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Articles 121 - 150 of 317
Full-Text Articles in Astrophysics and Astronomy
An Analytical Approach For Calculating Energy Spectra Of Relativistic Runaway Electron Avalanches In Air, Eric S. Crame, Joseph R. Dwyer, Shahab Arabshahi, Igor B. Vodopiyanov, Ningyu Liu, Hamid K. Rassoul
An Analytical Approach For Calculating Energy Spectra Of Relativistic Runaway Electron Avalanches In Air, Eric S. Crame, Joseph R. Dwyer, Shahab Arabshahi, Igor B. Vodopiyanov, Ningyu Liu, Hamid K. Rassoul
Aerospace, Physics, and Space Science Faculty Publications
Simplified equations describing the transport and energy spectrum of runaway electrons are derived from the basic kinematics of the continuity equations. These equations are useful in modeling the energy distribution of energetic electrons in strong electric fields, such as those found inside thunderstorms. Dwyer and Babich (2011) investigated the generation of low-energy electrons in relativistic runaway electron avalanches. The paper also developed simple analytical expressions to describe the detailed physics of Monte Carlo simulations of relativistic runaway electrons in air. In the current work, the energy spectra of the runaway electron population are studied in detail. Dependence of electron avalanche …
Uncovering The Deeply Embedded Active Galactic Nucleus Activity In The Nuclear Regions Of The Interacting Galaxy Arp 299, A Alonso-Herrero, Eric S. Perlman
Uncovering The Deeply Embedded Active Galactic Nucleus Activity In The Nuclear Regions Of The Interacting Galaxy Arp 299, A Alonso-Herrero, Eric S. Perlman
Aerospace, Physics, and Space Science Faculty Publications
We present mid-infrared (MIR) 8-13 μm spectroscopy of the nuclear regions of the interacting galaxy Arp 299 (IC 694+NGC 3690) obtained with CanariCam (CC) on the 10.4 m Gran Telescopio Canarias (GTC). The high angular resolution (∼0.″3-0.″6) of the data allows us to probe nuclear physical scales between 60 and 120 pc, which is a factor of 10 improvement over previous MIR spectroscopic observations of this system. The GTC/CC spectroscopy displays evidence of deeply embedded active galactic nucleus (AGN) activity in both nuclei. The GTC/CC nuclear spectrum of NGC 3690/Arp 299-B1 can be explained as emission from AGN-heated dust in …
Direct Observations Of Plasma Upflows And Condensation In A Catastrophically Cooling Solar Transition Region Loop, Norton B. Orange, David L. Chesney, Hakeem M. Oluseyi, Katie Hesterly, M Patel, Patrick Champey
Direct Observations Of Plasma Upflows And Condensation In A Catastrophically Cooling Solar Transition Region Loop, Norton B. Orange, David L. Chesney, Hakeem M. Oluseyi, Katie Hesterly, M Patel, Patrick Champey
Aerospace, Physics, and Space Science Faculty Publications
Minimal observational evidence exists for fast transition region (TR) upflows in the presence of cool loops. Observations of such occurrences challenge notions of standard solar atmospheric heating models as well as their description of bright TR emission. Using the EUV Imaging Spectrometer on boardHinode, we observe fast upflows (vλ −10 km s−1) over multiple TR temperatures (5.8 logT 6.0) at the footpoint sites of a cool loop (logT 6.0). Prior to cool loop energizing, asymmetric flows of + 5 km s−1 and −60 km s−1 are observed at footpoint sites. These flows, speeds, and patterns occur simultaneously with both magnetic …
Non-Potential Fields In The Quiet Sun Network: Extreme-Ultraviolet And Magnetic Footpoint Observations, David L. Chesney, Hakeem M. Oluseyi, Norton B. Orange
Non-Potential Fields In The Quiet Sun Network: Extreme-Ultraviolet And Magnetic Footpoint Observations, David L. Chesney, Hakeem M. Oluseyi, Norton B. Orange
Aerospace, Physics, and Space Science Faculty Publications
