Suppression Of Dielectronic Recombination Due To Finite Density Effects,
2013
Western Michigan University
Suppression Of Dielectronic Recombination Due To Finite Density Effects, D. Nikolić, T. W. Gorczyca, K. T. Korista, Gary J. Ferland, N. R. Badnell
Physics and Astronomy Faculty Publications
We have developed a general model for determining density-dependent effective dielectronic recombination (DR) rate coefficients in order to explore finite-density effects on the ionization balance of plasmas. Our model consists of multiplying by a suppression factor those highly-accurate total zero-density DR rate coefficients which have been produced from state-of-the-art theoretical calculations and which have been benchmarked by experiment. The suppression factor is based upon earlier detailed collision-radiative calculations which were made for a wide range of ions at various densities and temperatures, but used a simplified treatment of DR. A general suppression formula is then developed as a function of …
Erratum: 'Improved He I Emissivities In The Case B Approximation',
2013
University of Georgia
Erratum: 'Improved He I Emissivities In The Case B Approximation', R. L. Porter, Gary J. Ferland, P. J. Storey, M. J. Detisch
Physics and Astronomy Faculty Publications
No abstract provided.
Tuning Electronic Structure Via Exipatial Strain In Sr2Iro4 Thin Films,
2013
University of Kentucky
Tuning Electronic Structure Via Exipatial Strain In Sr2Iro4 Thin Films, J. Nichols, Jsaminka Terzic, Emily Geraldine Bittle, Oleksandr B. Korneta, Lance E. De Long, Joseph Brill, Gang Cao, Sung S. Ambrose Seo
Physics and Astronomy Faculty Publications
We have synthesized epitaxial Sr2IrO4 thin-films on various substrates and studied their electronic structure as a function of lattice-strain. Under tensile (compressive) strain, increased (decreased) Ir-O-Ir bond-angle is expected to result in increased (decreased) electronic bandwidth. However, we have observed that the two optical absorption peaks near 0.5 eV and 1.0 eV are shifted to higher (lower) energies under tensile (compressive) strain, indicating that the electronic-correlation energy is also affected by in-plane lattice-strain. The effective tuning of electronic structure under lattice-modification provides an important insight into the physics driven by the coexisting strong spin-orbit coupling and electronic …
A Variability Study Of The Typical Red Supergiant Antares A,
2013
The University of Western Ontario
A Variability Study Of The Typical Red Supergiant Antares A, Teznie J D Pugh
Electronic Thesis and Dissertation Repository
Red giants and red supergiants have long been known to be variable. In the last 40 years many of the features of this variability have been associated with large convective cells. Unfortunately, due to the long timescales of these variations they are not well studied, with the exception of the bright M-class supergiant Betelgeuse (α Orionis, M2 Iab). Betelgeuse has been well studied both observationally and theoretically, and has many features that are well described by models of convection. It was these studies of Betelgeuse that provided the main motivation for this thesis. We ask if the dramatic motions seen …
A Redline Starburst: Co(2-1) Observations Of An Eddington-Limited Galaxy Reveal Star Formation At Its Most Extreme,
2013
McGill University
A Redline Starburst: Co(2-1) Observations Of An Eddington-Limited Galaxy Reveal Star Formation At Its Most Extreme, J. E. Geach, R. C. Hickox, A. M. Diamond-Stanic, M. Krips
Dartmouth Scholarship
