T. N. Ukwatta
A5005532910- Gamma-ray bursts and supernovae
- SAS software applications and methods
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Microbial Metabolites in Food Biotechnology
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Particle Detector Development and Performance
- Dark Matter and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Statistical and numerical algorithms
- Geophysics and Gravity Measurements
- Neutrino Physics Research
- Medical Imaging Techniques and Applications
- Solar and Space Plasma Dynamics
- Particle physics theoretical and experimental studies
- Radio Astronomy Observations and Technology
- Nuclear Physics and Applications
- Advanced X-ray and CT Imaging
- Particle Accelerators and Free-Electron Lasers
- Diet, Metabolism, and Disease
- COVID-19 diagnosis using AI
Universidad de Guadalajara
2023
Radboud University Nijmegen
2023
The University of Tokyo
2023
Michigan State University
2011-2022
Los Alamos National Laboratory
2011-2020
Instituto Politécnico Nacional
2012-2018
Center for Research and Advanced Studies of the National Polytechnic Institute
2012-2018
Aix-Marseille Université
2018
Max Planck Society
2018
University of North Florida
2016
Gamma-ray bursts (GRBs) serve as powerful probes of the early Universe, with their luminous afterglows revealing locations and physical properties star forming galaxies at highest redshifts, potentially locating first generation (Population III) stars. Since GRB have intrinsically very simple spectra, they allow robust redshifts from low signal to noise spectroscopy, or photometry. Here we present a photometric redshift z~9.4 for Swift-detected 090429B based on deep observations...
The Swift/Burst Alert Telescope (BAT) hard X-ray transient monitor provides near real-time coverage of the sky in energy range 15-50 keV. BAT observes 88% each day with a detection sensitivity 5.3 mCrab for full-day observation and time resolution as fine 64 seconds. three main purposes are (1) discovery new sources, (2) outbursts or other changes flux known (3) generation light curves more than 900 sources spanning over eight years. primary interface is public web page. Between 2005...
The Crab Nebula is the brightest TeV gamma-ray source in sky and has been used for past 25 years as a reference astronomy, calibration verification of new instruments. High Altitude Water Cherenkov Observatory (HAWC), completed early 2015, to observe at high significance across nearly full spectrum energies which HAWC sensitive. unique its wide field-of-view, 2 sr any instant, high-energy reach, up 100 TeV. HAWC's sensitivity improves with energy. Above $\sim$1 driven by best background...
We present the second Swift Burst Alert Telescope (BAT) catalog of gamma-ray bursts (GRBs), which contains 476 detected by BAT between 2004 December 19 and 2009 21. This (hereafter BAT2 catalog) presents burst trigger time, location, 90% error radius, duration, fluence, peak flux, time-averaged spectral parameters, time-resolved parameters measured BAT. In correlation study various observed extracted from prompt emission data, we distinguish among long-duration GRBs (L-GRBs), short-duration...
The majority of short gamma-ray bursts (SGRBs) are thought to originate from the merger compact binary systems collapsing directly form a black hole. However, it has been proposed that both SGRBs and long (LGRBs) may, on rare occasions, an unstable millisecond pulsar (magnetar) prior final collapse. GRB 090515, detected by Swift satellite was extremely short, with T90 0.036 ± 0.016 s, had very low fluence 2 × 10−8 erg cm−2 faint optical afterglow. Despite this, 0.3–10 keV flux in first 200 s...
We present the first Swift Burst Alert Telescope (BAT) catalog of gamma-ray bursts (GRBs), which contains detected by BAT between 2004 December 19 and 2007 June 16. This (hereafter BAT1 catalog) burst trigger time, location, 90% error radius, duration, fluence, peak flux, time-averaged spectral parameters for each 237 GRBs, as measured BAT. The BAT-determined position reported here is within 1.75' X-Ray (XRT)-determined these GRBs. T90 T50 durations at 80 20 s, respectively. From...
To date, the Burst Alert Telescope (BAT) onboard Swift has detected ~ 1000 gamma-ray bursts (GRBs), of which 360 GRBs have redshift measurements, ranging from z = 0.03 to 9.38. We present analyses BAT-detected for past 11 years up through GRB151027B. report summaries both temporal and spectral GRB characteristics using event data (i.e., each photon within approximately 250 s before 950 after BAT trigger time), discuss instrumental sensitivity selection effects detections. also explore...
The High-Altitude Water Cherenkov (HAWC) Observatory is sensitive to gamma rays and charged cosmic at TeV energies.The detector still under construction, but data acquisition with the partially deployed started in 2013.An analysis of cosmic-ray arrival direction distribution based on 4.9 × 10 events recorded between June 2013 February 2014 shows anisotropy -4 level angular scales about • .The HAWC sky map exhibits three regions significantly enhanced flux; two these were first reported by...