The quiet Sun (QS) magnetic network is known to contain dynamics which are indicative of non-potential fields. Non-potential magnetic fields forming “S-shaped” loop arcades can lead to the breakdown of static activity and have only been observed in high temperature X-ray coronal structures—some of which show eruptive behavior. Thus, analysis of this type of atmospheric structuring has been restricted to large-scale coronal fields. Here we provide the first identification of non-potential loop arcades exclusive to the QS supergranulation network. High-resolution Atmospheric Imaging Assembly data from the Solar Dynamics Observatory have allowed for the first observations of fine-scale “S-shaped” loop arcades …
The Role Of Cross-Shock Potential On Pickup Ion Shock Acceleration In The Framework Of Focused Transport Theory, Pingbing Zuo, Ming Zhang, Hamid K. Rassoul
The Role Of Cross-Shock Potential On Pickup Ion Shock Acceleration In The Framework Of Focused Transport Theory, Pingbing Zuo, Ming Zhang, Hamid K. Rassoul
Aerospace, Physics, and Space Science Faculty Publications
The focused transport theory is appropriate to describe the injection and acceleration of low-energy particles at shocks as an extension of diffusive shock acceleration (DSA). In this investigation, we aim to characterize the role of cross-shock potential (CSP) originated in the charge separation across the shock ramp on pickup ion (PUI) acceleration at various types of shocks with a focused transport model. The simulation results of energy spectrum and spatial density distribution for the cases with and without CSP added in the model are compared.With sufficient acceleration time, the focused transport acceleration finally falls into the DSA regime with the …
X-Ray Nuclear Activity In S4g Barred Galaxies: No Link Between Bar Strength And Co-Occurrent Supermassive Black Hole Fueling, Mauricio Cristernas, Trisha Mizusawa
X-Ray Nuclear Activity In S4g Barred Galaxies: No Link Between Bar Strength And Co-Occurrent Supermassive Black Hole Fueling, Mauricio Cristernas, Trisha Mizusawa
Aerospace, Physics, and Space Science Faculty Publications
Stellar bars can lead to gas inflow toward the center of a galaxy and stimulate nuclear star formation. However, there is no compelling evidence on whether they also feed a central supermassive black hole: by measuring the fractions of barred active and inactive galaxies, previous studies have yielded conflicting results. In this paper, we aim to understand the lack of observational evidence for bar-driven active galactic nucleus (AGN) activity by studying a sample of 41 nearby (d < 35 Mpc) barred galaxies from the Spitzer Survey for Stellar Structure in Galaxies. We use Chandra observations to measure nuclear 2–10 keV X-ray luminosities and estimate Eddington ratios, together with Spitzer 3.6 μm imaging to quantify the strength of the stellar bar in two independent ways: (1) from its structure, as traced by its ellipticity and boxiness, and (2) from its gravitational torque Qb, taken as the maximum ratio of the tangential force to the mean background radial force. In this way, rather than discretizing the presence of both stellar bars and nuclear activity, we are able to account for the continuum of bar strengths and degrees of AGN activity. We find nuclear X-ray sources in 31 out of 41 galaxies with median X-ray luminosity and Eddington ratio of LX = 4.3×1038 erg s−1 and Lbol/LEdd = 6.9×10−6, respectively, consistent with low-luminosity AGN activity. Including upper limits for those galaxies without nuclear detections, we find no significant correlation between any of the bar strength indicators and the degree of nuclear activity, irrespective of galaxy luminosity, stellar mass, Hubble type, or bulge size. Strong bars do not favor brighter or more efficient nuclear activity, implying that at least for the low-luminosity regime, supermassive black hole fueling is not closely connected to large-scale features.
