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X­RAY STUDY OF CRAB­LIKE AND COMPOSITE SNRS
K. TORII, H. TSUNEMI
Osaka University
AND
P. SLANE
Harvard­Smithsonian Center for Astrophysics
1. Introduction
We have presented X­ray observations of Crab­like supernova remnants
(SNRs) (plerions) and (non­thermal) composite SNRs. We have observed
several objects including 3C58, CTA1, and G292.0+1.8. Since space is lim­
ited, here we summarize results on G292.0+1.8. For the other objects, please
refer to each publication (Slane et al. 1997; Torii et al. 1997).
2. G292.0+1.8 (MSH11--54)
The composite nature of G292.0+1.8 has previously been in doubt. Al­
though the center­filled radio morphology suggested an interior plerionic
component, strong X­ray emission lines seemed to rule out such specula­
tions. High resolution imaging with the Einstein HRI revealed its peculiar
morphology (Tuohy et al. 1982) and X­ray emission was found to come
from two distinct components, the central barlike feature and the ellip­
soidal disk of approximately uniform surface brightness. Both the elemental
abundances determined from X­ray spectra (Hughes et al. 1994) and the
peculiar morphology suggested a Type II SN explosion.
We have found that the hard X­ray image (figure 1 right) shows a center­
filled compact nebula in contrast to the extended morphology in the soft
band (figure 1 left). The position of the hard source coincides the radio
``ridge'' (Braun et al. 1986) and it is displaced to the east south­east direc­
tion from the apparent emission center. We interpret this component as a
synchrotron nebula embedded in the shock heated thermal plasma. Since
the X­ray morphology is far from a standard limb­brightened shell, possibly

2 K. TORII, H. TSUNEMI AND P. SLANE
suggesting the presence of circumstellar material, we have applied a self­
similar solution for a point explosion expanding into a non­uniform density
(Sedov 1993), ae ¸ r 02 , corresponding to a constant velocity stellar wind of
the progenitor. With a single component non ionization equilibrium model,
the temperature is obtained as kT ¸ 0:8 keV. The age and the explosion en­
ergy are estimated to be t age ¸ 47006200 yr and E SN ¸ (1:2560:07)210 50
ergs. Here we assumed the distance to the object of 4.8 kpc (Saken et al.
1992). From the estimated age, we derive the projected velocity of the pu­
tative pulsar born at the explosion center. If we adopt a nominal expansion
center obtained by optical observations (Braun et al. 1983) and assume
that the putative pulsar is at the center of the compact nebula, we obtain a
reasonable value (Lyne & Lorimer 1994) for the velocity, v trans ¸ 790 6 320
d 4:8kpc t 01
age;4700yr
km s 01 .
G292.0+1.8
0.5 ­ 2 keV
G292.0+1.8
2 ­ 10 keV
Figure 1. ASCA SIS images of G292.0+1.8. The images were deconvolved by the PSF
of the telescope. Left: 0.5--2 keV, Right: 2--10 keV.
References
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Lyne, A.G. and Lorimer, D.R. (1994) Nature, 369, 127
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Slane, P., Seward, F.D., Bandiera, R., Torii, K. and Tsunemi, H. (1997) ApJ, 485, 221
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submitted
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