A5085544525- Gamma-ray bursts and supernovae
- SAS software applications and methods
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Stellar, planetary, and galactic studies
- Radio Astronomy Observations and Technology
- Astro and Planetary Science
- Particle Accelerators and Free-Electron Lasers
- Adaptive optics and wavefront sensing
- Solar and Space Plasma Dynamics
- Superconducting Materials and Applications
- Calibration and Measurement Techniques
- Scientific Measurement and Uncertainty Evaluation
- Particle Detector Development and Performance
- Historical, Religious, and Philosophical Studies
- Astrophysics and Star Formation Studies
- Advanced X-ray Imaging Techniques
- X-ray Spectroscopy and Fluorescence Analysis
- Mechanics and Biomechanics Studies
- Medical Imaging Techniques and Applications
- Advanced X-ray and CT Imaging
Northern Kentucky University
2022-2024
Highland Community College - Illinois
2023-2024
Morehead State University
2014-2023
Universität Bayern
2019
Swift Engineering (United States)
2013-2017
Pennsylvania State University
2006-2015
Max Planck Institute for Radio Astronomy
2014-2015
Max Planck Society
1999-2015
Saint Mary's University
2011-2015
European Space Astronomy Centre
2015
After the All-Sky Automated Survey for SuperNovae (ASAS-SN) discovered a significant brightening of inner region NGC 2617, we began ~70 day photometric and spectroscopic monitoring campaign from X-ray through near-infrared (NIR) wavelengths. We report that 2617 went dramatic outburst, during which its flux increased by over an order magnitude followed increase optical/ultraviolet (UV) continuum almost magnitude. classified as Seyfert 1.8 galaxy in 2003, is now 1 due to appearance broad...
We present new observations of the early X-ray afterglows first 27 gamma-ray bursts (GRBs) well observed by Swift X-Ray Telescope (XRT). The show a canonical behavior, where light curve broadly consists three distinct power-law segments: (1) an initial very steep decay (∝t-α with 3 ≲ α1 5), followed (2) shallow (0.5 α2 1.0), and finally (3) somewhat steeper (1 α3 1.5). These segments are separated two corresponding break times, tbreak,1 500 s 103 tbreak,2 104 s. On top this many events have...
We present ground-based and Swift photometric spectroscopic observations of the candidate tidal disruption event (TDE) ASASSN-14li, found at center PGC 043234 ($d\simeq90$ Mpc) by All-Sky Automated Survey for SuperNovae (ASAS-SN). The source had a peak bolometric luminosity $L\simeq10^{44}$ ergs s$^{-1}$ total integrated energy $E\simeq7\times10^{50}$ radiated over $\sim6$ months presented. UV/optical emission is well-fit blackbody with roughly constant temperature $T\sim35,000$ K, while...
ASASSN-14ae is a candidate tidal disruption event (TDE) found at the center of SDSS J110840.11+340552.2 ($d\simeq200$~Mpc) by All-Sky Automated Survey for Supernovae (ASAS-SN). We present ground-based and Swift follow-up photometric spectroscopic observations source, finding that transient had peak luminosity $L\simeq8\times10^{43}$~erg~s$^{-1}$ total integrated energy $E\simeq1.7\times10^{50}$ ergs radiated over $\sim5$ months presented. The blackbody temperature remains roughly constant...
We report the discovery of ASASSN-15lh (SN 2015L), which we interpret as most luminous supernova yet found. At redshift z = 0.2326, reached an absolute magnitude M_{u,AB} -23.5+/-0.1 and bolometric luminosity L_bol (2.2+/-0.2)x 10^45 ergs s^-1, is more than twice any previously known supernova. It has several major features characteristic hydrogen-poor super-luminous supernovae (SLSNe-I), whose energy sources progenitors are currently poorly understood. In contrast to SLSNe-I that reside in...
We present observations of the early X-ray emission for a sample 40 gamma-ray bursts (GRBs) obtained using Swift satellite which narrow-field instruments were pointed at burst within 10 minutes trigger. Using data from Burst Alert and X-Ray Telescopes, we show that light curve can be well described by an exponential relaxes into power law, often with flares superimposed. The transition time between law provides physically defined timescale duration. In most breaks to shallower decay first...
We present the first systematic study of (non-radio-selected) radio-loud narrow-line Seyfert 1 (NLS1) galaxies. Cross-correlation Catalogue Quasars and Active Nuclei with several radio optical catalogs led to identification ∼11 NLS1 candidates, including four previously known ones. This almost triples number galaxies if all candidates are confirmed. Most compact, steep-spectrum sources accreting close or above Eddington limit. The our sample remarkable in that they occupy a rarely populated...
We systematically analyze the prompt emission and early afterglow data of a sample 31 GRBs detected by {\em Swift} before September 2005, estimate GRB radiative efficiency. BAT's narrow band inhibits precise determination spectral parameters, we have developed method to these parameters with hardness ratio information. The shallow decay component commonly existing in X-ray afterglows, if interpreted as continuous energy injection external shock, suggests that efficiency previously derived...
We present the catalog of sources detected in first 22 months data from hard X-ray survey (14--195 keV) conducted with BAT coded mask imager on \swift satellite. The contains 461 above 4.8 sigma level BAT. High angular resolution for every source Swift XRT or archival have allowed associations to be made known counterparts other wavelength bands over 97% detections, including discovery ~30 galaxies previously unknown as AGN and several new Galactic sources. A total 266 are associated Seyfert...
We report Swift observations of a sample 92 bright soft X-ray selected active galactic nuclei (AGN). This represents the largest number AGN observed to study spectral energy distribution (SED) with simultaneous optical/UV and data. The principal motivation this is understand SEDs in regime provide bolometric corrections which are important determining Eddington ratio L/Ledd. In particular, we rigorously explore dependence UV-EUV contribution correction on assumed EUV shape. find strong...
