Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Institution
-
- University of Massachusetts Amherst (21)
- Embry-Riddle Aeronautical University (19)
- University of Texas Rio Grande Valley (14)
- Brigham Young University (12)
- Clemson University (12)
-
- Dartmouth College (11)
- Tennessee State University (10)
- University of Kentucky (7)
- Florida Institute of Technology (6)
- University of New Hampshire (6)
- Munster Technological University (4)
- Selected Works (4)
- University of South Carolina (4)
- Old Dominion University (3)
- SelectedWorks (3)
- Swarthmore College (3)
- Kennesaw State University (2)
- San Jose State University (2)
- Smith College (2)
- Technological University Dublin (2)
- University of Northern Iowa (2)
- University of Tennessee, Knoxville (2)
- Andrews University (1)
- City University of New York (CUNY) (1)
- Claremont Colleges (1)
- East Tennessee State University (1)
- Eastern Illinois University (1)
- Illinois Math and Science Academy (1)
- The University of San Francisco (1)
- University of Arkansas, Fayetteville (1)
- Keyword
-
- White dwarfs (8)
- Spectroscopic binaries (6)
- 1.3 PHYSICAL SCIENCES (4)
- Astronomy (4)
- Pdf (4)
-
- Stars: abundances (4)
- Acoustic (3)
- Astronautics (3)
- Department of physical sciences (3)
- Extinction (3)
- Gamma rays: observations (3)
- Magnetospheric physics (3)
- Science (3)
- Space plasma physics (3)
- Stars: evolution (3)
- Starspots (3)
- Stellar activity (3)
- Supernova remnants (3)
- Technology (3)
- Atomic Processes (2)
- Atomic data (2)
- Circumstellar matter (2)
- Cosmic Rays (2)
- Cosmology (2)
- Diffusion (2)
- Dust (2)
- Emission line (2)
- Galaxies (2)
- Galaxies : formation (2)
- Galaxies: Active (2)
- Publication
-
- Publications (30)
- Astronomy Department Faculty Publication Series (19)
- Physics and Astronomy Faculty Publications and Presentations (14)
- Dartmouth Scholarship (11)
- Information Systems and Engineering Management Research Publications (10)
-
- Faculty Publications (7)
- Physics and Astronomy Faculty Publications (7)
- Aerospace, Physics, and Space Science Faculty Publications (6)
- Space Science Center (6)
- Theses and Dissertations (6)
- Journal of the South Carolina Academy of Science (4)
- John Cannon (3)
- Physical Sciences Publications (3)
- Physics & Astronomy Faculty Works (3)
- Richard Ignace (3)
- Astronomy: Faculty Publications (2)
- Cross Sections (2)
- Faculty and Research Publications (2)
- Todd M. Tripp (2)
- Alejandro Garcia (1)
- All Physics Faculty Publications (1)
- Articles (1)
- Blackrock Castle Observatory Publications (1)
- ETSU Faculty Works (1)
- IMSA Great Minds Program ® (1)
- Journal of the Adventist Theological Society (1)
- Journal of the Arkansas Academy of Science (1)
- Joy Cole Corning Distinguished Leadership Lecture Series (1)
- Masters (1)
- Masters Theses (1)
- Publication Type
Articles 31 - 60 of 160
Full-Text Articles in Physical Sciences and Mathematics
The Correlation Of Lithium And Beryllium In F And G Cluster Dwarf Stars, Ann Merchant Boesgaard, Eric Armengaud, Constantine P. Deliyannis, Alex Stephens, Jeremy R. King
The Correlation Of Lithium And Beryllium In F And G Cluster Dwarf Stars, Ann Merchant Boesgaard, Eric Armengaud, Constantine P. Deliyannis, Alex Stephens, Jeremy R. King
Publications
Although Li has been extensively observed in main-sequence field and cluster stars, there are relatively fewer observations of Be. We have obtained Keck HIRES spectra of 36 late F and early G dwarfs in order to study the Li-Be correlation we found previously in the temperature regime of 5900–6650 K. The sample size for this temperature range with detectable and (usually) depleted Li and Be is now 88, including Li and Be abundances in both cluster and field stars. Therefore we can now investigate the influence of other parameters such as age, temperature, and metallicity on the correlation. The Be …
