* Astronomy

Members Login
    Remember Me  
Post Info TOPIC: SNR W28


Posts: 131433

Title: Probing MHD Shocks with high-J CO observations: W28F
Authors: A. Gusdorf, S. Anderl, R. Guesten, J. Stutzki, H-W. Huebers, P. Hartogh, S. Heyminck, Y. Okada

Context. Observing supernova remnants (SNRs) and modelling the shocks they are associated with is the best way to quantify the energy SNRs re-distribute back into the Interstellar Medium (ISM).
Aims. We present comparisons of shock models with CO observations in the F knot of the W28 supernova remnant. These comparisons constitute a valuable tool to constrain both the shock characteristics and pre-shock conditions.
Methods. New CO observations from the shocked regions with the APEX and SOFIA telescopes are presented and combined. The integrated intensities are compared to the outputs of a grid of models, which were combined from an MHD shock code that calculates the dynamical and chemical structure of these regions, and a radiative transfer module based on the 'large velocity gradient' (LVG) approximation.
Results. We base our modelling method on the higher J CO transitions, which unambiguously trace the passage of a shock wave. We provide fits for the blue- and red-lobe components of the observed shocks. We find that only stationary, C-type shock models can reproduce the observed levels of CO emission. Our best models are found for a pre-shock density of 104 cm-3, with the magnetic field strength varying between 45 and 100 {\mu}G, and a higher shock velocity for the so-called blue shock (~25 km s-1) than for the red one (~20 km s-1). Our models also satisfactorily account for the pure rotational H2 emission that is observed with Spitzer.

Read more (5560kb, PDF)



Posts: 131433

Title: X-Ray Observations of the Supernova Remnant W28 with Suzaku --- I. Spectral Study of the Recombining Plasma
Authors: Makoto Sawada, Katsuji Koyama

We present the Suzaku results of the mixed-morphology supernova remnant W28. The X-ray spectra of the central region of W28 exhibit many bright emission lines from highly ionised atoms. An optically thin thermal plasma in collisional ionisation equilibrium, either of single-temperature or multi-temperature failed to reproduce the data with line-like and bump-like residuals at the Si Lyman alpha energy and at 2.4--5.0 keV, respectively. The bumps probably correspond to radiative recombination continua from He-like Si and S. A simple recombining plasma model nicely fit the bump structures, but failed to fit low energy bands. The overall spectra can be fit with a multi-ionisation temperature plasma with a common electron temperature. The multi-ionisation temperatures are interpreted as elemental difference of ionisation and recombination timescales. These results prefer the rarefaction scenario for the origin of the recombining plasma.

Read more (3027kb, PDF)

Page 1 of 1  sorted by
Quick Reply

Please log in to post quick replies.

Create your own FREE Forum
Report Abuse
Powered by ActiveBoard