Itai Sfaradi
A5025167451- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Astronomical Observations and Instrumentation
- Radio Astronomy Observations and Technology
- Astronomy and Astrophysical Research
- Neutrino Physics Research
- Superconducting and THz Device Technology
- Astro and Planetary Science
- Laser-Plasma Interactions and Diagnostics
- Galaxies: Formation, Evolution, Phenomena
- Nuclear Physics and Applications
- Atmospheric and Environmental Gas Dynamics
- Cosmology and Gravitation Theories
- Geophysics and Gravity Measurements
- Particle physics theoretical and experimental studies
- Solar and Space Plasma Dynamics
- Black Holes and Theoretical Physics
- Relativity and Gravitational Theory
- Stellar, planetary, and galactic studies
- Particle Accelerators and Free-Electron Lasers
Hebrew University of Jerusalem
2019-2024
Czech Academy of Sciences, Institute of Physics
2024
Abstract We present deep X-ray and radio observations of the fast blue optical transient (FBOT) AT 2020xnd/ZTF 20acigmel at z = 0.2433 from 13 days to 269 after explosion. 2020xnd belongs category optically luminous FBOTs with similarities archetypal event 2018cow. shows emission reaching L ν ≈ 8 × 10 29 erg s −1 Hz 20 GHz 75 post-explosion, accompanied by rapidly fading soft peaking X 6 42 . Interpreting in context synchrotron radiation explosion’s shock interaction environment, we find...
Binaries containing a compact object orbiting supermassive black hole are thought to be precursors of gravitational wave events, but their identification has been extremely challenging. Here, we report quasi-periodic variability in x-ray absorption, which interpret as outflows (QPOuts) from previously low-luminosity active galactic nucleus after an outburst, likely caused by stellar tidal disruption. We rule out several models based on observed properties and instead show using general...
ABSTRACT The Tidal Disruption Event (TDE) AT 2018hyz exhibited a delayed radio flare almost three years after the stellar disruption. Here, we report new observations of TDE with AMI-LA and ATCA spanning from month to more than four optical discovery 200 d since last reported observation. We detected no emission 30–220 in our at 15.5 GHz down 3σ level <0.14 mJy. fast-rising, is observed data set continues rise ∼1580 discovery. find that emission, first 972 discovery, evolves as t4.2 ±...
ABSTRACT Tidal disruption events (TDEs) are transient, multiwavelength in which a star is ripped apart by supermassive black hole. Observations show that small fraction of TDEs, short-lived, synchrotron emitting jet produced. We observed the newly discovered TDE AT2022cmc with slew radio facilities over first 100 d after its discovery. The light curve from Arcminute Microkelvin Imager Large Array interferometer shows day-time-scale variability we attribute to high brightness temperature...
We report here radio follow-up observations of the optical Tidal Disruption Event (TDE) AT 2019azh. Previously reported X-ray this TDE showed variability at early times and a dramatic increase in luminosity, by factor $\sim 10$, about 8 months after discovery. The emission is mainly dominated intermediate hard--soft X-rays exceptionally soft around peak, which $L_X \sim 10^{43} \rm \, erg s^{-1}$. high cadence $15.5$ GHz show an rise followed approximately constant light curve, late-time...
In this work we study the circumstellar material (CSM) around massive stars, and mass-loss rates depositing CSM, using a large sample of radio observations 325 core-collapse supernovae (CCSNe; only $\sim 22 \%$ them being detected). This comprises both archival data our new 99 CCSNe conducted with AMI-LA array in systematic approach devised to constrain at different stages stellar evolution. SN-CSM interaction model, observing peak emission SN provides CSM density given radius (and therefore...
Abstract In this work, we study the circumstellar material (CSM) around massive stars, and mass-loss rates depositing CSM, using a large sample of radio observations 325 core-collapse supernovae (CCSNe; only ~22% them being detected). This comprises both archival data our new 99 CCSNe conducted with AMI-LA array in systematic approach devised to constrain mass loss at different stages stellar evolution. supernova (SN)–CSM interaction model, observing peak emission an SN provides CSM density...
We present SN 2019tsf (ZTF19ackjszs) and 2019oys (ZTF19abucwzt). These two stripped envelope Type Ib supernovae suddenly showed a (re-)brightening in their late light curves. investigate this the context of circumstellar material (CSM) interaction with previously ejected material, phenomenon that is unusual among SE SNe. analyse observational data, consisting optical curves spectra. For we also have detections radio as well limits from UV X-rays. Both show spectacular re-brightening after...
Abstract Radio emission from tidal disruption events (TDEs) originates an interaction of outflow with the super-massive black hole (SMBH) circumnuclear material (CNM). In turn, this radio can be used to probe properties both launched at event and CNM. Until recently, was detected only for a relatively small number events. While observed pointed either relativistic or sub-relativistic outflows different nature, it also indicated that has been shortly after stellar disruption. Recently,...
