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Articles 6211 - 6240 of 8865

Full-Text Articles in Astrophysics and Astronomy

Sdss J102347.6+003841: A Millisecond Radio Pulsar Binary That Had A Hot Disk During 2000-2001, Zhongxiang Wang, Anne M. Archibald, John R. Thorstensen, Victoria M. Kaspi Oct 2009

Sdss J102347.6+003841: A Millisecond Radio Pulsar Binary That Had A Hot Disk During 2000-2001, Zhongxiang Wang, Anne M. Archibald, John R. Thorstensen, Victoria M. Kaspi

Dartmouth Scholarship

The Sloan Digital Sky Survey (SDSS) source J102347.6+003841 was recently revealed to be a binary 1.69 ms radio pulsar with a 4.75 hr orbital period and a ~0.2 M ☉ companion. Here, we analyze the SDSS spectrum of the source in detail. The spectrum was taken on 2001 February 1, when the source was in a bright state and showed broad, double-peaked hydrogen and helium lines—dramatically different from the G-type absorption spectrum seen from 2002 May onward. The lines are consistent with emission from a disk around the compact primary. We derive properties of the disk by fitting the SDSS …

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Case Studies Of Imf Driven Auroral Emissions, Ryan James Soldin Oct 2009

Case Studies Of Imf Driven Auroral Emissions, Ryan James Soldin

Master's Theses - Daytona Beach

The topic of solar wind - magnetosphere - ionosphere coupling has become increasingly important in recent years, as it deals with the energy transfer from the Sun to the Earth. The solar wind plasma has direct entry into Earth's ionosphere at the polar cusp. At the cusp Earth's magnetic fields lines are open and connect .directly to the magnetic field lines of the solar wind. The energy from the solar wind particles precipitating into the ionosphere are dissipated as the aurora. The purpose of this thesis was to present case studies of the coupled relationship between the periodic fluctuations in …

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An Aztec 1.1 Mm Survey Of The Goods-N Field - Ii. Multiwavelength Identifications And Redshift Distribution, Edward L. Chapin, Alexandra Pope, Douglas Scott, Itziar Aretxaga, Jason E. Austermann, Ranga Ram Chary, Kristen Coppin, Mark Halpern, David H. Hughes, James D. Lowenthal, Glenn E. Morrison, Thushara A. Perera, Kimberly S. Scott, Grant W. Wilson, Min S. Yun Oct 2009

An Aztec 1.1 Mm Survey Of The Goods-N Field - Ii. Multiwavelength Identifications And Redshift Distribution, Edward L. Chapin, Alexandra Pope, Douglas Scott, Itziar Aretxaga, Jason E. Austermann, Ranga Ram Chary, Kristen Coppin, Mark Halpern, David H. Hughes, James D. Lowenthal, Glenn E. Morrison, Thushara A. Perera, Kimberly S. Scott, Grant W. Wilson, Min S. Yun

Astronomy: Faculty Publications

We present results from a multiwavelength study of 29 sources (false detection probabilities cent) from a survey of the Great Observatories Origins Deep Survey-North (GOODS-N) field at 1.1 mm using the Astronomical Thermal Emission Camera (AzTEC). Comparing with existing 850 μm Submillimetre Common-User Bolometer Array (SCUBA) studies in the field, we examine differences in the source populations selected at the two wavelengths. The AzTEC observations uniformly cover the entire survey field to a 1σ depth of ∼1 mJy. Searching deep 1.4 GHz Very Large Array (VLA) and Spitzer 3-24 μm catalogues, we identify robust counterparts for 21 1.1 mm sources, …

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Lensed Cosmic Microwave Background Constraints On Post-General Relativity Parameters, P. Serra, A. Cooray, S. F. Daniel, R. R. Caldwell, A. Melchiorri Oct 2009

Lensed Cosmic Microwave Background Constraints On Post-General Relativity Parameters, P. Serra, A. Cooray, S. F. Daniel, R. R. Caldwell, A. Melchiorri

Dartmouth Scholarship

No abstract provided.