Exploring The Variable Sky With Linear. Iii. Classification Of Periodic Light Curves, Lovro Palaversa, Hakeem Oluseyi
Exploring The Variable Sky With Linear. Iii. Classification Of Periodic Light Curves, Lovro Palaversa, Hakeem Oluseyi
Aerospace, Physics, and Space Science Faculty Publications
We describe the construction of a highly reliable sample of ∼7000 optically faint periodic variable stars with light curves obtained by the asteroid survey LINEAR across 10,000 deg2 of the northern sky. The majority of these variables have not been cataloged yet. The sample flux limit is severalmagnitudes fainter than most other wide-angle surveys; the photometric errors range from ∼0.03 mag at r = 15 to ∼0.20 mag at r = 18. Light curves include on average 250 data points, collected over about a decade. Using Sloan Digital Sky Survey (SDSS) based photometric recalibration of the LINEAR data for about …
A Stis Atlas Of Ca Ii Triplet Absorption Line Kinematics In Galactic Nuclei, Daniel P. Batcheldor, David Axon, Monica Valluri, Jocelyn Mandalou, David Merritt
A Stis Atlas Of Ca Ii Triplet Absorption Line Kinematics In Galactic Nuclei, Daniel P. Batcheldor, David Axon, Monica Valluri, Jocelyn Mandalou, David Merritt
Aerospace, Physics, and Space Science Faculty Publications
The relations observed between supermassive black holes and their host galaxies suggest a fundamental link in the processes that cause these two objects to evolve. A more comprehensive understanding of these relations could be gained by increasing the number of supermassive black hole mass (M•) measurements. This can be achieved, in part, by continuing to model the stellar dynamics at the centers of galactic bulges using data of the highest possible spatial resolution. Consequently, we present here an atlas of galaxies in the Space Telescope Imaging Spectrograph (STIS) data archive that may have spectra suitable for new M• estimates. Archived …
Polarimetry And The High-Energy Emission Mechanisms In Quasar Jets: The Case Of Pks 1136-135, Mihai Cara, Eric S. Perlman
Polarimetry And The High-Energy Emission Mechanisms In Quasar Jets: The Case Of Pks 1136-135, Mihai Cara, Eric S. Perlman
Aerospace, Physics, and Space Science Faculty Publications
Since the discovery of kiloparsec-scale X-ray emission from quasar jets, the physical processes responsible for their high-energy emission have been poorly defined. A number of mechanisms are under active debate, including synchrotron radiation, inverse-Comptonized cosmic microwave background (IC/CMB) emission, and other Comptonization processes. In a number of cases, the optical and X-ray emission of jet regions are inked by a single spectral component, and in those, high-resolution multi-band imaging and polarimetry can be combined to yield a powerful diagnostic of jet emission processes. Here we report on deep imaging photometry of the jet of PKS 1136−135 obtained with the Hubble …
Exploring The Variable Sky With Linear. Ii. Halo Structure And Substructure Traced By Rr Lyrae Stars To 30 Kpc, Branimir Sesar, Hakeem Oluseyi
Exploring The Variable Sky With Linear. Ii. Halo Structure And Substructure Traced By Rr Lyrae Stars To 30 Kpc, Branimir Sesar, Hakeem Oluseyi
Aerospace, Physics, and Space Science Faculty Publications
We present a sample of ∼5000 RR Lyrae stars selected from the recalibrated LINEAR data set and detected at heliocentric distances between 5 kpc and 30 kpc over ∼8000 deg2 of sky. The coordinates and light curve properties, such as period and Oosterhoff type, are made publicly available. We analyze in detail the light curve properties and Galactic distribution of the subset of ∼4000 type ab RR Lyrae (RRab) stars, including a search for new halo substructures and the number density distribution as a function of Oosterhoff type. We find evidence for the Oosterhoff dichotomy among field RR Lyrae stars, …
The Impact Of Bars On Disk Breaks As Probed By S⁴G Imaging, Juan Carlos Muñoz-Mateos, Trisha Mizusawa