Abstract We present detailed observations of ZTF18abukavn (SN2018gep), discovered in high-cadence data from the Zwicky Transient Facility as a rapidly rising (1.4 ± 0.1 mag hr −1 ) and luminous ( mag) transient. It is spectroscopically classified broad-lined stripped-envelope supernova (Ic-BL SN). The high peak luminosity ), short rise time g band), blue colors at all resemble high-redshift Ic-BL iPTF16asu, well several other unclassified fast transients. early discovery SN2018gep (within an...
We report the discovery and panchromatic followup observations of young Type Ic supernova, SN2020oi, in M100, a grand design spiral galaxy at mere distance $14$ Mpc. followed up with radio, X-ray optical wavelengths from only few days to several months after explosion. The behaviour supernova is similar those other normal supernovae. event was not detected band but our radio observation revealed bright mJy source ($L_{\nu} \approx 1.2 \times 10^{27} {\rm erg\,s}^{-1} Hz}^{-1}$). Given,...
Abstract The optical-ultraviolet transient AT 2021loi is located at the center of its host galaxy. Its spectral features identify it as a member Bowen fluorescence flare (BFF) class. first this class was considered to be related tidal disruption event, but enhanced accretion onto an already active supermassive black hole suggested alternative explanation. Having occurred in previously known unobscured galactic nucleus, strengthens latter interpretation. light curve similar those previous...
Context . Mass loss from massive stars, especially towards the end of their lives, plays a key role in evolution. Radio emission core-collapse supernovae (SNe) serves as probe interaction SN ejecta with circumstellar medium (CSM) and can reveal mass-loss history progenitor. Aims We aim to present broadband radio observations CSM-interacting 2019oys. 2019oys was first detected optical classified Type Ib SN. Then, ~100 days after discovery, it showed an rebrightening spectral transition...
We present observations of a peculiar hydrogen- and helium-poor stripped-envelope (SE) supernova (SN) 2020wnt, primarily in the optical near-infrared (near-IR). Its peak absolute bolometric magnitude -20.9 mag rise time 69~days are reminiscent hydrogen-poor superluminous SNe (SLSNe~I), luminous transients potentially powered by spinning-down magnetars. Before main peak, there is brief lasting <10 days post-explosion, likely caused interaction with circumstellar medium (CSM) ejected ~years...
Abstract We present our analysis of supernovae serendipitously found to be radio-bright several years after their optical discovery. used recent observations from the Australian SKA Pathfinder taken as part pilot Variables and Slow Transients Rapid ASKAP Continuum Survey programs. identified 29 objects by cross-matching sources these with known core-collapse below a declination +40○ redshift z ≤ 0.15. Our results focus on eight cases that show potential late-time radio emission. These...
Context. Type Ibn supernovae (SNe Ibn) are a rare class of stripped envelope interacting with helium-rich circumstellar medium (CSM). The majority the SNe reported in literature display surprising homogeneity their fast-evolving lightcurves and typically found actively starforming spiral galaxies. Aims. We present discovery study SN 2020bqj (ZTF20aalrqbu), long-duration peak plateau lasting 40 days hosted by faint low-mass galaxy. aim to explain its peculiar properties using an extensive...
We present here broadband radio observations of the CSM interacting SN2019oys. SN2019oys was first detected in optical and classified as a Type Ib SN. Then, about $\sim 100$ days after discovery, it showed an rebrightening spectral transition to spectrum dominated by strong narrow emission lines, which suggests interaction with distant, dense, shell. modeled broadband, multi-epoch, spectra, covering 2.2 36 GHz spanning from 22 1425 synchrotron emitting source. Using this modeling we...
Context: The study of radio emission from core-collapse supernovae (SNe) probes the interaction ejecta with circumstellar medium (CSM) and reveals details mass-loss history progenitor. Aims: We report observations type IIP supernova SN\,2016X during plateau phase, at ages between 21 75 days, obtained Karl G. Jansky Very Large Array (VLA) observatory. Methods: modelled spectra as self-absorbed synchrotron emission, we characterised shockwave rate also combined our results previously reported...
Binaries containing a compact object orbiting supermassive black hole are thought to be precursors of gravitational wave events, but their identification has been extremely challenging. Here, we report quasi-periodic variability in X-ray absorption which interpret as outflows (QPOuts) from previously low-luminosity active galactic nucleus after an outburst, likely caused by stellar tidal disruption. We rule out several models based on observed properties and instead show using general...
We present our analysis of supernovae serendipitously found to be radio-bright several years after their optical discovery. used recent observations from the Australian SKA Pathfinder taken as part pilot Variables and Slow Transients Rapid ASKAP Continuum Survey programs. identified 29 objects by cross-matching sources these with known core-collapse below a declination $+40^{\circ}$ redshift $z\leq0.15$. Our results focus on eight cases that show potential late-time radio emission. These...