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Book Review: Finding The Big Bang, T. D. Oswalt Oct 2009

Book Review: Finding The Big Bang, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Finding the Big Bang edited by P. James E. Peebles, Lyman A. Page Jr., and R. Bruce Partridge Cambridge, 2009 571p, 9780521519823 $80.00

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Thermodynamics Of The Quantum Critical Point At Finite Doping In The Two-Dimensional Hubbard Model Studied Via The Dynamical Cluster Approximation, K. Mikelsons, Ehsan Khatami, D. Galanakis, A. Macridin, J. Moreno, M. Jarrell Oct 2009

Thermodynamics Of The Quantum Critical Point At Finite Doping In The Two-Dimensional Hubbard Model Studied Via The Dynamical Cluster Approximation, K. Mikelsons, Ehsan Khatami, D. Galanakis, A. Macridin, J. Moreno, M. Jarrell

Faculty Publications

We study the thermodynamics of the two-dimensional Hubbard model within the dynamical cluster approximation. We use continuous time quantum Monte Carlo as a cluster solver to avoid the systematic error which complicates the calculation of the entropy and potential energy (double occupancy). We find that at a critical filling, there is a pronounced peak in the entropy divided by temperature, S/T, and in the normalized double occupancy as a function of doping. At this filling, we find that specific heat divided by temperature, C/T, increases strongly with decreasing temperature and kinetic and potential energies vary like T2 ln T. These …

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Subcellular Min Oscillations As A Single-Cell Reporter Of The Action Of Polycations Protamine And Gentamicin On Escherichia Coli, Benjamin P.B. Downing, Andrew D. Rutenberg, Ahmed Touhami, Manfred Jericho Sep 2009

Subcellular Min Oscillations As A Single-Cell Reporter Of The Action Of Polycations Protamine And Gentamicin On Escherichia Coli, Benjamin P.B. Downing, Andrew D. Rutenberg, Ahmed Touhami, Manfred Jericho

Physics & Astronomy Faculty Publications

Background: In Escherichia coli, MinD-GFP fusion proteins show rapid pole to pole oscillations. The objective was to investigate the effects of extracellular cations on the subcellular oscillation of cytoplasmic MinD within Escherichia coli. Methodology/Principal Findings: We exposed bacteria to the extracellular cations Ca++, Mg++, the cationic antimicrobial peptide (CAP) protamine, and the cationic aminoglycoside gentamicin. We found rapid and substantial increases in the average MinD oscillation periods in the presence of any of these polyvalent cations. For Ca++ and Mg++ the increases in period were transient, even with a constant extracellular concentration, while increases in period for protamine or gentamicin …

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Advanced Characterization And Simulation Of Sonne: A Fast Neutron Spectrometer For Solar Probe Plus, R S. Woolf, James M. Ryan, Peter F. Bloser, U Bravar, E O. Fluckiger, Jason S. Legere, A L. Mackinnon, Procheta Mallik, Mark L. Mcconnell, B Pirard Sep 2009

Advanced Characterization And Simulation Of Sonne: A Fast Neutron Spectrometer For Solar Probe Plus, R S. Woolf, James M. Ryan, Peter F. Bloser, U Bravar, E O. Fluckiger, Jason S. Legere, A L. Mackinnon, Procheta Mallik, Mark L. Mcconnell, B Pirard

Space Science Center

SONNE, the SOlar NeutroN Experiment proposed for Solar Probe Plus, is designed to measure solar neutrons from 1-20 MeV and solar gammas from 0.5-10 MeV. SONNE is a double scatter instrument that employs imaging to maximize its signal-to-noise ratio by rejecting neutral particles from non-solar directions. Under the assumption of quiescent or episodic small-flare activity, one can constrain the energy content and power dissipation by fast ions in the low corona. Although the spectrum of protons and ions produced by nanoflaring activity is unknown, we estimate the signal in neutrons and γ−rays that would be present within thirty solar radii, …

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First Ligo Search For Gravitational Wave Bursts From Cosmic (Super)Strings, B. P. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, R. S. Amin, S. B. Anderson, W. G. Anderson, M. A. Arain, M. Araya, H. Armandula, P. Armor, Y. Aso, S. Aston, P. Aufmuth, C. Aulbert, S. Babak, P. Baker, S. Ballmer, C. Barker, D. Barker, B. Barr, P. Barriga, L. Barsotti, M. A. Barton, I. Bartos, R. Bassiri, M. Bastarrika, B. Behnke, M. Benacquista Sep 2009

