Browsing by Author "Papadogiannakis, Semeli"

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    ZTF Early Observations of Type Ia Supernovae. III. Early-time Colors As a Test for Explosion Models and Multiple Populations
    (2020) Bulla, Mattia; Miller, Adam A.; Yao, Yuhan; Dessart, Luc; Dhawan, Suhail; Papadogiannakis, Semeli; Biswas, Rahul; Goobar, Ariel; Kulkarni, S. R.; Nordin, Jakob; Nugent, Peter; Polin, Abigail; Sollerman, Jesper; Bellm, Eric C.; Coughlin, Michael W.; Dekany, Richard; Golkhou, V. Zach; Graham, Matthew J.; Kasliwal, Mansi M.; Kupfer, Thomas; Laher, Russ R.; Masci, Frank J.; Porter, Michael; Rusholme, Ben; Shupe, David L.
    Colors of Type Ia supernovae (SNe Ia) in the first few days after explosion provide a potential discriminant between different models. In this paper, we present g - r colors of 65 SNe Ia discovered within 5 days from first light by the Zwicky Transient Facility in 2018, a sample that is about three times larger than that in the literature. We find that g - r colors are intrinsically rather homogeneous at early phases, with about half of the dispersion attributable to photometric uncertainties (0.18 mag). Colors are nearly constant starting from 6 days after first light (g-r similar to -0.15 mag), while the time evolution at earlier epochs is characterized by a continuous range of slopes, from events rapidly transitioning from redder to bluer colors (slope of similar to-0.25 mag day(-1)) to events with a flatter evolution. The continuum in the slope distribution is in good agreement both with models requiring some amount of Ni-56 mixed in the outermost regions of the ejecta and with "double-detonation" models having thin helium layers (M-He = 0.01 M-circle dot) and varying carbon-oxygen core masses. At the same time, six events show evidence for a distinctive "red bump" signature predicted by double-detonation models with larger helium masses. We finally identify a significant correlation between the early-timeg - rslopes and supernova brightness, with brighter events associated to flatter color evolution (p-value = 0.006). The distribution of slopes, however, is consistent with being drawn from a single population, with no evidence for two components as claimed in the literature based on B - V colors.