M. F. Aller
A5086348462- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Neutrino Physics Research
- Particle Accelerators and Free-Electron Lasers
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- Dark Matter and Cosmic Phenomena
- Particle accelerators and beam dynamics
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Geophysics and Gravity Measurements
- Stellar, planetary, and galactic studies
- Ionosphere and magnetosphere dynamics
- GNSS positioning and interference
- Pulsars and Gravitational Waves Research
- Gyrotron and Vacuum Electronics Research
- Computational Physics and Python Applications
- Calibration and Measurement Techniques
- Particle physics theoretical and experimental studies
- Cosmology and Gravitation Theories
- Spectroscopy and Laser Applications
- Magnetic confinement fusion research
- Astrophysics and Star Formation Studies
University of Michigan–Ann Arbor
2015-2024
South University
2015-2024
Michigan United
1997-2022
Ann Arbor Center for Independent Living
2006-2016
Institute of Radio Astronomy
2015
National Radio Astronomy Observatory
1983-2013
Astronomy and Space
1990-2010
University of Birmingham
2008-2010
Vaisala (Finland)
2009
University of Turku
2009
(Abridged) We have conducted a detailed investigation of the broad-band spectral properties \gamma-ray selected blazars Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated gamma-ray spectra with Swift, radio, infra-red, optical and other hard X-ray/gamma-ray data, collected within three months LBAS data taking period, we were able to assemble high-quality quasi-simultaneous Spectral Energy Distributions (SED) for 48 blazars.The SED these sources is similar that...
We present results from monitoring the multi-waveband flux, linear polarization, and parsec-scale structure of quasar PKS 1510-089, concentrating on eight major gamma-ray flares that occurred during interval 2009.0-2009.5. The peaks were essentially simultaneous with maxima at optical wavelengths, although flux ratio two wavebands varied by an order magnitude. polarization vector rotated 720 degrees a 5-day period encompassing six these flares. This culminated in very bright, roughly 1 day,...
ABSTRACT We describe the parsec-scale kinematics of 200 active galactic nucleus (AGN) jets based on 15 GHz Very Long Baseline Array (VLBA) data obtained between 1994 August 31 and 2011 May 1. present new VLBA images these 59 additional AGNs from MOJAVE 2 cm Survey programs. Nearly all 60 most heavily observed show significant changes in their innermost position angle over a 12–16 yr interval, ranging 10° to 150° sky, corresponding intrinsic variations ∼0. ° 5 ∼2°. The BL Lac smaller than...
We present images from a long term program (MOJAVE: Monitoring of Jets in AGN with VLBA Experiments) to survey the structure and evolution parsec-scale jet phenomena associated bright radio-loud active galaxies northern sky. The observations consist 2424 15 GHz complete flux-density limited sample 135 above declination -20 degrees, spanning period 1994 August 2007 September. These data were acquired as part MOJAVE 2 cm Survey programs, archive. selection criteria are based on multi-epoch...
We present 5321 mas-resolution total intensity and linear polarization maps of 437 active galactic nuclei (AGNs) obtained with the VLBA at 15 GHz as part MOJAVE survey, also from NRAO data archive. The former is a long-term program to study structure evolution powerful parsec-scale outflows associated AGNs. targeted AGNs are drawn several flux-limited radio γ-ray samples, all have correlated flux densities greater than ∼50 mJy GHz. Approximately 80% these sources detected by Fermi LAT...
We present 1625 new 15 GHz (2 cm) VLBA images of 295 jets associated with active galactic nuclei (AGNs) from the MOJAVE and 2 cm surveys, spanning observations between 1994 Aug 31 2013 20. For 274 AGNs at least 5 epochs, we have analyzed kinematics 961 individual bright features in their parsec-scale jets. A total 122 these not been previously by program. In case 451 jet that had 10 also examined for possible accelerations. At half well-sampled non-radial and/or accelerating trajectories,...
Following the detection of strong TeV γ-ray flares from BL Lac object 1ES 1959+650 with Whipple 10 m Cerenkov telescope on 2002 May 16 and 17, we performed intensive target opportunity radio, optical, X-ray, observations 18 to August 14. Observations X-ray Rossi X-Ray Timing Explorer HEGRA telescopes revealed several flares, enabling us sensitively test X-ray-γ-ray flux correlation properties. Although fluxes seemed be correlated in general, found an "orphan" flare that was not accompanied...
We have examined the compact structure in 250 flat-spectrum extragalactic radio sources using interferometric fringe visibilities obtained with Very Long Baseline Array (VLBA) at 15 GHz. With projected baselines out to 440 Mλ, we are able investigate source on typical angular scales as small 0.05 mas. This scale is similar resolution of VLBI Space Observatory Programme data longer a lower frequency and somewhat poorer accuracy. For 171 our sample, more than half total flux density seen by...
view Abstract Citations (412) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectra and linear polarizations of extragalactic variable sources atcentimeter wavelengths. Aller, H. D. ; M. F. Latimer, G. E. Hodge, P. The results multifrequency observations the flux densities 97 obtained with University Michigan 26 m paraboloid through November 1984 are presented. were started at 8.0 GHz in June 1965, 14.5 February 1974, 4.8 September 1977....
view Abstract Citations (237) References (60) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The University of Michigan Radio Astronomy Data Base. I. Structure Function Analysis and the Relation between BL Lacertae Objects Quasi-stellar Hughes, P. A. ; Aller, H. D. M. F. We have performed a structure function analysis on well-observed group variable extragalactic sources, monitored in total polarized flux centimeter waveband since 1965. Total functions Lac...
