We have obtained 1087 NIR (JHK_s_) measurements of 21 SNe Ia using PAIRITEL, nearly doubling the number of well-sampled NIR SN Ia light curves. These data strengthen the evidence that SNe Ia are excellent standard candles in the NIR, even without correction for optical light-curve shape. We construct fiducial NIR templates for normal SNe Ia from our sample, excluding only the three known peculiar SNe Ia: SN 2005bl, SN 2005hk, and SN 2005ke. The H-band absolute magnitudes in this sample of 18 SNe Ia have an intrinsic rms of only 0.15mag with no correction for light-curve shape. We found a relationship between the H-band extinction and optical color excess of A_H_=0.2E(B-V). This variation is as small as the scatter in distance modulus measurements currently used for cosmology based on optical light curves after corrections for light-curve shape. Combining the homogeneous PAIRITEL measurements with 23 SNe Ia from the literature, these 41 SNe Ia have standard H-band magnitudes with an rms scatter of 0.16mag. The good match of our sample with the literature sample suggests there are few systematic problems with the photometry.

Cone search capability for table J/ApJ/689/377/Iasn (Type Ia supernovae JHKs peak magnitudes and apparent standard H-band magnitudes)