Issue |
A&A
Volume 398, Number 3, February II 2003
|
|
---|---|---|
Page(s) | 1021 - 1028 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20021554 | |
Published online | 28 January 2003 |
The mass and energy budget of Cassiopeia A
1
Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
2
SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands e-mail: J.A.M.Bleeker@sron.nl; K.J.van.der.Heyden@sron.nl; j.s.kaastra@sron.nl
Corresponding author: R. Willingale, rw@star.le.ac.uk
Received:
11
July
2002
Accepted:
25
October
2002
Further analysis of X-ray spectroscopy results
(Willingale et al. 2002) recently obtained from the MOS CCD
cameras on-board XMM-Newton provides a detailed description of the hot and cool
X-ray emitting plasma in Cas A.
Measurement of the Doppler broadening of the X-ray emission lines
is consistent with the expected ion velocities,
~1500 km s-1 along the line of sight, in the post shock plasma.
Assuming a distance of 3.4 kpc,
a constant total pressure throughout the remnant
and combining the X-ray observations with optical measurements
we estimate the total remnant mass as 10 and the
total thermal energy as
J. We derive the differential mass
distribution as a function of ionisation age for the hot and cool
X-ray emitting components. This distribution is consistent with a hot component
dominated by swept up mass heated by the primary shock and a cool
component which are ablated clumpy ejecta material which were and
are still being
heated by interaction with the preheated swept up material.
We calculate a balanced mass and
energy budget for the supernova explosion giving a grand total of
J in
an ejected mass; approximately ~0.4
of the ejecta were
diffuse with an initial rms velocity ~
km s-1
while the remaining ~1.8
were clumpy with an initial
rms velocity of ~2400 km s-1.
Using the Doppler velocity measurements of the X-ray spectral lines
we can project the mass into spherical coordinates about the remnant. This
provides quantitative evidence for mass and energy
beaming in the supernova explosion.
The mass and energy occupy less than 4.5 sr (<40% of the available
solid angle) around the remnant and 64% of the mass occurs in two
jets within 45 degrees of a jet axis. We calculate a swept up mass
of 7.9
in the emitting plasma
and estimate that the total mass lost from the progenitor
prior to the explosion could be as high as ~20
. We suggest
that the progenitor was a Wolf-Rayet star that formed a
dense nebular shell before the supernova explosion.
This shell underwent heating by the primary shock which was
energized by the fast diffuse ejecta.
Key words: ISM: supernova remnants / X-rays: ISM
© ESO, 2003
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