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2009

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Articles 151 - 180 of 245

Full-Text Articles in Astrophysics and Astronomy

Composition And Spectral Properties Of The 1 Au Quiet-Time Superthermal Ion Population During Solar Cycle 23, M. A. Dayeh, M. I. Desai, Joseph R. Dwyer, Hamid K. Rassoul, G. M. Mason, J. E. Mazur Mar 2009

Composition And Spectral Properties Of The 1 Au Quiet-Time Superthermal Ion Population During Solar Cycle 23, M. A. Dayeh, M. I. Desai, Joseph R. Dwyer, Hamid K. Rassoul, G. M. Mason, J. E. Mazur

Aerospace, Physics, and Space Science Faculty Publications

We have surveyed the spectral and compositional properties of suprathermal heavy ions during quiet times from 1995 January 1 to 2007 December 31 using Wind/Energetic Particles: Anisotropy, Composition, and Transport/SupraThermal-through-Energetic Particle Telescope and Advanced Composition Explorer/Ultra-low Energy Isotope Spectrometer at energies between 0.04 and 2.56 MeV nucleon−1. We find the following. (1) Quiet-time Fe/O and C/O abundances are correlated with solar cycle activity, reflecting corresponding values measured in solar energetic particle and interplanetary (IP) shock events during solar maximum, and those measured in the solar wind and corotating interaction regions (CIRs) during solar minimum conditions. (2) The 3He/4He ratio lies …

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Pulsar Timing And Spacetime Curvature, Teviet Creighton, Fredrick A. Jenet, Richard H. Price Mar 2009

Pulsar Timing And Spacetime Curvature, Teviet Creighton, Fredrick A. Jenet, Richard H. Price

Physics & Astronomy Faculty Publications

We analyze the effect of weak field gravitational waves on the timing of pulsars, with particular attention to gauge invariance, that is, to the effects that are independent of the choice of coordinates. We find (1) the Doppler shift cannot be separated into gauge invariant gravitational wave and kinetic contributions; (2) a gauge invariant separation can be made for the time derivative of the Doppler shift in which the gravitational wave contribution is directly related to the Riemann tensor, and the kinetic contribution is that for special relativity; (3) the gaugedependent effects in the Doppler shift play no role in …

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New Precision Orbits Of Bright Double-Lined Spectroscopic Binaries. Iii. Hd 82191, Ω Draconis, And 108 Herculis, Francis C. Fekel, Jocelyn Tomkin, Michael H. Williamson Mar 2009

New Precision Orbits Of Bright Double-Lined Spectroscopic Binaries. Iii. Hd 82191, Ω Draconis, And 108 Herculis, Francis C. Fekel, Jocelyn Tomkin, Michael H. Williamson

Information Systems and Engineering Management Research Publications

We have determined improved spectroscopic orbits for three double-lined binaries, HD 82191 (Am), ω Dra (F5 V), and 108 Her (Am), using radial velocities from the 2.1 m telescope at McDonald Observatory, the coudé feed telescope at Kitt Peak National Observatory, and 2 m telescope at Fairborn Observatory. The orbital periods range from 5.28 to 9.01 days, and all three systems have circular orbits. The new orbital dimensions (a1 sin i and a2 sin i) and minimum masses (m1 sin3 i and m2 sin3 i) have accuracies of 0.2% or better. Our improved results confirm the large minimum masses of …

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Chandra Observations Of Nuclear X-Ray Emission From Low Surface Brightness Galaxies, Stacy S. Mcgaugh Mar 2009

Chandra Observations Of Nuclear X-Ray Emission From Low Surface Brightness Galaxies, Stacy S. Mcgaugh

