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Register a new userPulsar Acceleration Shifts from nearby Supernova Explosion
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We show that when a supernova explodes, a nearby pulsar signal goes through a very specific change. The observed period first changes smoothly, then is followed by a sudden change in the time derivative. A stable millisecond pulsar can allow us to measure such an effect. This may improve our measurement of the total energy released in neutrinos and also the orientation of the supernova-pulsar system.
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In this work we report briefly on the gravitational wave (GW) signal computed in the context of a self-consistent, 3D simulation of a core-collapse supernova (CCSN) explosion of a 15M$_odot$ progenitor star. We present a short overview of the GW signal, including signal amplitude, frequency distribution, and the energy emitted in the form of GWs for each phase of explosion, along with neutrino luminosities, and discuss correlations between them.
When a supernova explodes, most of its energy is released in a shell of relativistic neutirnos which changes the surrounding geometry. We calculate the potentially observable responses to such a change in both pulsar scintillation and conventional interferometers. In both cases, the responses are permanent changes due to such a transient event. This is by-definition a memory effect. In addition to the transverse component in the usual gravitational memory (Christodolou effect) effect, it also has a longitudinal component. Furthermore it is different from the Christodolou effect as the transverse component of this memory effect also has a term that grows with time.
We report on the gravitational wave signal computed in the context of a three-dimensional simulation of a core collapse supernova explosion of a 15 Solar mass star. The simulation was performed with our neutrino hydrodynamics code Chimera. We detail the gravitational wave strains as a function of time, for both polarizations, and discuss their physical origins. We also present the corresponding spectral signatures. Gravitational wave emission in our model has two key features: low-frequency emission (< 200 Hz) emanates from the gain layer as a result of neutrino-driven convection and the SASI and high-frequency emission (> 600 Hz) emanates from the proto-neutron star due to Ledoux convection within it. The high-frequency emission dominates the gravitational wave emission in our model and emanates largely from the convective layer itself, not from the convectively stable layer above it, due to convective overshoot. Moreover, the low-frequency emission emanates from the gain layer itself, not from the proto-neutron star, due to accretion onto it. We provide evidence of the SASI in our model and demonstrate that the peak of our low-frequency gravitational wave emission spectrum corresponds to it. Given its origin in the gain layer, we classify the SASI emission in our model as p-mode emission and assign a purely acoustic origin, not a vortical-acoustic origin, to it. Our dominant proto-neutron star gravitational wave emission is not well characterized by emission from surface g-modes, complicating the relationship between peak frequencies observed and the mass and radius of the proto-neutron star expressed by analytic estimates under the assumption of surface g-mode emission. We present our frequency normalized characteristic strain along with the sensitivity curves of current- and next-generation gravitational wave detectors.
We have studied the fascinating dynamics of the nearby Vela pulsars nebula in a campaign comprising eleven 40ks observations with Chandra X-ray Observatory (CXO). The deepest yet images revealed the shape, structure, and motion of the 2-arcminute-long pulsar jet. We find that the jets shape and dynamics are remarkably consistent with that of a steadily turning helix projected on the sky. We discuss possible implications of our results, including free precession of the neutron star and MHD instability scenarios.
Progress in the three-dimensional modeling of supernovae (SN) prompts us to revisit the supernova remnant (SNR) phase. We continue our study of the imprint of a thermonuclear explosion on the SNR it produces, that we started with a delayed-detonation model of a Chandrasekhar-mass white dwarf. Here we compare two different types of explosion models, each with two variants: two delayed detonation models (N100ddt, N5ddt) and two pure deflagration models (N100def, N5def), where the N number parametrizes the ignition. The output of each SN simulation is used as input of a SNR simulation carried on until 500 yr after the explosion. While all SNR models become more spherical over time and overall display the theoretical structure expected for a young SNR, clear differences are visible amongst the models, depending on the geometry of the ignition and on the presence or not of detonation fronts. Compared to N100 models, N5 models have a strong dipole component, and produce asymmetric remnants. N5def produces a regular-looking, but offset remnant, while N5ddt produces a two-sided remnant. Pure deflagration models exhibit specific traits: a central over-density, because of the incomplete explosion, and a network of seam lines across the surface, boundaries between burning cells. Signatures from the SN dominate the morphology of the SNR up to 100 yr to 300 yr after the explosion, depending on the model, and are still measurable at 500 yr, which may provide a way of testing explosion models.
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