High-Resolution, Wide-Field Imaging Of The Galactic Center Region At 330 Mhz, Michael E. Nord, T. Joseph W. Lazio, Namir E. Kassim, Scott D. Hyman, Ted W. La Rosa, Crystal L. Brogan, Nebojsa Duric
High-Resolution, Wide-Field Imaging Of The Galactic Center Region At 330 Mhz, Michael E. Nord, T. Joseph W. Lazio, Namir E. Kassim, Scott D. Hyman, Ted W. La Rosa, Crystal L. Brogan, Nebojsa Duric
Faculty and Research Publications
We present a wide-field, subarcminute-resolution VLA image of the Galactic center region at 330 MHz. With a resolution of ~7'' × 12'' and an rms noise of 1.6 mJy beam-1, this image represents a significant increase in resolution and sensitivity over the previously published VLA image at this frequency. The improved sensitivity has more than tripled the census of small-diameter sources in the region, has resulted in the detection of two new nonthermal filaments (NTFs), 18 NTF candidates, and 30 pulsar candidates, reveals previously known extended sources in greater detail, and has resulted in the first detection of …
A Search For Tev Gamma-Ray Emission From High-Peaked Flat-Spectrum Radio Quasars Using The Whipple Air Cerenkov Telescope, P. T. Reynolds, Et. Al.
A Search For Tev Gamma-Ray Emission From High-Peaked Flat-Spectrum Radio Quasars Using The Whipple Air Cerenkov Telescope, P. T. Reynolds, Et. Al.
Physical Sciences Publications
Blazars have traditionally been separated into two broad categories based on their optical emission characteristics. Blazars with faint or no emission lines are referred to as BL Lacertae objects (BL Lacs), and blazars with prominent, broad emission lines are commonly referred to as flat-spectrum radio quasars (FSRQs). The spectral energy distribution of FSRQs has generally been thought of as being more akin to the low-peaked BL Lacs, which exhibit a peak in the infrared region of the spectrum, as opposed to high-peaked BL Lacs (HBLs), which exhibit a peak in UV/X-ray region of the spectrum. All blazars that are currently …
Photometric Identification Of Cool White Dwarfs, M. Kilic, D. E. Winget, Ted Von Hippel, C. F. Claver
Photometric Identification Of Cool White Dwarfs, M. Kilic, D. E. Winget, Ted Von Hippel, C. F. Claver
Publications
We investigate the use of a narrowband DDO51 filter for photometric identification of cool white dwarfs. We report photometric observations of 30 known cool white dwarfs with temperatures ranging from 10,000 K down to very cool temperatures (3500 K). Follow-up spectroscopic observations of a sample of objects selected using this filter and our photometric observations show that DDO51 filter photometry can help select cool white dwarf candidates for follow-up multiobject spectroscopy by rejecting 65% of main-sequence stars with the same broadband colors as the cool white dwarfs. This technique is not selective enough to efficiently feed single-object spectrographs. We present …
Optically Thick Clumps – Not The Solution To The Wolf-Rayet Wind Momentum Problem?, J. Brown, J. Cassinelli, Q. Li, A. Kholtygin, Richard Ignace
Optically Thick Clumps – Not The Solution To The Wolf-Rayet Wind Momentum Problem?, J. Brown, J. Cassinelli, Q. Li, A. Kholtygin, Richard Ignace
ETSU Faculty Works
The hot star wind momentum problem eta = M-upsiloninfinity/(L/c) much greater than 1 is revisited, and it is shown that the conventional belief, that it can be solved by a combination of clumping of the wind and multiple scattering of photons, is not self-consistent for optically thick clumps. Clumping does reduce the mass loss rate. M, and hence the momentum supply, required to generate a specified radio emission measure epsilon, while multiple scattering increases the delivery of momentum from a specified stellar luminosity L. However, in the case of thick clumps, when combined the two effects act in opposition rather …
