Piran, Tsvi, Shaviv, Nir J., Nakar, Ehud
Recent measurements of the positron/electron ratio in the cosmic ray (CR) flux exhibits an apparent anomaly, whereby this ratio increases between 10 and 100 GeV. In contrast, this ratio should...
Shaviv, Nir J., Nakar, Ehud, Piran, Tsvi
Recent measurements of the positron/electron ratio in the cosmic ray (CR) flux exhibits an apparent anomaly, whereby this ratio increases with energy between 10 and 100 GeV. In contrast, this ratio...
On the behaviour of stellar winds that exceed the photon-tiring limit (2008)
Van Marle, Allard Jan, Owocki, Stanley P., Shaviv, Nir J.
Stars can produce steady-state winds through radiative driving as long as the mechanical luminosity of the wind does not exceed the radiative luminosity at its base. This upper bound on the mass loss...
Shortly after the discovery of the binary system PSR J0737-3039 we predicted that it has a small proper motion and suggested that this implies that the progenitor mass of the younger pulsar (B) must...
The Origin of the Binary Pulsar J0737-3039 (2005)
It is generally accepted that neutron stars form in core collapse events that are accompanied by a supernovae (types II or Ib or Ic). Typical progenitors are, therefore, larger than $\sim 2.1 \Ms$....
Open Cluster Birth Analysis and Multiple Spiral Arm Sets in the Milky Way (2005)
The Milky Way spiral arm dynamics is studied using the birth place of open clusters. We separately study the nearby spiral arms, and find evidence for multiple spiral sets. In particular, the...
Heyl, Jeremy S., Lloyd, Don, Shaviv, Nir J.
In the presence of strong magnetic fields, the vacuum becomes a birefringent medium. We show that this QED effect couples the direction of the polarization of photons leaving the NS surface, to the...
The Origin of the Binary Pulsar J0737-3039B (2004)
Evolutionary scenarios suggest that the progenitor of the new binary pulsar J0737-3039B \cite{ref1,ref2} was a He-star with $M > 2.1-2.3~\Ms$ \cite{ref3,ref4}. We show that this case implies that the...
Owocki, Stanley P., Gayley, Kenneth G., Shaviv, Nir J.
We examine radiatively driven mass loss from stars near and above the Eddington limit (Ledd). We begin by reviewing the instabilities that are expected to form extensive structure near Ledd. We...
On climate response to changes in the cosmic ray flux and radiative budget (2004)
We examine the results linking cosmic ray flux (CRF) variations to global climate change. We then proceed to study various periods over which there are estimates for the radiative forcing,...
On the Low Progenitor Mass of the Binary Pulsar J0737-3039B (2004)
The observed orbital parameters of the recently discovered binary pulsar J0737-3039 are used to constrain the progenitor system. In particular, the small observed eccentricity and the small inferred...
Standard solar models predict a solar luminosity that gradually increased by about 30% over the past 4.5 billion years. Under the faint sun, Earth should have been frozen solid for most of its...
Photo-evaporation by thermal winds in dwarf galaxies (2003)
Shaviv, Nir J., Dekel, Avishai
We revisit the evaporation process of gas from dwarf galaxies after it has been photo-ionized by the UV flux from the first stars and AGNs and heated to T~10^4K or 2x10^4K respectively. Earlier...
Heyl, Jeremy S., Shaviv, Nir J., Lloyd, Don
In the presence of strong magnetic fields, the vacuum becomes a birefringent medium. We show that this QED effect decouples the polarization modes of photons leaving the NS surface. Both the total...
The Spiral Structure of the Milky Way, Cosmic Rays, and Ice Age Epochs on Earth (2002)
The short term variability of the Galactic cosmic ray flux (CRF) reaching Earth has been previously associated with variations in the global low altitude cloud cover. This CRF variability arises from...
We construct a Galactic cosmic ray (CR) diffusion model while considering that CR sources reside predominantly in the Galactic spiral arms. We find that the CR flux (CRF) reaching the solar system...
Classical Novae as Super-Eddington Objects (2002)
Several of the inconsistencies plaguing the field of novae are resolved once we consider novae to be steady state super-Eddington objects. In particular, we show that the super-Eddington shell...