The HAWC experiment reports the first ground-based measurement of all-particle cosmic-ray spectrum in 10-500 TeV energy range. This data overlaps with direct measurements made by balloon-borne detectors as well those other higher air-shower detectors. closes an important gap between these different experiments.
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...
We report a correlation based on spectral simulation study of the prompt emission spectra gamma-ray bursts (GRBs) detected by Swift Burst Alert Telescope (BAT). The is between Epeak energy, which peak energy in \nu F_\nu spectrum, and photon index (\Gamma) derived from simple power-law model. - \Gamma relation, assuming typical smoothly broken spectrum GRBs, \log = 3.258 0.829\Gamma (1.3 < 2.3). take into account not only range energies fluences, but also distributions for both low-energy...
Spectral lag, the time difference between arrival of high-energy and low-energy photons, is a common feature in gamma-ray bursts (GRBs). Norris et al. reported correlation spectral lag isotropic peak luminosity GRBs based on limited sample. More recently, number authors have provided further support for this using arbitrary energy bands various instruments. In paper, we report systematic extraction lags largest Swift sample to date 31 with measured redshifts. We extracted all combinations...
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.
GRB 090618 was an extremely bright burst, detected across the electromagnetic spectrum. It has a redshift of 0.54 and supernova (SN) identified in ground-based photometry. We present thorough analysis prompt early afterglow emission using data from Swift, Fermi Gamma-ray Burst Monitor ROTSE, which we track evolution synchrotron spectral peak during through steep decay phase. find evidence thermal X-ray component alongside expected non-thermal power-law continuum. Such is rare among gamma-ray...
We present results from daily monitoring of gamma rays in the energy range $\sim0.5$ to $\sim100$ TeV with first 17 months data High Altitude Water Cherenkov (HAWC) Observatory. Its wide field view 2 steradians and duty cycle $>95$% are unique features compared other observatories that allow us observe every source transits over HAWC for up $\sim6$ hours each sidereal day. This regular sampling yields unprecedented light curves unbiased measurements independent seasons or weather conditions....
The High Altitude Water Cherenkov (HAWC) observatory is a wide field-of-view detector sensitive to gamma rays of 100 GeV few hundred TeV. Located in central Mexico at 19\ifmmode^\circ\else\textdegree\fi{} North latitude and 4100 m above sea level, HAWC will observe cosmic with an array water detectors. full scheduled be operational Spring 2015. In this paper, we study the sensitivity gamma-ray signatures high-mass (multi-TeV) dark matter annihilation. diverse searches for annihilation,...
Abstract We present a new catalog of TeV gamma-ray sources using 1523 days data from the High-Altitude Water Cherenkov (HAWC) Observatory. The represents most sensitive survey northern sky at energies above several TeV, with three times exposure compared to previous HAWC catalog, 2HWC. report 65 detected ≥5 σ significance, along positions and spectral fits for each source. contains eight that have no counterpart in 2HWC but are within 1° previously emitters, 20 more than away any Of these...
The first limits on the prompt emission from long gamma-ray burst (GRB) 130427A in $>100\nobreakspace\rm{GeV}$ energy band are reported. GRB was most powerful ever detected with a redshift $z\lesssim0.5$ and featured longest lasting above $100\nobreakspace\rm{MeV}$. spectrum extends at least up to $95\nobreakspace\rm{GeV}$, clearly range observable by High Altitude Water Cherenkov (HAWC) Gamma-ray Observatory, new extensive air shower detector currently under construction central Mexico....
A survey of the inner Galaxy region Galactic longitude l in [+15, +50] degree and latitude b [-4,+4] is performed using one-third High Altitude Water Cherenkov (HAWC) Observatory operated during its construction phase. To address ambiguities arising from unresolved sources data, we use a maximum likelihood technique to identify point source candidates. Ten candidate are identified this analysis. Eight these associated with known TeV but not all have differential fluxes compatible previous...
The High Altitude Water Cherenkov (HAWC) gamma-ray observatory is a wide field-of-view sensitive to 500 GeV - 100 TeV gamma rays and cosmic rays. With its observations over 2/3 of the sky every day, HAWC variety astrophysical sources, including possible from dark matter. Dark matter annihilation decay in Milky Way Galaxy should produce signals across many degrees on sky. instantaneous 2 sr enables extended regions sky, such as those Galactic halo. Here we show limits cross-section lifetime...
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...
Abstract We report on the spectral cross-calibration results of Konus-Wind, Suzaku/WAM, and Swift/BAT instruments using simultaneously observed gamma-ray bursts (GRBs). This is first attempt to use GRBs as a calibration source understand systematic problems among instruments. Based these joint fits, we find that (1) although constant factor (a normalization factor) agrees within 20% instruments, BAT shows systematically smaller value by 10%–20% compared (2) there trend low-energy photon...