Suchergebnisse

We present optical and near infrared (NIR) observations of the nearby Type Ia SN 2014J. Seventeen optical and 23 NIR spectra were obtained from 10 days before (-10d) to 10 days after (+10d) the time of maximum B-band brightness. The relative strengths of absorption features and their patterns of development can be compared at one day intervals throughout most of this period. Carbon is not detected in the optical spectra, but we identify C I lambda 1.0693 in the NIR spectra. Mg II lines with high oscillator strengths have higher initial velocities than other Mg II lines. We show that the velocity differences can be explained by differences in optical depths due to oscillator strengths. The spectra of SN 2014J show that it is a normal SN Ia, but many parameters are near the boundaries between normal and high-velocity subclasses. The velocities for OI, Mg II, Si II, S Ca a, and Fell suggest that SN 2014J has a layered structure with little or no mixing. That result is consistent with the delayed detonation explosion models. We also report photometric observations, obtained from -10d to +29d, in the UBVRIJH and K-s bands. The template fitting package SNooPy is used to interpret the light curves and to derive photometric parameters. Using R-v = 1.46, which is consistent with previous studies, SNooPy finds that A(v) = 1.80 for E(B - V)(host) = 1.23 +/- 0.06 mag. The maximum B-band brightness of -19.19 +/- 0.10 mag was reached on February 1.74 UT +/- 0.13 days and the supernova has a decline parameter, Delta m(15), of 1.12 +/- 0.02 mag. ; Department of Space, Government of India ; Hungarian OTKA NN-107637 ; NSF AST-1109801, AST-1151462, AST-1211196 ; NSF Astronomy and Astrophysics Postdoctoral Fellowship AST-1302771 ; NASA through a grant from the Space Telescope Science Institute GO-12540 ; NASA NAS5-26555 ; Swedish Research Council ; Swedish National Space Board ; Danish Agency for Science and Technology and Innovation realized through a Sapere Aude Level 2 grant ; Astronomy

The Type Ia supernova (SN Ia) LSQ14fmg exhibits exaggerated properties that may help to reveal the origin of the "super-Chandrasekhar" (or 03fg-like) group. The optical spectrum is typical of a 03fg-like SN Ia, but the light curves are unlike those of any SNe Ia observed. The light curves of LSQ14fmg rise extremely slowly. At -23 rest-frame days relative toB-band maximum, LSQ14fmg is already brighter thanJandHbands, far more luminous than any 03fg-like SNe Ia with near-infrared observations. At 1 month past maximum, the optical light curves decline rapidly. The early, slow rise and flat color evolution are interpreted to result from an additional excess flux from a power source other than the radioactive decay of the synthesized Ni-56. The excess flux matches the interaction with a typical superwind of an asymptotic giant branch (AGB) star in density structure, mass-loss rate, and duration. The rapid decline starting at around 1 month pastB-band maximum may be an indication of rapid cooling by active carbon monoxide (CO) formation, which requires a low-temperature and high-density environment. These peculiarities point to an AGB progenitor near the end of its evolution and the core degenerate scenario as the likely explosion mechanism for LSQ14fmg. ; National Science Foundation (NSF) AST-1008343 AST-1613426 AST-1613455 AST-1613472 AST-1008962 AST-1907570 AST1920392 AST-1911074 AST-1515927 AST1908570 AST-0908816 Danish Agency for Science and Technology and Innovation through a Sapere Aude Level 2 grant European Union's Horizon 2020 research and innovation program under Marie Sklodowska-Curie grant 839090 European Union (EU) PGC2018-095317-B-C21 DiRAC Institute in the Department of Astronomy at the University of Washington George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy Mitchell Foundation Academy of Finland 324504 328898 National Aeronautics & Space Administration (NASA) 80NSSC19K1717 Gordon and Betty Moore Foundation GBMF5490 Mt. Cuba Astronomical Foundation Ohio State University Chinese Academy of Sciences South America Center for Astronomy (CASSACA) Villum Foundation Independent Research Fund Denmark (IRFD) 8021-00170B VILLUM FONDEN 13261 28021 ESO Telescopes at the Paranal Observatory 099. D-0022(A)