Optically Thick Clumps – Not The Solution To The Wolf-Rayet Wind Momentum Problem?, J. C. Brown, J. P. Cassinelli, Q. Li, A. F. Kholtygin, R. Ignace
Optically Thick Clumps – Not The Solution To The Wolf-Rayet Wind Momentum Problem?, J. C. Brown, J. P. Cassinelli, Q. Li, A. F. Kholtygin, R. Ignace
Richard Ignace
The hot star wind momentum problem eta = M-upsiloninfinity/(L/c) much greater than 1 is revisited, and it is shown that the conventional belief, that it can be solved by a combination of clumping of the wind and multiple scattering of photons, is not self-consistent for optically thick clumps. Clumping does reduce the mass loss rate. M, and hence the momentum supply, required to generate a specified radio emission measure epsilon, while multiple scattering increases the delivery of momentum from a specified stellar luminosity L. However, in the case of thick clumps, when combined the two effects act in opposition rather …
Single-Sided Czt Strip Detectors, John R. Macri, B Donmez, Mark Widholm, L A. Hamel, Manuel Julien, T Narita, James M. Ryan, Mark L. Mcconnell
Single-Sided Czt Strip Detectors, John R. Macri, B Donmez, Mark Widholm, L A. Hamel, Manuel Julien, T Narita, James M. Ryan, Mark L. Mcconnell
Space Science Center
We report progress in the study of thick CZT strip detectors for 3-d imaging and spectroscopy and discuss two approaches to device design. We present the spectroscopic, imaging, detection efficiency and response uniformity performance of prototype devices. Unlike double-sided strip detectors, these devices feature both row and column contacts implemented on the anode surface. This electron-only approach circumvents problems associated with poor hole transport in CZT that normally limit the thickness and energy range of double-sided strip detectors. These devices can achieve similar performance to pixel detectors. The work includes laboratory and simulation studies aimed at developing compact, efficient, detector …
Kinematics Of X‐Ray–Emitting Components In Cassiopeia A, Tracey Delaney, Lawrence Rudnick, Robert A. Fesen, T. W. Jones
Kinematics Of X‐Ray–Emitting Components In Cassiopeia A, Tracey Delaney, Lawrence Rudnick, Robert A. Fesen, T. W. Jones
Dartmouth Scholarship
We present high-resolution X-ray proper-motion measurements of Cassiopeia A using Chandra X-Ray Observatory observations from 2000 and 2002. We separate the emission into four spectrally distinct classes: Si-dominated, Fe-dominated, low-energy-enhanced, and continuum-dominated. These classes also represent distinct spatial and kinematic components. The Si- and Fe-dominated classes are ejecta and have a mean expansion rate of 0.2% yr-1. This is the same as for the forward shock filaments but less than the 0.3% yr-1 characteristic of optical ejecta. The low-energy-enhanced spectral class possibly illuminates a clumpy circumstellar component and has a mean expansion rate of 0.05% yr-1. The continuum-dominated emission likely …
Dirac-Fock Energy Levels And Transition Probabilities For Oxygen-Like Fe Xix, V. Jonauskas, F. P. Keenan, M. E. Foord, R. F. Heeter, S. J. Rose, Gary J. Ferland, R. Kisielius, Peter A. M. Van Hoof, P. H. Norrington
Dirac-Fock Energy Levels And Transition Probabilities For Oxygen-Like Fe Xix, V. Jonauskas, F. P. Keenan, M. E. Foord, R. F. Heeter, S. J. Rose, Gary J. Ferland, R. Kisielius, Peter A. M. Van Hoof, P. H. Norrington
Physics and Astronomy Faculty Publications
Multiconfigurational Dirac-Fock calculations are reported for 656 energy levels and the 214 840 electric dipole (E1), electric quadrupole (E2) and magnetic dipole (M1) transition probabilities in oxygen-like FeXIX. The spectroscopic notations as well as the total transition probabilities from each energy level are provided. Good agreement is found with data compiled by NIST.
