A5025283376- Gamma-ray bursts and supernovae
- Advanced Power Generation Technologies
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- Neutrino Physics Research
- Nuclear reactor physics and engineering
- Laser-Plasma Interactions and Diagnostics
- Cosmology and Gravitation Theories
- Ionosphere and magnetosphere dynamics
- Global Energy Security and Policy
- Radiation Therapy and Dosimetry
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astrophysics and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Geophysics and Gravity Measurements
Princeton University
2023-2024
Hebrew University of Jerusalem
2017-2023
European Southern Observatory
2016
Tel Aviv University
2014
We study a sample of 23 Type II plateau supernovae (SNe II-P), all observed with the same set instruments. Analysis their photometric evolution confirms that typical duration is 100 d little scatter, showing tendency to get shorter for more energetic SNe. examine claimed correlation between luminosity and rise time from explosion plateau. analyse spectra, measuring ejecta velocities, confirm they follow well-behaved power-law decline. find indications high-velocity material in spectra six...
What are Type II-Linear supernovae (SNe II-L)? This class, which has been ill defined for decades, now receives significant attention – both theoretically, in order to understand what happens stars the ∼15–25 M⊙ range, and observationally, with two independent studies suggesting that they cannot be cleanly separated photometrically from regular hydrogen-rich SNe II-P characterized by a marked plateau their light curve. Here, we analyse multiband curves extensive spectroscopic coverage of...
We reduced ESO's archival linear spectropolarimetry data (4000-9000\AA) of 6 highly polarized and 8 unpolarized standard stars observed between 2010 2016, for a total 70 epochs, with the FOcal Reducer low dispersion Spectrograph (FORS2) mounted at Very Large Telescope. provide very accurate polarization measurements as function wavelength, test performance spectropolarimetric mode (PMOS) FORS2. used to time stability PMOS mode, found small ($\leq$0.1%), but statistically significant, on-axis...
Type IIP supernovae (SNe IIP), which represent the most common class of core-collapse (CC) SNe, show a rapid increase in continuum polarization just after entering tail phase. This feature can be explained by highly asymmetric helium core, is exposed when hydrogen envelope becomes transparent. Here we report case SN (SN~2017gmr) that shows an unusually early rise polarization, $\gtrsim 30$ days before start implies SN~2017gmr has very extended asphericity. The asymmetries are not confined to...
In this work we present a uniform analysis of the temperature evolution and bolometric luminosity sample 29 type-II supernovae (SNe), by fitting black body model to their multi-band photometry. Our includes only SNe with high quality data relatively well sampled time coverage. Most in our were detected less than week after explosion so light curves cover both before recombination starts playing role. We use study signature hydrogen recombination, which is expected appear once observed drops...
The origin of the diverse light-curve shapes Type II supernovae (SNe), and whether they come from similar or distinct progenitors, has been actively discussed for decades. Here we report spectropolarimetry two fast declining (Type IIL) SNe: SN 2013ej 2017ahn. exhibited high continuum polarization very soon after explosion to radioactive tail phase with time-variable angles. this polarimetric behavior can be interpreted as combination different aspherical structures, namely an interaction...
We present high-cadence ultraviolet (UV), optical, and near-infrared (NIR) data on the luminous Type II-P supernova SN 2017gmr from hours after discovery through first 180 days. does not show signs of narrow, high-ionization emission lines in early optical spectra, yet lightcurve evolution suggests that an extra energy source circumstellar medium (CSM) interaction must be for at least 2 days explosion. Modeling indicates a ~500R$_{\odot}$ progenitor radius, consistent with rather compact red...
Abstract The light curves of Type II supernovae (SNe II) are believed to be highly affected by recombination hydrogen that takes place in their envelopes. In this work, we analytically investigate the transition from a fully ionized envelope partially recombined one and its effects on SN curve. motivation is establish underlying processes dominate evolution at late times when envelope, yet early enough so 56 Ni decay negligible source energy. We consider diffusion photons through while...
When the shock wave generated in a supernova explosion breaks out of stellar envelope, first photons, typically X-ray to UV range, escape observer. Following this breakout emission, radiation from deeper shells diffuses envelope as ejecta expands. Previous studies have shown that throughout planar phase (i.e., before expanding has doubled its radius) originates same mass coordinate, called `breakout shell'. We derive self-similar solution for inside and show claim is incorrect, diffusion...
A new type of self-similarity is found in the problem a plane-parallel, ultra-relativistic blast wave, propagating powerlaw density profile form $\rho \propto z^{-k}$. Self-similar solutions first kind can be for $k<7/4$ using dimensional considerations. For steeper gradients with $k>2$, second are obtained by eliminating singularity from equations. However, intermediate indices $7/4<k<2$ flow does not obey any known types self-similarity. Instead, belong to class which self-similar dynamics...
A new type of self-similarity is found in the problem a plane-parallel, ultra-relativistic blastwave, propagating power-law density profile form ρ∝z−k. Self-similar solutions first kind can be for k &lt; 7∕4 using dimensional considerations. For steeper gradients with &gt; 2, second are obtained by eliminating singularity from equations. However, intermediate indices 7/4&lt;k&lt;2, flow does not obey any known types self-similarity. Instead, belong to class which self-similar...
Acoustic perturbations to stellar envelopes can lead the formation of weak shock waves via nonlinear wave-steepening. Close surface, wave increases in strength and potentially expulsion part envelope. While accurate analytic solutions fluid equations exist limits low amplitude or strong shocks, connecting these phases generally requires simulations. We address this problem using fact that plane parallel Euler equations, presence a constant gravitational field, admit exact Riemann invariants...
Abstract Acoustic perturbations to stellar envelopes can lead the formation of weak shock waves via nonlinear wave steepening. Close surface, increases in strength and potentially expulsion part envelope. While accurate analytic solutions fluid equations exist limits low-amplitude or strong shocks, connecting these phases generally requires simulations. We address this problem using fact that plane-parallel Euler equations, presence a constant gravitational field, admit exact Riemann...
We calculate the observed luminosity and spectrum following emergence of a relativistic shock wave from stellar edges. Shock waves propagating at $0.6<\Gamma_\text{sh}\beta_\text{sh}$, where $\Gamma_\text{sh}$ is Lorentz factor $\beta_\text{sh}$ its associated reduced velocity, heat envelope to temperatures exceeding $\sim 50$ keV, allowing for vigorous production electron positron pairs. Pairs significantly increase scattering optical depth regulate temperature through photon generation,...
The hydrodynamics of an ultrarelativistic flow, enclosed by a strong shock wave, are described the well-known Blandford–McKee solutions in spherical geometry. These solutions, however, become inaccurate at distance ∼R/2 behind where R is radius, as flow approaches Newtonian velocities. In this work, we find new self-similar solution that extension to and describes interior part blast reaches mildly relativistic We velocity profile internal does not depend on value Lorentz factor, Γ, accurate...
Nonlinear acoustic evolution is often discussed in the context of wave-steepening that leads to shock formation, and special interest applications where continues strengthen due a narrowing its channel or stratification medium. Accurate scalings govern low amplitude waves strong shocks, but connecting these phases, describing are nonlinear from outset, generally requires simulation. We address this problem using fact within plane-parallel, isentropic gravitationally stratified atmosphere...