A5049799335- Gamma-ray bursts and supernovae
- SAS software applications and methods
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Astronomy and Astrophysical Research
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Pulsars and Gravitational Waves Research
- Astro and Planetary Science
- Particle Detector Development and Performance
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Radio Astronomy Observations and Technology
- Statistical and numerical algorithms
- Nuclear Physics and Applications
- Neutrino Physics Research
- High-pressure geophysics and materials
- Adaptive optics and wavefront sensing
- Geophysics and Gravity Measurements
- Particle Accelerators and Free-Electron Lasers
- Geomagnetism and Paleomagnetism Studies
- Planetary Science and Exploration
- Superconducting Materials and Applications
- Space Exploration and Technology
- History and Developments in Astronomy
George Washington University
2012-2025
Adıyaman University
2016-2025
Institute of Nuclear Physics, Polish Academy of Sciences
2023
Universidade Federal de Uberlândia
2023
Goddard Space Flight Center
2011-2013
Universities Space Research Association
2011-2013
United States Naval Research Laboratory
2012
College of Charleston
2012
University of Alabama in Huntsville
2012
Michigan State University
2012
We present multiwavelength observations of the afterglow GRB 130427A, brightest (in total fluence) gamma-ray burst (GRB) past 29 yr. Optical spectroscopy from Gemini-North reveals redshift to be z = 0.340, indicating that its unprecedented brightness is primarily result relatively close proximity Earth; intrinsic luminosities both and are not extreme in comparison other bright GRBs. a large suite spanning 300 s 130 days after demonstrate shows simple, smooth evolution at all frequencies,...
We report the discovery of unusually bright long-duration gamma-ray burst (GRB), GRB 221009A, as observed by Neil Gehrels Swift Observatory (Swift), Monitor All-sky X-ray Image (MAXI), and Neutron Star Interior Composition Explorer Mission (NICER). This energetic was located relatively nearby (z = 0.151), allowing for sustained observations afterglow. The large luminosity low Galactic latitude (b 4.3 degrees) make 221009A a powerful probe dust in Milky Way. Using echo tomography we map...
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...
Spectral lag, which is defined as the difference in time of arrival high and low energy photons, a common feature Gamma-ray Bursts (GRBs). Previous investigations have shown correlation between this lag isotropic peak luminosity for long duration bursts. However, most previous used lags extracted observer-frame only. In work (based on sample 43 Swift GRBs with known redshifts), we present an analysis lag-luminosity relation GRB source-frame. Our indicates higher degree -0.82 +/- 0.05 (chance...
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...
Binary black hole (BH) central engine description for the unique blazar OJ 287 predicted that next secondary BH impact-induced bremsstrahlung flare should peak on 2019 July 31. This prediction was based detailed general relativistic modeling of trajectory around primary and its accretion disk. The expected termed Eddington to commemorate centennial celebrations now-famous solar eclipse observations test relativity by Sir Arthur Eddington. We analyze multi-epoch Spitzer between 31 September...
We have investigated the time variations in light curves from a sample of long and short Fermi/GBM Gamma ray bursts (GRBs) using an impartial wavelet analysis. The results indicate that source frame, variability scales for differ bursts, variabilities on order few milliseconds are not uncommon, intriguing relationship exists between minimum burst duration.
Abstract We present a timing study of the gamma and X-ray observations analysis sample bright gamma-ray bursts (GRBs; i.e. GRB 180720B, 181222B, 211211A 220910A), including very long (a.k.a. kilonova candidate). They have been detected observed by Atmosphere-Space Interactions Monitor (ASIM) installed on International Space Station (ISS) Gamma-ray Burst (GBM) on-board Fermi mission. The early (T − T0 ≈ s) high-energy (0.3-20 MeV) ASIM High Energy Detector (HED) (150 keV-30 (BGO) light curves...
Abstract Asteroid Justitia is a special main-belt object, being an extremely red body with steeper spectral slope than any other D-type asteroid. Conversely, its and polarimetric properties resemble organics-rich Centaurs trans-Neptunian objects. For this reason, it was chosen as main target of the MBR Explorer space mission. It crucial for mission planning operations to have in advance best estimate size, spin, shape, surface. In particular, size determination high demand before extensive...
We examine 288 GRBs detected by the Fermi Gamma-ray Space Telescope's Burst Monitor (GBM) that fell within field-of-view of Fermi's Large Area Telescope (LAT) during first 2.5 years observations, which showed no evidence for emission above 100 MeV. report photon flux upper limits in 0.1-10 GeV range prompt phase as well fixed 30 s and integrations starting from trigger time each burst. compare these with fluxes would be expected extrapolations spectral fits presented GBM catalog infer...