Redefining The Empirical Zz Ceti Instability Strip, Anjum S. Mukadam, Ted Von Hippel, Et Al.
Redefining The Empirical Zz Ceti Instability Strip, Anjum S. Mukadam, Ted Von Hippel, Et Al.
Publications
We use the new ZZ Ceti stars (hydrogen-atmosphere white dwarf variables; DAVs) discovered within the Sloan Digital Sky Survey (Mukadam et al. 2004) to redefine the empirical ZZ Ceti instability strip. This is the first time since the discovery of white dwarf variables in 1968 that we have a homogeneous set of spectra acquired using the same instrument on the same telescope, and with consistent data reductions, for a statistically significant sample of ZZ Ceti stars. The homogeneity of the spectra reduces the scatter in the spectroscopic temperatures, and we find a narrow instability strip of width ~950 K, from …
Spin Mass Of An Electron Liquid, Zhixin Qian, Giovanni Vignale, D C. Marinescu
Spin Mass Of An Electron Liquid, Zhixin Qian, Giovanni Vignale, D C. Marinescu
Publications
We show that in order to calculate correctly the spin current carried by a quasiparticle in an electron liquid one must use an effective ‘‘spin mass’’ ms that is larger than both the band mass mb, which determines the charge current, and the quasiparticle effective mass m, which determines the heat capacity. We present two independent estimates of the spin mass enhancement, ms=mb, in two- and three-dimensional electron liquids, based on (i) previously calculated values of the Landau parameters and (ii) a recent theory of the dynamical local field factor in the spin channel. Both methods yield a significant spin …
Book Review: Sky Vistas: Astronomy For Binoculars And Richestfield Telescopes, T. D. Oswalt
Book Review: Sky Vistas: Astronomy For Binoculars And Richestfield Telescopes, T. D. Oswalt
Publications
This document is Dr. Oswalt’s review of Sky Vistas : Astronomy for Binoculars and Richestfield Telescopes by Craig Crossen and Gerald Rhemann Springer, 2004 279p, 3211008519 $69.95
Is The Initial Mass Function Of Low Surface Brightness Galaxies Dominated By Low-Mass Stars?, Hyun Chul Lee, Brad K. Gibson, Chris Flynn, Daisuke Kawata, Michael A. Beasley
Is The Initial Mass Function Of Low Surface Brightness Galaxies Dominated By Low-Mass Stars?, Hyun Chul Lee, Brad K. Gibson, Chris Flynn, Daisuke Kawata, Michael A. Beasley
Physics and Astronomy Faculty Publications and Presentations
The rotation curves of low surface brightness (LSB) galaxies suggest that they possess significantly higher mass-to-light (M/L) ratios than their high surface brightness counterparts, indicating that LSB galaxies may be dark matter dominated. This interpretation is hampered by the difficulty of disentangling the disc and dark halo contributions from the disc dynamics of LSB galaxies. Recently, Fuchs has attempted such a disentanglement using spiral arm density wave and swing amplification theory, allowing an independent measurement of the disc mass; this work suggests that LSB discs are significantly more massive than previously believed. This would considerably reduce the amount of matter …
Mechanical Properties Of Carbon Nanotubes Composites, David Hui, Mircea Chipara, Jagannathan Sankar, K. T. Lau
Mechanical Properties Of Carbon Nanotubes Composites, David Hui, Mircea Chipara, Jagannathan Sankar, K. T. Lau
Physics and Astronomy Faculty Publications and Presentations
A critical review of theoretical models aiming to explain the physical properties of composites based on polymeric matrices reinforced with carbon nanotubes is presented. Attention is paid to descriptions based on molecular dynamics, continuum mechanics, and finite element analysis. It is shown that both the continuum mechanics approximation and the finite size element analyses fail to describe composites with very thin interfaces, while the performances of molecular dynamics simulations are still restricted by computer's performances. The limitations of the continuum mechanics approximation are analyzed in detail.
