A5076156077- Gamma-ray bursts and supernovae
- SAS software applications and methods
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astrophysics and Cosmic Phenomena
- Astro and Planetary Science
- Radio Astronomy Observations and Technology
- Galaxies: Formation, Evolution, Phenomena
- Pulsars and Gravitational Waves Research
- Innovations in Educational Methods
- Career Development and Diversity
- Spectroscopy and Laser Applications
- Geophysics and Gravity Measurements
- Innovative Teaching Methods
- Atmospheric Ozone and Climate
- Molecular Spectroscopy and Structure
- Science Education and Pedagogy
- Solar and Space Plasma Dynamics
- Advanced Combustion Engine Technologies
- Advanced Fiber Laser Technologies
- Advanced Optical Sensing Technologies
- Microbial Metabolites in Food Biotechnology
University of North Carolina at Chapel Hill
2005-2019
North Carolina Agricultural and Technical State University
2014-2017
Center for Astrophysics Harvard & Smithsonian
1997-1998
Harvard University
1998
Harvard University Press
1994
A maximum likelihood analysis of the NGC 4258 maser positions and velocities reveals a ~2 sigma deviation from Keplerian motion in projected rotation curve high-velocity features, corresponding to ~9 km/s, or 0.8%, flattening LOS with respect over range masers. While there are number potential explanations for this flattening, we argue pure an inclination-warped disk based on ability model explain otherwise puzzling features system. radial gradient inclination 0.034 mas^{-1} is not only...
We present the first reported case of simultaneous metallicity determination a gamma-ray burst (GRB) host galaxy, from both afterglow absorption lines as well strong emission-line diagnostics. Using spectroscopic and imaging observations long-duration Swift GRB 121024A at z = 2.30, we give one most complete views host/environment to date. observe damped Lyα absorber (DLA) with hydrogen column density log |$N({\rm H\,{\small I}})\,=\,21.88\pm 0.10$|, H2 in Lyman–Werner bands (molecular...
We have conducted VLBI observations at subparsec resolution of water maser and radio continuum emission in the nucleus nearby active galaxy NGC 3079. The 22 GHz arises compact (~0.01 pc a distance 16 Mpc) clumps, distributed over ~2 along an axis that is approximately aligned with major galactic disk. Doppler velocities clumps are consistent their lying inner parsec molecular disk binding mass ~106 M☉, rotating same sense as edge-on kiloparsec-scale observed CO emission. However, velocity...
A long and intense gamma-ray burst (GRB) was detected by INTEGRAL on July 11 2012 with a duration of ~115s fluence 2.8x10^-4 erg cm^-2 in the 20 keV-8 MeV energy range. GRB 120711A at z~1.405 produced soft emission (>20 keV) for least ~10 ks after trigger. The observed several ground-based telescopes that powerful optical flash peaking an R-band brightness ~11.5 mag ~126 s We present comprehensive temporal spectral analysis long-lasting 20-200 keV band INTEGRAL, Fermi/LAT post-GRB detection...
Gamma-ray bursts (GRBs) are the most luminous explosions in Universe, yet nature and physical properties of their energy sources far from understood. Very important clues, however, can be inferred by studying afterglows these events. We present optical X-ray observations GRB 130831A obtained Swift, Chandra, Skynet, Reionization And Transients Infra-Red camera, Maidanak, International Scientific Optical-Observation Network, Nordic Optical Telescope, Liverpool Telescope Gran Telescopio...
Panchromatic Robotic Optical Monitoring and Polarimetry Telescopes (PROMPT) observed the early-time optical afterglow of gamma-ray burst (GRB) 060607A obtained a densely sampled multiwavelength light curve that begins only tens seconds after GRB. Located at Cerro Tololo Inter-American Observatory in Chile, PROMPT is designed to observe afterglows γ-ray bursts using multiple automated 0.4 m telescopes image simultaneously many filters when bright may be highly variable. The data span interval...
The extragalactic radio source NGC 6334B is the most strongly scattered object known, with an angular size of 3'' at 20 cm wavelength. Its scales as square observing wavelength, and its phase structure function has a power-law dependence on projected baseline length. These properties suggest that point source, probably quasar, scatter broadened by intervening region turbulent plasma. line sight to intercepts northern lobe bipolar H II 6334A, which scattering. We discuss observations VLA 1.4,...
Sigma clipping is commonly used in astronomy for outlier rejection, but the number of standard deviations beyond which one should clip data from a sample ultimately depends on size sample. Chauvenet rejection oldest, and simplest, ways to account this, but, like sigma clipping, it sample's mean deviation, neither are robust quantities: both easily contaminated by very outliers they being reject. Many, more measures central tendency, exist, each has trade-off with precision. Here we...
Based on five years of observations with the 40-foot telescope at Green Bank Observatory (GBO), Reichart & Stephens (2000) found that radio source Cassiopeia A had either faded more slowly between mid-1970s and late 1990s than Baars et al. (1977) it to be fading 1940s mid-1970s, or rebrightened then resumed sometime mid-1990s, in L band (1.4 GHz). Here, we present 15 additional Cas Cyg band, three a half A, Tau Vir GBO's recently refurbished 20-meter X (9 GHz) bands. We also sophisticated...
We present a parsec-scale image of the OH maser in nucleus active galaxy IIIZw35, made using Very Long Baseline Array at wavelength 18 cm. detected two distinct components, with projected separation 50 pc (for D=110 Mpc) and Doppler velocity 70 km/s, which contain 50% total flux. Velocity gradients within these components could indicate rotation clouds binding mass densities ~7000 solar masses per cubic parsec, or more than 500,000 masses. Emission 1665-MHz line is roughly coincident...
view Abstract Citations (25) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A New Survey for Low-Luminosity Emission-Line Galaxies Boroson, Todd A. ; Salzer, John J. Trotter, Adam survey low-luminosity emission-line galaxies is described in which deep CCD images have been obtained through five narrow-band ({DELTA}λ = 80 A) filters. The covers 0.7 square degrees to a depth corresponding monochromatic magnitude m_6600_ 21.2 the emission line...
GRB 141221A was observed from infrared to soft gamma-ray bands. Here, we investigate its properties, in light of the standard model. We find that optical curve afterglow this burst presents an unusual steep/quick rise. The broad-band spectral energy distribution taken near maximum emission either a thermal component or break. In former case, properties are then very unusual, but could explain lack apparent jet breaks Swift curves. latter more usual, and can see curves passing through...
We present a single-dish mapping algorithm with number of advantages over traditional techniques. (1) Our makes use weighted modeling, instead averaging, to interpolate between signal measurements. This smooths the data, but without blurring data beyond instrumental resolution. Techniques that rely on averaging blur point sources sometimes as much 40%. (2) local, global, modeling separate astronomical from and/or environmental drift along telescope's scans. Other techniques, such basket...
We present a comprehensive temporal and spectral analysis of the long Swift GRB 120327A afterglow data to investigate possible causes observed early time colour variations. collected from various instruments/telescopes in different bands (X-rays, ultra- violet, optical near-infrared) determined shapes early-time light curves. studied overall behaviour energy distributions late times. The ultra-violet, optical, near-infrared curves can be modelled with single power-law component between 200...