Asymmetric Explosions of Thermonuclear Supernovae

Abstract

A type Ia supernova explosion starts in a white dwarf as a laminar deflagration at the center of the star and soon several hydrodynamic instabilities (in particular, the Rayleigh-Taylor (R-T) instability) begin to act. In previous work (Ghezzi, de Gouveia Dal Pino, & Horvath 2001), we addressed the propagation of an initially laminar thermonuclear flame in presence of a magnetic field assumed to be dipolar. We were able to show that, within the framework of a fractal model for the flame velocity, the front is affected by the field through the quenching of the R-T instability growth in the direction perpendicular to the field lines. As a consequence, an asymmetry develops between the magnetic polar and the equatorial axis that gives a prolate shape to the burning front. We have here computed numerically the total integrated asymmetry as the flame front propagates outward through the expanding shells of decreasing density of the magnetized white dwarf progenitor, for several chemical compositions, and found that a total asymmetry of about 50 % is produced between the polar and equatorial directions for progenitors with a surface magnetic field B ~ 5 x 10^{7} G, and a composition C12 = 0.2 and O16 = 0.8 (in this case, the R-T instability saturates at scales \~ 20 times the width of the flame front). This asymmetry is in good agreement with the inferred asymmetries from spectropolarimetric observations of very young supernova remnants, which have recently revealed intrinsic linear polarization interpreted as evidence of an asymmetric explosion in several objects,such as SN1999by, SN1996X, and SN1997dt. Larger magnetic field strengths will produce even larger asymmetries. We have also found that for lighter progenitors the total asymmetry is larger.

arXiv comment21 pages, 8 figures, AASTEX macros, Accepted for publication in Monthly Notices of The Royal Astronomical Society

References in corpus (6)

• The Thermonuclear Explosion Of Chandrasekhar Mass White Dwarfs
• Evidence for Asphericity in a Subluminous Type Ia Supernova: Spectropolarimetry of SN 1999by
• The Progenitors of Subluminous Type Ia Supernovae
• Polarimetry of the Type Ia Supernova SN 1996X
• Magnetic Field Evolution in Accreting White Dwarfs
• Magnetic field effects on the thermonuclear combustion front of Chandrasekhar mass white dwarfs

Cited by in corpus (6)

• Spectropolarimetry of the Peculiar Type Ia SN 2005hk
• Thermonuclear Supernovae: Probing Magnetic Fields by Late-Time IR Line Profiles
• Late-time near-infrared observations of SN 2005df
• Magneto-Hydrodynamical Effects on Nuclear Deflagration Fronts in Type Ia Supernovae
• The Data Big Bang and the Expanding Digital Universe: High-Dimensional, Complex and Massive Data Sets in an Inflationary Epoch
• Effects of magnetic fields on the propagation of nuclear flames in magnetic white dwarfs