Faculty Scholarship

We present Chandra detections of X-ray emission from the active galactic nuclei (AGN) in two giant low surface brightness (LSB) galaxies, UGC 2936 and UGC 1455. Their X-ray luminosities are 1.8 × 1042 ergs s -1 and 1.1 × 1040 ergs s-1 respectively. Of the two galaxies, UGC 2936 is radio loud. Together with another LSB galaxy UGC 6614 (XMM-Newton archival data) both appear to lie above the X-ray-radio fundamental plane, and their AGN have black hole masses that are low compared to similar galaxies lying on the correlation. However, the bulges in these galaxies are well developed, and we …

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Quest For Our Origins, Scott Gaudi '91 Mar 2009

Quest For Our Origins, Scott Gaudi '91

Special Lectures

Dr. Scott Gaudi earned his B.S. from Michigan State University, and his M.S. and Ph.D. from the Ohio State University. He was a Hubble Fellow at the Institute for Advanced Study, and a Menzel Fellow at the Harvard-Smithsonian Center for Astrophysics, before joining the faculty in the Department of Astronomy at the Ohio State University in 2006. He was named one of "20 Scientists to Watch in 20 Years" by Discover Magazine in 2000, was named one of Astronomy Magazine's "10 Rising Stars of Astronomy" in 2008, and was recently awarded the Helen B. Warner Prize for "significant contribution to …

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The Transit Light Curve Project. X. A Christmas Transit Of Hd 17156b, Joshua N. Winn, Matthew J. Holman, Gregory W. Henry, Guillermo Torres, Debra A. Fischer, John Asher Johnson, Geoffrey W. Marcy, Avi Shporer, Tsevi Mazeh Mar 2009

The Transit Light Curve Project. X. A Christmas Transit Of Hd 17156b, Joshua N. Winn, Matthew J. Holman, Gregory W. Henry, Guillermo Torres, Debra A. Fischer, John Asher Johnson, Geoffrey W. Marcy, Avi Shporer, Tsevi Mazeh

Information Systems and Engineering Management Research Publications

Photometry is presented of the 2007 December 25 transit of HD 17156b, which has the longest orbital period and highest orbital eccentricity of all the known transiting exoplanets. New measurements of the stellar radial velocity are also presented. All the data are combined and integrated with stellar-evolutionary modeling to derive refined system parameters. The planet's mass and radius are found to be 3.212+0.069−0.082 MJup and 1.023+0.070−0.055 RJup. The corresponding stellar properties are 1.263+0.035−0.047 M☉ and 1.446+0.099−0.067 R☉. The planet is smaller by 1σ than a theoretical solar-composition gas giant with the same mass and equilibrium temperature, a possible indication of …

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Broad Relativistic Iron Emission Line Observed In Sax J1808.4-3658, E. M. Cackett, D. Altamirano, A. Patruno, J. M. Miller, M. Reynolds, M. Linares, R. Wijnands Mar 2009

Broad Relativistic Iron Emission Line Observed In Sax J1808.4-3658, E. M. Cackett, D. Altamirano, A. Patruno, J. M. Miller, M. Reynolds, M. Linares, R. Wijnands

Physics and Astronomy Faculty Research Publications

During the 2008 September-October outburst of the accreting millisecond pulsar SAX J1808.4-3658, the source was observed by both Suzaku and XMM-Newton approximately 1 day apart. Spectral analysis reveals a broad relativistic Fe Kα emission line which is present in both data sets, as has recently been reported for other neutron star low-mass X-ray binaries. The properties of the Fe K line observed during each observation are very similar. From modeling the Fe line, we determine the inner accretion disk radius to be 13.2 ± 2.5 GM c-2. The inner disk radius measured from the Fe K line suggests …

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Blue-Shifted Emission In Cdte/Znse Heterostructured Nanocrystals, Nishshanka N. Hewa-Kasakarage, Nilanka P. Gurusinghe, Mikhail Zamkov Mar 2009

Blue-Shifted Emission In Cdte/Znse Heterostructured Nanocrystals, Nishshanka N. Hewa-Kasakarage, Nilanka P. Gurusinghe, Mikhail Zamkov