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...
Eight optical and four radio observatories have been intensively monitoring the BL Lac object 0716+714 in last years: 4854 data points collected UBVRI bands since 1994, while light curves extend back to 1978. Many of these are presented here for first time. The long-term trend shown by seems vary with a characteristic time scale about 3.3 years, longer period 5.5-6 years characterize variations. In general, colour indices only weakly correlated brightness. flux behaviour at different...
We have investigated the rapid variations of BL Lac object S5 0716+714 in radio, optical, ultraviolet, and x-ray regimes. Several simultaneous multifrequency campaigns been carried out. Here we describe complete analysis a four-week monitoring campaign at three radio optical frequency bands, optical-UV optical-x-ray observations, correlations between changes on longer time scales. also investigate polarization properties regime. The major observational results are high duty cycle variability...
We report results from an intensive multiwavelength monitoring campaign on the TeV blazar Mrk 421 over period of 2003-2004. The source was observed simultaneously at energies with Whipple 10 m telescope and X-ray Rossi X-Ray Timing Explorer (RXTE) during each clear night within observing windows. Supporting observations were also frequently carried out optical radio wavelengths to provide simultaneous or contemporaneous coverages. large amount data has allowed us examine variability in...
view Abstract Citations (252) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Polarized radio outbursts in BL Lacertae. II. The flux and polarization of a piston-driven shock. Hughes, P. A. ; Aller, H. D. M. F. We present discussion the variable source Lac that occurred during 1982 1983 were seen both total polarized at 4.8, 8.0, 14.5 GHz. These are interpreted terms compressions propagate from an optically thick to thin part beam. Each is...
We have compared the radio emission from a sample of parsec-scale AGN jets as measured by VLBA at 15 GHz, with their associated gamma-ray properties that are reported in Fermi LAT 3-month bright source list. find our radio-selected photon flux correlates well quasi-simultaneously compact density. The LAT-detected complete generally higher densities, and cores brighter (i.e., brightness temperature) than non-detected objects. This suggests preferentially Doppler-boosting factors. In addition,...
We present time-resolved broad-band observations of the quasar 3C 279 obtained from multi-wavelength campaigns conducted during first two years Fermi Gamma-ray Space Telescope mission. While investigating previously reported gamma-ray/optical flare accompanied by a change in optical polarization, we found that emission appears delayed with respect to gamma-ray about 10 days. X-ray reveal pair `isolated' flares separated ~90 days, only weak counterparts. The spectral structure measured...
We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard gamma-ray bands. Our unique set has allowed us demonstrate that selection method strongly influences results, producing biases cannot be ignored. Almost all BL Lac objects have been detected by Fermi-LAT, whereas ~40% of flat-spectrum radio quasars (FSRQs) radio, X-ray selected are still below detection limit even after integrating 27 months...
We present the results of extensive multi-waveband monitoring blazar 3C~279 between 1996 and 2007 at X-ray energies (2-10 keV), optical R band, 14.5 GHz, as well imaging with Very Long Baseline Array (VLBA) 43 GHz. In all bands power spectral density corresponds to "red noise" that can be fit by a single law over sampled time scales. Variations in flux three wavebands are significantly correlated. The delay high low frequency changes substantially on scales years. A major multi-frequency...
We have obtained milliarcsecond-scale spectral index distributions for a sample of 190 extragalactic radio jets through the MOJAVE project. The sources were observed in 2006 at 8.1, 8.4, 12.1, and 15.4 GHz, we study four-frequency spectrum individual jet features. performed detailed simulations to effects image alignment (u,v)-plane coverage on maps verify our results. core indices are average flat, while is general steep with mean -1.04. A simple power-law fit often inadequate regions, as...
We report observations of Faraday rotation measures for a sample 191 extragalactic radio jets observed within the MOJAVE program. Multifrequency Very Long Baseline Array were carried out over 12 epochs in 2006 at four frequencies between 8 and 15 GHz. detect parsec-scale 149 sources find quasars to have larger on average than BL Lac objects. The median core are significantly higher jet components. This is especially true where we significant negative correlation magnitude measure...
We present observations of a major outburst at centimeter, millimeter, optical, X-ray, and γ-ray wavelengths the BL Lacertae object AO 0235+164. analyze timing multi-waveband variations in flux linear polarization, as well changes Very Long Baseline Array images λ = 7 mm with ∼0.15 milliarcsec resolution. The association events different wavebands is confirmed high statistical significance by probability arguments Monte Carlo simulations. A series sharp peaks optical pronounced maximum...