Einstein@Home All-Sky Search For Periodic Gravitational Waves In Ligo S5 Data,
2013
The University of Texas Rio Grande Valley
Einstein@Home All-Sky Search For Periodic Gravitational Waves In Ligo S5 Data, J. Aasi, J. Abadie, B. P. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Malik Rakhmanov, Volker Quetschke, Joseph D. Romano
Physics & Astronomy Faculty Publications
This paper presents results of an all-sky search for periodic gravitational waves in the frequency range [50,1 190] Hz and with frequency derivative range of ∼[−20,1.1]×10−10 Hz s−1 for the fifth LIGO science run (S5). The search uses a noncoherent Hough-transform method to combine the information from coherent searches on time scales of about one day. Because these searches are very computationally intensive, they have been carried out with the Einstein@Home volunteer distributed computing project. Postprocessing identifies eight candidate signals; deeper follow-up studies rule them out. Hence, since no gravitational wave signals have been found, we report upper limits on …
A Magnetic Confinement Versus Rotation Classification Of Massive-Star Magnetospheres,
2013
Swarthmore College
A Magnetic Confinement Versus Rotation Classification Of Massive-Star Magnetospheres, V. Petit, S. P. Owocki, G. A. Wade, David H. Cohen, J. O. Sundqvist, M. Gagné, J. Maíz Apellániz, M. E. Oksala, D. A. Bohlender, T. Rivinius, H. F. Henrichs, E. Alecian, R. H.D. Townsend, A. Ud-Doula
Physics & Astronomy Faculty Works
Building on results from the Magnetism in Massive Stars (MiMeS) project, this paper shows how a two-parameter classification of massive-star magnetospheres in terms of the magnetic wind confinement (which sets the Alfvén radius RA) and stellar rotation (which sets the Kepler co-rotation radius RK) provides a useful organization of both observational signatures and theoretical predictions. We compile the first comprehensive study of inferred and observed values for relevant stellar and magnetic parameters of 64 confirmed magnetic OB stars with Teff ≳ 16 kK. Using these parameters, we locate the stars in the magnetic confinement–rotation diagram, a log–log plot of RK …
A Report On The X-Ray Properties Of The Τ Sco Class Of Stars.,
2013
East Tennessee State University
A Report On The X-Ray Properties Of The Τ Sco Class Of Stars., Richard Ignace, L. Oskinova, D. Massa
ETSU Faculty Works
An increasing number of OB stars have been shown to possess magnetic fields. Although the sample remains small, it is surprising that the magnetic and X-ray properties of these stars appear to be far less correlated than expected. This contradicts model predictions, which generally indicate that the X-rays from magnetic stars are harder and more luminous than their non-magnetic counterparts. Instead, the X-ray properties of magnetic OB stars are quite diverse. τ Sco is one example where the expectations are better met. This bright main-sequence, early B star has been studied extensively in a variety of wavebands. It has a …
Discovery Of Tev Gamma-Ray Emission From Cta 1 By Veritas,
2013
Cork Institute of Technology
Discovery Of Tev Gamma-Ray Emission From Cta 1 By Veritas, P. T. Reynolds, Et. Al.