First Ligo Search For Gravitational Wave Bursts From Cosmic (Super)Strings, B. P. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, R. S. Amin, S. B. Anderson, W. G. Anderson, M. A. Arain, M. Araya, H. Armandula, P. Armor, Y. Aso, S. Aston, P. Aufmuth, C. Aulbert, S. Babak, P. Baker, S. Ballmer, C. Barker, D. Barker, B. Barr, P. Barriga, L. Barsotti, M. A. Barton, I. Bartos, R. Bassiri, M. Bastarrika, B. Behnke, M. Benacquista

Faculty Publications

We report on a matched-filter search for gravitational wave bursts from cosmic string cusps using LIGO data from the fourth science run (S4) which took place in February and March 2005. No gravitational waves were detected in 14.9 days of data from times when all three LIGO detectors were operating. We interpret the result in terms of a frequentist upper limit on the rate of gravitational wave bursts and use the limits on the rate to constrain the parameter space (string tension, reconnection probability, and loop sizes) of cosmic string models. Many grand unified theory-scale models (with string tension Gμ/c2≈10-6) …

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An Oosterhoff Analysis Of The Galactic Bulge Field Rr Lyrae Stars: Implications On Their Absolute Magnitudes, Andrea Kunder, Brian Chaboyer Sep 2009

An Oosterhoff Analysis Of The Galactic Bulge Field Rr Lyrae Stars: Implications On Their Absolute Magnitudes, Andrea Kunder, Brian Chaboyer

Dartmouth Scholarship

We present an analysis of the period-V-amplitude plane for RR0 Lyrae stars (fundamental mode pulsators) with "normal" light curves in the bulge using the MACHO bulge fields. Although bulge globular clusters (GCs) have RR Lyraes that divide into two reasonable distinct groups according to the average period of the RR0 Lyraes, there is no evidence of a gap between Oosterhoff I (OoI) and II (OoII) stars in the bulge field star sample. The majority of the bulge RR0 Lyrae field star population have a difference in period compared to the OoI cluster M3 (Δlog P) that is …

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First Ligo Search For Gravitational Wave Bursts From Cosmic (Super)Strings, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, R. Grosso, K. Hayama, H. Lei, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone Sep 2009

First Ligo Search For Gravitational Wave Bursts From Cosmic (Super)Strings, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, R. Grosso, K. Hayama, H. Lei, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone

Physics & Astronomy Faculty Publications

We report on a matched-filter search for gravitational wave bursts from cosmic string cusps using LIGO data from the fourth science run (S4) which took place in February and March 2005. No gravitational waves were detected in 14.9 days of data from times when all three LIGO detectors were operating. We interpret the result in terms of a frequentist upper limit on the rate of gravitational wave bursts and use the limits on the rate to constrain the parameter space (string tension, reconnection probability, and loop sizes) of cosmic string models. Many grand unified theory-scale models (with string tension ��⁢��/��2≈10−6) …

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Dynamics Of Lyman Break Galaxies And Their Host Halos, James D. Lowenthal, David C. Koo, Luc Simard, Eelco Van Kampen Sep 2009

Dynamics Of Lyman Break Galaxies And Their Host Halos, James D. Lowenthal, David C. Koo, Luc Simard, Eelco Van Kampen

Astronomy: Faculty Publications

We present deep two-dimensional spectra of 22 candidate and confirmed Lyman break galaxies (LBGs) at redshifts 2 < z < 4 in the Hubble Deep Field (HDF) obtained at the Keck II telescope. The targets were preferentially selected with spatial extent and/or multiple knot morphologies, and we used slitmasks and individual slits tilted to optimize measurement of any spatially resolved kinematics. Our sample is more than 1 mag fainter and is at higher redshift than the kinematic LBG targets previously studied by others. The median target magnitude was I814 = 25.3, and total exposure times ranged from 10 to 50 ks. We measure redshifts, some new, ranging from z = 0.2072 to z = 4.056, including two interlopers at z < 1, and resulting in a sample of 14 LBGs with a median redshift z = 2.424. The morphologies and kinematics of the close pairs and multiple knot sources in our sample are generally inconsistent with galaxy formation scenarios postulating that LBGs occur only at the bottom of the potential wells of massive host halos; rather, they support "collisional starburst" models with significant …