We report observations of the CO(2-1) emission of SDSSJ1506+54, a compact (r_e~135pc) starburst galaxy at z=0.6. SDSSJ1506+54 appears to be forming stars close to the limit allowed by stellar radiation pressure feedback models: the measured L_IR/L'_CO 1500 is one of the highest measured for any galaxy. With its compact optical morphology but extended low surface brightness envelope, post-starburst spectral features, high infrared luminosity (L_IR>10^12.5 L_Sun), low gas fraction (M_H2/M_stars~15%), and short gas depletion time (tens of Myr), we speculate that this is a feedback- limited central starburst episode at the conclusion of a major merger. Taken as such, SDSSJ1504+54 …
Using Photometry To Probe The Circumstellar Environment Of Δ Scorpii,
2013
Western University
Using Photometry To Probe The Circumstellar Environment Of Δ Scorpii, Carol E. Jones, Paul A. Wiegert, Christopher Tycner, Gregory W. Henry, Richard P. Cyr, Robbie J. Halonen, Matthew W. Muterspaugh
Information Systems and Engineering Management Research Publications
We acquired Johnson BV photometry of the binary Be disk system δ Scorpii during its 2009, 2010, 2011, and 2012 observing seasons and used it to probe the innermost regions of the disk. We found that several disk building events have occurred during this time, resulting in an overall brightening in the V band and reddening of the system. In addition to these long-term trends, we found cyclical variability in each observing season on timescales between 60 and 100 days. We were able to reproduce the changes in the magnitude and color of δ Sco using our theoretical models and …
Acceleration Of Low-Energy Ions At Parallel Shocks With A Focused Transport Model,
2013
Florida Institute of Technology
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 …
Tracers Of Chromospheric Structure. I. Ca Ii H&K Emission Distribution Of 13,000 F, G, And K Stars In Sdss Dr7 Spectroscopic Sample,
2013
Chinese Academy of Sciences, Beijing
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, T. D. Oswalt, G. Zhao, Q. H. Lu, A. L. Luo, L. Y. Zhang
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 …
Tracers Of Chromospheric Structure. I. Caii H&K Emission Distribution Of 13000 F, G And K Stars In Sdss Dr7 Spectroscopic Sample,
2013
Chinese Academy of Sciences
Tracers Of Chromospheric Structure. I. Caii H&K Emission Distribution Of 13000 F, G And K Stars In Sdss Dr7 Spectroscopic Sample, J. K. Zhao, T. D. Oswalt, G. Zhao, Q. H. Lu, L. Y. Zhang
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 S 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. …
X-Ray Source Variability Study Of The M31 Central Field Using Chandra Hrc-1,
2013
Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße
X-Ray Source Variability Study Of The M31 Central Field Using Chandra Hrc-1, F. Hofmann, W. Pietsch, M. Henze, F. Haberl, R. Sturm, M. Della Valle, Dieter H. Hartmann, D. Hatzidimitriou
Publications
Context. The central field of the Andromeda galaxy (M 31) has been monitored, using the Chandra HRC-I detector (about 0.1-10 keV energy range) from 2006 to 2012 with the main aim to detect X-rays from optical novae. We present a systematic analysis of all X-ray sources found in the 41 nova monitoring observations, along with 23 M 31 central field HRC-I observations available from the Chandra data archive starting in December 1999. Aims. Based on these observations, we studied the X-ray long-term variability of the source population and especially of X-ray binaries in M 31. Methods. We created a catalogue …
The Cluster And Field Galaxy Active Galactic Nucleus Fraction At Z = 1-1.5: Evidence For A Reversal Of The Local Anticorrelation Between Environment And Agn Fraction,
2013
The Ohio State University
The Cluster And Field Galaxy Active Galactic Nucleus Fraction At Z = 1-1.5: Evidence For A Reversal Of The Local Anticorrelation Between Environment And Agn Fraction, Paul Martini, E. D. Miller, M. Brodwin, S. A. Stanford, Anthony H. Gonzalez, M. Bautz, R. C. Hickox
