms that PSN J12271283+0925132 is indeed very young. Continued monitoring of this feature and better constraints on the explosion date will determine whether the high velocity is intrinsic to the SN or an optical depth effect, possibly placing the spectrum even closer to the time of explosion than the SpeX spectrum of SN 2011fe. There is no convincing detection of a C I feature from the FIRE spectrum.