A5055346768- Galaxies: Formation, Evolution, Phenomena
- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Astrophysics and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Adaptive optics and wavefront sensing
- Pulsars and Gravitational Waves Research
- Astronomical Observations and Instrumentation
- Dark Matter and Cosmic Phenomena
- Particle Detector Development and Performance
- Magnetic confinement fusion research
- Particle physics theoretical and experimental studies
- Impact of Light on Environment and Health
- Geophysics and Gravity Measurements
- COVID-19 impact on air quality
- Urban Heat Island Mitigation
- Particle Accelerators and Free-Electron Lasers
- Statistical and numerical algorithms
- Relativity and Gravitational Theory
- Particle accelerators and beam dynamics
- Cosmology and Gravitation Theories
- Radio Astronomy Observations and Technology
- Laser-Plasma Interactions and Diagnostics
University of Haifa
2014-2024
Center for Theoretical Physics
2023
Carmel (Israel)
2010-2020
Tel Aviv University
2001-2013
Institute for Advanced Study
2005-2009
Canadian Institute for Theoretical Astrophysics
2008-2009
University of Toronto
2008-2009
Princeton University
2008
Albert Einstein College of Medicine
2005-2008
The International Axion Observatory (IAXO) will be a forth generation axion helioscope. As its primary physics goal, IAXO look for axions or axion-like particles (ALPs) originating in the Sun via Primakoff conversion of solar plasma photons. In terms signal-to-noise ratio, about 4–5 orders magnitude more sensitive than CAST, currently most powerful helioscope, reaching sensitivity to axion-photon couplings down few × 10−12 GeV−1 and thus probing large fraction unexplored ALP parameter space....
Abstract The Ultraviolet Transient Astronomy Satellite (ULTRASAT) is scheduled to be launched geostationary orbit in 2027. It will carry a telescope with an unprecedentedly large field of view (204 deg 2 ) and near-ultraviolet (NUV; 230–290 nm) sensitivity (22.5 mag, 5 σ , at 900 s). ULTRASAT conduct the first wide-field survey transient variable NUV sources revolutionize our ability study hot Universe. explore new parameter space energy timescale (months-long light curves minutes cadence),...
We present the first results from ongoing, intensive, multi-wavelength monitoring program of luminous Seyfert 1 galaxy Mrk 817. While this AGN was, in part, selected for its historically unobscured nature, we discovered that X-ray spectrum is highly absorbed, and there are new blueshifted, broad narrow UV absorption lines, which suggest a dust-free, ionized obscurer located at inner line region partially covers central source. Despite obscuration, measure optical continuum reverberation lags...
We present a detailed spectral analysis of the data obtained from NGC 3783 during period 2000-2001 using Chandra. The were split in various ways to look for time- and luminosity-dependent variations. This analysis, along with measured equivalent widths large number X-ray lines photoionization calculations, lead us following results conclusions. (1) fluctuated luminosity by factor ~1.5 individual observations (most which 170 ks duration). These fluctuations not associated significant (2) On...
Abstract We present the first results from a 100-day Swift, NICER, and ground-based X-ray–UV–optical reverberation mapping campaign of Narrow-line Seyfert 1 Mrk 335, when it was in an unprecedented low X-ray flux state. Despite dramatic suppression variability, we still observe UV–optical lags as expected disk reverberation. Moreover, are consistent with archival observations luminosity >10 times higher. Interestingly, both low- high-flux states reveal that 6–11 longer than thin disk....
Abstract An intensive reverberation mapping campaign of the Seyfert 1 galaxy Mrk 817 using Cosmic Origins Spectrograph on Hubble Space Telescope revealed significant variations in response broad UV emission lines to fluctuations continuum emission. The prominent changes over an ∼60 day duration, resulting distinctly different time lags various segments light curve 14 month observing campaign. One-dimensional echo-mapping models fit these if a slowly varying background is included for each...