Physics and Astronomy Faculty Publications

Properties of colloidal heterostructured nanocrystals are largely determined by the spatial distribution of photogenerated carriers across the junction of semiconductor materials that form the heterostructure. The two known types of carrier distributions are identified based on whether both carriers reside within the same (type I) or opposite (type II) sides of the heterojunction. Here we demonstrate the existence of another type of spatial carrier distribution in heteronanocrystals, which corresponds to the localization of both charges along the material junction. Such localization. pattern was realized in novel CdTe/ZnSe heteronanocrystals, where the expected type I infrared emission was dominated by more intense …

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Long-Term Optical And X-Ray Variability Of The Seyfert Galaxy Markarian 79, E. Breedt, P. Arévalo, I. M. Mchardy, P. Uttley, S. G. Sergeev, T. Minezaki, Y. Yoshii, C. M. Gaskell, E. M. Cackett, K. Horne, S. Koshida Mar 2009

Long-Term Optical And X-Ray Variability Of The Seyfert Galaxy Markarian 79, E. Breedt, P. Arévalo, I. M. Mchardy, P. Uttley, S. G. Sergeev, T. Minezaki, Y. Yoshii, C. M. Gaskell, E. M. Cackett, K. Horne, S. Koshida

Physics and Astronomy Faculty Research Publications

We present the results of concurrent X-ray and optical monitoring of the Seyfert 1 galaxy Mrk 79 over a period of more than 5yr. We find that on short to medium time-scales (days to a few tens of days) the 2-10 keV X-ray and optical u- and V-band fluxes are significantly correlated, with a delay between the bands consistent with 0d. We show that most of these variations may be well reproduced by a model where the short-term optical variations originate from reprocessing of X-rays by an optically thick accretion disc. The optical light curves, however, also display long time-scale …

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Aztec Millimetre Survey Of The Cosmos Field - Ii. Source Count Overdensity And Correlations With Large-Scale Structure, J. E. Austermann, I. Aretxaga, D. H. Hughes, Y. Kang, S. Kim, James D. Lowenthal, T. A. Perera, D. B. Sanders, K. S. Scott, N. Scoville, G. W. Wilson, M. S. Yun Mar 2009

Aztec Millimetre Survey Of The Cosmos Field - Ii. Source Count Overdensity And Correlations With Large-Scale Structure, J. E. Austermann, I. Aretxaga, D. H. Hughes, Y. Kang, S. Kim, James D. Lowenthal, T. A. Perera, D. B. Sanders, K. S. Scott, N. Scoville, G. W. Wilson, M. S. Yun

Astronomy: Faculty Publications

We report an overdensity of bright submillimetre galaxies (SMGs) in the 0.15 deg AzTEC/COSMOS survey and a spatial correlation between the SMGs and the optical-IR galaxy density at z ≲ 1.1. This portion of the COSMOS field shows a ∼3σ overdensity of robust SMG detections when compared to a background, or 'blank-field', population model that is consistent with SMG surveys of fields with no extragalactic bias. The SMG overdensity is most significant in the number of very bright detections (14 sources with measured fluxes S > 6 mJy), which is entirely incompatible with sample variance within our adopted blank-field number densities …

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Orion's Bar: Physical Conditions Across The Definitive H+/H0/H2 Interface, E. W. Pellegrini, J. A. Baldwin, Gary J. Ferland, G. Shaw, S. Heathcote Mar 2009

Orion's Bar: Physical Conditions Across The Definitive H+/H0/H2 Interface, E. W. Pellegrini, J. A. Baldwin, Gary J. Ferland, G. Shaw, S. Heathcote

Physics and Astronomy Faculty Publications

Previous work has shown the Orion Bar to be an interface between ionized and molecular gas, viewed roughly edge-on, which is excited by the light from the Trapezium cluster. Much of the emission from any star-forming region will originate from such interfaces, so the Bar serves as a foundation test of any emission model. Here we combine X-ray, optical, infrared (IR), and radio data sets to derive emission spectra along the transition from H+ to H0 to H2 regions. We then reproduce the spectra of these layers with a simulation that simultaneously accounts for the detailed microphysics …