Physical Sciences Publications
We report the discovery of TeV gamma-ray emission coincident with the shell-type radio supernova remnant (SNR) CTA 1 using the VERITAS gamma-ray observatory. The source, VER J0006+729, was detected as a 6.5 standard deviation excess over background and shows an extended morphology, approximated by a two-dimensional Gaussian of semimajor (semiminor) axis 0fdg30 (0fdg24) and a centroid 5' from the Fermi gamma-ray pulsar PSR J0007+7303 and its X-ray pulsar wind nebula (PWN). The photon spectrum is well described by a power-law dN/dE = N 0(E/3 TeV)–Γ, with a differential spectral index of Γ = 2.2 ± 0.2stat ± 0.3sys, and normalization …
The Radio And Optical Luminosity Evolution Of Quasars Ii -- The Sdss Sample,
2013
University of Richmond
The Radio And Optical Luminosity Evolution Of Quasars Ii -- The Sdss Sample, Jack Singal, V. Petrosian, L. Stawarz, A. Lawrence
Physics Faculty Publications
We determine the radio and optical luminosity evolutions and the true distribution of the radio-loudness parameter R, defined as the ratio of the radio to optical luminosity, for a set of more than 5000 quasars combining Sloan Digital Sky Survey optical and Faint Images of the Radio Sky at Twenty cm (FIRST) radio data. We apply the method of Efron and Petrosian to access the intrinsic distribution parameters, taking into account the truncations and correlations inherent in the data. We find that the population exhibits strong positive evolution with redshift in both wavebands, with somewhat greater radio evolution than optical. …
Stochastic Acceleration Of Suprathermal Particles Under Pressure Balance Conditions,
2013
Ruhr-Universität Bochum
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,
2013
Florida Institute of Technology
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 …
Spurious Behavior Of Shock-Capturing Methods By The Fractional
Step Approach: Problems Containing Stiff Source Terms And
Discontinuities,
2013
NASA Ames Research Center
Spurious Behavior Of Shock-Capturing Methods By The Fractional Step Approach: Problems Containing Stiff Source Terms And Discontinuities, H.C. Yee, D.V. Kotov, Wei Wang, Chi-Wang Shu
United States National Aeronautics and Space Administration: Publications
The goal of this paper is to relate numerical dissipations that are inherited in high order shock-capturing schemes with the onset of wrong propagation speed of discontinuities. For pointwise evaluation of the source term, previous studies indicated that the phenomenon of wrong propagation speed of discontinuities is connected with the smearing of the discontinuity caused by the discretization of the advection term. The present study focuses only on solving the reactive system by the fractional step method using the Strang splitting. Studies shows that the degree of wrong propagation speed of discontinuities is highly dependent on the accuracy of the …
The Stellar Activity-Rotation Relationship,
2013
Harvard-Smithsonian Center for Astrophysics
The Stellar Activity-Rotation Relationship, Nick J. Wright, Jeremy J. Drake, Eric E. Mamajek, Gregory W. Henry
Information Systems and Engineering Management Research Publications
Using a new catalog of 824 solar and late-type stars with measured X-ray luminosities and rotation periods we have studied the relationship between rotation and stellar activity that is believed to be a probe of the underlying stellar dynamo. Using an unbiased subset of the sample we calculate the power law slope of the unsaturated regime of the activity-rotation relationship as LX/Lbol α Roβ, where β = –2.70 ± 0.13. Notably this is inconsistent with the canonical β = –2 slope to a confidence of 5σ are argues for an interface-type dynamo. Super-saturation is observed for the fastest rotators in …
Retrograde Versus Prograde Models Of Accreting Black Holes,
2013
Kennesaw State University
Retrograde Versus Prograde Models Of Accreting Black Holes, David Garofalo
Faculty Articles
There is a general consensus that magnetic fields, accretion disks, and rotating black holes are instrumental in the generation of the most powerful sources of energy in the known universe. Nonetheless, because magnetized accretion onto rotating black holes involves both the complications of nonlinear magnetohydrodynamics that currently cannot fully be treated numerically, and uncertainties about the origin of magnetic fields that at present are part of the input, the space of possible solutions remains less constrained. Consequently, the literature still bears witness to the proliferation of rather different black hole engine models. But the accumulated wealth of observational data is …
