arXiv subjects

Erez Michaely

Publications and source records attributed to Erez Michaely.

26 records · Page 2Linked to original sources

arXiv2017

Supernova and prompt gravitational-wave precursors to LIGO gravitational-wave sources and short-GRBs

Binary black-holes (BHs) and binary neutron-stars (NSs) mergers had been recently detected through gravitational-wave (GW) emission, with the latter followed by post-merger electromagnetic counterparts, appearing seconds up to weeks after the merger. While post-merger electromagnetic counterparts had been anticipated theoretically, very little electromagnetic precursors to GW-sources had been proposed, and non observed yet. Here we show that a fraction of ${\rm a}\,{\rm few\times}10^{-4}-10^{-1}$ of LIGO GW-sources and short-GRBs, could be preceded by supernovae-explosions years up to decades before the merger. Each of the BH/NS-progenitors in GW-sources are thought to form following a supernova, likely accompanied by a natal velocity-kick to the newly born compact object. The evolution and natal-kicks determine the orbits of surviving binaries, and hence the delay-time between the birth of the compact-binary and its final merger through GW-emission. We use data from binary evolution population-synthesis models to show that the delay-time distribution has a non-negligible tail of ultra-short delay-times between 1-100 yrs, thereby giving rise to potentially observable supernovae precursors to GW-sources. Moreover, future LISA/DECIGO GW space-detectors will enable the detection of GW-inspirals in the pre-mergers stage weeks to decades before the final merger. These ultra-short delay-time sources could therefore produce a unique type of promptly appearing LISA/DECIGO-GW-sources accompanied by \emph{coincident} supernovae. The archival (and/or direct) detection of precursor (coincident) SNe with GW and/or short-GRBs will provide unprecedented characterizations of the merging-binaries, and their prior evolution through supernovae and natal kicks, otherwise inaccessible through other means.

astro-ph.HE↗

arXiv2016

Generalized Hill-Stability Criteria for Hierarchical Three-Body Systems at Arbitrary Inclinations

A fundamental aspect of the three-body problem is its stability. Most stability studies have focused on the co-planar three-body problem, deriving analytic criteria for the dynamical stability of such pro/retrograde systems. Numerical studies of inclined systems phenomenologically mapped their stability regions, but neither complement it by theoretical framework, nor provided satisfactory fit for their dependence on mutual inclinations. Here we present a novel approach to study the stability of hierarchical three-body systems at arbitrary inclinations, which accounts not only for the instantaneous stability of such systems, but also for the secular stability and evolution through Lidov-Kozai cycles and evection. We generalize the Hill-stability criteria to arbitrarily inclined triple systems, explain the existence of quasi-stable regimes and characterize the inclination dependence of their stability. We complement the analytic treatment with an extensive numerical study, to test our analytic results. We find excellent correspondence up to high inclinations $(\sim120^{\circ}$), beyond which the agreement is marginal. At such high inclinations the stability radius is larger, the ratio between the outer and inner periods becomes comparable, and our secular averaging approach is no longer strictly valid. We therefore combine our analytic results with polynomial fits to the numerical results to obtain a generalized stability formula for triple systems at arbitrary inclinations. Besides providing a generalized secular-based physical explanation for the stability of non co-planar systems, our results have direct implications for any triple systems, and in particular binary planets and moon/satellite systems; we briefly discuss the latter as a test case for our models.

astro-ph.EP↗

arXiv2016

Neutron star natal kicks: Collisions, $μ$TDEs, faint SNe, GRBs and GW sources with preceding electromagnetic counterparts

Based on the observed high velocity of pulsars it is thought that neutron stars (NSs) receive a significant velocity kick at birth. Such natal kicks are considered to play an important role in the the evolution of binary-NS systems. The kick given to the NS (together with the effect of mass loss due to the supernova explosion of the NS progenitor) may result in the binary disruption or lead to a significant change of the binary orbital properties. Here we explore in detail the dynamical aftermath of natal kicks in binary systems, determine their possible outcomes and characterize their relative frequency, making use of analytic arguments and detailed population synthesis models. In a fraction of the cases the kick may cast the NS in such a trajectory as to collide with the binary companion, or pass sufficiently close to it as to disrupt it (micro tidal disruption event; $μ$TDE), or alternatively it could be tidally-captured into a close orbit, eventually forming an X-ray binary. We calculate the rates of direct post-kick physical collisions and the possible potential production of Thorne-Zytkow objects or long-GRBs through this process, estimate the rates X-ray binaries formation and determine the rates of $μ$TDEs and faint supernovae from white dwarf disruptions by NSs. Finally we suggest that natal kicks can produce BH-NS binaries with very short gravitational-wave merger time, possibly giving rise to a new type of promptly appearing eLISA gravitational wave (GW) sources, as well as producing aLIGO binary-merger GW sources with a unique (likely type Ib/c) supernova electromagnetic counterpart which precedes the GW merger.

astro-ph.HE↗

arXiv2015

Tidal capture formation of Low Mass X-Ray Binaries from wide binaries in the field