The Impact Of Bars On Disk Breaks As Probed By S⁴G Imaging, Juan Carlos Muñoz-Mateos, Trisha Mizusawa
Aerospace, Physics, and Space Science Faculty Publications
We have analyzed the radial distribution of old stars in a sample of 218 nearby face-on disks, using deep 3.6μm images from the Spitzer Survey of Stellar Structure in Galaxies. In particular, we have studied the structural properties of those disks with a broken or down-bending profile. We find that, on average, disks with a genuine single-exponential profile have a scale length and a central surface brightness which are intermediate to those of the inner and outer components of a down-bending disk with the same total stellar mass. In the particular case of barred galaxies, the ratio between the break …
70 Da White Dwarfs Identified In Lamost Pilot Survey, J K. Zhao, A L. Luo, Terry D. Oswalt, G Zhao
70 Da White Dwarfs Identified In Lamost Pilot Survey, J K. Zhao, A L. Luo, Terry D. Oswalt, G Zhao
Aerospace, Physics, and Space Science Faculty Publications
We present a spectroscopically identified catalog of 70 DA white dwarfs (WDs) from the LAMOST pilot survey. Thirty-five are found to be new identifications after cross-correlation with the Eisenstein et al. and Villanova catalogs. The effective temperature and gravity of these WDs are estimated by Balmer lines fitting. Most of them are hot WDs. The cooling times and masses of these WDs are estimated by interpolation in theoretical evolution tracks. The peak of the mass distribution is found to be ∼0.6 M⊙, which is consistent with prior work in the literature. The distances of these WDs are estimated using the …
Planet Hunters: A Transiting Circumbinary Planet In A Quadruple Star System, Megan E. Schwamb, William C. Keel
Planet Hunters: A Transiting Circumbinary Planet In A Quadruple Star System, Megan E. Schwamb, William C. Keel
Aerospace, Physics, and Space Science Faculty Publications
We report the discovery and confirmation of a transiting circumbinary planet (PH1b) around KIC 4862625, an eclipsing binary in the Kepler field. The planet was discovered by volunteers searching the first six Quarters of publicly available Kepler data as part of the Planet Hunters citizen science project. Transits of the planet across the larger and brighter of the eclipsing stars are detectable by visual inspection every ∼137 days, with seven transits identified in Quarters 1–11. The physical and orbital parameters of both the host stars and planet were obtained via a photometric-dynamical model, simultaneously fitting both the measured radial velocities …
Tracers Of Chromospheric Structure.I. Ca Ii H&K Emission Distribution Of 13,000 F, G, And K Stars In Sdss Dr7 Spectroscopic Sample, J K. Zhao, Terry D. Oswalt, G Zhao, Q H. Lu, A L. Luo, L Y. Zhang
Tracers Of Chromospheric Structure.I. Ca Ii H&K Emission Distribution Of 13,000 F, G, And K Stars In Sdss Dr7 Spectroscopic Sample, J K. Zhao, Terry D. Oswalt, G Zhao, Q H. Lu, A L. Luo, L Y. Zhang
Aerospace, Physics, and Space Science Faculty Publications
We present chromospheric activity index SHK measurements for over 13,000 F, G, and K disk stars with high signal-to-noise ratio (>60) spectra in the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) spectroscopic sample. A parameter δS is defined as the difference between SHK and a “zero” emission line fitted by several of the most inactive stars. The SHK indices of subgiant stars tend to be much lower than dwarfs, which provide a way to distinguish dwarfs and giants with relatively low-resolution spectra. Cooler stars are generally more active and display a larger scatter than hotter stars. Stars …
Acceleration Of Low-Energy Ions At Parallel Shocks With A Focused Transport Model, Pingbing Zuo, Ming Zhang, Hamid K. Rassoul
Acceleration Of Low-Energy Ions At Parallel Shocks With A Focused Transport Model, Pingbing Zuo, Ming Zhang, Hamid K. Rassoul