QED and the High Polarization of the Thermal Radiation from Neutron Stars (2002)
Heyl, Jeremy S., Shaviv, Nir J.
The thermal emission of strongly magnetized neutron-star atmospheres is thought to be highly polarized. However, because of the different orientations of the magnetic field over the surface of the...
Atmospheres having a significant radiative support are shown to be intrinsically unstable at luminosities above a critical fraction Gamma_crit ~ 0.5-0.85 of the Eddington limit, with the exact value...
Super Eddington Atmospheres and their Winds (2000)
We present a model for the steady state winds of super-Eddington systems. These radiatively driven winds are expected to be optically thick and clumpy as they arise from a porous atmosphere. The...
The Theory of Steady State Super-Eddington Winds and its Application to Novae (2000)
We present a model for steady state winds of systems with super-Eddington luminosities. These radiatively driven winds are expected to be optically thick and clumpy as they arise from an instability...
The porous atmosphere of eta Carinae (2000)
We analyze the wind generated by the great 20 year long super-Eddington outburst of eta-Carinae. We show that using classical stellar atmospheres and winds theory, it is impossible to construct a...
Polarization Evolution in Strong Magnetic Fields (1999)
Heyl, Jeremy S., Shaviv, Nir J.
Extremely strong magnetic fields change the vacuum index of refraction. Although this polarization dependent effect is small for typical neutron stars, it is large enough to decouple the polarization...
Magnetic Lensing near Ultramagnetized Neutron Stars (1999)
Shaviv, Nir J., Heyl, Jeremy S., Lithwick, Yoram
Extremely strong magnetic fields change the vacuum index of refraction. This induces a lensing effect that is not unlike the lensing phenomenon in strong gravitational fields. The main difference...
Can Nonlinear Structure Form at the Era of Decoupling? (1998)
The effects that large scale fluctuations had on small scale isothermal modes at the epoch of recombination are analysed. We find that: (a) Albeit the fact that primordial fluctuations were at this...
Life Extinctions By Cosmic Ray Bursts (1997)
Dar, Arnon, Laor, Ari, Shaviv, Nir J.
High energy cosmic ray jets from nearby mergers or accretion induced collapse (AIC) of neutron stars (NS) that hit the atmosphere can produce lethal fluxes of atmospheric muons at ground level,...
Solution To The Gamma Ray Burst Mystery? (1996)
Photoexcitation and ionization of partially ionized heavy atoms in highly relativistic flows by interstellar photons, followed by their reemission in radiative recombination and decay, boost...
Life Extinction Due To Neutron Star Mergers (1996)
Dar, Arnon, Laor, Ari, Shaviv, Nir J.
Cosmic ray bursts (CRBs) from mergers or accretion induced collapse of neutron stars that hit an Earth-like planet closer than $\sim 1 kpc$ from the explosion produce lethal fluxes of atmospheric...
On The Origin of Gamma Ray Bursts (1996)
We propose that repeated photoexcitation/ionization of high Z atoms of highly relativistic flows by star light in dense stellar regions followed by emission of decay/recombination photons, which are...
The Extragalactic Neutrino Background Radiations From Blazars and Cosmic Rays (1995)
Blazar emission of gamma rays and cosmic ray production of gamma rays in gas-rich clusters have been proposed recently as alternative sources of the high energy extragalactic diffuse gamma ray...
On the Source and Location of Temporal Variability in Fireballs (1995)
Most cosmological models for gamma-ray bursts invoke the production of a ``fireball'' in a compact region, as indicated by the short time variability of the observed GRBs. The high density of...
ORIGIN OF THE HIGH ENERGY EXTRAGALACTIC DIFFUSE GAMMA RAY BACKGROUND (1995)
We show that cosmic rays in external galaxies, groups and clusters rich in gas, with an average flux similar to that observed in the Milky Way, could have produced the observed extragalactic diffuse...
Gamma Ray Bursts from Minijets (1994)
Striking similarities exist between high energy gamma ray emission from active galactic nuclei (AGN) and gamma ray bursts (GRBs). They suggest that GRBs are generated by inverse Compton scattering...