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Detections Of Water Ice, Hydrocarbons, And 3.3 ΜM Pah In Z ~ 2 Ulirgs, Anna Sajina, Henrik Spoon, Lin Yan, Masatoshi Imanishi, Dario Fadda, Moshe Elitzur Sep 2009

Detections Of Water Ice, Hydrocarbons, And 3.3 ΜM Pah In Z ~ 2 Ulirgs, Anna Sajina, Henrik Spoon, Lin Yan, Masatoshi Imanishi, Dario Fadda, Moshe Elitzur

Physics and Astronomy Faculty Publications

We present the first detections of the 3 μm water ice and 3.4 μm amorphous hydrocarbon (HAC) absorption features in z ~ 2 ULIRGs. These are based on deep rest-frame 2-8 μm Spitzer Infrared Spectrograph spectra of 11 sources selected for their appreciable silicate absorption. The HAC-to-silicate ratio for our z ~ 2 sources is typically higher by a factor of 2-5 than that observed in the Milky Way. This HAC “excess” suggests compact nuclei with steep temperature gradients as opposed to predominantly host obscuration. Beside the above molecular absorption features, we detect the 3.3 μm …

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Simultaneous Multiwavelength Observations Of Markarian 421 During Outburst, P. T. Reynolds, Veritas, Magic Sep 2009

Simultaneous Multiwavelength Observations Of Markarian 421 During Outburst, P. T. Reynolds, Veritas, Magic

Physical Sciences Publications

We report on the results of two coordinated multiwavelength campaigns that focused on the blazar Markarian 421 during its 2006 and 2008 outbursts. These campaigns obtained UV and X-ray data using the XMM-Newton satellite, while the gamma-ray data were obtained utilizing three imaging atmospheric Cerenkov telescopes, the Whipple 10 m telescope and VERITAS, both based in Arizona, as well as the MAGIC telescope, based on La Palma in the Canary Islands. The coordinated effort between the gamma-ray groups allowed for truly simultaneous data in UV/X-ray/gamma-ray wavelengths during a significant portion of the XMM-Newton observations. This simultaneous coverage allowed for a …

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Five Planets And An Independent Confirmation Of Hd 196885ab From Lick Observatory, Debra A. Fischer, Peter Driscoll, Howard Isaacson, Matthew J. Giguere, Geoffrey W. Marcy, Jeff A. Valenti, Jason T. Wright, Gregory W. Henry, John Asher Johnson, Andrew W. Howard, Kathryn M. G. Peek, Chris Mccarthy Sep 2009

Five Planets And An Independent Confirmation Of Hd 196885ab From Lick Observatory, Debra A. Fischer, Peter Driscoll, Howard Isaacson, Matthew J. Giguere, Geoffrey W. Marcy, Jeff A. Valenti, Jason T. Wright, Gregory W. Henry, John Asher Johnson, Andrew W. Howard, Kathryn M. G. Peek, Chris Mccarthy

Information Systems and Engineering Management Research Publications

We present time series Doppler data from Lick Observatory that reveal the presence of long-period planetary companions orbiting nearby stars. The typical eccentricity of these massive planets are greater than the mean eccentricity of known exoplanets. HD 30562b has Msin i = 1.29 MJup, with semimajor axis of 2.3 AU and eccentricity 0.76. The host star has a spectral type F8V and is metal rich. HD 86264b has Msin i = 7.0 MJup, arel = 2.86 AU, an eccentricity e = 0.7 and orbits a metal-rich, F7V star. HD 87883b has Msin i = 1.78 MJup, arel = 3.6 AU, …

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Dissecting Galaxy Formation. I. Comparison Between Pure Dark Matter And Baryonic Models, Emilio Romano-Diaz, Isaac Shlosman, Clayton Heller, Yehuda Hoffman Sep 2009

Dissecting Galaxy Formation. I. Comparison Between Pure Dark Matter And Baryonic Models, Emilio Romano-Diaz, Isaac Shlosman, Clayton Heller, Yehuda Hoffman

