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Near Infrared Spectrum of SN Ia 2011fe Resembles Fast Decliners Observed A Week Before Maximum

ATel #3599; Harvard, CfA
on 27 Aug 2011; 00:03 UT
Credential Certification: Howie Marion (gmarion@cfa.harvard.edu)

Subjects: Infra-Red, Supernovae

Referred to by ATel #: 3605, 4119

We observed SN 2011fe with the IRTF 3.0m and the SpeX instrument on August 26.3. The spectrum reveals strong absorption features from MgII at 13500 km/s. The CaII infrared triplet forms a strong and broad feature with a minimum at about 22000 km/s. SiII and OI are also detected at about 12500 km/s. The presence of evolved MgII features in this NIR spectrum is suggestive of a phase no more than one week before maximum light. This estimate is different than about two weeks pre-maximum which would be inferred for this observation date from ATEL 3581. The strong MgII features are also indicative of SN Ia with fast decline rates: delta_m15 > 1.3. If SN 2011fe has a fast rise and fast decline, these observations will be closer to the maximum which is consistent with both aspects of the NIR spectrum. We thank John Rayner for making IRTF time available and Eric Volquardsen for help with the observations.