We report optical photometric and Southern Astrophysical Research spectroscopic observations of an X-ray source found within the localization error Fermi Large Area Telescope unidentified γ-ray 1FGL J0523.5−2529. The data show periodic flux modulation radial velocity variations indicative a binary with 16.5 hr period. suggest massive non-degenerate secondary (≳ 0.8 M☉), we argue is likely pulsar binary. velocities have good phase coverage evidence for measurable eccentricity (e = 0.04)....
Flaring episodes in blazars represent one of the most violent processes observed extra-galactic objects. Studies such events shed light on energetics physical occurring innermost regions blazars, which cannot otherwise be resolved by any current instruments. In this work, we present some largest and rapid flares captured optical band 3C 279, OJ 49, S4 0954+658, TXS 1156+295 PG 1553+113. The source flux was to increase nearly ten times within a timescale few weeks. We applied several methods...
We present a comprehensive analysis of bright, long duration (T90 ~ 257 s) GRB 110205A at redshift z= 2.22. The optical prompt emission was detected by Swift/UVOT, ROTSE-IIIb and BOOTES telescopes when the still radiating in gamma-ray band. Nearly 200 s observations were obtained simultaneously from optical, X-ray to gamma-ray, which makes it one exceptional cases study broadband spectral energy distribution across 6 orders magnitude during phase. By fitting time resolved spectra, we clearly...
We present follow-up photometric and spectroscopic observations, subsequent analysis of Gaia20eae. This source triggered alerts during 2020 after showing a $\sim$3 mag increase in its brightness. Its Gaia Alert light curve showed the shape typical eruptive young star. carried out observations to confirm Gaia20eae as an star classify it. pre-outburst spectral energy distribution shows that is moderately embedded Class II object with $L_\mathrm{bol} = 7.22$ L$_\odot$. The color-color...
For a sample of Swift and Fermi GRBs, we show that the minimum variability timescale spectral lag prompt emission is related to bulk Lorentz factor in complex manner: small $\Gamma$'s, exhibits shallow (plateau) region. large declines steeply as function $\Gamma$ ($\delta T\propto\Gamma^{-4.05\pm0.64}$). Evidence also presented for an intriguing correlation between peak times, t$_p$, afterglow timescale.
Curvature effects in Gamma-ray bursts (GRBs) have long been a source of considerable interest. In collimated relativistic GRB jet, photons that are off-axis relative to the observer arrive at later times than on-axis and also expected be spectrally softer. this work, we invoke relatively simple kinematic two-shell collision model for uniform jet profile compare its predictions prompt-emission data observations attributed curvature such as peak-flux--peak-frequency relation, i.e., relation...
Abstract We investigate the prompt emission and afterglow properties of short-duration gamma-ray burst (sGRB) 130603B another eight sGRB events during 2012–2015, observed by several multiwavelength facilities including Gran Canarias Telescope 10.4 m telescope. Prompt high energy data were obtained INTEGRAL-SPI-ACS, Swift-BAT, Fermi-GBM satellites. The INTEGRAL in range 0.1–10 MeV for 130603B, 140606A, 140930B, 141212A, 151228A do not show any signature extended or precursor activity their...
Abstract We describe results of a planetary defense exercise conducted during the close approach to Earth by near-Earth asteroid (99942) Apophis 2020 December–2021 March. The community has been conducting observational campaigns since 2017 test operational readiness global capabilities. These community-led exercises were carried out with support NASA’s Planetary Defense Coordination Office and International Asteroid Warning Network. campaign is third in our series exercises. goal this was...
Context. The paper is comprised of optical identification and multiwavelength studies a new X-ray source discovered by the Spectrum Roentgen-Gamma (SRG) observatory during ART-XC survey its follow-up observations. Aims. We aim to identify SRGA J213151.5+491400 in wavelengths. determine spectra light curves high low states find periodicities resolve emission lines system using ground-based data. intend study spectral temporal characteristics SRG surveys NICER data state. Methods. present from...
We report optical photometric and polarimetric observations of the blazar OJ 287 gathered during 2016/17. The high level activity, noticed after General Relativity Centenary flare, is argued to be part follow-up flares that exhibited levels polarization originated in primary black hole jet. propose were induced as a result accretion disk perturbations, travelling from site impact towards SMBH. timings inferred our allowed us estimate propagation speed these perturbations. Additionally, we...