Dartmouth Scholarship
The fraction of cluster galaxies that host luminous active galactic nuclei (AGNs) is an important probe of AGN fueling processes, the cold interstellar medium at the centers of galaxies, and how tightly black holes and galaxies co-evolve. We present a new measurement of the AGN fraction in a sample of 13 clusters of galaxies (M >= 1014 M ⊙) at 1 < z < 1.5 selected from the Spitzer/IRAC Shallow Cluster Survey, as well as the field fraction in the immediate vicinity of these clusters, and combine these data with measurements from the literature to quantify the relative evolution of cluster and field AGN from the present to z ~ 3. We estimate that the cluster AGN fraction at 1 < z < 1.5 is f_A = 3.0^{+2.4}_{-1.4}% for AGNs with a rest-frame, hard X-ray luminosity greater than L X, H >= 1044 erg s-1. This fraction is measured relative to all cluster galaxies more luminous than M^*_{3.6}(z) + 1, where M^*_{3.6}(z) is the absolute magnitude of the break in the galaxy luminosity …
Kelvin-Helmholtz Instability Of The Cme Reconnection Outflow Layer In The Low Corona,
2013
University of Warwick
Kelvin-Helmholtz Instability Of The Cme Reconnection Outflow Layer In The Low Corona, Claire Foullon, Erwin Verwichte, Katariina Nykyri, Markus J. Aschwanden, Iain G. Hannah
Publications
New capabilities for studying the Sun allow us to image for the first time the magnetic Kelvin–Helmholtz (KH) instability developing at the surface of a fast coronal mass ejecta (CME) less than 150 Mm above the solar surface. We conduct a detailed observational investigation of this phenomenon, observed off the east solar limb on 2010 November 3, in the EUV with SDO/AIA. In conjunction with STEREO-B/EUVI, we derive the CME source surface position. We ascertain the timing and early evolution of the CME outflow leading to the instability onset. We perform image and spectral analysis, exploring the CME plasma structuring …
Expanded Iron Uta Spectra—Probing The Thermal Stability Limits In Agn Clouds,
2013
University of Kentucky
Expanded Iron Uta Spectra—Probing The Thermal Stability Limits In Agn Clouds, Gary J. Ferland, R. Kisielius, F. P. Keenan, P. A. M. Van Hoof, V. Jonauskas, Matt L. Lykins, R. L. Porter, R. J. R. Williams
Physics and Astronomy Faculty Publications
The Fe unresolved transition arrays (UTAs) produce prominent features in the ~15-17 Å wavelength range in the spectra of active galactic nuclei (AGNs). Here, we present new calculations of the energies and oscillator strengths of inner-shell lines from Fe XIV, Fe XV, and Fe XVI. These are crucial ions since they are dominant at inflection points in the gas thermal stability curve, and UTA excitation followed by autoionization is an important ionization mechanism for these species. We incorporate these, and data reported in previous papers, into the plasma simulation code Cloudy. This updated physics is subsequently employed to reconsider the …
Simulating Exoplanet Detection Of Kepler Via Monte-Carlo Techniques,
2013
Utah State University
Simulating Exoplanet Detection Of Kepler Via Monte-Carlo Techniques, Manuel Marcano, Mario Yuuji Harper
Mario Yuuji Harper
The Kepler mission was launched in 2009 with the intent to find earth-like planets around other star systems. Since it's launch, the number of known (and suspected) exoplanets have increased substantially from 200 to 3000. With this increase in data now available, we have chosen to model through a monte-carlo simulation, the possibility of being able to see exoplanets in a random part of the sky (using the parameters of the Kepler spacecraft). We show that there is a 0.18 to 0.01 percent chance of being able to detect exoplanets.