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Neutrosophic Logic, Wave Mechanics, And Other Stories: Selected Works 2005-2008, Florentin Smarandache, Victor Christianto Mar 2009

Neutrosophic Logic, Wave Mechanics, And Other Stories: Selected Works 2005-2008, Florentin Smarandache, Victor Christianto

Branch Mathematics and Statistics Faculty and Staff Publications

There is beginning for anything; we used to hear that phrase. The same wisdom word applies to us too. What began in 2005 as a short email on some ideas related to interpretation of the Wave Mechanics results in a number of papers and books up to now. Some of these papers can be found in Progress in Physics or elsewhere. It is often recognized that when a mathematician meets a physics-inclined mind then the result is either a series of endless debates or publication. In our story, we prefer to publish rather than perish. Therefore, our purpose with this …

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Discovery Of X-Ray Emission From The Wolf-Rayet Star Wr 142 Of Oxygen Subtype., L. Oskinova, W.-R. Hamann, A. Feldmeier, Richard Ignace, Y.-H. Chu Mar 2009

Discovery Of X-Ray Emission From The Wolf-Rayet Star Wr 142 Of Oxygen Subtype., L. Oskinova, W.-R. Hamann, A. Feldmeier, Richard Ignace, Y.-H. Chu

ETSU Faculty Works

We report the discovery of weak yet hard X-ray emission from the Wolf-Rayet (WR) star WR 142 with the XMM-Newton X-ray telescope. Being of spectral subtype WO2, WR 142 is a massive star in a very advanced evolutionary stage shortly before its explosion as a supernova or gamma-ray burst. This is the first detection of X-ray emission from a WO-type star. We rule out any serendipitous X-ray sources within approximate to 1 '' of WR 142. WR 142 has an X-ray luminosity of L(X) approximate to 7 x 10(30) erg s(-1), which constitutes only less than or similar to 10(-8) …

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Scattering Polarization Due To Light Source Anisotropy Ii. Envelope Of Arbitrary Shape., Richard Ignace, M. Al-Malki, J. Simmons, J. Brown, D. Clarke, J. Carson Mar 2009

Scattering Polarization Due To Light Source Anisotropy Ii. Envelope Of Arbitrary Shape., Richard Ignace, M. Al-Malki, J. Simmons, J. Brown, D. Clarke, J. Carson

ETSU Faculty Works

Aims. We consider the polarization arising from scattering in an envelope illuminated by a central anisotropic source. This work extends the theory introduced in a previous paper (Al-Malki et al. 1999) in which scattering polarization from a spherically symmetric envelope illuminated by an anisotropic point source was considered. Here we generalize to account for the more realistic expectation of a non-spherical envelope shape. Methods. Spherical harmonics are used to describe both the light source anisotropy and the envelope density distribution functions of the scattering particles. This framework demonstrates how the net resultant polarization arises from a superposition of three basic …

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The Contribution Of Halo White Dwarf Binaries To The Laser Interferometer Space Antenna Signal, Ashley J. Ruiter, Krzysztof Belczynski, Matthew Benacquista, Kelly Holley-Bockelmann Mar 2009

The Contribution Of Halo White Dwarf Binaries To The Laser Interferometer Space Antenna Signal, Ashley J. Ruiter, Krzysztof Belczynski, Matthew Benacquista, Kelly Holley-Bockelmann

Physics & Astronomy Faculty Publications

Galactic double white dwarfs were postulated as a source of confusion limited noise for the Laser Interferometer Space Antenna (LISA), the future space-based gravitational wave observatory. Until very recently, the Galactic population consisted of a relatively well-studied disk population, a somewhat studied smaller bulge population and a mostly unknown, but potentially large halo population. It has been argued that the halo population may produce a signal that is much stronger (factor of ∼5 in spectral amplitude) than the disk population. However, this surprising result was not based on an actual calculation of a halo white dwarf population, but was derived …