Abstract We present the results of a nearly decade-long photometric reverberation mapping (PRM) survey H α emission line in nearby (0.01 ≲ z 0.05) Seyfert galaxies using small (15–40 cm) telescopes. Broadband filters were used to trace continuum emission, while narrowband tracked -line signal. introduce new PRM formalism determine time delay between and combinations auto- cross-correlation functions. obtain robust delays for 33/80 objects, allowing us estimate broad-line region (BLR) size....
We present results from a simultaneous Chandra High Energy Transmission Grating and XMM-Newton observation of NGC 3516. find evidence several narrow components Fe Kα along with broad line. consider the possibility that lines arise in blob material ejected nucleus velocity ~0.25c. also an origin neutral accretion disk, suffering enhanced illumination at 35Rg 175Rg, perhaps as result magnetic reconnection. The presence these features indicates there is no Comptonizing region line sight to...
Using a sample of almost 7000 strong MgII absorbers with 0.4 < z 2.2 detected in the SDSS DR4 dataset, we investigate gravitational lensing and dust extinction effects they induce on background quasars. After carefully quantifying several selection biases, isolate reddening as function redshift absorber rest equivalent width, W_0. We find amount to increase cosmic time (1+z)^(-1.1 +/- 0.4), following evolution star density or integrated formation rate. measure over factor 30 E(B-V) column...
We estimate the mean dust-to-gas ratio of MgII absorbers as a function rest equivalent width W_0 and redshift over range 0.5 W_0, an indicator gas velocity dispersion. By combining these results with recent dust-reddening measurements we show that does not appreciably depend on width. Assuming that, average, is proportional to metallicity, find its evolution be consistent L^star galaxies from z=0.5 1.4 our constraints disfavor dwarf origin such absorbers. discuss other scenarii favor...
We present Hubble Space Telescope far-UV spectra of 4 QSOs whose sightlines pass through the halo NGC 1097 at impact parameters 48 -165 kpc. is a nearby spiral galaxy that has undergone least two minor merger events, but no apparent major mergers, and relatively isolated with respect to other bright galaxies. This makes good case study for exploring baryons in paradigmatic bright-galaxy halo. Lyman-alpha absorption detected along all Si III 1206 found 3 smallest parameter sightlines; metal...
The Ultraviolet Transient Astronomy Satellite (ULTRASAT) is scheduled to be launched geostationary orbit in 2026. It will carry a telescope with an unprecedentedly large field of view (204 deg$^2$) and NUV (230-290nm) sensitivity (22.5 mag, 5$\sigma$, at 900s). ULTRASAT conduct the first wide-field survey transient variable sources revolutionize our ability study hot universe: explore new parameter space energy time-scale (months long light-curves minutes cadence), extra-Galactic volume...
Context. NGC 1566 is a local face-on Seyfert galaxy and known for exhibiting recurrent outbursts that are accompanied by changes in spectral type. The most recent transient event occurred from 2017 to 2019 was reported be change classification 1.8 1.2. Aims. We aim study the detail analyzing variations optical broad-line profiles. In particular, we intend determine structure kinematics of region. Methods. analyzed data an spectroscopic variability campaign taken with 9.2 m Southern African...
Extreme gravitational lensing and relativistic frequency shifts, combined together, imply that radiation emitted from a black hole's vicinity can echo at different frequencies times, leading to spectrotemporal correlations in observed signals. If such are uncovered by future observations, they could provide probe of the spacetime geometry strong-field region near holes. Here, motivated these prospects, we numerically compute two-point correlation function specific flux fluctuations simple...
We present a new approach for calculating the physical properties of highly ionized X-ray flows in active galactic nuclei. Our method relies on detailed treatment structure, dynamics, and spectrum gas. A quantitative comparison our model predictions with 900 ks Chandra HETG NGC 3783 shows following: (1) The outflow is driven by thermal pressure gradients, radiation force less important. (2) full-featured dynamical that provides very good fit to high-resolution requires multiphased flow...