A Statistical Analysis Of Electromagnetic Ion Cyclotron (Emic) Waves And Their Correlation To The 11-Year Solar Cycle,
2013
University of New Hampshire - Main Campus
A Statistical Analysis Of Electromagnetic Ion Cyclotron (Emic) Waves And Their Correlation To The 11-Year Solar Cycle, Erik A. Lindgren
Honors Theses and Capstones
This thesis presents a statistical analysis of EMIC waves measured at Halley Research Station from 2008 through 2012. An introduction covering the origin of and theory behind EMIC waves is provided, along with a background covering previous statistical research regarding EMIC waves. Guidelines regarding EMIC wave definition and analysis are described along with examples of how they were used. The data shows an increase in the total number of EMIC waves as well as the number and percentage of EMIC waves with maximum frequency above 1 Hz during the 5-year period. The results suggest that the total number of EMIC …
Discovery Of Fe Kα X-Ray Reverberation Around The Black Holes In Mcg-5-23-16 And Ngc 7314,
2013
University of Maryland
Discovery Of Fe Kα X-Ray Reverberation Around The Black Holes In Mcg-5-23-16 And Ngc 7314, A. Zoghbi, C. Reynolds, E. M. Cackett, G. Miniutti, E. Kara, A. C. Fabian
Physics and Astronomy Faculty Research Publications
Several X-ray observations have recently revealed the presence of reverberation time delays between spectral components in active galactic nuclei. Most of the observed lags are between the power-law Comptonization component, seen directly, and the soft excess produced by reflection in the vicinity of the black hole. NGC 4151 was the first object to show these lags in the iron K band. Here, we report the discovery of reverberation lags in the Fe K band in two other sources: MCG-5-23-16 and NGC 7314. In both objects, the 6-7 keV band, where the Fe Kα line peaks, lags the bands at lower …
The Nature Of The H2-Emitting Gas In The Crab Nebula,
2013
Michigan State University
The Nature Of The H2-Emitting Gas In The Crab Nebula, C. T. Richardson, J. A. Baldwin, Gary J. Ferland, E. D. Loh, C. A. Kuehn, A. C. Fabian, Philippe Salomé
Physics and Astronomy Faculty Publications
Understanding how molecules and dust might have formed within a rapidly expanding young supernova remnant is important because of the obvious application to vigorous supernova activity at very high redshift. In previous papers, we have mapped the Crab nebula (the Crab) in a rotovibrational H2emission line, and then measured the molecular excitation temperature for a few of the brighter H2-emitting knots that we have found to be scattered throughout the Crab's filaments. We found that H2 emission is often quite strong, correlates with optical low-ionization emission lines and has a surprisingly high excitation temperature. Here, …
Application Of The No-Core Symplectic Shell Model To Beryllium And Carbon Isotopes,
2013
Louisiana State University
Application Of The No-Core Symplectic Shell Model To Beryllium And Carbon Isotopes, Mia Cherise Ferriss
Honors Theses
No abstract provided.
Confirmation Of The Nature Of The Absorber In Iras 09104+4109,
2013
Institute of Astronomy, University of Cambridge
Confirmation Of The Nature Of The Absorber In Iras 09104+4109, Chia-Ying Chiang, E. M. Cackett, P. Gandhi, A. C. Fabian
Physics and Astronomy Faculty Research Publications
We present the first long Suzaku observation of the hyperluminous infrared galaxy IRAS 09104+4109 which is dominated by a Type 2 AGN. The infrared to X-ray spectral energy distribution (SED) indicates that the source is an obscured quasar with a Compton-thin absorber. However, the 3σ hard X-ray detection of the source with the BeppoSAX PDS suggested a reflection-dominated, Compton-thick view. The high-energy detection was later found to be possibly contaminated by another Type 2 AGN, NGC 2785, which is only 17 arcmin away. Our new Suzaku observation offers simultaneous soft and hard X-ray coverage and excludes contamination from NGC 2785. …
Revealing The X-Ray Source In Iras 13224-3809 Through Flux-Dependent Reverberation Lags,
2013
Institute of Astronomy, Cambridge
Revealing The X-Ray Source In Iras 13224-3809 Through Flux-Dependent Reverberation Lags, E. Kara, A. C. Fabian, E. M. Cackett, G. Miniutti, P. Uttley
Physics and Astronomy Faculty Research Publications
IRAS 13224-3809 was observed in 2011 for 500 ks with the XMM-Newton observatory. We detect highly significant X-ray lags between soft (0.3-1 keV) and hard (1.2-5 keV) energies. The hard band lags the soft at low frequencies (i.e. hard lag), while the opposite (i.e. soft lag) is observed at high frequencies. In this paper, we study the lag during flaring and quiescent periods. We find that the frequency and absolute amplitude of the soft lag are different during high-flux and low-flux periods. During the low-flux intervals, the soft lag is detected at higher frequencies and with smaller amplitude. Assuming that …