A Soft X-Ray Reverberation Lag In The Agn Eso 113-G010,
2013
Wayne State University
A Soft X-Ray Reverberation Lag In The Agn Eso 113-G010, E. M. Cackett, A. C. Fabian, A. Zogbhi, E. Kara, C. Reynolds, P. Uttley
Physics and Astronomy Faculty Research Publications
Reverberation lags have recently been discovered in a handful of nearby, variable active galactic nuclei (AGNs). Here, we analyze a ~100 ks archival XMM-Newton observation of the highly variable AGN, ESO 113-G010, in order to search for lags between hard, 1.5-4.5 keV, and soft, 0.3-0.9 keV, energy X-ray bands. At the lowest frequencies available in the light curve (lsim 1.5 × 10-4 Hz), we find hard lags where the power-law-dominated hard band lags the soft band (where the reflection fraction is high). However, at higher frequencies in the range (2-3) × 10-4 Hz we find a soft lag …
2006 May–July Major Radio Flare Episodes In Cygnus X-3: Spectrotiming Analysis Of The X-Ray Data,
2013
Aalto University
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 …
Mapping Light Pollution At Utah State University,
2013
Utah State University
Mapping Light Pollution At Utah State University, Rachel Nydegger, Shane L. Larson
Research on the Hill (Salt Lake City)
One of the beauties of modern civilization is seeing the city lighting at night. It provides a feeling of security and is indicative of the power and endeavors of humanity, but over-lighting is a form of pollution. Many outdoor light fixtures spread light in all directions, sending a majority of the light into the sky, away from where we want the light to be on the ground. This light spreading upward is not only wasted light, but it is wasted energy and money, destroys our ability to view the night sky, and has profound effects on nocturnal creatures. The direct …
Investigating The Spectroscopic, Magnetic And Circumstellar Variability Of The O9 Subgiant Star Hd 57682.,
2013
Queens University
Investigating The Spectroscopic, Magnetic And Circumstellar Variability Of The O9 Subgiant Star Hd 57682., J. Grunhut, G. Wade, J. Sundqvist, A. Ud-Doula, C. Neiner, Richard Ignace, W. Marcolino, Th. Rivinius, A. Fullerton, L. Kaper, B. Mauclaire, C. Buil, T. Garrel, J. Ribeiro, S. Ubaud
ETSU Faculty Works
The O9IV star HD 57682, discovered to be magnetic within the context of the Magnetism in Massive Stars (MiMeS) survey in 2009, is one of only eight convincingly detected magnetic O-type stars. Among this select group, it stands out due to its sharp-lined photospheric spectrum. Since its discovery, the MiMeS Collaboration has continued to obtain spectroscopic and magnetic observations in order to refine our knowledge of its magnetic field strength and geometry, rotational period and spectral properties and variability. In this paper we report new Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) spectropolarimetric observations of HD 57682, which …
Search For Gravitational Waves From Binary Black Hole Inspiral Merger And Ringdown In Ligo-Virgo Data From 2009-2010,
2013
The University of Texas Rio Grande Valley
Search For Gravitational Waves From Binary Black Hole Inspiral Merger And Ringdown In Ligo-Virgo Data From 2009-2010, J. Aasi, J. Abadie, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Malik Rakhmanov, Robert Stone, Cristina V. Torres
Physics & Astronomy Faculty Publications
We report a search for gravitational waves from the inspiral, merger and ringdown of binary black holes (BBH) with total mass between 25 and 100 solar masses, in data taken at the LIGO and Virgo observatories between July 7, 2009 and October 20, 2010. The maximum sensitive distance of the detectors over this period for a (20,20)M⊙ coalescence was 300 Mpc. No gravitational wave signals were found. We thus report upper limits on the astrophysical coalescence rates of BBH as a function of the component masses for nonspinning components, and also evaluate the dependence of the search sensitivity on component …
Class Of Ferromagnetic Semiconductors,
2013
University of Kentucky
Class Of Ferromagnetic Semiconductors, Larysa Shlyk, Sergiy A. Kryukov, Lance E. De Long, Barbara Schüpp-Niewa, Rainer Niewa
Physics and Astronomy Faculty Patents
Single crystal and polycrystal oxoruthenates having the generalized compositions (Baz,Sr1−z)FexCoyRu6−(x+y)O11 (1≦(x+y)≦5; 0≦z≦1) and (Ba,Sr)M2±xRu4∓xO11 (M=Fe,Co) belong to a novel class of ferromagnetic semiconductors with applications in spin-based field effect transistors, spin-based light emitting diodes, and magnetic random access memories.