Sb9: The Ninth Catalogue Of Spectroscopic Binary Orbits, Dimitri Pourbaix, Andrei A. Tokovinin, Alan H. Batten, Francis C. Fekel, William I. Hartkopf, Hugo Levato, Nidia I. Morrell, Guillermo Torres, Stephane Udry
Sb9: The Ninth Catalogue Of Spectroscopic Binary Orbits, Dimitri Pourbaix, Andrei A. Tokovinin, Alan H. Batten, Francis C. Fekel, William I. Hartkopf, Hugo Levato, Nidia I. Morrell, Guillermo Torres, Stephane Udry
Information Systems and Engineering Management Research Publications
The Ninth Catalogue of Spectroscopic Binary Orbits (http://sb9.astro.ulb.ac.be) continues the series of compilations of spectroscopic orbits carried out over the past 35 years by Batten and collaborators. As of 2004 May 1st, the new Catalogue holds orbits for 2386 systems. Some essential differences between this catalogue and its predecessors are outlined and three straightforward applications are presented: (1) completeness assessment: period distribution of SB1s and SB2s; (2) shortest periods across the H-R diagram; (3) period-eccentricity relation.
The Oxford-Dartmouth Thirty Degree Survey - I. Observations And Calibration Of A Wide-Field Multiband Survey, Emily C. Macdonald, Paul Allen, Gavin Dalton, Leonidas A. Moustakas, Catherine Heymans, Edward Edmondso N, Chris Blake, Lee Clewley, Molly C. Hammell, Ed Olding, Lance Miller, Steve Rawlings, Jasper Wall, Gary Wegner, Christian Wolf
The Oxford-Dartmouth Thirty Degree Survey - I. Observations And Calibration Of A Wide-Field Multiband Survey, Emily C. Macdonald, Paul Allen, Gavin Dalton, Leonidas A. Moustakas, Catherine Heymans, Edward Edmondso N, Chris Blake, Lee Clewley, Molly C. Hammell, Ed Olding, Lance Miller, Steve Rawlings, Jasper Wall, Gary Wegner, Christian Wolf
Dartmouth Scholarship
The Oxford–Dartmouth Thirty Degree Survey (ODTS) is a deep, wide, multiband imaging survey designed to cover a total of 30 deg2 in BV Ri′Z, with a subset of U- and K-band data, in four separate fields of 5–10 deg2 centred at 00:18:24 +34:52, 09:09:45 +40:50, 13:40:00 +02:30 and 16:39:30 +45:24. Observations have been made using the Wide Field Camera on the 2.5-m Isaac Newton Telescope (INT) in La Palma to average limiting depths (5σ Vega, aperture magnitudes) of U= 24.8, B= 25.6, V= 25.0, R= 24.6 and i′= …
Spectral Properties Of Heavy Ions Associated With The Passage Of Interplanetary Shocks At 1 Au, Mihir I. Desai, Joseph R. Dwyer
Spectral Properties Of Heavy Ions Associated With The Passage Of Interplanetary Shocks At 1 Au, Mihir I. Desai, Joseph R. Dwyer
Aerospace, Physics, and Space Science Faculty Publications
We have surveyed the energy spectra of ∼0.1-100 MeV nucleonˉ¹ C, O, and Fe nuclei associated with the passage of 72 interplanetary (IP) shocks observed on board the ACE spacecraft during the period 1997 October-2002 October. Our main results are as follows: (1) The spectral fit parameters are independent of the local shock properties. (2) About 7% of the events exhibit increasing Fe/O ratios with energy; the remaining events have Fe/O ratios that either remain constant or decrease with energy. (3) The Fe/O ratio in the shock-associated particles is typically ∼30% lower than in the ambient population. (4) The fractionation …
The Li Overabundance Of J37: Diffusion Or Accretion?, J F. Ashwell, R D. Jeffries, C P. Deliyannis, A Steinhauer, Jeremy R. King
The Li Overabundance Of J37: Diffusion Or Accretion?, J F. Ashwell, R D. Jeffries, C P. Deliyannis, A Steinhauer, Jeremy R. King
Publications