We present the first systematic investigation of morphological and timing properties flares in GRBs observed by Swift XRT. consider a large sample drawn from all detected Swift, INTEGRAL, HETE-2 prior to 2006 January 31, which had an XRT follow-up showed significant flaring. Our 33 includes long short, at low high redshift, total 69 flares. The strongest occur early phases, with clear anticorrelation between flare peak intensity time occurrence. Fitting each X-ray Gaussian model, we find...
We present the black hole mass-bulge velocity dispersion relation for a complete sample of 75 soft X-ray-selected active galactic nuclei (AGNs): 43 broad-line Seyfert 1 galaxies (BLS1s) and 32 narrow-line (NLS1s). use luminosity FWHM(Hβ) as surrogates mass FWHM([O III]) surrogate bulge dispersion. find that NLS1s lie below MBH-σ BLS1s, confirming Mathur et al. result. The statistical result is robust not due to any systematic measurement error. This has important consequences toward our...
We have conducted a multiwavelength survey of 42 radio loud narrow-1ine Seyfert 1 galaxies (RLNLS1s), selected by searching among all the known sources this type and omitting those with steep spectra. analyse data from frequencies to X-rays, supplement these information available online catalogues literature in order cover full electromagnetic spectrum. This is largest for source. detected 90% X-rays found 17% at γ rays. Extreme variability high energies was also found, down timescales as...
We analyze the multifrequency behavior of quasar 3C 454.3 during three prominent \gamma-ray outbursts: 2009 Autumn, 2010 Spring, and Autumn. The data reveal a repeating pattern, including triple flare structure, in properties each outburst, which implies similar mechanism(s) location for all events. multi-frequency indicates that lower frequency events are co-spatial with outbursts, although emission varies on shortest timescales. determine variability from UV to IR wavelengths an outburst...
Recent intensive Swift monitoring of the Seyfert 1 galaxy NGC 5548 yielded 282 usable epochs over 125 days across six UV/optical bands and X-rays. This is densest extended AGN continuum sampling ever obtained, with a mean rate <0.5 day. Approximately daily HST UV was also obtained. The light curves show strong correlations (r_max = 0.57 - 0.90) clearest measurement to date interband lags. These lags are well-fit by \tau propto \lambda^4/3 wavelength dependence, normalization that indicates...
We present ground-based and Swift photometric spectroscopic observations of the tidal disruption event (TDE) ASASSN-15oi, discovered at centre 2MASX J20390918−3045201 (d ≃ 216 Mpc) by All-Sky Automated Survey for SuperNovae. The source peaked a bolometric luminosity L 1.3 × 1044 erg s−1 radiated total energy E 6.6 1050 over first ∼3.5 months observations. early optical/UV emission can be fit blackbody with temperature increasing from T ∼ 2 104 K to 4 while declines 2.3 1043 s−1, requiring...
ABSTRACT We present ground-based optical photometric monitoring data for NGC 5548, part of an extended multiwavelength reverberation mapping campaign. The light curves have nearly daily cadence from 2014 January to July in nine filters ( BVRI and ugriz ). Combined with ultraviolet the Hubble Space Telescope Swift , we confirm significant time delays between continuum bands as a function wavelength, extending wavelength coverage 1158 Å z band (~9160 Å). find that lags at wavelengths longer...
We present the observations of GRB090510 performed by Fermi Gamma-Ray Space Telescope and Swift observatory. This is a bright, short burst that shows an extended emission detected in GeV range. Furthermore, its optical initially rises, feature so far observed only long bursts, while X-ray flux initial shallow decrease, followed steeper decay. exceptional behavior enables us to investigate physical properties GRB outflow, poorly known bursts. discuss internal shock external models for...
Abstract Swift intensive accretion disk reverberation mapping of four AGN yielded light curves sampled ∼200–350 times in 0.3–10 keV X-ray and six UV/optical bands. Uniform reduction cross-correlation analysis these data sets yields three main results: (1) The X-ray/UV correlations are much weaker than those within the UV/optical, posing severe problems for lamp-post reprocessing model which variations a central corona drive power surrounding disk. (2) interband lags generally consistent with...
We describe the first results from a six-month long reverberation-mapping experiment in ultraviolet based on 170 observations of Seyfert 1 galaxy NGC 5548 with Cosmic Origins Spectrograph Hubble Space Telescope. Significant correlated variability is found continuum and broad emission lines, amplitudes ranging ~30% to factor two lines three continuum. The variations all strong lag behind those continuum, He II 1640 lagging by ~2.5 days Lyman alpha 1215, C IV 1550, Si 1400 ~5-6 days....
We present 3-50 keV NuSTAR observations of the AGN Mrk 335 in a very low flux state. The spectrum is dominated by strong features at energies iron line 5-7 and Compton hump from 10-30 keV. source variable during observation, with variability concentrated energies, which suggesting either relativistic reflection or absorption scenario. In this work we focus on interpretation, making use new models that self consistently calculate fraction, blurring angle-dependent for different coronal...
The narrow-line Seyfert 1 Galaxy 1H 0707−495 went into a low state from 2010 December to 2011 February, discovered by monitoring campaign using the X-Ray Telescope on Swift satellite. We triggered 100 ks XMM–Newton observation of source in January, revealing have dropped factor 10 soft band, below keV, and 2 at 5 compared with long 2008. sharp spectral drop usually seen around 7 keV now extends lower energies, 6 our frame. spectrum is well fitted relativistically blurred reflection similar...