Volume 534, October 2011
|Number of page(s)||4|
|Published online||18 October 2011|
Letter to the Editor
A study of the color diversity around maximum light in Type Ia supernovae
Departamento de AstronomíaUniversidad de Chile,
2 Department of Astronomy, Yale University, New Haven, CT 06520, USA
3 Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583, Japan
4 Departamento Ciencias Físicas, Universidad Andres Bello, Av. República 252, Santiago, Chile
Accepted: 2 October 2011
From a sample of 12 well-observed Type Ia supernovae, we find clear evidence of correlations between early phase (U − B), (V − R), and (V − I) colors and the velocity shifts of the [Fe II] λ7155 and [Ni II] λ7378 nebular lines measured from late-phase spectra. As these lines are thought to trace the ashes of the initial deflagration process, our findings provide additional support to the new paradigm of off-center explosions in Type Ia supernovae, and we interpret these correlations as viewing angle effects in the observed colors. We also show that the nebular velocity shifts are related to the strength and width of the Ca II and IR-triplet lines near-maximum light. The evidence presented here implies that the viewing angle must be taken into account when deriving extinction values and distances in future cosmological studies based on Type Ia supernovae.
Key words: distance scale / supernovae: general
© ESO, 2011
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