Browsing by Author "Sollerman, Jesper"

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    POLARIMETRY OF THE SUPERLUMINOUS SUPERNOVA LSQ14MO: NO EVIDENCE FOR SIGNIFICANT DEVIATIONS FROM SPHERICAL SYMMETRY
    (IOP PUBLISHING LTD, 2015) Leloudas, Giorgos; Patat, Ferdinando; Maund, Justyn R.; Hsiao, Eric; Malesani, Daniele; Schulze, Steve; Contreras, Carlos; D Ugarte Postigo, Antonio; Sollerman, Jesper; Stritzinger, Maximilian D.; Taddia, Francesco; Wheeler, J. Craig; Gorosabel, Javier
    We present the first polarimetric observations of a Type I superluminous supernova (SLSN). LSQ14mo was observed with VLT/FORS2 at five different epochs in the V band, with the observations starting before maximum light and spanning 26 days in the rest frame (z. = 0.256). During this period, we do not detect any statistically significant evolution (<2 sigma) in the Stokes parameters. The average values we obtain, corrected for interstellar polarization in the Galaxy, are Q = -0.01% (+/- 0.15%) and U = -0.50% (+/- 0.14%). This low polarization can be entirely due to interstellar polarization in the SN host galaxy. We conclude that, at least during the period of observations and at the optical depths probed, the photosphere of LSQ14mo does not present significant asymmetries, unlike most lower-luminosity hydrogen-poor SNe Ib/c. Alternatively, it is possible that we may have observed LSQ14mo from a special viewing angle. Supporting spectroscopy and photometry confirm that LSQ14mo is a typical SLSN I. Further studies of the polarization of Type I SLSNe are required to determine whether the low levels of polarization are a characteristic of the entire class and to also study the implications for the proposed explosion models.
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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.