Aerospace, Physics, and Space Science Faculty Publications
We present a test particle simulation on the injection and acceleration of low-energy suprathermal particles by parallel shocks with a focused transport model. The focused transport equation contains all necessary physics of shock acceleration, but avoids the limitation of diffusive shock acceleration (DSA) that requires a small pitch angle anisotropy. This simulation verifies that the particles with speeds of a fraction of to a few times the shock speed can indeed be directly injected and accelerated into the DSA regime by parallel shocks. At higher energies starting from a few times the shock speed, the energy spectrum of accelerated particles …
Transport Of Solar Energetic Particles Accelerated By Icme Shocks: Reproducing The Reservoir Phenomenon, Gang Qin, Y Wang, Ming Zhang, Silvia Dalla
Transport Of Solar Energetic Particles Accelerated By Icme Shocks: Reproducing The Reservoir Phenomenon, Gang Qin, Y Wang, Ming Zhang, Silvia Dalla
Aerospace, Physics, and Space Science Faculty Publications
In this work, gradual solar energetic particle (SEP) events observed by multiple spacecraft are investigated with model simulations. Based on a numerical solution of the Fokker-Planck focused transport equation including perpendicular diffusion of particles, we obtained the fluxes of SEPs accelerated by an interplanetary coronal mass ejection driven shock as it propagates outward through the three-dimensional Parker interplanetary magnetic field. The shock is treated as a moving source of energetic particles with an assumed particle distribution function. We look at the time profiles of particle flux as they are observed simultaneously by multiple spacecraft located at different locations. The dependence …
Stochastic Acceleration Of Suprathermal Particles Under Pressure Balance Conditions, Thorsten Antecki, Reinhard Schlickeiser, Ming Zhang
Stochastic Acceleration Of Suprathermal Particles Under Pressure Balance Conditions, Thorsten Antecki, Reinhard Schlickeiser, Ming Zhang
Aerospace, Physics, and Space Science Faculty Publications
The acceleration of suprathermal charged particles in the heliosphere under pressure balance conditions including for the first time the radial spatial particle diffusion and convection in the solar wind is investigated. The physical conditions are derived for which the stationary phase space distribution of suprathermal particles approaches the power-law distribution f ∝ p −5,which is often seen in spacecraft observations. For separable source distributions in momentum and position we analytically solve the stationary particle transport equation for a radially constant solar wind speed V0 and a momentum-independent radial spatial diffusion coefficient. The resulting stationary solution at any position within the …
Galactic Cosmic-Ray Modulation In A Realistic Global Magnetohydrodynamic Heliosphere, Xi Luo, Ming Zhang, Hamid K. Rassoul, Nikolai V. Pogorelov, Jacob Heerikhuisen
Galactic Cosmic-Ray Modulation In A Realistic Global Magnetohydrodynamic Heliosphere, Xi Luo, Ming Zhang, Hamid K. Rassoul, Nikolai V. Pogorelov, Jacob Heerikhuisen
Aerospace, Physics, and Space Science Faculty Publications
To understand the behavior of cosmic-ray modulation seen by the two Voyager spacecraft in the region near the termination shock (TS) and in the heliosheath at a distance of >100 AU, a realistic magnetohydrodynamic global heliosphere model is incorporated into our cosmic-ray transport code, so that the detailed effects of the heliospheric boundaries and their plasma/magnetic geometry can be revealed. A number of simulations of cosmic-ray modulation performed with this code result in the following conclusions. (1) Diffusive shock acceleration by the TS can significantly affect the level of cosmic-ray flux and, in particular, its radial gradient profile in the …