Physics & Astronomy: Faculty Publications

We compare assembly of dark matter (DM) halos with and without baryons from identical initial conditions, within the context of cosmological evolution in the ΛCDM WMAP3 Universe (baryons+DM, hereafter BDM model, and pure DM, PDM model). In representative PDM and BDM models, we find that baryons contribute decisively to the evolution of the central region, leading to an isothermal DM cusp, and thereafter to a flat DM density core—the result of heating by dynamical friction of the DM+baryon substructure during a quiescent evolution epoch. This process ablates the cold gas from an embedded disk, cutting the star formation rate by …

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Search For Gravitational Wave Ringdowns From Perturbed Black Holes In Ligo S4 Data, B. P. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, R. S. Amin, S. B. Anderson, W. G. Anderson, M. A. Arain, M. Araya, H. Armandula, P. Armor, Y. Aso, S. Aston, P. Aufmuth, C. Aulbert, S. Babak, P. Baker, S. Ballmer, C. Barker, D. Barker, B. Barr, P. Barriga, L. Barsotti, M. A. Barton, I. Bartos, R. Bassiri, M. Bastarrika, B. Behnke, M. Benacquista, Tiffany Z. Summerscales Sep 2009

Search For Gravitational Wave Ringdowns From Perturbed Black Holes In Ligo S4 Data, B. P. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, R. S. Amin, S. B. Anderson, W. G. Anderson, M. A. Arain, M. Araya, H. Armandula, P. Armor, Y. Aso, S. Aston, P. Aufmuth, C. Aulbert, S. Babak, P. Baker, S. Ballmer, C. Barker, D. Barker, B. Barr, P. Barriga, L. Barsotti, M. A. Barton, I. Bartos, R. Bassiri, M. Bastarrika, B. Behnke, M. Benacquista, Tiffany Z. Summerscales

Faculty Publications

According to general relativity a perturbed black hole will settle to a stationary configuration by the emission of gravitational radiation. Such a perturbation will occur, for example, in the coalescence of a black hole binary, following their inspiral and subsequent merger. At late times the waveform is a superposition of quasinormal modes, which we refer to as the ringdown. The dominant mode is expected to be the fundamental mode, l=m=2. Since this is a well-known waveform, matched filtering can be implemented to search for this signal using LIGO data. We present a search for gravitational waves from black hole ringdowns …

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The 8 Μm Phase Variation Of The Hot Saturn Hd 149026b, Heather Knutson, David Charbonneau, Nicolas B. Cowan, Jonathan J. Fortney, Adam P. Showman, Eric Agol, Gregory W. Henry Sep 2009

The 8 Μm Phase Variation Of The Hot Saturn Hd 149026b, Heather Knutson, David Charbonneau, Nicolas B. Cowan, Jonathan J. Fortney, Adam P. Showman, Eric Agol, Gregory W. Henry

Information Systems and Engineering Management Research Publications

We monitor the star HD 149026 and its Saturn-mass planet at 8.0 μm over slightly more than half an orbit using the Infrared Array Camera on the Spitzer Space Telescope. We find an increase of 0.0227% ± 0.0066% (3.4σ significance) in the combined planet–star flux during this interval. The minimum flux from the planet is 45% ± 19% of the maximum planet flux, corresponding to a difference in brightness temperature of 480 ± 140 K between the two hemispheres. We derive a new secondary eclipse depth of 0.0411% ± 0.0076% in this band, corresponding to a dayside brightness temperature of …

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Synthesis Of Znse/Cds/Znse Nanobarbells Showing Photoinduced Charge Separation, Maria Kirsanova, Alexander Nemchinov, Nishshanka N. Hewa-Kasakarage, Nicholas Schmall, Mikhail Zamkov Sep 2009

Synthesis Of Znse/Cds/Znse Nanobarbells Showing Photoinduced Charge Separation, Maria Kirsanova, Alexander Nemchinov, Nishshanka N. Hewa-Kasakarage, Nicholas Schmall, Mikhail Zamkov

