After the death of a runaway massive star, its supernova shock wave interacts with the bow shocks produced by its defunct progenitor, and may lose energy, momentum and its spherical symmetry before ...expanding into the local interstellar medium (ISM). We investigate whether the initial mass and space velocity of these progenitors can be associated with asymmetric supernova remnants. We run hydrodynamical models of supernovae exploding in the pre-shaped medium of moving Galactic
core-collapse progenitors. We find that bow shocks that accumulate more than about 1.5 M⊙ generate asymmetric remnants. The shock wave first collides with these bow shocks 160-750 yr after the supernova, and the collision lasts until 830-4900 yr. The shock wave is then located 1.35-5 pc from the centre of the explosion, and it expands freely into the ISM, whereas in the opposite direction it is channelled into the region of undisturbed wind material. This applies to an initially 20 M⊙ progenitor moving with velocity 20 km s-1 and to our initially 40 M⊙ progenitor. These remnants generate mixing of ISM gas, stellar wind and supernova ejecta that is particularly important upstream from the centre of the explosion. Their light curves are dominated by emission from optically thin cooling and by X-ray emission of the shocked ISM gas. We find that these remnants are likely to be observed in the O iii λ 5007 spectral line emission or in the soft energy-band of X-rays. Finally, we discuss our results in the context of observed Galactic supernova remnants such as 3C 391 and the Cygnus Loop.
Close-in hot Jupiters are exposed to a tremendous photon flux that ionizes the neutral escaping material from the planet leaving an observable imprint that makes them an interesting laboratory for ...testing theoretical models. In this work, we present 3D hydrodynamic simulations with radiation transfer calculations of a close-in exoplanet in a blow-off state. We calculate the Ly α absorption and compare it with observations of HD 209458b and previous simplified model results. Our results show that the hydrodynamic interaction together with a proper calculation of the photoionization process are able to reproduce the main features of the observed Ly α absorption, in particular at the blue-shifted wings of the line. We found that the ionizing stellar flux produce an almost linear effect on the amount of absorption in the wake. Varying the planetary mass-loss rate and the radiation flux, we were able to reproduce the 10 per cent absorption observed at −100 km s−1.
3D MHD simulation of polarized emission in SN 1006 Schneiter, E. M; Velázquez, P. F; Reynoso, E. M ...
Monthly notices of the Royal Astronomical Society,
05/2015, Letnik:
449, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We use three-dimensional magnetohydrodynamic simulations to model the supernova remnant SN 1006. From our numerical results, we have carried out a polarization study, obtaining synthetic maps of the ...polarized intensity, the Stokes parameter Q, and the polar-referenced angle, which can be compared with observational results. Synthetic maps were computed considering two possible particle acceleration mechanisms: quasi-parallel and quasi-perpendicular. The comparison of synthetic maps of the Stokes parameter Q maps with observations proves to be a valuable tool to discern unambiguously which mechanism is taking place in the remnant of SN 1006, giving strong support to the quasi-parallel model.
ABSTRACT
A significative fraction of all massive stars in the Milky Way move supersonically through their local interstellar medium (ISM), producing bow shock nebulae by wind-ISM interaction. The ...stability of these observed astrospheres around cool massive stars challenges precedent 2D (magneto-)hydrodynamical (MHD) simulations of their surroundings. We present 3D MHD simulations of the circumstellar medium of runaway M-type red supergiant stars moving with velocity $v_{\star }=50\, \rm km\, \rm s^{-1}$. We treat the stellar wind with a Parker spiral and assume a $7\, \rm \mu G$ magnetization of the ISM. Our free parameter is the angle θmag between ISM flow and magnetization, taken to 0°, 45°, and 90°. It is found that simulation dimension, coordinate systems, and grid effects can greatly affect the development of the modelled astrospheres. Nevertheless, as soon as the ISM flow and magnetization directions differs by more than a few degrees (θmag ≥ 5°), the bow shock is stabilized, most clumpiness and ragged structures vanishing. The complex shape of the bow shocks induce important projection effects, e.g. at optical H α line, producing complex of astrospheric morphologies. We speculate that those effects are also at work around earlier-type massive stars, which would explain their diversity of their observed arc-like nebula around runaway OB stars. Our 3D MHD models are fitting well observations of the astrospheres of several runaway red supergiant stars. The results interpret the smoothed astrosphere of IRC-10414 and Betelgeuse (αOri) are stabilized by an organized non-parallel ambient magnetic field. Our findings suggest that IRC-10414 is currently in a steady state of its evolution, and that Betelgeuse’s bar is of interstellar origin.
