Spectropolarimetric Signatures of Clumpy Supernova Ejecta

Abstract

Polarization has been detected at early times for all types of supernova, indicating that such systems result from or quickly develop some form of asymmetry. In addition, the detection of strong line polarization in supernovae is suggestive of chemical inhomogeneities ("clumps") in the layers above the photosphere, which may reflect hydrodynamical instabilities during the explosion. We have developed a fast, flexible, approximate semi-analytic code for modeling polarized line radiative transfer within 3-D inhomogeneous rapidly-expanding atmospheres. Given a range of model parameters, the code generates random sets of clumps in the expanding ejecta and calculates the emergent line profile and Stokes parameters for each configuration. The ensemble of these configurations represents both the effects of various host geometries and of different viewing angles. We present results for the first part of our survey of model geometries, specifically the effects of the number and size of clumps (and the related effect of filling factor) on the emergent spectrum and Stokes parameters. Our simulations show that random clumpiness can produce line polarization in the range observed in SNe Ia (~1-2%), as well as the Q-U loops that are frequently seen in all SNe. We have also developed a method to connect the results of our simulations to robust observational parameters such as maximum polarization and polarized equivalent width in the line. Our models, in connection with spectropolarimetric observations, can constrain the 3-D structure of supernova ejecta and offer important insight into the SN explosion physics and the nature of their progenitor systems.

Accepted to ApJ; 19 pages, 15 figures

References in corpus (7)

• The Supernova -- Gamma-Ray Burst Connection
• Spectropolarimetry of Supernovae
• Time Dependent Monte Carlo Radiative Transfer Calculations For 3-Dimensional Supernova Spectra, Lightcurves, and Polarization
• A non-spherical core in the explosion of supernova SN 2004dj
• The Dual-Axis Circumstellar Environment of the Type IIn Supernova 1997eg
• Spectropolarimetry of the Type IIb Supernova 2001ig
• Spectropolarimetry of the Unique Type Ib Supernova 2005bf: Larger Asymmetry Revealed by Later-Phase Data

Cited by in corpus (14)

• Observational clues to the progenitors of Type-Ia supernovae
• Modeling SNR Cassiopeia A from the Supernova Explosion to its Current Age: The role of post-explosion anisotropies of ejecta
• Supernova 1987A: a Template to Link Supernovae to their Remnants
• Role of ejecta clumping and back-reaction of accelerated cosmic rays in the evolution of Type Ia supernova remnants
• A review of type Ia supernova spectra
• 3D MHD modeling of the expanding remnant of SN 1987A. Role of magnetic field and non-thermal radio emission
• Three-Dimensional Explosion Geometry of Stripped-Envelope Core-Collapse Supernovae. II. Modelling of Polarization
• Three-Dimensional Explosion Geometry of Stripped-Envelope Core-Collapse Supernovae. I. Spectropolarimetric Observations
• Spectropolarimetry of the Type Ib Supernova iPTF 13bvn: Revealing the complex explosion geometry of a stripped-envelope core-collapse supernova
• On the observational behaviour of the highly polarized Type IIn supernova SN 2017hcc
• Evidence for Rapid Variability in the Optical Light Curve of the Type Ia SN 2014J
• The Hanle Effect as a Diagnostic of Magnetic Fields in Stellar Envelopes. V. Thin Lines from Keplerian Disks
• Modeling the Remnants of Core-collapse Supernovae from Luminous Blue Variable stars
• First systematic high-precision survey of bright supernovae I. Methodology for identifying early bumps