J. R. Webb
A5033613466- Astrophysics and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Solar and Space Plasma Dynamics
- Astronomy and Astrophysical Research
- Radio Astronomy Observations and Technology
- Stellar, planetary, and galactic studies
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Dark Matter and Cosmic Phenomena
- Astro and Planetary Science
- Ionosphere and magnetosphere dynamics
- Particle physics theoretical and experimental studies
- Gyrotron and Vacuum Electronics Research
- Particle Accelerators and Free-Electron Lasers
- Galaxies: Formation, Evolution, Phenomena
- History and Developments in Astronomy
- Adaptive optics and wavefront sensing
- Particle accelerators and beam dynamics
- Neutrino Physics Research
- Cyclone Separators and Fluid Dynamics
- Pulsars and Gravitational Waves Research
- Space Satellite Systems and Control
- Superconducting Materials and Applications
- Calibration and Measurement Techniques
- Geophysics and Gravity Measurements
Florida International University
2012-2023
Embry–Riddle Aeronautical University
2022
Mount Stromlo Observatory
2018-2021
University of Florida
1986-2008
South African Radio Astronomy Observatory
2007
University of Missouri–Kansas City
2002
Kitt Peak National Observatory
1998
Colgate University
1994
Stephen F. Austin State University
1989-1990
Georgia State University
1990
The blazar 3C 279, one of the brightest identified extragalactic objects in γ-ray sky, underwent a large (factor ~10 amplitude) flare γ-rays toward end 3 week pointing by Compton Gamma Ray Observatory (CGRO), 1996 January-February. peak represents highest intensity ever recorded for this object. During high state, extremely rapid variability was seen, including an increase factor 2.6 ~8 hr, which strengthens case relativistic beaming. Coordinated multifrequency observations were carried out...
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...
Broadband photographic observations of 22 optically violent variable (OVV) active galactic nuclei are presented. Over 3100 made between 1968 and 1986 at Rosemary Hill Observatory tabulated displayed graphically. The majority the were in either Johnson B system or international (PG) system. Multicolor data presented for a few objects. Descriptions light curves include assignment each OVV to an arbitrary variability subclass. curves, some extending over 18 yr, analyzed linear trends underlying...
Aims. Since the CGRO operation in 1991–2000, one of primary unresolved questions about blazar γ-ray emission has been its possible correlation with low-energy (in particular optical) emission. To help answer this problem, Whole Earth Blazar Telescope (WEBT) consortium organized GLAST-AGILE Support Program (GASP) to provide optical-to-radio monitoring data be compared detections by AGILE and GLAST satellites. This new WEBT project started early September 2007, just before a strong detection...
view Abstract Citations (128) References (59) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Simultaneous Multiwavelength Spectrum and Variability of 3C 279 from 10 9 to 24 Hz Hartman, R. C. ; Webb, J. Marscher, A. P. Travis, Dermer, D. Aller, H. M. F. Balonek, T. Bennett, K. Bloom, S. Fujimoto, Hermsen, W. Hughes, Jenkins, Kii, Kurfess, Makino, Mattox, von Montigny, Ohashi, Robson, I. Ryan, Sadun, Schoenfelder, V. Smith, G. Teraesranta, Tornikoski, Turner,...
We report results from a 1 week multi-wavelength campaign to monitor the BL Lac object S5 0716+714 (on December 9-16, 2009). In radio bands source shows rapid (~ (0.5-1.5) day) intra-day variability with peak amplitudes of up ~ 10 %. The at 2.8 cm leads by about day 6 and 11 cm. This time lag more variations suggests an intrinsic contribution source's intraday cm, while interstellar scintillation (ISS) seems predominate. Large quasi-sinusoidal 0.8 mag were detected in V, R I-bands. X-ray...
We describe the remote facilities operated by Southeastern Association for Research in Astronomy (SARA), a consortium of colleges and universities US partnered with Lowell Observatory, Chilean National Telescope Allocation Committee, Instituto de Astrofisica Canarias. SARA observatories comprise 0.96m telescope at Kitt Peak, Arizona; 0.6m instrument on Cerro Tololo, Chile; 1m Jacobus Kapteyn Roque los Muchachos, La Palma, Spain. All are using standard VNC or Radmin protocols communicating...
We present the TRansient Image Processing Pipeline (TRIPP), a transient and variable source detection pipeline that employs both difference imaging light curve analysis techniques for astronomical data. Additionally, we demonstrate TRIPP's rapid capability by detecting candidates in near-real time. TRIPP was tested using image data of supernova SN2023ixf from Local Galactic Transient Survey (LGTS) collected Las Cumbres Observatory's (LCO) network 0.4 m telescopes. To verify methods employed...
We discuss our transient search for directed energy systems in local galaxies, with calculations indicating the ability of modest searches to detect optical Search Extraterrestrial Intelligence (SETI) sources closest galaxies. Our analysis follows Lubin (2016) where a messenger civilization beacon strategy we call "intelligent targeting." plot required laser time achieve an SNR 10 and find blind transmission target all stars Milky Way be achievable galactic civilizations. As high cadence sky...
