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Date and Time of the Query: 2019-07-16 T19:51:12 PDT
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For refcode 2017MNRAS.464.4476C:
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Copyright by Royal Astronomical Society. 2017MNRAS.464.4476C Early observations of the nearby Type Ia supernova SN 2015F Cartier, R.; Sullivan, M.; Firth, R. E.; Pignata, G.; Mazzali, P.; Maguire, K.; Childress, M. J.; Arcavi, I.; Ashall, C.; Bassett, B.; Crawford, S. M.; Frohmaier, C.; Galbany, L.; Gal-Yam, A.; Hosseinzadeh, G.; Howell, D. A.; Inserra, C.; Johansson, J.; Kasai, E. K.; McCully, C.; Prajs, S.; Prentice, S.; Schulze, S.; Smartt, S. J.; Smith, K. W.; Smith, M.; Valenti, S.; Young, D. R. Abstract. We present photometry and time series spectroscopy of the nearby Type Ia supernova (SN Ia) SN 2015F over -16 d to +80 d relative to maximum light, obtained as part of the Public ESO Spectroscopic Survey of Transient Objects. SN 2015F is a slightly sub-luminous SN Ia with a decline rate of Deltam_15_(B) = 1.35 +/- 0.03 mag, placing it in the region between normal and SN 1991bg-like events. Our densely sampled photometric data place tight constraints on the epoch of first light and form of the early-time light curve. The spectra exhibit photospheric C II lambda6580 absorption until -4 days, and high-velocity Ca II is particularly strong at <-10 d at expansion velocities of ~=23 000 km s^-1^. At early times, our spectral modelling with SYN++ shows strong evidence for iron-peak elements (Fe II, Cr II, Ti II, and V II) expanding at velocities >14 000 km s^-1^, suggesting mixing in the outermost layers of the SN ejecta. Although unusual in SN Ia spectra, including V II in the modelling significantly improves the spectral fits. Intriguingly, we detect an absorption feature at ~6800 A that persists until maximum light. Our favoured explanation for this line is photospheric Al II, which has never been claimed before in SNe Ia, although detached high-velocity C II material could also be responsible. In both cases, the absorbing material seems to be confined to a relatively narrow region in velocity space. The nucleosynthesis of detectable amounts of Al II would argue against a low-metallicity white dwarf progenitor. We also show that this 6800 A feature is weakly present in other normal SN Ia events and common in the SN 1991bg-like sub-class. Key words: supernovae: general, supernovae: individual: (SN 2015F)
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