Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 11 of 11
Full-Text Articles in Physical Sciences and Mathematics
The Emergence Of Negative Superhumps In Cataclysmic Variables: Smoothed Particle Hydrodynamics Simulations, David M. Thomas, Matt A. Wood
The Emergence Of Negative Superhumps In Cataclysmic Variables: Smoothed Particle Hydrodynamics Simulations, David M. Thomas, Matt A. Wood
Aerospace, Physics, and Space Science Faculty Publications
Negative superhumps are believed to arise in cataclysmic variable systems when the accretion disk is tilted with respect to the orbital plane. Slow retrograde precession of the line-of-nodes results in a signal—the negative superhump—with a period slightly less than the orbital period. Previous studies have shown that tilted disks exhibit negative superhumps, but a consensus on how a disk initially tilts has not been reached. Analytical work by Lai (1999, ApJ, 524, 1030) suggests that a magnetic field on the primary can lead to a tilt instability in a disk when the dipole moment is offset in angle from 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 …
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 …
The Kepler Light Curves Of V1504 Cygni And V344 Lyrae: A Study Of The Outburst Properties, John K. Cannizzo, Alan P. Smale, Matt A. Wood, Martin D. Still, Steve B. Howell
The Kepler Light Curves Of V1504 Cygni And V344 Lyrae: A Study Of The Outburst Properties, John K. Cannizzo, Alan P. Smale, Matt A. Wood, Martin D. Still, Steve B. Howell
Aerospace, Physics, and Space Science Faculty Publications
We examine the Kepler light curves of V1504 Cyg and V344 Lyr, encompassing ~736 days at one-minute cadence. During this span each system exhibited ~64–65 outbursts, including 6 superoutbursts. We find that, in both systems, the normal outbursts lying between two superoutbursts increase in duration over time by a factor ~1.2–1.9, and then reset to a small value after the following superoutburst. In both systems the trend of quiescent intervals between normal outbursts is to increase to a local maximum about halfway through the supercycle—the interval from one superoutburst to the next—and then to decrease back to a small value …
The Evolution Of Ultracompact X-Ray Binaries, Lennart M. Van Haaften, Gijs A. Nelemans, Rasmus Voss, Matt A. Wood, Jan Kuijpers
The Evolution Of Ultracompact X-Ray Binaries, Lennart M. Van Haaften, Gijs A. Nelemans, Rasmus Voss, Matt A. Wood, Jan Kuijpers
Aerospace, Physics, and Space Science Faculty Publications
Context. Ultracompact X-ray binaries (UCXBs) typically consist of a white dwarf donor and a neutron star or black hole accretor. The evolution of UCXBs and very low mass ratio binaries in general is poorly understood. In particular, the dynamical behavior of an accretion disk extending to a large radius (relative to the orbit) is unclear. Aims. We investigate the evolution of UCXBs in order to learn for which mass ratios and accretor types these systems can exist, and if they do, what are their orbital and neutron star spin periods, mass transfer rates and evolutionary timescales. Methods. We compute tracks …
Spitzer Mid-Infrared Spectroscopy Of Compact Symmetric Objects: What Powers Radio-Loud Active Galactic Nuclei?, Kyle W. Willett, John T. Stocke, Jeremy K. Darling, Eric S. Perlman
Spitzer Mid-Infrared Spectroscopy Of Compact Symmetric Objects: What Powers Radio-Loud Active Galactic Nuclei?, Kyle W. Willett, John T. Stocke, Jeremy K. Darling, Eric S. Perlman
Aerospace, Physics, and Space Science Faculty Publications
We present low- and high-resolution mid-infrared (mid-IR) spectra and photometry for eight compact symmetric objects (CSOs) taken with the Infrared Spectrograph on the Spitzer Space Telescope. The hosts of these young, powerful radio galaxies show significant diversity in their mid-IR spectra. This includes multiple atomic fine-structure lines, H2 gas, polycyclic aromatic hydrocarbon (PAH) emission, warm dust from T = 50 to150 K, and silicate features in both emission and absorption. There is no evidence in the mid-IR of a single template for CSO hosts, but 5/8 galaxies show similar moderate levels of star formation (<10 M ⊙ yr-1 from PAH emission) and silicate dust in a clumpy torus. The total amount of extinction ranges from AV ∼ 10 to 30, and the high-ionization [Ne V] 14.3 and 24.3 μm transitions are not detected for any galaxy in the sample. Almost all CSOs show contributions both from star formation and active galactic nuclei (AGNs), suggesting that they occupy a continuum between pure starbursts and AGNs. This is consistent with the hypothesis that radio galaxies are created following a galactic merger; the timing of the radio activity onset means that contributions to the IR luminosity from both merger-induced star formation and the central AGN are likely. Bondi accretion is capable of powering the radio jets for almost all CSOs in the sample; the lack of [Ne V] emission suggests an advection-dominated accretion flow mode as a possible candidate. Merging black holes (BHs) with M BH > 108 M ⊙ likely exist …