In September 2002 the discovery of a super Li-rich F-dwarf (J37) in NGC 6633, an iron poor analogue of the better studied Hyades and Praecepe open clusters, was announced. This unique star was thought to be the smoking gun for the action of diffusion, models of which predict a narrow ”Li-peak” at approximately the correct temperature. However, with more detailed studies into J37s abundance pattern this star provides firm evidence for the accretion of planetesimals or other material from the circumstellar environment of new born stars. Thanks to the specific predictions made about the behaviour of Be abundances, (the most …
Lorentz-Violating Electromagnetostatics, Quentin G. Bailey
Lorentz-Violating Electromagnetostatics, Quentin G. Bailey
Publications
In this talk, the stationary limit of Lorentz-violating electrodynamics is discussed. As illustrated by some simple examples, the general solution includes unconventional mixing of electrostatic and magnetostatic effects. I discuss a high-sensitivity null-type measurement, exploiting Lorentz-violating electromagnetostatic effects, that could improve existing limits on parity-odd coefficients for Lorentz violation in the photon sector.
Free-Free Spectral Energy Distributions Of Hierarchically Clumped Hii Regions., Richard Ignace, Ed Churchwell
Free-Free Spectral Energy Distributions Of Hierarchically Clumped Hii Regions., Richard Ignace, Ed Churchwell
Richard Ignace
In an effort to understand unusual power-law spectral slopes observed in some hypercompact HII regions, we consider the radio continuum energy distribution from an ensemble of spherical clumps. An analytic expression for the free-free emission from a single spherical clump is derived. The radio continuum slope (with F_\nu \nu^\alpha) is governed by the population of clump optical depths N(tau), such that (a) at frequencies where all clumps are thick, a continuum slope of +2 is found, (b) at frequencies where all clumps are optically thin, a flattened slope of -0.11 is found, and (c) at intermediate frequencies, a power-law segment …
On The Variability Of The Fine Structure Constant, Jason Lott Evans
On The Variability Of The Fine Structure Constant, Jason Lott Evans
Theses and Dissertations
This thesis addresses the issue of the time variability of the fine structure constant, alpha. Recent claims of a varying alpha are set against the established standards of quantum electrodynamical theory and experiments. A study of the feasibility of extracting data on the time dependence of alpha using particles in Penning traps is compared to the results obtained by existing methods, including those using astrophysical data and those obtained in atomic clock experiments. Suggestions are made on the nature of trapped particles and the trapping fields.
The Clustering Of Galaxies Around Three Z ∼ 3 Damped Lyα Absorbers, Nicolas Bouché, James D. Lowenthal
The Clustering Of Galaxies Around Three Z ∼ 3 Damped Lyα Absorbers, Nicolas Bouché, James D. Lowenthal
Astronomy: Faculty Publications
We present our results on the cross-correlation of Lyman break galaxies (LBGs) around three damped Lyα absorbers (DLAs) at z ≃ 3 from deep [μ (sky) ≃ 27.6 mag arcsec ] UBVI KPNO 4 m/MOSAIC images. The large area of the MOSAIC images, 0.31 deg or ∼65 × 65 h Mpc comoving at redshift z = 3, allows us to probe the clustering of LBGs on scales up to 20 Mpc comoving. Our survey covers a total of 1 deg and contains ∼3000 LBGs with photometric redshifts between 2.8 and 3.5. Using the redshift likelihood distributions with m as a …
Proper Motion Objects In The Hubble Deep Field, M. Kilic, Ted Von Hippel, Et Al.