We present results of broad band photometric reverberation mapping (RM) to measure the radius line region, and subsequently black hole mass (M$_{\rm BH}$), in nearby, low luminosity active galactic nuclei (AGN) NGC 4395. Using Wise Observatory's 1m telescope equipped with SDSS g$'$, r$'$ i$'$ filters, we monitored 4395 for 9 consecutive nights obtained 3 light curves each over 250 data points. The g$'$ bands include time variable contributions from H$\beta$ H$\alpha$ (respectively) plus...
ABSTRACT The radius and surface composition of an exploding massive star, as well the explosion energy per unit mass, can be measured using early UV observations core-collapse supernovae (SNe). We present first results from a simultaneous GALEX /PTF search for ultraviolet (UV) emission SNe. Six SNe II one Type superluminous SN (SLSN-II) are clearly detected in near-UV (NUV) data. compare our detection rate with theoretical estimates based on early, shock-cooling light curves calculated...
We report on the detection of reddening toward z ∼ 0.2 galaxy clusters. This is measured by correlating Sloan Digital Sky Survey cluster and quasar catalogs comparing photometric spectroscopic properties quasars behind clusters to those in field. find mean E(B − V) values a few × 10−3 mag for sight lines passing ~Mpc from clusters' centers. The curve typical dust but cannot be used distinguish between different types. radial dependence extinction shallow near center suggesting that most...
Abstract We present reverberation mapping measurements for the prominent ultraviolet broad emission lines of active galactic nucleus Mrk 817 using 165 spectra obtained with Cosmic Origins Spectrograph on Hubble Space Telescope. Our observations are accompanied by X-ray, optical, and near-infrared as part AGN Telescope Optical Reverberation Mapping Program 2 (AGN STORM 2). Using cross-correlation lag analysis method, we find significant correlated variations in continuum emission-line light...
Aims. Our aim is to examine the size, kinematics, and geometry of broad-line region (BLR) in double-lensed quasar Q 0957+561 by analyzing impact microlensing on various rest-frame ultraviolet broad-emission lines (BELs). Methods. We explore influence intrinsic variability C IV, III], Mg II emission through multiple spectroscopic observations taken between April 1999 January 2017. By utilizing line cores as a reference for no correcting long time delay images, we estimate sizes regions...
A new Chandra observation and archival observations by ASCA are used to investigate spectral variations in the Seyfert 1 galaxy NGC 3516 over a period of 7 yr. large change flux (factor ~50 at keV) is observed between an 1994 2000, with source close all-time maximum minimum X-ray states, respectively. We find spectra these epochs be consistent constant column density line-of-sight material reacting changes ionizing continuum. The data from two simple decrease (by factor 8-10) luminosity...
We present the results of a search for metal absorption lines in spectra background QSOs whose sightlines pass close to foreground QSOs. detect MgII(2796,2803) Sloan Digital Sky Survey (SDSS) four z>1.5 sight within 26-98 kpc lower redshift (z~0.5-1.5) The 100% [4/4 pairs] detection MgII is clearly at odds with incidence associated (z_abs ~ z_em) systems -- absorbers which exist towards only few percent Although quality our QSO not as high SDSS data, seen one does show up same strength...
We give detailed predictions for the spectral signatures arising from photon–particle oscillations in astrophysical objects. The calculations include quantum electrodynamic effects and due to active relativistic plasma. show that, by studying spectra of compact sources, it may be possible directly detect (pseudo-)scalar particles, such as axion, with much greater sensitivity, up three orders magnitude, than is currently achievable other methods. In particular, if particles exist masses ma <...
We describe a search for MgII(2796,2803) absorption lines in Sloan Digital Sky Survey (SDSS) spectra of QSOs whose sight pass within impact parameters 200 kpc galaxies with photometric redshifts z=0.46-0.6 and redshift errors Delta z~0.05. The selected have the same colors luminosities as Luminous Red Galaxy (LRG) population previously from SDSS. A Mg II interval +/-0.1 galaxy's shows that by these is rare: covering fraction ~ 10-15% between 20 100 kpc, rest equivalent widths Wr >= 0.6{\AA},...