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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
Braun, R., Goss, W.M., Danziger, I.J. and Boksenberg, A. (1983) Supernova Remnants
and Their X­ray Emissions. Reidel, Dordrecht.
Braun, R., Goss, W.M. and Roger, R.S. (1986) A&A, 162, 259
Hughes, J.P. and Singh, K.P. (1994) ApJ, 422, 126
Lyne, A.G. and Lorimer, D.R. (1994) Nature, 369, 127
Saken, J.M., Fesen, R.A. and Shull, J.M. (1992) ApJS, 81, 715
Sedov, L.I. (1993) Similarity and Dimensional Methods in Mechanics 10th Edition. CRC
Press, Boca Raton.
Slane, P., Seward, F.D., Bandiera, R., Torii, K. and Tsunemi, H. (1997) ApJ, 485, 221
Torii, K., Kinugasa, K., Hashimotodani, K., Tsunemi, H. and Slane, P.O. (1997) PASJ,
submitted
Tuohy, I.R., Clark, D.H. and Burton, W.M. (1982) ApJL, 260, L65