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All-Sky Ligo Search For Periodic Gravitational Waves In The Early Fifth-Science-Run 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 Mar 2009

All-Sky Ligo Search For Periodic Gravitational Waves In The Early Fifth-Science-Run 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

Physics & Astronomy Faculty Publications

We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50–1100 Hz and with the frequency’s time derivative in the range −5×10−9–0  Hz s−1. Data from the first eight months of the fifth LIGO science run (S5) have been used in this search, which is based on a semicoherent method (PowerFlux) of summing strain power. Observing no evidence of periodic gravitational radiation, we report 95% confidence-level upper limits on radiation emitted by any unknown isolated rotating neutron stars within the search range. Strain limits below 10−24 are obtained over a 200-Hz band, …

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The Dust Cloud Around The White Dwarf G 29-38. Ii. Spectrum From 5 To 40 Μm And Mid-Infrared Photometric Variability, William T. Reach, Ted Von Hippel, Et Al. Mar 2009

The Dust Cloud Around The White Dwarf G 29-38. Ii. Spectrum From 5 To 40 Μm And Mid-Infrared Photometric Variability, William T. Reach, Ted Von Hippel, Et Al.

Publications

We model the mineralogy and distribution of dust around the white dwarf G29-39 using the infrared spectrum from 1 to 35 μm. The spectral model for G29-38 dust combines a wide range of materials based on spectral studies of comets and debris disks. In order of their contribution to the mid-infrared emission, the most abundant minerals around G29-38 are amorphous carbon (λ < 8 μm), amorphous and crystalline silicates (5-40 μm), water ice (10-15 and 23-35 μm), and metal sulfides (18-28 μm). The amorphous C can be equivalently replaced by other materials (like metallic Fe) with featureless infrared spectra. The best-fitting crystalline silicate is Fe-rich pyroxene. In order to absorb enough starlight to power the observed emission, the disk must either be much thinner than the stellar radius (so that it can be heated from above and below) or it must have an opening angle wider than 2°. A "moderately optically thick" torus model fits well if the dust extends inward to 50 times the white dwarf radius, all grains hotter than 1100 K are vaporized, the optical depth from the star through the disk is τ∥ = 5, and the radial density profile ∝r –2.7; the total mass of this model disk is 2 × 1019 g. A physically thin (less than the white dwarf radius) and optically thick disk can contribute to the near-infrared continuum only; such a disk cannot …

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Book Review: Electronic Imaging In Astronomy: Detectors And Instrumentation 2nd Ed., T. D. Oswalt Mar 2009

Book Review: Electronic Imaging In Astronomy: Detectors And Instrumentation 2nd Ed., T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Electronic imaging in astronomy : detectors and instrumentation 2nd ed. by Ian S. McLean, Springer/Praxis, 2008 552p, 9783540765820 $99.00

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Infrared Spectroscopy Of Symbiotic Stars. Vii. Binary Orbit And Long Secondary Period Variability Of Ch Cygni, Kenneth H. Hinkle, Francis C. Fekel, Richard R. Joyce Feb 2009

Infrared Spectroscopy Of Symbiotic Stars. Vii. Binary Orbit And Long Secondary Period Variability Of Ch Cygni, Kenneth H. Hinkle, Francis C. Fekel, Richard R. Joyce

Information Systems and Engineering Management Research Publications

High-dispersion spectroscopic observations are used to refine orbital elements for the symbiotic binary CH Cyg. The current radial velocities, added to a previously published 13 year time series of infrared velocities for the M giant in the CH Cyg symbiotic system, more than double the length of the time series to 29 years. The two previously identified velocity periods are confirmed. The long period, revised to 15.6 ± 0.1 yr, is shown to result from a binary orbit with a 0.7 M☉ white dwarf and 2 M☉ M giant. Mass transfer to the white dwarf is responsible for the symbiotic …

