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Author:
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Pignata, Giuliano; Benetti, Stefano; Mazzali, P. A.; Kotak, Rubina; Patat, F.; Meikle, P.; Stehle, M.; Leibundgut, B.; Suntzeff, N. B.; Buson, L. M.; Cappellaro, E.; Clocchiatti, A.; Hamuy, Mario; Maza, J.; Mendez, J.; Ruiz-Lapuente, P.; Salvo, M.; Schmidt, B. P.; Turatto, M.; W. Hillebrandt, W.
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Abstract:
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As part of the European Supernova Collaboration, we obtained extensive photometry and
spectroscopy of the Type Ia supernova (SN Ia) SN 2002dj covering epochs from 11 d before to
nearly two years after maximum. Detailed optical and near-infrared observations showthat this
object belongs to the class of the high-velocity gradient events as indicated by Si, S and Ca lines.
The light curve shape and velocity evolution of SN 2002dj appear to be nearly identical to SN
2002bo. The only significant difference is observed in the optical to near-infrared colours and
a reduced spectral emission beyond 6500 Å. For high-velocity gradient SNe Ia, we tentatively
identify a faster rise to maximum, a more pronounced inflection in the V and R light curves
after maximum and a brighter, slower declining late-time B light curve as common photometric
properties of this class of objects. They also seem to be characterized by a different colour and
colour evolution with respect to ‘normal’ SNe Ia. The usual light curve shape parameters do not
distinguish these events. Stronger, more blueshifted absorption features of intermediate-mass
elements and lower temperatures are the most prominent spectroscopic features of SNe Ia
displaying high-velocity gradients. It appears that these events burn more intermediate-mass
elements in the outer layers. Possible connections to the metallicity of the progenitor star are
explored. |