Sph Simulations Of Direct Impact Accretion In The Ultracompact Am Cvn Binaries, Joshua Dolence, Matt A. Wood, Isaac Silver
Sph Simulations Of Direct Impact Accretion In The Ultracompact Am Cvn Binaries, Joshua Dolence, Matt A. Wood, Isaac Silver
Aerospace, Physics, and Space Science Faculty Publications
The ultracompact binary systems V407 Vul (RX J1914.4+2456) and HM Cnc (RX J0806.3+1527), a two-member subclass of the AM CVn stars, continue to generate interest because they defy unambiguous classification. Three proposed models remain viable at this time, but none of the three are significantly more compelling than the remaining two, and all three can satisfy the observational constraints if parameters in the models are tuned. One of the three proposed models is the direct impact model of Marsh & Steeghs, in which the accretion stream impacts the surface of a rapidly rotating primary white dwarf directly, but at a …
The Physical Origin Of Negative Superhumps In Cataclysmic Variables, Matt A. Wood, Christopher J. Burke
The Physical Origin Of Negative Superhumps In Cataclysmic Variables, Matt A. Wood, Christopher J. Burke
Aerospace, Physics, and Space Science Faculty Publications
It has been suspected for over 20 years that the observed negative superhumps in cataclysmic variables are due to the retrograde precession of a tilted disk. We present new smooth particle hydrodynamics simulation results that demonstrate that the source of the modulation of the luminosity of the light in a negatively superhumping cataclysmic variable is the transit of the bright spot across the face of an accretion disk that is tilted out of the orbital plane. In an untilted disk the bright spot is always located on the outer edge of the disk, and the intrinsic brightness of the accretion …
Further Evidence For Variable Synchrotron Emission In Xte J1118+480 In Outburst, Robert I. Hynes, Edward L. Robinson, Kevin J. Pearson, Dawn M. Gelino, Wei Cui, Yongquan Xue, Matt A. Wood, Todd K. Watson, Don Earl Winget, Isaac M. Silver
Further Evidence For Variable Synchrotron Emission In Xte J1118+480 In Outburst, Robert I. Hynes, Edward L. Robinson, Kevin J. Pearson, Dawn M. Gelino, Wei Cui, Yongquan Xue, Matt A. Wood, Todd K. Watson, Don Earl Winget, Isaac M. Silver
Aerospace, Physics, and Space Science Faculty Publications
We present simultaneous multicolor infrared and optical photometry of the black hole X-ray transient XTE Jill 8+480 during its short 2005 January outburst, supported by simultaneous X-ray observations. The variability is dominated by short timescales, ∼10 s, although a weak superhump also appears to be present in the optical. The optical rapid variations, at least, are well correlated with those in X-rays. Infrared JHKS photometry, as in the previous outburst, exhibits especially large-amplitude variability. The spectral energy distribution (SED) of the variable infrared component can be fitted with a power law of slope α = -0.78 ± 0.07, where Fᵧ …
Dq Herculis In Profile: Whole Earth Telescope Observations And Smoothed Particle Hydrodynamics Simulations Of An Edge-On Cataclysmic Variable System, Matt A. Wood
Aerospace, Physics, and Space Science Faculty Publications
The old nova DQ Herculis was the Whole Earth Telescope Northern Hemisphere target for the 1997 July campaign and was observed on four nights with the SARA 0.9 m telescope during 2003 June. We present updated ephemerides for the eclipse and 71 s timings. The Fourier transform displays power at the presumed white dwarf spin period of 71.0655 s, but no significant power at either 142 or 35.5 s. The mean pulsed light curve is obtained by folding on the orbital period modulus the mean ephemeris of the 71 s period, and from this we calculate an O - C …
Time Series Energy Production In Smoothed Particle Hydrodynamics Accretion Disks: Superhumps In The Am Canum Venaticorum Stars, James C. Simpson, Matt A. Wood
Time Series Energy Production In Smoothed Particle Hydrodynamics Accretion Disks: Superhumps In The Am Canum Venaticorum Stars, James C. Simpson, Matt A. Wood
Aerospace, Physics, and Space Science Faculty Publications
The energy production time series of our purely hydrodynamic accretion disk simulations display remarkable similarities with the observed light curves of dwarf novae superhumps in general and the AM CVn stars in particular. The superhump period excess as a function of mass ratio agrees well with earlier theoretical and numerical results, and the amplitudes and relative phases of the harmonics in the power spectra agree well with the observations. The morphology of the mean pulse profile appears to be a useful predictor of system mass ratio. Our modified smoothed particle hydrodynamics code time symmetrizes the interparticle forces when individual time …