We present a potentially efficient dynamical formation scenario for Low Mass X-ray Binaries (LMXBs) in the field, focusing on black-hole (BH) LMXBs. In this formation channel LMXBs are formed from wide binaries $(>1000$ AU) with a BH component and a stellar companion. The wide binary is perturbed by fly-by's of field stars and its orbit random-walks and changes over time. This diffusion process can drive the binary into a sufficiently eccentric orbit such that the binary components tidally interact at peri-center and the binary evolves to become a short period binary, which eventually evolves into an LMXB. The formation rate of LMXBs through this channel mostly depends on the number of such BH wide binaries progenitors, which in turn depends on the velocity kicks imparted to BHs (or NSs) at birth. We consider several models for the formation and survival of such wide binaries, and calculate the LMXB formation rates for each model. We find that models where BHs form through direct collapse with no/little natal kicks can give rise to high formation rates comparable with those inferred from observations. This formation scenario had several observational signatures: (1) the number density of LMXBs generally follows the background stellar density and (2) the mass function of the BH stellar companion should be comparable to the mass function of the background stellar population, likely peaking at $0.4-0.6$ M$_{\odot}$. The latter aspect, in particular, is unique to this model compared with previously suggested LMXB formation models following common envelope binary stellar evolution. We note that NS LMXBs can similarly form from wide binaries, but their formation rate through this channel is likely significantly smaller due to their much higher natal kicks.

astro-ph.SR↗

arXiv2015

On the existence of regular and irregular outer moons orbiting the Pluto-Charon system

The dwarf planet Pluto is known to host an extended system of five co-planar satellites. Previous studies have explored the formation and evolution of the system in isolation, neglecting perturbative effects by the Sun. Here we show that secular evolution due to the Sun can strongly affect the evolution of outer satellites and rings in the system, if such exist. Although precession due to extended gravitational potential from the inner Pluto-Charon binary quench such secular evolution up to $a_{crit}\sim0.0035$ AU ($\sim0.09$ $R_{Hill}$ the Hill radius; including all of the currently known satellites), outer orbits can be significantly altered. In particular, we find that \emph{co-planar} rings and satellites should not exist beyond $a_{crit}$; rather, satellites and dust particles in these regions secularly evolve on timescales ranging between $10^{4}-10^{6}$ yrs, and quasi-periodically change their inclinations and eccentricities through secular evolution (Lidov-Kozai oscillations). Such oscillations can lead to high inclinations and eccentricities, constraining the range where such satellites (and dust particles) can exist without crossing the orbits of the inner satellites, or crossing the outer Hill stability range. Outer satellites, if such exist are therefore likely to be \emph{irregular} satellites, with orbits limited to be non-circular and/or highly inclined. These could be potentially detected and probed by the New-Horizon mission, possibly providing direct evidence for the secular evolution of the Pluto satellite system, and shedding new light on its origins.

astro-ph.EP↗

arXiv2014

Secular dynamics in hierarchical three-body systems with mass loss and mass transfer

Recent studies have shown that secular evolution of triple systems can play a major role in the evolution and interaction of their inner binaries. Very few studies explored the stellar evolution of triple systems, and in particular the mass loss phase of the evolving stellar components. Here we study the dynamical secular evolution of hierarchical triple systems undergoing mass loss. We use the secular evolution equations and include the effects of mass-loss and mass-transfer, as well as general relativistic effects. We present various evolutionary channels taking place in such evolving triples, and discuss both the effects of mass-loss and mass-transfer in the inner binary system, as well as the effects of mass-loss/transfer from an outer third companion. We discuss several distinct types/regimes of triple secular evolution, where the specific behavior of a triple system can sensitively depend on its hierarchy and the relative importance of classical and general relativistic effects. We show that the orbital changes due to mass-loss and/or mass-transfer processes can effectively transfer a triple system from one dynamical regime to another. In particular, mass loss/transfer can both induce and quench high amplitude (Lidov-Kozai) variations in the eccentricity and inclination of the inner binaries of evolving triples. They can also change the system dynamics from an orderly periodic behavior to a chaotic one, and vice versa.

astro-ph.SR↗

arXiv2012

Statistical Properties of the one dimensional Anderson model relevant for the Nonlinear Schrödinger Equation in a random potential

The statistical properties of overlap sums of groups of four eigenfunctions of the Anderson model for localization as well as combinations of four eigenenergies are computed. Some of the distributions are found to be scaling functions, as expected from the scaling theory for localization. These enable to compute the distributions in regimes that are otherwise beyond the computational resources. These distributions are of great importance for the exploration of the Nonlinear Schrödinger Equation (NLSE) in a random potential since in some explorations the terms we study are considered as noise and the present work describes its statistical properties.

cond-mat.dis-nn↗

arXiv2012

Effective noise theory for the Nonlinear Schrödinger Equation with disorder

For the Nonlinear Shrödinger Equation with disorder it was found numerically that in some regime of the parameters Anderson localization is destroyed and subdiffusion takes place for a long time interval. It was argued that the nonlinear term acts as random noise. In the present work the properties of this effective noise are studied numerically. Some assumptions made in earlier work were verified, the dependence of various quantities on the localization length of the linear problem were computed. A scenario for the possible breakdown of the theory for a very long time is outlined.

cond-mat.dis-nn↗