A5011392477- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- SAS software applications and methods
- Astronomy and Astrophysical Research
- Pulsars and Gravitational Waves Research
- Nuclear Physics and Applications
- Adaptive optics and wavefront sensing
- Stellar, planetary, and galactic studies
- Liver Disease Diagnosis and Treatment
- Solar and Space Plasma Dynamics
- Galaxies: Formation, Evolution, Phenomena
- Radio Astronomy Observations and Technology
- Mitochondrial Function and Pathology
- Statistical and numerical algorithms
- Scientific Research and Discoveries
- Viral gastroenteritis research and epidemiology
- Particle physics theoretical and experimental studies
- Sports Dynamics and Biomechanics
- Geophysics and Gravity Measurements
- Biofield Effects and Biophysics
- Relativity and Gravitational Theory
- Calibration and Measurement Techniques
- Neutrino Physics Research
Isaac Newton Group
2018-2024
AlbaNova
2013-2019
Stockholm University
2013-2019
Nordic Optical Telescope
2016-2018
Constructor University
2011
ABSTRACT OJ 287 is a quasi-periodic quasar with roughly 12 year optical cycles. It displays prominent outbursts that are predictable in binary black hole model. The model predicted major outburst 2015 December. We found the did occur within expected time range, peaking on December 5 at magnitude 12.9 R -band. Based Swift /XRT satellite measurements and polarization data, we find it included thermal component. Its timing provides an accurate estimate for spin of primary hole, . present also...
Abstract Results from regular monitoring of relativistic compact binaries like PSR 1913+16 are consistent with the dominant (quadrupole) order emission gravitational waves (GWs). We show that observations associated binary black hole (BBH) central engine blazar OJ 287 demand inclusion radiation reaction effects beyond quadrupolar order. It turns out even certain hereditary contributions to GW required predict impact flare timings 287. develop an approach incorporates this effect into BBH...
We perform hydro- and magnetohydrodynamical general relativistic simulations of a tidal disruption $0.1\,M_\odot$ red dwarf approaching $10^5\,M_\odot$ non-rotating massive black hole on close (impact parameter $\beta=10$) elliptical (eccentricity $e=0.97$) orbit. track the debris self-interaction, circularization, accompanying accretion through horizon. find that precession leads to formation self-crossing shock. The dissipated kinetic energy heats up incoming efficiently generates...
Abstract We present the results of our power spectral density analysis for BL Lac object OJ 287, utilizing Fermi -LAT survey at high-energy γ -rays, Swift -XRT in X-rays, several ground-based telescopes and Kepler satellite optical, radio GHz frequencies. The light curves are modeled terms continuous-time autoregressive moving average (CARMA) processes. Owing to inclusion data, we were able construct first time optical variability spectrum a blazar without any gaps across ∼6 dex temporal Our...
Abstract We present the results of relativistic smoothed particle hydrodynamics simulations tidal disruptions stars by rotating supermassive black holes, for a wide range impact parameters and hole spins. For deep encounters, we find that: precession creates debris geometries impossible to obtain with Newtonian equations; part fluid can be launched on plunging orbits, reducing fallback rate mass resulting accretion disc; multiple squeezings bounces at periapsis may generate distinctive X-ray...
Solitary stars that wander too close to their galactic centres can become tidally disrupted, if the tidal forces due supermassive black hole residing there overcome self-gravity of star. If star is only partially so a fraction survives as self-bound object, this remaining core will experience net gain in specific orbital energy, which translates into velocity 'kick' up ∼103 km s−1. In paper, we present result smoothed particle hydrodynamics simulations such partial disruptions, and analyse...
We propose an approximate approach for studying the relativistic regime of stellar tidal disruptions by rotating massive black holes. It combines exact description hydrodynamical evolution a test fluid in fixed curved spacetime with Newtonian treatment fluid's self-gravity. Explicit expressions equations motion are derived Kerr using two different coordinate systems. implement new methodology within existing Smoothed Particle Hydrodynamics code and show that including additional physics...
We introduce our new binary tree code for neighbour search and gravitational force calculations in an N-particle system. The is built a "top-down" fashion by "recursive coordinate bisection" where on each level we split the longest side of cell through its centre mass. This procedure continues until average number particles lowest has dropped below prescribed value. To calculate forces lowest-level interaction into near- far-field. Since main intended applications are SPH simulations,...
