A method for computing synchrotron and inverse-Compton emission from hydrodynamic simulations of supernova remnants

The observational signature of supernova remnants (SNRs) is very complex, in terms of both their geometrical shape and their spectral properties, dominated by non-thermal synchrotron and inverse-Compton scattering. We propose a post-processing method to analyse the broad-band emission of SNRs based on three-dimensional hydrodynamical simulations. From the hydrodynamical data, we estimate the distribution of non-thermal electrons accelerated at the shock wave and follow the subsequent evolution as they lose or gain energy by adiabatic expansion or compression and emit energy by radiation. As a first test case, we use a simulation of a bipolar supernova expanding into a cloudy medium. We find that our method qualitatively reproduces the main observational features of typical SNRs and produces fluxes that agree with observations to within a factor of a few. allowing for further use in more extended sets of models.Comment: 15 pages, 3 figures; accepted, HEDLA 2014 special issue of High Energy Density Physic

A Spallation Model for the Titanium-rich Supernova Remnant Cassiopeia A

Titanium-rich subluminous supernovae are rare and challenge current SN nucleosynthesis models. We present a model in which ejecta from a standard Supernova is impacted by a second explosion of the neutron star (a Quark-nova), resulting in spallation reactions that lead to 56Ni destruction and 44Ti creation under the right conditions. Basic calculations of the spallation products shows that a delay between the two explosions of ~ 5 days reproduces the observed abundance of 44Ti in Cas A and explains its low luminosity as a result of the destruction of 56Ni. Our results could have important implications for lightcurves of subluminous as well as superluminous supernovae.Comment: Accepted/to be published in Physical Review Letters. [ for more info on the Quark Nova, see: http://quarknova.ucalgary.ca/

Multiwavelength appearance of Vela Jr.: Is it up to expectations?

Vela Jr. is one of the youngest and likely nearest among the known galactic supernova remnants (SNRs). Discovered in 1997 it has been studied since then at quite a few wavelengths, that spread over almost 20 decades in energy. Here we present and discuss Vela Jr. properties revealed by these multiwavelength observations, and confront them with the SNR model expectations. Questions that remained unanswered at the time of publication of the paper of Iyudin et al. (2005), e.g. what is the nature of the SNR's proposed central compact source CXOU J085201.4-461753, and why is the ISM absorption column density apparently associated with RX J0852.0-4622 much greater than the typical column of the Vela SNR, can be addressed using the latest radio and X-ray observations of Vela Jr.. These, and other related questions are addressed in the following.Comment: 8 pages, 7 figures. Accepted for publication in ESA SP-622, Proceedings of the 6th INTEGRAL Workshop held in Moscow, Russia, July 02-08, 200

The Polar Regions of Cassiopeia A: The Aftermath of a Gamma Ray Burst?

Probably not, but it is interesting nevertheless to investigate just how close Cas A might have come to generating such an event. Focusing on the northeast jet filaments, we analyze the polar regions of the recently acquired very deep 1 Ms Chandra X-ray observation. We infer that the so-called "jet" regions are indeed due to jets emanating from the explosion center, and not due to polar cavities in the circumstellar medium at the time of explosion. We place limits on the equivalent isotropic explosion energy in the polar regions (around 2.3 x 10^52 ergs), and the opening angle of the x-ray emitting ejecta (around 7 degrees), which give a total energy in the NE jet of order 10^50 ergs; an order of magnitude or more lower than inferred for "typical" GRBs. While the Cas A progenitor and explosion exhibit many of the features associated with GRB hosts, e.g. extensive presupernova mass loss and rotation, and jets associated with the explosion, we speculate that the recoil of the compact central object, with velocity 330 km/s, may have rendered the jet unstable. In such cases the jet rapidly becomes baryon loaded, if not truncated altogether. Although unlikely to have produced a gamma ray burst, the jets in Cas A suggest that such outflows may be common features of core-collapse SNe.Comment: 35 pages, 7 figures, accepted by Ap

Interstellar absorptions and shocked clouds towards supernova remnant RX J0852.0-4622