Physics and Astronomy Faculty Publications

We report on it colloidal synthesis of barbell-shaped nanocrystals comprising a type II hetero-junction of ZnSe and US domains and showing compelling evidence of photoinduced charge separation at the interface of ZnSe and US materials. The nanobarbells were fabricated in a two-step procedure by growing ZnSe caps onto polar facets of US nanorods. Under present synthetic conditions, minimal growth of ZnSe shell in the lateral direction and focusing of the barbell length distribution were observed. Formation of epitaxial interfaces between nearly lattice-matched ZnSe and US crystal phases was primarily evidenced by the observation of "spatially indirect" fluorescence and long radiative …

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Using Population Synthesis Of Massive Stars To Study The Interstellar Medium Near Ob Associations, R. Voss, R. Diehl, Dieter H. Hartmann, M. Cerviño, J. S. Vink, G. Meynet, M. Limongi, A. Chieffi Sep 2009

Using Population Synthesis Of Massive Stars To Study The Interstellar Medium Near Ob Associations, R. Voss, R. Diehl, Dieter H. Hartmann, M. Cerviño, J. S. Vink, G. Meynet, M. Limongi, A. Chieffi

Publications

Aims. We study the massive stars in OB associations and their surrounding interstellar medium environment, using a population synthesis code. Methods. We developed a new population synthesis code for groups of massive stars, where we model the emission of different forms of energy and matter from the stars of the association. In particular, the ejection of the two radioactive isotopes 26Al and 60Fe is followed, as well as the emission of hydrogen ionizing photons, and the kinetic energy of the stellar winds and supernova explosions. We investigate various alternative astrophysical inputs and the resulting output sensitivities, especially effects due to …

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No Transition Disk? Infrared Excess, Pah, H-2, And X-Rays From The Weak-Lined T Tauri Star Doar 21, Eric L.N. Jensen, David H. Cohen, M. Gagné Sep 2009

No Transition Disk? Infrared Excess, Pah, H-2, And X-Rays From The Weak-Lined T Tauri Star Doar 21, Eric L.N. Jensen, David H. Cohen, M. Gagné

Physics & Astronomy Faculty Works

As part of a program to understand disk dispersal and the interplay between circumstellar disks and X-ray emission, we present new high-resolution mid-infrared (IR) imaging, high-resolution optical spectroscopy, and Chandra grating X-ray spectroscopy of the weak-lined T Tauri star DoAr 21. DoAr 21 (age < 10(6) yr and mass similar to 2.2M(circle dot) based on evolutionary tracks) is a strong X-ray emitter, with conflicting evidence in the literature about its disk properties. It shows weak but broad H alpha emission (reported here for the first time since the 1950s); polarimetric variability; polycyclic aromatic hydrocarbon (PAH) and H-2 emission; and a strong, spatially resolved 24 mu m excess in archival Spitzer photometry. Gemini sub-arcsecond-resolution 9-18 mu m images show that there is little or no excess mid-IR emission within 100 AU of the star; the excess emission is extended over several arcseconds and is quite asymmetric. The extended emission is bright in the ultraviolet (UV)-excited lambda = 11.3 mu m PAH emission feature. A new high-resolution X-ray grating spectrum from Chandra shows that the stellar X-ray emission is very hard and dominated by continuum emission; it is well fit by a multi-temperature thermal model, typical of hard coronal sources, and shows no evidence of unusually high densities. A flare during the X-ray observation shows a temperature approaching 10(8) K. We argue that the far-UV emission from the transition region is sufficient to excite the observed extended PAH and continuum emission, and that the H-2 emission may be similarly extended and excited. While this extended emission may be a disk in the final stages of clearing, it also could be more akin to a small-scale photodissociation region than a protoplanetary disk, highlighting both the very young ages (<10(6) yr) at which some stars are found without disks and the extreme radiation environment around even late-type pre-main-sequence stars.

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Kinematic And Photometric Evidence For A Bar In Ngc 2683, Stacy S. Mcgaugh Sep 2009

Kinematic And Photometric Evidence For A Bar In Ngc 2683, Stacy S. Mcgaugh

Faculty Scholarship

We present optical long-slit and SparsePak Integral Field Unit emission line spectroscopy along with optical broadband and near-IR images of the edge-on spiral galaxy NGC 2683. We find a multi-valued, figure-of-eight velocity structure in the inner 45″ of the long-slit spectrum and twisted isovelocity contours in the velocity field. We also find, regardless of wavelength, that the galaxy isophotes are boxy. We argue that taken together, these kinematic and photometric features are evidence for the presence of a bar in NGC 2683. We use our data to constrain the orientation and strength of the bar.

