Evolution of the Radio Remnant of SN 1987A: 1990-2001

Abstract

The development of the radio remnant of SN 1987A has been followed using the Australia Telescope Compact Array since its first detection in 1990 August. The remnant has been observed at four frequencies, 1.4, 2.4, 4.8, and 8.6 GHz, at intervals of 4–6 weeks since the first detection. These data are combined with the 843 MHz data set of Ball et al. (2001) obtained at Molonglo Observatory to study the spectral and temporal variations of the emission. These observations show that the remnant continues to increase in brightness, with a larger rate of increase at recent times. They also show that the radio spectrum is becoming flatter, with the spectral index changing from −0.97 to −0.88 over the 11 years. In addition, at roughly yearly intervals since 1992, the remnant has been imaged at 9 GHz using super-resolution techniques to obtain an effective synthesised beamwidth of about 0″.5. The imaging observations confirm the shell morphology of the radio remnant and show that it continues to expand at ˜3000 km s−1. The bright regions of radio emission seen on the limb of the shell do not appear to be related to the optical hot spots which have subsequently appeared in surrounding circumstellar material.

X-Ray Evolution of SNR 1987a: The Radial Expansion

“…The addition of bilateral lobes approximates the morphology of the radio remnant (Gaensler et al 1997;Manchester et al 2002Manchester et al , 2005Ng et al 2008). The morphology of the X-ray remnant in the earliest epochs resembled that of the radio remnant with emission approximated by opposite bilateral regions of increased brightness.…”

“…The goal for our empirical models is to characterize the Chandra X-ray images in a more realistic way and in a similar spirit as those of the radio studies (Gaensler et al 1997;Manchester et al 2002Manchester et al , 2005Ng et al 2008) in order to obtain a measurement for the radial expansion of the remnant. The inner ring is inclined by 43 • to the line of sight (Crotts & Heathcote 1991).…”

ChandraLETG Observations of Supernova Remnant 1987A

“…The radio emission from SNR 1987A is non-thermal (Gaensler et al 1997;Manchester et al 2002) and is probably produced by relativistic electrons accelerated by the reverse shock (Manchester et al 2005). Park et al (2005) have noted that the hard X-ray light curve resembles the radio light curve of SNR 1987A and have suggested that the radio emission and the hard X-rays might have a common origin.…”

Radio emission from SNe and young SNRs

“…So far, this has been directly possible for two objects, SN1987A and SN1993J, although in some cases the deceleration can be estimated from model fitting to the radio light curves. Manchester, et al [29] have shown that the blastwave from the explosion of SN1987A traveled through the tenuous medium of the bubble created by the high speed wind of its BSG progenitor at an average speed of ~10% of the speed of light (~ 35,000 km s" 1 ), but has decelerated dramatically to only ~ 3,000 km s" 1 since it has reached the inner edge of the prominent optical ring.…”