Proper Motion Objects In The Hubble Deep Field, M. Kilic, Ted Von Hippel, Et Al.
Publications
Using the deepest and finest resolution images of the universe acquired with the Hubble Space Telescope and a similar image taken 7 yr later for the Great Observatories Origins Deep Survey, we have derived proper motions for the point sources in the Hubble Deep Field–North. Two faint blue objects, HDF 2234 and HDF 3072, are found to display significant proper motion, 10:0 ± 2:5 and 15:5 ± 3:8 mas yr¯1. Photometric distances and tangential velocities for these stars are consistent with disk white dwarfs located at ~500 pc. The faint blue objects analyzed by Ibata et al. and Mendez & …
Interplanetary Transport Mechanisms Of Solar Energetic Particles, Gang Qin, Ming Zhang, Joseph R. Dwyer, Hamid K. Rassoul
Interplanetary Transport Mechanisms Of Solar Energetic Particles, Gang Qin, Ming Zhang, Joseph R. Dwyer, Hamid K. Rassoul
Aerospace, Physics, and Space Science Faculty Publications
Numerical simulations of charged particle trajectories in a Parker field with model turbulence are used to study the transport mechanisms of solar energetic particles (SEPs): magnetic focusing, pitch-angle diffusive transport due to magnetic fluctuations, and adiabatic cooling. The results of the simulations are compared with analytical formulae for the transport effects. We find that adiabatic cooling is significant for SEPs traveling from the Sun to 1 AU. The simulation results agree much better with the anisotropic adiabatic cooling effect theory than with the isotropic one. Also, we show that the simulation results agree well with the theory of magnetic focusing …
The Hanle Effect As A Diagnostic Of Magnetic Fields In Stellar Envelopes Iv. Application To Polarized P Cygni Wind Lines., R. Ignace, K. H. Nordsieck, J. P. Cassinelli
The Hanle Effect As A Diagnostic Of Magnetic Fields In Stellar Envelopes Iv. Application To Polarized P Cygni Wind Lines., R. Ignace, K. H. Nordsieck, J. P. Cassinelli
Richard Ignace
The Hanle effect has been proposed as a new diagnostic of circumstellar magnetic fields for early-type stars, for which it is sensitive to field strengths in the 1-300 G range. In this paper we compute the polarized P-Cygni line profiles that result from the Hanle effect. For modeling the polarization, we employ a variant of the ``last scattering approximation''. For cases in which the Sobolev optical depths are greater than unity, the emergent line intensity is assumed to be unpolarized; while for smaller optical depths, the Stokes source functions for the Hanle effect with optically thin line scattering are used. …
The Near-Infared Survey Of The N49 Region Around The Soft Gamma Repeater Sgr 0526-66, S. Klose, A. A. Henden, U. Geppert, J. Greiner, H. H. Guetter, Dieter H. Hartmann, C. Kouveliotou, C. B. Luginbuhl, B. Stecklum, F. J. Vrba
The Near-Infared Survey Of The N49 Region Around The Soft Gamma Repeater Sgr 0526-66, S. Klose, A. A. Henden, U. Geppert, J. Greiner, H. H. Guetter, Dieter H. Hartmann, C. Kouveliotou, C. B. Luginbuhl, B. Stecklum, F. J. Vrba
Publications
We report the results of a deep near-infrared survey with the Very Large Telescope/Infrared Spectrometer and Array Camera of the environment of the supernova remnant N49 in the Large Magellanic Cloud, which contains the soft gamma repeater SGR 0526-66. Two of the four confirmed SGRs are potentially associated with compact stellar clusters. We thus searched for a similar association of SGR 0526-66 and imaged a young stellar cluster at a projected distance of ∼30 pc from the SGR. This constitutes the third cluster–SGR link and lends support to scenarios in which SGR progenitors originate in young dusty clusters. If confirmed, …
