# # Program information file # PROGRAM_ID 2021A043 PROGRAM_TITLE Revealing the outer layers of supernovae with SpeX PROGRAM_INV1 Chris Ashall PROGRAM_INV2 Ben Shappee PROGRAM_INV3 Thomas dejaeger PROGRAM_INV4 Michael Tucker PROGRAM_INV5 Melissa Shahbandeh PROGRAM_SCICAT extra-galactic PROGRAM_ABSTRACT_BEG We request for 12 hours of ToO and 5 classic half nights to obtain SpeX spectra of all types of supernovae [SN] on the rise to maximum light. With early SpeX observations, we can estimate critical explosion parameters, delineate between leading explosion models, and study the local environment of all SN types. For Type Ia SN early spectra will allow us to measure the presence and extent of the unburnt carbon region, which will enable us to distinguish between leading exploding scenarios [Chandrasekhar-mass vs. sub-Chandrasekhar mass]. For stripped-envelope SN early NIR spectra provide a direct measurement on the amount of He in the outermost layers. This will shed light on the mass loss mechanisms, and the presence of residual He in SN~Ic. For type II SN NIR spectra will provide critical information on the stage of reionization, and the structure of circumstellar material. All spectra will form an integral part of a multi-wavelength follow-up of transient sources discovered by the University of Hawaii surveys [i.e. ASAS-SN, ATLAS, Pan-STARRS]. NIR observations of transient sources have been historically underused, and this sample will provide critical information on the outermost layers of the ejecta and provide insight into SN physics. PROGRAM_ABSTRACT_END