1999ApJ...527..866L -
Astrophys. J., 527, 866-878 (1999/December-3)
DA 530: a supernova remnant in a stellar wind bubble.
LANDECKER T.L., ROUTLEDGE D., REYNOLDS S.P., SMEGAL R.J., BORKOWSKI K.J. and SEWARD F.D.
Abstract (from CDS):
The high-latitude supernova remnant (SNR) DA 530 (G93.3+6.9), apparently a typical shell remnant, has highly polarized radio continuum emission and a very uniform circumferential magnetic field. We present new radio continuum (408 and 1420 MHz) and H I line observations, made with the Dominion Radio Astrophysical Observatory Synthesis Telescope, and we have made the first detection of X-ray emission from the SNR, using the ROSAT Position-Sensitive Proportional Counter. The SNR lies within a shell of H I, possibly created by an earlier stellar wind, whose kinematic distance is nominally 2.5 kpc but whose actual distance may be larger. The X-ray emission is extremely faint. A Raymond-Smith ionization-equilibrium model fits the data and suggests a very low density, ∼0.05 cm–3, consistent with the occurrence of the supernova in a stellar wind cavity, but this model yields an explosion energy 100 times lower than the accepted value. A nonequilibrium shock model, incorporating a range of ionization timescales, is able to give more realistic physical parameters for the supernova remnant. On the balance of the evidence, we place DA 530 at a distance of 3.5 kpc, the largest distance permitted by the H I observations, where it lies 420 pc above the Galactic plane. The explosion, probably a Type Ia supernova, in a low-density cavity has resulted in weak X-ray emission and slow evolution. The explosion energy was 3.9x1050 ergs and the age is ∼5000 years. The remnant, having swept up 3.9 M☉ in an ambient density of ∼0.01 cm–3, is only now in the adiabatic phase, and this explains the absence of detected optical emission. Despite the low ambient density the efficiency of generation of synchrotron radio emission is ∼0.4%, higher than in some historical SNRs. The ratio of radio to X-ray flux is about 100 times that for the remnant of SN 1006, which has comparable radio continuum properties. The very uniform magnetic field is not explained. DA 530 joins a small group of remnants at high Galactic latitude with unusual features, perhaps resulting from low ambient densities. Inhomogeneous nonequilibrium ionization models may be required for the interpretation of the X-ray emission from many other older SNRs.
Abstract Copyright:
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Journal keyword(s):
ISM: Bubbles - ISM: individual (DA 530) - Radio Continuum: ISM - ISM: Supernova Remnants - X-Rays: ISM
Nomenclature:
Table 2: [LRR99a] N (Nos 1-7).
Simbad objects:
12
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