Search results for "EJECTA"
showing 10 items of 76 documents
Neutron-star merger ejecta as obstacles to neutrino-powered jets of gamma-ray bursts
2015
We present the first special relativistic, axisymmetric hydrodynamic simulations of black hole-torus systems (approximating general relativistic gravity) as remnants of binary-neutron star (NS-NS) and neutron star-black hole (NS-BH) mergers, in which the viscously driven evolution of the accretion torus is followed with self-consistent energy-dependent neutrino transport and the interaction with the cloud of dynamical ejecta expelled during the NS-NS merging is taken into account. The modeled torus masses, BH masses and spins, and the ejecta masses, velocities, and spatial distributions are adopted from relativistic merger simulations. We find that energy deposition by neutrino annihilation…
Numerical models of blackbody-dominated gamma-ray bursts -- II. Emission properties
2014
Blackbody-dominated (BBD) gamma-ray bursts (GRBs) are events characterized by long durations and the presence of a significant thermal component following the prompt emission, as well as by the absence of a typical afterglow. GRB 101225A is the most prominent member of this class. A plausible progenitor system for it and for BBD-GRBs is the merger a neutron star and a helium core of an evolved, massive star. Using relativistic hydrodynamic simulations we model the propagation of ultrarelativistic jets through the environments created by such mergers. In a previous paper we showed that the thermal emission in BBD-GRBs is linked to the interaction of an ultrarelativistic jet with the ejected …
Discovery of a jet-like structure with overionized plasma in the SNR IC443
2018
IC443 is a supernova remnant located in a quite complex environment since it interacts with nearby clouds. Indications for the presence of overionized plasma have been found though the possible physical causes of overionization are still debated. Moreover, because of its peculiar position and proper motion, it is not clear if the pulsar wind nebula (PWN) within the remnant is the relic of the IC443 progenitor star or just a rambling one seen in projection on the remnant. Here we address the study of IC443 plasma in order to clarify the relationship PWN-remnant, the presence of overionization and the origin of the latter. We analyzed two \emph{XMM-Newton} observations producing background-su…
The termination region of high-mass microquasar jets
2011
The environment of high-mass X-ray binaries can be characterized either by the SNR that forms these systems, or by the wind from the companion massive star. These regions should be tenuous but very hot, and surrounded by a dense and cold shocked ISM shell. The interaction between the jet and such a complex medium, also affected by the system proper motion, can lead to very different jet termination structures. The evolution of the jet termination regions during the life of a high-mass microquasar is simulated to improve the present understanding of these structures. Also, the evolving emission characteristics are modeled to inform potential observational campaigns for this class of object. …
Limit to the radio emission from a putative central compact source in SN1993J
2013
SN1993J in M81 is the best studied young radio-luminous supernova in the Northern Hemisphere. We recently reported results from the analysis of a complete set of VLBI observations of this supernova at 1.7, 2.3, 5.0, and 8.4 GHz, covering a time baseline of more than one decade. Those reported results were focused on the kinematics of the expanding shock, the particulars of its evolving non-thermal emission, the density profile of the circumstellar medium, and the evolving free-free opacity by the supernova ejecta. In the present paper, we complete our analysis by performing a search for any possible signal from a compact source (i.e., a stellar-mass black hole or a young pulsar nebula) at t…
The role of weak interactions in dynamic ejecta from binary neutron star mergers
2017
Weak reactions are critical for the neutron richness of the matter dynamically ejected after the merger of two neutron stars. The neutron richness, defined by the electron fraction (Ye), determines which heavy elements are produced by the r-process and thus directly impacts the kilonova light curve. In this work, we have performed a systematic and detailed post-processing study of the impact of weak reactions on the distribution of the electron fraction and of the entropy on the dynamic ejecta obtained from an equal mass neutron star binary merger simulated in full general relativity and with microscopic equation of state. Previous investigations indicated that shocks increase Ye, however o…
Radio emission of SN1993J: the complete picture. I. Re-analysis of all the available VLBI data
2010
We have performed a complete re-calibration and re-analysis of all the available VLBI observations of supernova SN1993J, following an homogeneous and well-defined methodology. Observations of SN1993J at 69 epochs, spanning 13 years, were performed by two teams, which used different strategies and analysis tools. The results obtained by each group are similar, but their conclusions on the supernova expansion and the shape and evolution of the emitting region differ significantly. From our analysis of the combined set of observations, we have obtained an expansion curve with unprecedented time resolution and coverage. We find that the data from both teams are compatible when analyzed with the…
Spectral Evolution of the X-Ray Remnant of SN 1987A: A High-Resolution $Chandra$ HETG Study
2021
Based on observations with the $Chandra$ X-ray Observatory, we present the latest spectral evolution of the X-ray remnant of SN 1987A (SNR 1987A). We present a high-resolution spectroscopic analysis using our new deep ($\sim$312 ks) $Chandra$ HETG observation taken in March 2018, as well as archival $Chandra$ gratings spectroscopic data taken in 2004, 2007, and 2011 with similarly deep exposures ($\sim$170 - 350 ks). We perform detailed spectral model fits to quantify changing plasma conditions over the last 14 years. Recent changes in electron temperatures and volume emission measures suggest that the shocks moving through the inner ring have started interacting with less dense circumstell…
A population of isolated hard X-ray sources near the supernova remnant Kes 69
2012
Recent X-ray observations of the supernova remnant IC443 interacting with molecular clouds have shown the presence of a new population of hard X-ray sources related to the remnant itself, which has been interpreted in terms of fast ejecta fragment propagating inside the dense environment. Prompted by these studies, we have obtained a deep {\sl XMM-Newton} observation of the supernova remnant (SNR) Kes 69, which also shows signs of shock-cloud interaction. We report on the detection of 18 hard X-ray sources in the field of Kes 69, a significant excess of the expected galactic source population in the field, spatially correlated with CO emission from the cloud in the remnant environment. The …
23 GHz VLBI Observations of SN 2008ax
2009
We report on phase-referenced 23 GHz Very-Long-Baseline-Interferometry (VLBI) observations of the type IIb supernova SN 2008ax, made with the Very Long Baseline Array (VLBA) on 2 April 2008 (33 days after explosion). These observations resulted in a marginal detection of the supernova. The total flux density recovered from our VLBI image is 0.8$\pm$0.3 mJy (one standard deviation). As it appears, the structure may be interpreted as either a core-jet or a double source. However, the supernova structure could be somewhat confused with a possible close by noise peak. In such a case, the recovered flux density would decrease to 0.48$\pm$0.12 mJy, compatible with the flux densities measured with…