Mon. Not. R. Astron. Soc., 476, 4592-4616 (2018/June-1)
Observed Type II supernova colours from the Carnegie Supernova Project-I.
DE JAEGER T., ANDERSON J.P., GALBANY L., GONZALEZ-GAITAN S., HAMUY M., PHILLIPS M.M., STRITZINGER M.D., CONTRERAS C., FOLATELLI G., GUTIERREZ C.P., HSIAO E.Y., MORRELL N., SUNTZEFF N.B., DESSART L. and FILIPPENKO A.V.
Abstract (from CDS):
We present a study of observed Type II supernova (SN II) colours using optical/near-infrared photometric data from the Carnegie Supernovae Project-I. We analyse four colours (B - V, u - g, g - r, and g - Y) and find that SN II colour curves can be described by two linear regimes during the photospheric phase. The first (s_1, colour_) is steeper and has a median duration of ∼40 d. The second, shallower slope (s_2, colour_) lasts until the end of the 'plateau' (∼80 d). The two slopes correlate in the sense that steeper initial colour curves also imply steeper colour curves at later phases. As suggested by recent studies, SNe II form a continuous population of objects from the colour point of view as well. We investigate correlations between the observed colours and a range of photometric and spectroscopic parameters including the absolute magnitude, the V-band light-curve slopes, and metal-line strengths. We find that less luminous SNe II appear redder, a trend that we argue is not driven by uncorrected host-galaxy reddening. While there is significant dispersion, we find evidence that redder SNe II (mainly at early epochs) display stronger metal-line equivalent widths. Host-galaxy reddening does not appear to be a dominant parameter, neither driving observed trends nor dominating the dispersion in observed colours. Intrinsic SN II colours are most probably dominated by photospheric temperature differences, with progenitor metallicity possibly playing a minor role. Such temperature differences could be related to differences in progenitor radius, together with the presence or absence of circumstellar material close to the progenitor stars.
© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
supernovae: general - dust, extinction
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