Non-Equilibrium Casimir Force Between Vibrating Plates,
2013
University of Texas Rio Grande Valley
Non-Equilibrium Casimir Force Between Vibrating Plates, Andreas Hanke
Physics & Astronomy Faculty Publications
We study the fluctuation-induced, time-dependent force between two plates confining a correlated fluid which is driven out of equilibrium mechanically by harmonic vibrations of one of the plates. For a purely relaxational dynamics of the fluid we calculate the fluctuation-induced force generated by the vibrating plate on the plate at rest. The time-dependence of this force is characterized by a positive lag time with respect to the driving. We obtain two distinctive contributions to the force, one generated by diffusion of stress in the fluid and another related to resonant dissipation in the cavity. The relation to the dynamic Casimir …
Discovery Of A Magnetic Field In The Rapidly-Rotating O-Type Secondary Of The Colliding-Wind Binary Hd 47129 (Plaskett’S Star).,
2013
Royal Military College of Canada
Discovery Of A Magnetic Field In The Rapidly-Rotating O-Type Secondary Of The Colliding-Wind Binary Hd 47129 (Plaskett’S Star)., J. Grunhut, G. Wade, M. Leutenegger, V. Petit, G. Rauw, C. Neiner, F. Martins, D. Cohen, M. Gagné, Richard Ignace, S. Mathis, S. De Mink, A. Moffat, S. Owocki, M. Shultz, J. Sundqvist, Mimes Collaboration
ETSU Faculty Works
We report the detection of a strong, organized magnetic field in the secondary component of the massive O8III/I+O7.5V/III double-lined spectroscopic binary system HD 47129 (Plaskett's star) in the context of the Magnetism in Massive Stars survey. Eight independent Stokes V observations were acquired using the Echelle SpectroPolarimetric Device for the Observations of Stars (ESPaDOnS) spectropolarimeter at the Canada–France–Hawaii Telescope and the Narval spectropolarimeter at the Télescope Bernard Lyot. Using least-squares deconvolution we obtain definite detections of signal in Stokes V in three observations. No significant signal is detected in the diagnostic null (N) spectra. The Zeeman signatures are broad and …
Rapid Tev Gamma-Ray Flaring Of Bl Lacertae,
2013
Cork Institute of Technology
Rapid Tev Gamma-Ray Flaring Of Bl Lacertae, P. T. Reynolds, Veritas
Physical Sciences Publications
We report on the detection of a very rapid TeV gamma-ray flare from BL Lacertae on 2011 June 28 with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The flaring activity was observed during a 34.6 minute exposure, when the integral flux above 200 GeV reached (3.4 ± 0.6) × 10–6 photons m–2 s–1, roughly 125% of the Crab Nebula flux measured by VERITAS. The light curve indicates that the observations missed the rising phase of the flare but covered a significant portion of the decaying phase. The exponential decay time was determined to be 13 ± 4 minutes, …
Limits On The Stochastic Gravitational Wave Background From The North American Nanohertz Observatory For Gravitational Waves,
2013
The University of Texas Rio Grande Valley
Limits On The Stochastic Gravitational Wave Background From The North American Nanohertz Observatory For Gravitational Waves, P. B. Demorest, R. D. Ferdman, M. E. Gonzalez, D. Nice, S. Ransom, I. H. Stairs, Z. Arzoumanian, A. Brazier, S. Burke-Spolaor, Fredrick Jenet
Physics & Astronomy Faculty Publications
We present an analysis of high-precision pulsar timing data taken as part of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) project. We have observed 17 pulsars for a span of roughly five years using the Green Bank and Arecibo radio telescopes. We analyze these data using standard pulsar timing models, with the addition of time-variable dispersion measure and frequency-variable pulse shape terms. Sub-microsecond timing residuals are obtained in nearly all cases, and the best rms timing residuals in this set are &thk30-50 ns. We present methods for analyzing post-fit timing residuals for the presence of a gravitational wave …