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Constraining The Nfw Potential With Observations And Modeling Of Low Surface Brightness Galaxy Velocity Fields, Stacy S. Mcgaugh, J. Christopher Mihos Feb 2009

Constraining The Nfw Potential With Observations And Modeling Of Low Surface Brightness Galaxy Velocity Fields, Stacy S. Mcgaugh, J. Christopher Mihos

Faculty Scholarship

We model the Navarro-Frenk-White (NFW) potential to determine if, and under what conditions, the NFW halo appears consistent with the observed velocity fields of low surface brightness (LSB) galaxies. We present mock DensePak Integral Field Unit (IFU) velocity fields and rotation curves of axisymmetric and nonaxisymmetric potentials that are well matched to the spatial resolution and velocity range of our sample galaxies. We find that the DensePak IFU can accurately reconstruct the velocity field produced by an axisymmetric NFW potential and that a tilted-ring fitting program can successfully recover the corresponding NFW rotation curve. We also find that nonaxisymmetric potentials …

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In Situ Probes Of The First Galaxies And Reionization: Gamma-Ray Bursts, Matthew Mcquinn, Joshua S. Bloom, Jonathan Grindlay, David Band, S. D. Barthemy, E. Berger, A. Corsi, S. Covino, G. J. Fishman, Steven R. Furlanetto, Neil Gehrels, Dieter H. Hartmann, Chryssa Kouveliotou, A S. Kutyrev, Abraham Loeb, S Harvard Moseley, Tsvi Piran, L Piro, J X. Prochaska, R Salvaterra, P Schady, A M. Soderberg, G Tagliaferri Feb 2009

In Situ Probes Of The First Galaxies And Reionization: Gamma-Ray Bursts, Matthew Mcquinn, Joshua S. Bloom, Jonathan Grindlay, David Band, S. D. Barthemy, E. Berger, A. Corsi, S. Covino, G. J. Fishman, Steven R. Furlanetto, Neil Gehrels, Dieter H. Hartmann, Chryssa Kouveliotou, A S. Kutyrev, Abraham Loeb, S Harvard Moseley, Tsvi Piran, L Piro, J X. Prochaska, R Salvaterra, P Schady, A M. Soderberg, G Tagliaferri

Publications

The first structures in the Universe formed at z > 7, at higher redshift than all currently known galaxies. Since GRBs are brighter than other cosmological sources at high redshift and exhibit simple power-law afterglow spectra that is ideal for absorption studies, they serve as powerful tools for studying the early universe. New facilities planned for the coming decade will be able to obtain a large sample of high-redshift GRBs. Such a sample would constrain the nature of the first stars, galaxies, and the reionization history of the Universe.

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High Order Well-Balanced Schemes And Applications To Non-Equilibrium Flow With Stiff Source Terms, Wei Wang, Chi-Wang Shu, H. C. Yee, Björn Sjögreen Feb 2009

High Order Well-Balanced Schemes And Applications To Non-Equilibrium Flow With Stiff Source Terms, Wei Wang, Chi-Wang Shu, H. C. Yee, Björn Sjögreen

United States National Aeronautics and Space Administration: Publications

The stiffness of the source terms in modeling non-equilibrium ow problems containing finite-rate chemistry or combustion poses additional numerical difficulties beyond that for solving non-reacting flows. A well-balanced scheme, which can preserve certain non-trivial steady state solutions exactly, may help minimize some of these difficulties. In this paper, a simple one dimensional non-equilibrium model with one temperature is considered. We first describe a general strategy to design high order well-balanced finite difference schemes and then study the well-balanced properties of the high order finite difference weighted essentially non-oscillatory (WENO) scheme, modified balanced WENO schemes and various TVD schemes. The advantages …