2006 May–July Major Radio Flare Episodes In Cygnus X-3: Spectrotiming Analysis Of The X-Ray Data, K. I. I. Koljonen, M. L. Mccollough, D. C. Hannikainen, R. Droulans
2006 May–July Major Radio Flare Episodes In Cygnus X-3: Spectrotiming Analysis Of The X-Ray Data, K. I. I. Koljonen, M. L. Mccollough, D. C. Hannikainen, R. Droulans
Aerospace, Physics, and Space Science Faculty Publications
We analyse in detail the X-ray data of the microquasar Cygnus X-3 obtained during major radio flaring episodes in 2006 with multiple observatories. The analysis consists of two parts: probing the fast (∼1min) X-ray spectral evolution with principal component analysis followed by subsequent spectral fits to the time-averaged spectra (∼3 ks). Based on the analysis we find that the overall X-ray variability during major flaring episodes can be attributed to two principal components whose evolution based on spectral fits is best reproduced by a hybrid Comptonization component and a bremsstrahlung or saturated thermal Comptonization component. The variability of the thermal …
The 72-H Webt Microvariability Observation Of Blazar S5 0716+714 In 2009, G Bhatta, Stéphane Vennes
The 72-H Webt Microvariability Observation Of Blazar S5 0716+714 In 2009, G Bhatta, Stéphane Vennes
Aerospace, Physics, and Space Science Faculty Publications
Context. The international Whole Earth Blazar Telescope (WEBT) consortium planned and carried out three days of intensive micro-variability observations of S5 0716+714 from February 22, 2009 to February 25, 2009. This object was chosen due to its bright apparent magnitude range, its high declination, and its very large duty cycle for micro-variations. Aims. We report here on the long continuous optical micro-variability light curve of 0716+714 obtained during the multi-site observing campaign during which the Blazar showed almost constant variability over a 0.5 mag range. The resulting light curve is presented here for the first time. Observations from participating observatories …
Modeling The X-Ray Light Curves Of Cygnus X-3 Possible Role Of The Jet, Osmi Vilhu, Diana Carina Hannikainen
Modeling The X-Ray Light Curves Of Cygnus X-3 Possible Role Of The Jet, Osmi Vilhu, Diana Carina Hannikainen
Aerospace, Physics, and Space Science Faculty Publications
Context. We address the physics behind the soft X-ray light curve asymmetries in Cygnus X-3, a well-known microquasar. Aims. Observable eff ects of the jet close to the line-of-sight were investigated and interpreted within the frame of light curve physics. Methods. The path of a hypothetical imprint of the jet, advected by theWolf-Rayet-wind, was computed and its crossing with the line-of-sight during the binary orbit determined. We explored the possibility that physically this “imprint” is a formation of dense clumps triggered by jet bow shocks in the wind (“clumpy trail”). Models for X-ray continuum and emission line light curves were …
Azimuthal Anisotropy Of Π⁰ And Η Mesons In Au + Au Collisions At √Snn=200, Andrew Marshall Adare, Gyöngyi Baksay, László A. Baksay, Marcus Hohlmann
Azimuthal Anisotropy Of Π⁰ And Η Mesons In Au + Au Collisions At √Snn=200, Andrew Marshall Adare, Gyöngyi Baksay, László A. Baksay, Marcus Hohlmann
Aerospace, Physics, and Space Science Faculty Publications
The azimuthal anisotropy coefficients v₂ and v₄ of π⁰ and η mesons are measured in Au + Au collisions at √sNN=200 GeV as a function of transverse momentum pT (1-14 GeV/c) and centrality. The extracted v₂ coefficients are found to be consistent between the two meson species over the measured pT range. The ratio of v₄/v₂² for π⁰ mesons is found to be independent of pT for 1-9 GeV/c, implying a lack of sensitivity of the ratio to the change of underlying physics with pT. Furthermore, the ratio of v₄/v₂² is systematically larger in central collisions, which may reflect the …
Breaks In Thin And Thick Disks Of Edge-On Galaxies Imaged In The Spitzer Survey Of Stellar Structure In Galaxies (S4g), Sébastien Comerón, Trisha Mizusawa
