238 research outputs found
Secondary Maximum in the Near-Infrared Lightcurves of Type Ia Supernovae
We undertake a theoretical study of the near-infrared (NIR) lightcurves of
Type Ia supernovae (SNe Ia). In these bands, the lightcurves are distinguished
by a secondary maximum occurring roughly 20 to 30 days after the initial one.
Using time-dependent multi-group radiative transfer calculations, we calculate
the UBVRIJHK-band lightcurves of model SN Ia ejecta structures. Our synthetic
NIR lightcurves show distinct secondary maxima, and provide favorable fits to
observed SNe Ia. We offer a detailed explanation of the origin of the NIR
secondary maximum, which is shown to relate directly to the ionization
evolution of iron group elements in the ejecta. This understanding provides
immediate intuition into the dependence of the NIR lightcurves on the physical
properties of the ejecta, and in particular explains why brighter supernovae
have a later and more prominent secondary maximum. We demonstrate the
dependence of the NIR lightcurves on the mass of 56Ni, the degree of 56Ni
mixing, the mass of electron caputre elements, the progenitor metallicity, and
the abundance of intermediate mass elements (especially calcium). The secondary
maximum is shown to be a valuable diagnostic of these important physical
parameters. The models further confirm that SNe Ia should be excellent standard
candles in the NIR, with a dispersion < 0.2 mag even when the physical
properties of the ejecta are varied widely. This study emphasizes the
consummate value of NIR observations in probing the structure of SNe Ia and in
furthering their cosmological utility.Comment: 14 pages; ApJ accepte
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