We present results of survey of interstellar absorptions towards supernova remnant (SNR) RX J0852.0-4622. The distribution of KI absorbers along the distance of the background stars is indicative of a local region (d<600pc) strongly depopulated by KI line-absorbing clouds. This fact is supported by the behavior of the interstellar extinction. We find four high-velocity CaII components with velocities of >100km/s towards three stars and identify them with shocked clouds of Vela SNR. We reveal and measure acceleration of two shocked clouds at the approaching and receding sides of Vela SNR along the same sight line. The clouds acceleration, velocity, and CaII column density are used to probe cloud parameters. The total hydrogen column density of both accelerating clouds is found to be similar (~6*10^{17} cm$^{-2}$) which indicates that possibly there is a significant amount of small-size clouds in the vicinity of Vela SNR.Comment: accepted in MNRA

The Coma Cluster at gamma-ray energies: multifrequency constraints

The Coma cluster exhibits evidence for a high-energetic non-thermal particle population. At frequencies >1 GHz recent radio halo observations confirm a significant spectral steepening of the volume-integrated emission. We calculate the volume-averaged high-energy spectrum due to inverse Compton scattering off the CMB radiation field and non-thermal bremsstrahlung according to an exponential cutoff in the electron spectrum as deduced from the radio observations. The synchrotron radiation from secondary pairs, created from the decay of charged mesons produced in hadronic pp-interactions, is found to set significant constraints on the energy content of relativistic hadrons in Coma. This limits the maximum flux at high energies. Our findings support a low ratio of relativistic hadron to thermal energy density. Predictions for Coma's high energy emission are discussed in the light of current and expected abilities of upcoming gamma-ray instruments.Comment: 7 pages, 2 figures, A&A, accepted; Minor changes to reflect the accepted versio

Resonant Scattering and Recombination in CAL 87

The eclipsing supersoft X-ray binary CAL 87 has been observed with Chandra on August 13/14, 2001 for nearly 100 ksec, covering two full orbital cycles and three eclipses. The shape of the eclipse light curve derived from the zeroth-order photons indicates that the size of the X-ray emission region is about 1.5 solar radii. The ACIS/LETG spectrum is completely dominated by emission lines without any noticeable continuum. The brightest emission lines are significantly redshifted and double-peaked, suggestive of emanating in a 2000 km/s wind. We model the X-ray spectrum by a mixture of recombination and resonant scattering. This allows us to deduce the temperature and luminosity of the ionizing source to be kT = 50-100 eV and L_X = 5E37 erg/s.Comment: To appear in Proceedings of IAU Coll. 194 "Compact binaries in the Galaxy and beyond" (Rev. Mex. A&A Conf. Series), eds. G. Tovmassian and E. Sio

Limits to the Cas A 44^{44}Ti Line Flux and Constraints on the Ejecta Energy and the Compact Source

Two long observations of Cas A supernova remnant were made by the \emph{Rossi X-ray Timing Explorer} in 1996 and 1997 to search for hard X-ray line emission at 67.9 and 78.4 keV from decay of $^{44}$Ti formed during the supernova event. Continuum flux was detected up to 100 keV, but the $^{44}$Ti lines were not detected. The 90% confidence upper limit to the line flux is 3.6$\times10^{-5}$ photons cm$^{-2}$s$^{-1}$. This is consistent with the recent \emph{BeppoSAX} detection and with the \emph{CGRO}/COMPTEL detection of the companion transition line flux for $^{44}$Sc decay. The mean \emph{BeppoSAX}--COMPTEL flux indicates that 1.5$\pm$0.3 $\times10^{-4}$M$_\odot$ of $^{44}$Ti was produced in the supernova explosion. Based upon recent theoretical calculations, and optical observations suggesting a WN Wolf-Rayet progenitor with an initial mass of $\geq$25 M$_\odot$, the observed $^{44}$Ti yield implies that the Cas A supernova ejecta energy was $\sim2\times10^{51}$ ergs, and as a result a neutron star was formed, rather than a black hole. We suggest Cas A is possibly in the early stages of the AXP/SGR scenario in which the push-back disk has yet to form, and when the disk does form, the accretion will increase the luminosity to that of present-day AXP/SGRs and pulsed emission will commence.Comment: 12 pages, 3 tables, 1 figure, accepted for publication in the Astrophysical Journa