Breaks In Thin And Thick Disks Of Edge-On Galaxies Imaged In The Spitzer Survey Of Stellar Structure In Galaxies (S4g), Sébastien Comerón, Trisha Mizusawa
Aerospace, Physics, and Space Science Faculty Publications
Breaks in the radial luminosity profiles of galaxies have until now been mostly studied averaged over disks. Here, we study separately breaks in thin and thick disks in 70 edge-on galaxies using imaging from the Spitzer Survey of Stellar Structure in Galaxies. We built luminosity profiles of the thin and thick disks parallel to midplanes and we found that thin disks often truncate (77%). Thick disks truncate less often (31%), but when they do, their break radius is comparable with that in the thin disk. This suggests either two different truncation mechanisms—one of dynamical origin affecting both disks simultaneously and …
Exploring The Effects Of Stellar Rotation And Wind Clearing: Debris Disks Around F Stars, Trisha F. Mizusawa, Luisa M. Rebull, John R. Stauffer, Geoffrey Bryden, Michael Meyer, Inseok Song
Exploring The Effects Of Stellar Rotation And Wind Clearing: Debris Disks Around F Stars, Trisha F. Mizusawa, Luisa M. Rebull, John R. Stauffer, Geoffrey Bryden, Michael Meyer, Inseok Song
Aerospace, Physics, and Space Science Faculty Publications
We have conducted a study of debris disks around F stars in order to explore correlations between rotation, stellar winds, and circumstellar disks. We obtained new 24 {mu}m photometry from the Multiband Imaging Photometer for Spitzer (MIPS) camera for a sample of 188 relatively nearby F dwarfs with various rotation rates and optical colors, and combined it with archival MIPS data for 66 more F stars, as well as Wide-field Infrared Survey Explorer data for the entire sample, plus 9 more F stars. Based on the objects' K{sub s} - [24] and [3.4] - [22] colors, we identify 22 stars …
Periodic Structure In The Megaparsec-Scale Jet Of Pks 0637-752, L. E.H. Godfrey, E. S. Perlman
Periodic Structure In The Megaparsec-Scale Jet Of Pks 0637-752, L. E.H. Godfrey, E. S. Perlman
Aerospace, Physics, and Space Science Faculty Publications
We present 18 GHz Australia Telescope Compact Array imaging of the megaparsec-scale quasar jet PKS 0637–752 with angular resolution ~0farcs58. We draw attention to a spectacular train of quasi-periodic knots along the inner 11'' of the jet, with average separation ~1.1 arcsec (7.6 kpc projected). We consider two classes of model to explain the periodic knots: those that involve a static pattern through which the jet plasma travels (e.g., stationary shocks) and those that involve modulation of the jet engine. Interpreting the knots as re-confinement shocks implies the jet kinetic power Q jet ~ 1046 erg s–1, but the constant …
A Method For Localizing Energy Dissipation In Blazars Using Fermi Variability, Amanda Dotson, Markos Georganopoulos, Demosthenes Kazanas, Eric S. Perlman
A Method For Localizing Energy Dissipation In Blazars Using Fermi Variability, Amanda Dotson, Markos Georganopoulos, Demosthenes Kazanas, Eric S. Perlman
Aerospace, Physics, and Space Science Faculty Publications
The distance of a Fermi-detected blazar γ-ray emission site from a supermassive black hole is a matter of active debate. Here we present a method for testing if the GeV emission of powerful blazars is produced within the subparsec-scale broad-line region (BLR) or farther out in the parsec-scale molecular torus (MT) environment If the GeV emission takes place within the BLR, the inverse Compton (IC) scattering of the BLR ultraviolet (UV) seed photons that produces the γ-rays takes place at the onset of the Klein–Nishina regime. This causes the electron cooling time to become practically energy-independent and the variation of …
Self-Consistent Model Of The Interstellar Pickup Protons, Alfvenic Turbulence, And Core Solar Wind In The Outer Heliosphere, Konstantin V. Gamayunov, Ming Zhang, Hamid K. Rassoul, Nikolai V. Pogorelov, Jacob Heerikhuisen