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A Search For Periodic Gravitational Waves From Three Recycled Pulsars Using The Auriga Detector, A. Mion, M. J. Benacquista, M. Kramer, P. P.C. Freire, A. Possenti Sep 2009

A Search For Periodic Gravitational Waves From Three Recycled Pulsars Using The Auriga Detector, A. Mion, M. J. Benacquista, M. Kramer, P. P.C. Freire, A. Possenti

Physics & Astronomy Faculty Publications

Aims.We report on a search for continuous gravitational wave emission from three recycled radio pulsars, performed by using the data of the resonant detector AURIGA. Given the spin rate of the selected targets - the isolated pulsar PSR J1939+2134 and the binary pulsars PSR J0024-7204J and PSR J0218+4232 - the expected frequency of the emitted gravitational waves falls in the high sensitivity range of the detector. Methods.The main topic is the method, meaning that the statistical analysis is performed by implementing a slightly modified version of the Feldman and Cousins Unified Approach. Results.By using ephemerides provided by suitable radio observations …

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Search For Gravitational Wave Ringdowns From Perturbed Black Holes In Ligo S4 Data, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, R. Grosso, K. Hayama, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone, Lappoon R. Tang Sep 2009

Search For Gravitational Wave Ringdowns From Perturbed Black Holes In Ligo S4 Data, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, R. Grosso, K. Hayama, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone, Lappoon R. Tang

Physics & Astronomy Faculty Publications

According to general relativity a perturbed black hole will settle to a stationary configuration by the emission of gravitational radiation. Such a perturbation will occur, for example, in the coalescence of a black hole binary, following their inspiral and subsequent merger. At late times the waveform is a superposition of quasinormal modes, which we refer to as the ringdown. The dominant mode is expected to be the fundamental mode, l=m=2. Since this is a well-known waveform, matched filtering can be implemented to search for this signal using LIGO data. We present a search for gravitational waves from black hole ringdowns …

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Stochastic Particle Acceleration In The Lobes Of Giant Radio Galaxies, Stephen O'Sullivan, Brian Reville, Andrew Taylor Sep 2009

Stochastic Particle Acceleration In The Lobes Of Giant Radio Galaxies, Stephen O'Sullivan, Brian Reville, Andrew Taylor

Articles

We investigate the acceleration of particles by Alfv ́en waves via the second-order Fermi process in the lobes of giant radio galaxies. Such sites are candidates for the accelerators of ultra-high-energy cosmic rays (UHECR). We focus on the nearby Fanaroff–Riley type I radio galaxy Centaurus A. This is motivated by the coincidence of its position with the arrival direction of several of the highest energy Auger events. The conditions necessary for consistency with the acceleration time-scales predicted by quasi-linear theory are reviewed. Test particle calculations are performed in fields which guarantee electric fields with no component parallel to the local …

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Detection Of Extended Vhe Gamma Ray Emission From G106.3+2.7 With Veritas, P. T. Reynolds, Et Al Aug 2009

Detection Of Extended Vhe Gamma Ray Emission From G106.3+2.7 With Veritas, P. T. Reynolds, Et Al

Physical Sciences Publications

We report the detection of very-high-energy (VHE) gamma-ray emission from supernova remnant (SNR) G106.3+2.7. Observations performed in 2008 with the VERITAS atmospheric Cherenkov gamma-ray telescope resolve extended emission overlapping the elongated radio SNR. The 7.3σ (pre-trials) detection has a full angular extent of roughly 06 by 04. Most notably, the centroid of the VHE emission is centered near the peak of the coincident 12CO (J = 1-0) emission, 04 away from the pulsar PSR J2229+6114, situated at the northern end of the SNR. Evidently the current-epoch particles from the pulsar wind nebula are not participating in the gamma-ray production. …