Photometric data are reported for 144 extragalactic sources observed during a 19 yr program of photographic monitoring. An additional 22 objects that were classified as optically violent variables (OVVs) have been discussed by Webb et al. (1988). The present paper summarizes results the generally less active not included in earlier publication. Of these, 92 exhibited optical variations at confidence level 95% or more. Light curves presented 25 more interesting objects, three which displayed...
A multiwavelength campaign to observe the BL Lac object AO 0235+16 (z = 0.94) was set up by Whole Earth Blazar Telescope (WEBT) collaboration during observing seasons 2003-2004 and 2004-2005, involving radio, near-IR optical photometric monitoring, VLBA spectral three pointings XMM-Newton satellite.Here we report on results of first season, which involved participation 24 telescopes 4 radio telescopes, as well pointing, occurred January 18-19, 2004.Unpublished data from previous epochs were...
The quasar 3C 279 was the target of an extensive multiwavelength monitoring campaign from 2006 January through April. An optical-IR-radio by Whole Earth Blazar Telescope (WEBT) collaboration organized around target-of-opportunity X-ray and soft γ-ray observations with Chandra INTEGRAL in mid-January, additional coverage RXTE Swift XRT. In this paper we focus on results WEBT campaign. source exhibited substantial variability optical flux spectral shape, a characteristic timescale few days....
view Abstract Citations (128) References (40) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multifrequency Observations of Blazars. III. The Spectral Shape the Radio to X-Ray Continuum Brown, L. M. J. ; Robson, E. I. Gear, W. K. Hughes, D. H. Griffin, Geldzahler, B. Schwartz, P. R. Smith, G. A. Shepherd, Webb, Valtaoja, Terasranta, Salonen, We present multifrequency, quasi-simultaneous spectra for a sample 11 blazars. spectral shape violently variable...
Here we report on the results of WEBT photo-polarimetric campaign targeting blazar S5~0716+71, organized in March 2014 to monitor source simultaneously BVRI and near IR filters. The resulted an unprecedented dataset spanning $\sim 110$\,h nearly continuous, multi-band observations, including two sets densely sampled polarimetric data mainly R filter. During campaign, displayed pronounced variability with peak-to-peak variations about $30\%$ "bluer-when-brighter" spectral evolution,...
We present intensive optical, infrared, and radio monitoring observations of the BL Lac object OJ 287, taken between years 1993-1998. Two large optical outbursts were detected at predicted times in November 1994 December 1995. The detection these supports binary black hole model for 287. Optical polarisation show variability degree position angle, very similar to those observed during 1983/84 outburst angles behaviour observations, indicating that, least, magnetic field orientations bands...
In this work, we present the results of our multi-band microvariability study famous blazar BL Lac. We performed microvariablity observations source in optical VRI bands for four nights 2016. studied intranight flux and spectral variability detail with an objective to characterize blazars, a frequently observed phenomenon blazars. The show that often displays fast amplitude as large ~0.2 magnitude within few hours, color similar time scales can be characterized “bluer-when-brighter” trend....
view Abstract Citations (72) References (63) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multifrequency Observations of BL Lacertae Bregman, Joel N. ; Glassgold, A. E. Huggins, P. J. Neugebauer, G. Soifer, B. T. Matthews, K. Elias, H. Webb, R. Pollock, Leacock, Smith, Aller, D. M. F. Hughes, Maccagni, Garilli, Giommi, Miller, S. Stephens, Balonek, Dent, W. Kinsel, Wisniewski, Z. Williams, Brand, L. Ku, -M. We present 20 years optical, infrared, and radio...
view Abstract Citations (103) References (47) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multifrequency Observations of the Superluminal Quasar 3C 345 Bregman, Joel N. ; Glassgold, A. E. Huggins, P. J. Neugebauer, G. Soifer, B. T. Matthews, K. Elias, Webb, Pollock, Pica, Leacock, R. Smith, Aller, H. D. M. F. Hodge, Dent, W. Balonek, Barvainis, Roellig, L. Wisniewski, Z. Rieke, Lebofsky, Wills, Ku, -M. Jesse Witteborn, C. Lester, Impey, Hackwell, The...
view Abstract Citations (75) References (77) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The QSO 1156+295 : a multifrequency study of recent activity. Wills, B. J. ; Pollock, T. Aller, H. D. M. F. Balonek, Barvainis, R. E. Binzel, P. Chaffee, Dent, W. A. Douglas, N. Fanti, C. Garrett, Gregorini, L. Henry, Hill, Howard, Jeske, Kepler, S. O. Leacock, Mantovani, O'Dea, Padrielli, Perley, Pica, Puschell, Sanduleak, Shields, G. Smith, Thuan, X. Wade,...
The occurrence of low-amplitude flux variations in blazars on hourly timescales, commonly known as microvariability, is still a widely debated subject high-energy astrophysics. Several competing scenarios have been proposed to explain such occurrences, including various jet plasma instabilities leading the formation shocks, magnetic reconnection sites, and turbulence. In this Letter, we present results our detailed investigation prominent, five-hour-long optical microflare detected during...