Self-Consistent Model Of The Interstellar Pickup Protons, Alfvenic Turbulence, And Core Solar Wind In The Outer Heliosphere, Konstantin V. Gamayunov, Ming Zhang, Hamid K. Rassoul, Nikolai V. Pogorelov, Jacob Heerikhuisen
Aerospace, Physics, and Space Science Faculty Publications
A self-consistent model of the interstellar pickup protons, the slab component of the Alfvenic turbulence, and core solar wind (SW) protons is presented for r {>=} 1 along with the initial results of and comparison with the Voyager 2 (V2) observations. Two kinetic equations are used for the pickup proton distribution and Alfvenic power spectral density, and a third equation governs SW temperature including source due to the Alfven wave energy dissipation. A fraction of the pickup proton free energy, f{sub D} , which is actually released in the waveform during isotropization, is taken from the quasi-linear consideration without …
Self-Consistent Model Of The Interstellar Pickup Protons, Alfvenic Turbulence, And Core Solar Wind In The Outer Heliosphere, Konstantin V. Gamayunov, Ming Zhang, Nikolai V. Pogorelov, Jacob Heerikhuisen, Hamid K. Rassoul
Self-Consistent Model Of The Interstellar Pickup Protons, Alfvenic Turbulence, And Core Solar Wind In The Outer Heliosphere, Konstantin V. Gamayunov, Ming Zhang, Nikolai V. Pogorelov, Jacob Heerikhuisen, Hamid K. Rassoul
Aerospace, Physics, and Space Science Faculty Publications
A self-consistent model of the interstellar pickup protons, the slab component of the Alfvenic turbulence, and core solar wind (SW) protons is presented for r {>=} 1 along with the initial results of and comparison with the Voyager 2 (V2) observations. Two kinetic equations are used for the pickup proton distribution and Alfvenic power spectral density, and a third equation governs SW temperature including source due to the Alfven wave energy dissipation. A fraction of the pickup proton free energy, f{sub D} , which is actually released in the waveform during isotropization, is taken from the quasi-linear consideration without …
A Theory Of Bimodal Acceleration Of Pickup Ions By Compressive Solar Wind Turbulence Under Pressure Balance, Ming Zhang, Reinhard Schlickeiser
A Theory Of Bimodal Acceleration Of Pickup Ions By Compressive Solar Wind Turbulence Under Pressure Balance, Ming Zhang, Reinhard Schlickeiser
Aerospace, Physics, and Space Science Faculty Publications
Recently, it was demonstrated that stochastic acceleration of particles going through a series of compressive plasma waves can be efficient and fast. It could be too fast so that the pressure built up by the accelerated particles may in turn modify the amplitude of waves to prevent the particles from having an exploding pressure. We call this condition pressure balance. In this paper, we take into account the fact that active acceleration of particles only occupies a limited volume of space due to a possible intermittent nature of plasma waves or turbulence. We develop a bimodal acceleration theory that treats …
A Multi-Wavelength Study Of The Jet, Lobes, And Core Of The Quasar Pks 2101-490, Leith E.H. Godfrey, Eric S. Perlman
A Multi-Wavelength Study Of The Jet, Lobes, And Core Of The Quasar Pks 2101-490, Leith E.H. Godfrey, Eric S. Perlman
Aerospace, Physics, and Space Science Faculty Publications
We present a detailed study of the x-ray, optical, and radio emission from the jet, lobes, and core of the quasar PKS 2101−490 as revealed by new Chandra, Hubble Space Telescope (HST), and ATCA images. We extract the radio to x-ray spectral energy distributions from seven regions of the 13'' jet, and model the jet x-ray emission in terms of Doppler beamed inverse Compton scattering of the cosmic microwave background (IC/CMB) for a jet in a state of equipartition between particle and magnetic field energy densities. This model implies that the jet remains highly relativistic hundreds of kiloparsecs from the …