High-redshift gamma-ray bursts (GRBs) offer several advantages when studying the distant Universe, providing unique information about structure and properties of galaxies in which they exploded. Spectroscopic identification with large ground-based telescopes has improved our knowledge this kind events. We present multi-wavelength analysis high-zSwift GRB 140515A (z = 6.327). The best estimate neutral hydrogen fraction intergalactic medium towards burst is xHI ≤ 0.002. spectral absorption...
Context. The origin of the blue supergiant (BSG) progenitor Supernova (SN) 1987A has long been debated, along with role that its sub-solar metallicity played. We now have a sample SN 1987A-like events arise from rare core collapse (CC) massive (~20 M⊙) and compact (≲100 R⊙) BSGs.
We introduce a new algorithm for the calculation of multidimensional optical depths in approximate radiative transport schemes, equally applicable to neutrinos and photons. Motivated by (but not limited to) neutrino three-dimensional simulations core-collapse supernovae neutron star mergers, our method makes no assumptions about geometry matter distribution, apart from expecting optically transparent boundaries. Based on local information opacities, figures out an escape route that tends...
We present an update on the overall integration progress of WEAVE next-generation spectroscopy facility for William Herschel Telescope (WHT), now scheduled first light in early-2021, with almost all components arrived at observatory. also a summary current planning behind 5-year initial phase survey operations, and some detailed end-to-end science simulations that have been implemented to evaluate final on-sky performance after data processing. will provide optical ground-based follow up...
We analyse the light curve in R band of blazar OJ287, gathered during 2015/2016 observing season. did a search for quasi-periodic oscillations (QPOs) using several methods over wide range timescales. No statistically significant periods were found high-frequency domain both ground-based data and Kepler observations. In longer-period domain, Lomb–Scargle periodogram revealed peaks above 99% significance level. The longest one—about 95 days—corresponds to innermost stable circular orbit (ISCO)...
WEAVE is the next-generation spectroscopic facility for William Herschel Telescope (WHT) <sup>1,2</sup>. offers multi-object (1000 fibres) and integral-field spectroscopy at two resolutions (R ~ 5000, 20000) over a 2-deg field of view prime focus will mainly provide follow up ground-based (LOFAR) space-based (GAIA) surveys. The <strong>Observatory Control System </strong>(OCS) responsible providing software control feedback framework through which be operated. This paper summarizes design...
The William Herschel Telescope Enhanced Area Velocity Explorer (WEAVE) is a new, massively multiplexing spectrograph that allows us to collect about one thousand spectra over 3 square degree field in observation. WEAVE Stellar Population Survey (WEAVE-StePS) the next 5 years will exploit this new instrument obtain high-S/N for magnitude-limited ($I_ AB = 20.5$) sample of sim 25 000 galaxies at moderate redshifts ($ z 0.3$), providing insights into galaxy evolution as yet unexplored redshift...
The WHT Enhanced Area Velocity Explorer (WEAVE) is a new, massively multiplexing spectrograph. This new instrument will be exploited to obtain high S/N spectra of $\sim$25000 galaxies at intermediate redshifts for the WEAVE Stellar Population Survey (WEAVE-StePS). We test machine learning methods retrieving key physical parameters from WEAVE-StePS-like using both photometric and spectroscopic information various S/Ns redshifts. simulated $\sim$105000 galaxy assuming SFH with an exponentially...
We present a detailed study of the large-scale shock front in Stephan's Quintet, byproduct past and ongoing interactions. Using integral-field spectroscopy from new William Herschel Telescope Enhanced Area Velocity Explorer (WEAVE), recent 144 MHz observations LOFAR Two-metre Sky Survey (LoTSS), archival data Very Large Array James Webb Space (JWST), we obtain measurements key properties determine its impact on system. Harnessing WEAVE large integral field unit's (LIFU) view (90 $\times$ 78...
We analyse the light curve in R-band gathered during 2015/16 observing season of OJ287. did a search for QPOs using several methods wide time domain. No statistically significant periods were found high frequency domain both ground data and also K2 observations. In longer Lomb-Scargle periodogram revealed peaks above 99\% significance level. The longest one, about 95-day, corresponds to ISCO period more massive SMBH. 43-day could be an alias or can attributed accretion form two armed spiral wave.