The Upper Limit For Ch4 In The Protostellar Disk Toward Hl Tauri, E L. Gibb, T Rettig, Sean D. Brittain, R Haywood, Theodore Simon, C Kulesa
The Upper Limit For Ch4 In The Protostellar Disk Toward Hl Tauri, E L. Gibb, T Rettig, Sean D. Brittain, R Haywood, Theodore Simon, C Kulesa
Publications
We used high-resolution infrared spectra of the heavily embedded T Tauri star HL Tau to search for evidence of absorption due to the R0, R1, and R2 gas-phase CH4 ν3 lines near 3.3 μm. From this, we report a 3 σ upper limit of 1.3 × 1015 cm-2 for the CH4 gas column density toward HL Tau. Our results are compared to those found for CO gas toward this source and to the recent model for chemistry in the inner (10 AU) disks around T Tauri stars by Markwick et al. We find that the upper limit of methane ice+gas …
Photospheric Temperature Measurements In Young Main Sequence Stars, Katia Biazzo, Antonio Frasca, Gregory W. Henry, S. Catalano, Ettore Marilli
Photospheric Temperature Measurements In Young Main Sequence Stars, Katia Biazzo, Antonio Frasca, Gregory W. Henry, S. Catalano, Ettore Marilli
Information Systems and Engineering Management Research Publications
As part of our program to study stellar photospheric and chromospheric activity, we have examined several young solar type stars with activity levels intermediate between the Sun and the very active RS CVn binaries. We have analysed contemporaneous spectroscopic data obtained at Catania Observatory (Serra La Nave station, Mt. Etna) and photometric data acquired in the Stromgren bands with an automatic photometric telescope (APT) at Fairborn Observatory (Arizona, USA). Surface inhomogeneities have been detected from the rotational modulation of stellar brightness as well as from the modulation of several photospheric line-depth ratios (LDRs). The presence of chromospheric plage-like regions has …
Why Do Some Spotted Stars Become Bluer As They Become Fainter?, Vidar Aarum-Ulvås, Gregory W. Henry
Why Do Some Spotted Stars Become Bluer As They Become Fainter?, Vidar Aarum-Ulvås, Gregory W. Henry
Information Systems and Engineering Management Research Publications
Chromospherically active, spotted stars generally become redder as well as fainter when large starspots rotate into view on the stellar disc. However, the RS CVn system UX Ari (a triple-lined system), becomes bluer as it gets fainter. One possible explanation is that hot, bright facular regions accompany the cool, dark photospheric spots of the active component. The bluer flux of the hotter, inactive component does not appear to be sufficient to explain the observed behaviour. We have begun a search for additional chromospherically active stars with a similar relation between colour and brightness, to investigate whether these relations can be …
Going Slitless: Images Of Forbidden Line Emission Regions Of Classical T Tauri Stars Observed With The Hubble Space Telescope, Patrick Hartigan, Suzan Edwards, Rachel Pierson
Going Slitless: Images Of Forbidden Line Emission Regions Of Classical T Tauri Stars Observed With The Hubble Space Telescope, Patrick Hartigan, Suzan Edwards, Rachel Pierson
Astronomy: Faculty Publications
We have observed five classical T Tauri stars known to have strong forbidden-line emission with STIS in slitless mode on the Hubble Space Telescope. This technique makes it possible to image jets within a few tens of AU of their exciting sources, a region of great interest for models of accretion disks and jets. Slitless images generate emission-line images at all wavelengths, including those where no narrowband filters exist. Images of the forbidden-line regions around each object, constructed by subtracting the stellar continuum and combining observations taken at different orientations, show [O I] jets from CW Tau, HN Tau, …