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Search For Gravitational Waves From Low Mass Compact Binary Coalescence In 186 Days Of Ligo's Fifth Science Run, B. P. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, R. S. Amin, S. B. Anderson, W. G. Anderson, M. A. Arain, M. Araya, H. Armandula, P. Armor, Y. Aso, S. Aston, P. Aufmuth, C. Aulbert, S. Babak, P. Baker, S. Ballmer, C. Barker, D. Barker, B. Barr, P. Barriga, L. Barsotti, M. A. Barton, I. Bartos, R. Bassiri, M. Bastarrika, B. Behnke, M. Benacquista, Tiffany Z. Summerscales Aug 2009

Search For Gravitational Waves From Low Mass Compact Binary Coalescence In 186 Days Of Ligo's Fifth Science Run, B. P. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, R. S. Amin, S. B. Anderson, W. G. Anderson, M. A. Arain, M. Araya, H. Armandula, P. Armor, Y. Aso, S. Aston, P. Aufmuth, C. Aulbert, S. Babak, P. Baker, S. Ballmer, C. Barker, D. Barker, B. Barr, P. Barriga, L. Barsotti, M. A. Barton, I. Bartos, R. Bassiri, M. Bastarrika, B. Behnke, M. Benacquista, Tiffany Z. Summerscales

Faculty Publications

We report on a search for gravitational waves from coalescing compact binaries, of total mass between 2 and 35M, using LIGO observations between November 14, 2006 and May 18, 2007. No gravitational-wave signals were detected. We report upper limits on the rate of compact binary coalescence as a function of total mass. The LIGO cumulative 90%-confidence rate upper limits of the binary coalescence of neutron stars, black holes and black hole-neutron star systems are 1.4×10-2, 7.3×10-4 and 3.6×10-3yr-1L10-1, respectively, where L10 is 1010 times the blue solar luminosity. © 2009 The American Physical Society.

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From The Big Bang To Fossil Butte: The Cosmic Biography Of An Atom, Shane L. Larson Aug 2009

From The Big Bang To Fossil Butte: The Cosmic Biography Of An Atom, Shane L. Larson

Public Talks

No abstract provided.

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Weibel Instability And Associated Strong Fields In A Fully 3d Simulation Of A Relativistic Shock, K.-I. Nishikawa, J. Niemiec, P. E. Hardee, M. Medvedev, H. Sol, Y. Mizuno, B. Zhang, M. Pohl, M. Oka, Dieter H. Hartmann Aug 2009

Weibel Instability And Associated Strong Fields In A Fully 3d Simulation Of A Relativistic Shock, K.-I. Nishikawa, J. Niemiec, P. E. Hardee, M. Medvedev, H. Sol, Y. Mizuno, B. Zhang, M. Pohl, M. Oka, Dieter H. Hartmann

Publications

Plasma instabilities (e.g., Buneman, Weibel and other two-stream instabilities) excited in collision-less shocks are responsible for particle (electron, positron, and ion) acceleration. Using a new 3-D relativistic particle-in-cell code, we have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. The simulation has been performed using a long simulation system in order to study the nonlinear stages of the Weibel instability, the particle acceleration mechanism, and the shock structure. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic …

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Grape: A Balloon-Borne Gamma-Ray Polarimeter, Mark L. Mcconnell, Chris Bancroft, Peter F. Bloser, Taylor Connor, Jason S. Legere, James M. Ryan Aug 2009

Grape: A Balloon-Borne Gamma-Ray Polarimeter, Mark L. Mcconnell, Chris Bancroft, Peter F. Bloser, Taylor Connor, Jason S. Legere, James M. Ryan

Space Science Center

The Gamma-RAy Polarimeter Experiment (GRAPE) is a concept for an astronomical hard X-ray Compton polarimeter operating in the 50 - 500 keV energy band. The instrument has been optimized for wide-field polarization measurements of transient outbursts from energetic astrophysical objects such as gamma-ray bursts and solar flares. The GRAPE instrument is composed of identical modules, each of which consists of an array of scintillator elements read out by a multi-anode photomultiplier tube (MAPMT). Incident photons Compton scatter in plastic scintillator elements and are subsequently absorbed in inorganic scintillator elements; a net polarization signal is revealed by a characteristic asymmetry in …

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