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Register a new userSupernova Remnants, Pulsars and the Interstellar Medium - Summary of a Workshop Held at U Sydney, March 1999
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Vikram Dwarkadas
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We summarise the proceedings of the SRCfTA workshop on ``Supernova Remnants, Pulsars and the Interstellar Medium that was held at the University of Sydney on Mar 18 and 19, 1999.
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The Debrecen workshop was one of a number held in preparation for the UNESCO-ICSU World Conference on Science, which will be held in Budapest, June 1999. A report representing the views of the workshop, prepared for that conference and containing a number of recommended actions, is included with this summary. The workshop affirmed the ongoing importance of physics for its own sake and as part of our culture, as a key element in our increasingly unified science and as an essential contributor to the solution of environmental and energy problems. The problems faced by physics as an activity and as an educational subject were discussed and actions for both society as a whole and the physics community itself were put forward.
The results obtained by the Working Group on Supersymmetry at the 1999 Les Houches Workshop on Collider Physics are summarized. Separate chapters treat general supersymmetry, R-parity violation, gauge mediated supersymmetry breaking, and anomaly mediated supersymmetry breaking.
We present Wide Field Camera 3 images taken with the Hubble Space Telescope within a single field in the southern grand design star-forming galaxy M83. Based on their size, morphology and photometry in continuum-subtracted H$alpha$, [SII], H$beta$, [OIII] and [OII] filters, we have identified 60 supernova remnant candidates, as well as a handful of young ejecta-dominated candidates. A catalog of these remnants, their sizes and, where possible their H$alpha$ fluxes are given. Radiative ages and pre-shock densities are derived from those SNR which have good photometry. The ages lie in the range $2.62 < log(tau_{rm rad}/{rm yr}) < 5.0$, and the pre-shock densities at the blast wave range over $0.56 < n_0/{rm cm^{-3}} < 1680$. Two populations of SNR have been discovered. These divide into a nuclear and spiral arm group and an inter-arm population. We infer an arm to inter-arm density contrast of 4. The surface flux in diffuse X-rays is correlated with the inferred pre-shock density, indicating that the warm interstellar medium is pressurised by the hot X-ray plasma. We also find that the interstellar medium in the nuclear region of M83 is characterized by a very high porosity and pressure and infer a SNR rate of one per 70-150 yr for the nuclear ($R<300 $pc) region. On the basis of the number of SNR detected and their radiative ages, we infer that the lower mass of Type II SNe in M83 is $M_{rm min} = 16^{+7}_ {-5}$ M$_{odot}$. Finally we give evidence for the likely detection of the remnant of the historical supernova, SN1968L.
Observations have been made with the University of Durham Mark 6 telescope of a number of supernova remnants and young pulsars (Vela pulsar, PSR B1055-52, PSR J1105-6107, PSR J0537-6910 and PSR B0540-69). No VHE gamma ray emission, either steady or pulsed, has been detected from these objects.
The age of a supernova remnant (SNR) is, though undoubtedly one of the most important properties for study of its evolution, difficult to estimate reliably in most cases. In this study, we compare the dynamical and plasma ages of the SNRs and characteristic ages of their associated pulsars with the corresponding SNRs ages that are generally thought to be reliable ($t_{rm r}$): historical and light-echo ages of the SNRs, kinematic ages of the ejecta knots and kinematic ages of the associated neutron stars (NS). The kinematic age of ejecta knots or a NS is the time that they have taken to reach the current positions from the explosion center. We use all of the available 24 systems for which $t_{rm r}$ is already available (historical, light-echo, and ejecta kinematic ages) or measurable (NS kinematic age). We estimate the NS kinematic ages for eight SNR-NS systems by determining quantitatively the geometric centers of the SNR shells. The obtained $t_{rm r}$ ranges from 33 yr to $approx 400$ kyr. We find that the two SNR ages, dynamical and plasma ages, are consistent with $t_{rm r}$ within a factor of four, whereas the characteristic ages of the pulsars differ from $t_{rm r}$ by more than a factor of four in some systems. Using the $t_{rm r}$ summarized in this work, we present the initial spin periods of the associated pulsars, which are more strictly constrained than the previous works, as well.
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