We present narrow-band optical and near-IR imaging and optical long-slit spectroscopic observations of Hu 1-2, a Galactic planetary nebula (PN) with a pair of N ii-bright, fast-moving (>340 km s−1) ...bipolar knots. Intermediate-dispersion spectra are used to derive physical conditions and abundances across the nebula, and high-dispersion spectra to study the spatio-kinematical structure. Generally, Hu 1-2 has high He/H (≈0.14) and N/O ratios (≈0.9), typical of Type I PNe. On the other hand, its abundances of O, Ne, S, and Ar are low as compared with the average abundances of Galactic bulge and disc PNe. The position–velocity maps can be generally described as an hour-glass shaped nebula with bipolar expansion, although the morphology and kinematics of the innermost regions cannot be satisfactorily explained with a simple, tilted equatorial torus. The spatio-kinematical study confines the inclination angle of its major axis to be within 10° of the plane of sky. As in the irradiated bow-shocks of IC 4634 and NGC 7009, there is a clear stratification in the emission peaks of O iii, Hα, and N ii in the north-west (NW) knot of Hu 1-2. Fast collimated outflows in PNe exhibit higher excitation than other low-ionization structures. This is particularly the case for the bipolar knots of Hu 1-2, with He ii emission levels above those of collimated outflows in other Galactic PNe. The excitation of the knots in Hu 1-2 is consistent with the combined effects of shocks and UV radiation from the central star. The mechanical energy and luminosity of the knots are similar to those observed in the PNe known to harbour a post-common envelope (post-CE) close binary central star.
Abstract
We present a polarization study towards the supernova remnant (SNR) Puppis A based on original observations performed with the Australia Telescope Compact Array. Based on the analysis of a ...feature detected outside the SNR shell (called ‘the tail’ throughout the paper), it was possible to disentangle the emission with origin in Puppis A itself from that coming from the foreground Vela SNR. We found a very low polarization fraction, of about 3 per cent on average. The upper limit of the magnetic field component parallel to the line of sight is estimated to be B∥ ∼ 20 $\mu$G. The statistical behaviour of the magnetic vectors shows two preferential directions, almost perpendicular to each other, which are approximately aligned with the flat edges of Puppis A. A third, narrow peak oriented perpendicular to the Galactic plane suggests the existence of an interstellar magnetic field locally aligned in this direction. There is evidence that the magnetic vectors along the shell are aligned with the shock front direction. The low polarization fraction and the statistical behaviour of the magnetic vectors are compatible with a scenario where the SNR evolves inside a stellar wind bubble with a box-like morphology, produced by the interaction of the different stellar winds, one of them magnetized, launched by the SN progenitor. This scenario can furthermore explain the morphology of Puppis A, rendering little support to the previously accepted picture which involved strong density gradients to explain the flat, eastern edge of the shell.
ABSTRACT
Pulsar wind nebulae are a possible final stage of the circumstellar evolution of massive stars, where a fast-rotating, magnetized neutron star produces a powerful wind that interacts with ...the supernova ejecta. The shape of these so-called plerionic supernova remnants is influenced by the distribution of circumstellar matter at the time of the explosion, itself impacted by the magnetic field of the ambient medium, responsible for the expansion of the circumstellar bubble of the progenitor star. To understand the effects of magnetization on the circumstellar medium and resulting pulsar nebulae, we conduct 2D magnetohydrodynamic simulations. Our models explore the impact of the interstellar medium’s (ISM) magnetic field on the morphology of a supernova remnant and pulsar wind nebula that develop in the circumstellar medium of massive star progenitor in the warm phase of the Milky Way’s ISM. Our simulations reveal that the jet-like structures formed on both sides perpendicularly to the equatorial plane of the pulsar, creating complex radio synthetic synchrotron emissions. This morphology is characterized by a rectangular-like remnant, which is typical of the circumstellar medium of massive stars in a magnetized medium, along with the appearance of a spinning top structure within the projected rectangle. We suggest that this mechanism may be partially responsible for the complex morphologies observed in pulsar wind nebulae that do not conform to the typical torus/jet or bow shock/tail shapes observed in most cases.
ABSTRACT
We performed three-dimensional magnetohydrodynamic simulations to study the evolution of a supernova remnant (SNR) in a turbulent neutral atomic interstellar medium. The media used as ...background shares characteristics with the Solar neighbourhood and the SNR has mass and energy similar to those of a Type Ia object. Our initial conditions consist of dense clouds in a diluted medium, with the main difference between simulations being the average magnitude of the magnetic field. We measured amplifications of the magnetic energy of up to 34 ${{\rm per\ cent}}$, and we generated synthetic maps that illustrate how the same object can show different apparent geometries and physical properties when observed through different lines of sight.
ABSTRACT
We have performed 3D magnetohydrodynamics (MHD) numerical simulations with the aim of exploring the scenario in which the initial mass distribution of a supernova (SN) explosion is ...anisotropic. The purpose is to analyse if this scenario can also explain the radio-continuum emission and the expansion observed in young supernova remnants (SNRs). To study the expansion, synthetic polarized synchrotron emission maps were computed from the MHD simulations. We found a good agreement (under a number of assumptions) between this expansion study and previous observational results applied to Tycho’s SNR, which represents a good example of asymmetric young SNRs. Additionally, both the observed morphology and the brightness distribution are qualitatively reproduced.
ABSTRACT
We examine the evolution and emission of the supernova remnant (SNR) CTB 109 using 3D magnetohydrodynamics simulations. The SNR evolves in a medium divided by a plane interface into two ...media with different densities and pressure equilibrium. Our results reveal that a remnant with the characteristics of CTB 109 is formed provided the supernova (SN) explosion takes place in the less dense medium and also if the interstellar magnetic field (ISMF) is almost uniform. Finally, we conclude that the quasi-parallel mechanism can explain the brightness synchrotron emission and the position angle of the projected ISMF reported in previous works.
PDF
