SN 2003du: 480 days in the life of a normal type Ia supernova

Abstract

Aims. We present a study of the optical and near-infrared (NIR) properties of the Type Ia Supernova (SN Ia) 2003du. Methods. An extensive set of optical and NIR photometry and low-resolution long-slit spectra was obtained using a number of facilities. The observations started 13 days before B-band maximum light and continued for 480 days with exceptionally good time sampling. The optical photometry was calibrated through the S-correction technique. Results. The UBVRIJHK light curves and the color indices of SN 2003du closely resemble those of normal SNeIa. SN 2003du reached a B-band maximum of 13.49 ± 0.02 mag on JD2 452 766.38 ± 0.5. We derive a B-band stretch parameter of 0.988 ± 0.003, which corresponds to Δm 15 = 1.02 ± 0.05, indicative of a SN Ia of standard luminosity. The reddening in the host galaxy was estimated by three methods, and was consistently found to be negligible. Using an updated calibration of the V and JHK absolute magnitudes of SNeIa, we find a distance modulus μ = 32.79 ± 0.15 mag to the host galaxy, UGC 9391. We measure a peak uvoir bolometric luminosity of 1.35(±0.20) x 10 43 erg s -1 and Arnett's rule implies that M 56Nι ≃ 0.68 ± 0.14M ⊙ of 56 Ni was synthesized during the explosion. Modeling of the uvoir bolometric light curve also indicates M56 Ni in the range 0.6-0.8 M ⊙ . The spectral evolution of SN 2003du at both optical and NIR wavelengths also closely resembles normal SNe Ia. In particular, the Si II ratio at maximum R(Si II) = 0.22 ± 0.02 and the time evolution of the blueshift velocities of the absorption line minima are typical. The pre-maximum spectra of SN 2003du showed conspicuous high-velocity features in the Call H&K doublet and infrared triplet, and possibly in Si II λ6355, lines. We compare the time evolution of the profiles of these lines with other well-observed SNe Ia and we suggest that the peculiar pre-maximum evolution of SiII λ6355 line in many SNe Ia is due to the presence of two blended absorption components.