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Discovery Of A Low-Mass Companion To The Solar-Type Star Tyc 2534-698-1, Stephen R. Kane, Suvrath Mahadevan, William D. Cochran, Rachel A. Street, Sivarani Thirupathi, Gregory W. Henry, Michael H. Williamson Feb 2009

Discovery Of A Low-Mass Companion To The Solar-Type Star Tyc 2534-698-1, Stephen R. Kane, Suvrath Mahadevan, William D. Cochran, Rachel A. Street, Sivarani Thirupathi, Gregory W. Henry, Michael H. Williamson

Information Systems and Engineering Management Research Publications

Brown dwarfs and low-mass stellar companions are interesting objects to study since they occupy the mass region between deuterium and hydrogen burning. We report here the serendipitous discovery of a low-mass companion in an eccentric orbit around a solar-type main-sequence star. The stellar primary, TYC 2534-698-1, is a G2V star that was monitored both spectroscopically and photometrically over the course of several months. Radial velocity observations indicate a minimum mass of 0.037 M☉ and an orbital period of ∼103 days for the companion. Photometry outside of the transit window shows the star to be stable to within ∼6 millimags. The …

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Veritas Observations Of A Very High Energy Gamma-Ray Flare From The Blazar 3c 66a, P. T. Reynolds, Et Al Feb 2009

Veritas Observations Of A Very High Energy Gamma-Ray Flare From The Blazar 3c 66a, P. T. Reynolds, Et Al

Physical Sciences Publications

The intermediate-frequency peaked BL Lacertae (IBL) object 3C 66A is detected during 2007-2008 in VHE (very high energy; E > 100 GeV) γ rays with the VERITAS stereoscopic array of imaging atmospheric Cherenkov telescopes. An excess of 1791 events is detected, corresponding to a significance of 21.2 standard deviations (σ), in these observations (32.8 hr live time). The observed integral flux above 200 GeV is 6% of the Crab Nebula's flux and shows evidence for variability on the timescale of days. The measured energy spectrum is characterized by a soft power law with photon index Γ = 4.1 ± 0.4stat ± …

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The Evolution Of Late-Time Optical Emission From Sn 1979c, Dan Milisavljevic, Robert A. Fesen, Robert P. Kirshner, Peter Challis Feb 2009

The Evolution Of Late-Time Optical Emission From Sn 1979c, Dan Milisavljevic, Robert A. Fesen, Robert P. Kirshner, Peter Challis

Dartmouth Scholarship

Optical spectra of the bright Type II-L supernova SN 1979C obtained in April 2008 with the 6.5 m Multiple Mirror Telescope are compared with archival late-time spectra to follow the evolution of its optical emission over the age range of 11-29 years. We estimate an Hα flux decrease of around 35% from 1993 to 2008 but noticeable increases in the strength of blueshifted emission of forbidden oxygen lines. While the maximum expansion of the broad ~6700 km s–1 Hα emission appears largely unchanged from 1993, we find a significant narrowing of the double-peaked emission profiles in the [O I] …

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Lisa: Seeing The Cosmos In Low Frequency Gravitational Waves, Shane L. Larson Feb 2009

Lisa: Seeing The Cosmos In Low Frequency Gravitational Waves, Shane L. Larson

Colloquia and Seminars

No abstract provided.

