Fourier Modeling of the Radio Torus Surrounding Supernova 1987A

Abstract

We present detailed Fourier modeling of the radio remnant of Supernova 1987A, using high-resolution 9 GHz and 18 GHz data taken with the Australia Telescope Compact Array over the period 1992 to 2008. We develop a parameterized three-dimensional torus model for the expanding radio shell, in which the emission is confined to an inclined equatorial belt; our model also incorporates both a correction for light travel-time effects and an overall east-west gradient in the radio emissivity. By deriving an analytic expression for the two-dimensional Fourier transform of the projected three-dimensional brightness distribution, we can fit our spatial model directly to the interferometric visibility data. This provides robust estimates to the radio morphology at each epoch. The best-fit results suggest a constant remnant expansion at 4000 +/- 400 km/s over the 16-year period covered by the observations. The model fits also indicate substantial mid-latitude emission, extending to 40 degree on either side of the equatorial plane. This likely corresponds to the extra-planar structure seen in H$\alpha$ and Ly$\alpha$ emission from the supernova reverse shock, and broadly supports hydrodynamic models in which the complex circumstellar environment was produced by a progression of interacting winds from the progenitor. Our model quantifies the clear asymmetry seen in the radio images: we find that the eastern half of the radio remnant is consistently ~40 brighter than the western half at all epochs, which may result from an asymmetry in the ejecta distribution between these two hemispheres.

accepted by ApJ, 11 figures, some have been scaled down in resolution

References in corpus (6)

• The Triple-Ring Nebula around SN1987A: Fingerprint of a binary merger
• Fitting Pulsar Wind Tori. II. Error Analysis and Applications
• SN 1993J VLBI (IV): A Geometric Determination of the Distance to M81 with the Expanding Shock Front Method
• 8.4GHz VLBI observations of SN2004et in NGC6946
• Fifteen Years of High-Resolution Radio Imaging of Supernova 1987A
• Chandra Observations of Supernova 1987A

Cited by in corpus (10)

• The Stellar Ancestry of Supernovae in the Magellanic Clouds - I. the Most Recent Supernovae in the Large Magellanic Cloud
• Spectral and morphological analysis of the remnant of Supernova 1987A with ALMA & ATCA
• High-resolution radio observations of SNR 1987A at high frequencies
• The matter beyond the ring: the recent evolution of SN 1987A observed by the Hubble Space Telescope
• Multi-dimensional simulations of the expanding supernova remnant of SN 1987A
• Thermal Emission and Radioactive Lines, but No Pulsar, in the Broadband X-Ray Spectrum of Supernova 1987A
• Expected gamma-ray emission of supernova remnant SN 1987A
• Polarized radio emission unveils the structure of the pre-supernova circumstellar magnetic field and the radio emission in SN1987A
• Linking gamma-ray spectra of supernova remnants to the cosmic ray injection properties in the aftermath of supernovae
• The Radio Remnant of Supernova 1987A - A Broader View