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A Deep Xmm-Newton Observation Of The Quasar 3c 287, G. Salvesen, J. M. Miller, E. Cackett, A. Siemiginowska Feb 2009

A Deep Xmm-Newton Observation Of The Quasar 3c 287, G. Salvesen, J. M. Miller, E. Cackett, A. Siemiginowska

Physics and Astronomy Faculty Research Publications

We report on an XMM-Newton observation of the z = 1.055 quasar and Gigahertz Peaked Spectrum (GPS) source 3C 287. Our 62.3 ks observation provides an exceptional X-ray view of a prominent member of this important subclass of active galactic nuclei (AGNs). The X-ray spectra of 3C 287 are consistent with a simple absorbed power law with a spectral index of Γ = 1.72 ± 0.02. Our fits imply a bolometric luminosity of L = 5.8 ± 0.2 × 1045 erg s-1 over the 0.3-10.0 keV band; this gives a mass lower limit of M BH min >= …

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Hd 100453: A Link Between Gas-Rich Protoplanetary Disks And Gas-Poor Debris Disks, K A. Collins, C A. Grady, K Hamaguchi, J P. Wisniewski, Sean D. Brittain, M Sitko, W J. Carpenter, J P. Williams, G S. Mathews, G M. Williger, R Van Boekel, A Carmona, Th. Henning, M E. Van Den Ancker, G Meeus, X P. Chen, R Petre, B E. Woodgate Feb 2009

Hd 100453: A Link Between Gas-Rich Protoplanetary Disks And Gas-Poor Debris Disks, K A. Collins, C A. Grady, K Hamaguchi, J P. Wisniewski, Sean D. Brittain, M Sitko, W J. Carpenter, J P. Williams, G S. Mathews, G M. Williger, R Van Boekel, A Carmona, Th. Henning, M E. Van Den Ancker, G Meeus, X P. Chen, R Petre, B E. Woodgate

Publications

HD 100453 has an IR spectral energy distribution (SED) which can be fit with a power law plus a blackbody. Previous analysis of the SED suggests that the system is a young Herbig Ae star with a gas-rich, flared disk. We reexamine the evolutionary state of the HD 100453 system by refining its age (based on a candidate low-mass companion) and by examining limits on the disk extent, mass accretion rate, and gas content of the disk environment. We confirm that HD 100453B is a common proper motion companion to HD 100453A, with a spectral type of M4.0V-M4.5V, and derive …

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Grb060602b = Swift J1749.4-2807: An Unusual Transiently Accreting Neutron-Star X-Ray Binary, R. Wijnands, E. Rol, E. Cackett, R. L. C. Starling, R. A. Remillard Feb 2009

Grb060602b = Swift J1749.4-2807: An Unusual Transiently Accreting Neutron-Star X-Ray Binary, R. Wijnands, E. Rol, E. Cackett, R. L. C. Starling, R. A. Remillard

Physics and Astronomy Faculty Research Publications

We present an analysis of the Swift Burst Alert Telescope (BAT) and X-ray telescope (XRT) data of GRB060602B, which is most likely an accreting neutron star in a binary system and not a gamma-ray burst. Our analysis shows that the BAT burst spectrum is consistent with a thermonuclear flash (type I X-ray burst) from the surface of an accreting neutron star in a binary system. The X-ray binary nature is further confirmed by the report of a detection of a faint point source at the position of the XRT counterpart of the burst in archival XMM-Newton data approximately six year …

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Fluorescent Excitation Of Balmer Lines In Gaseous Nebulae: Case D, V. Luridiana, S. Simón-Díaz, M. Cerviño, R. M. González Delgado, R. L. Porter, Gary J. Ferland Feb 2009

Fluorescent Excitation Of Balmer Lines In Gaseous Nebulae: Case D, V. Luridiana, S. Simón-Díaz, M. Cerviño, R. M. González Delgado, R. L. Porter, Gary J. Ferland

Physics and Astronomy Faculty Publications

Nonionizing stellar continua are a potential source of photons for continuum pumping in the hydrogen Lyman transitions. In the environments where these transitions are optically thick, de-excitation occurs through higher series lines. As a result, the emitted flux in the affected lines has a fluorescent contribution in addition to the usual recombination one; in particular, Balmer emissivities are systematically enhanced above case B predictions. The effectiveness of such a mechanism in H II regions and the adequacy of photoionization models as a tool to study it are the two main focuses of this work. We find that photoionization models of …

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