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Articles 31 - 38 of 38
Full-Text Articles in Stars, Interstellar Medium and the Galaxy
Relativistic Iron Emission Lines In Neutron Star Low-Mass X-Ray Binaries As Probes Of Neutron Star Radii, Edward M. Cackett, Jon M. Miller, Sudip Bhattacharyya, Jonathan E. Grindlay, Jeroen Homan, Michiel Van Der Klis, M. Coleman Miller, Tod E. Strohmayer, Rudy Wijnands
Relativistic Iron Emission Lines In Neutron Star Low-Mass X-Ray Binaries As Probes Of Neutron Star Radii, Edward M. Cackett, Jon M. Miller, Sudip Bhattacharyya, Jonathan E. Grindlay, Jeroen Homan, Michiel Van Der Klis, M. Coleman Miller, Tod E. Strohmayer, Rudy Wijnands
Physics and Astronomy Faculty Research Publications
Using Suzaku observations of three neutron star low-mass X-ray binaries (Ser X-1, 4U 1820-30, and GX 349+2) we have found broad, asymmetric, relativistic Fe K emission lines in all three objects. These Fe K lines can be well fit by a model for lines from a relativistic accretion disk (``diskline''), allowing a measurement of the inner radius of the accretion disk and hence an upper limit on the neutron star radius. These upper limits correspond to 14.5-16.5 km for a 1.4 Msolar neutron star. The inner disk radii that we measure with Fe K lines are in good agreement …
Optical Imaging And Spectroscopy Of The Galactic Supernova Remnant 3c 58 (G130.7+3.1), Robert Fesen, Gwen Rudie, Alan Hurford, Aljeandro Soto
Optical Imaging And Spectroscopy Of The Galactic Supernova Remnant 3c 58 (G130.7+3.1), Robert Fesen, Gwen Rudie, Alan Hurford, Aljeandro Soto
Dartmouth Scholarship
We present a comprehensive imaging and spectroscopic survey of optical emission knots associated with the young Galactic supernova remnant 3C 58. Hα images show hundreds of clumpy filaments and knots arranged in a complex structure covering a nearly circular area roughly 400'' in diameter. A quite different emission structure is seen in [O III], where the brightest features are less clumpy and largely confined to the remnant's northwest quadrant. Measured radial velocities of over 450 knots reveal two distinct kinematic populations; one with average and peak expansion velocities of 770 and 1100 km s−1, respectively, forming a thick …
Masses, Luminosities, And Orbital Coplanarities Of The Μ Orionis Quadruple-Star System From Phases Differential Astrometry, Matthew W. Muterspaugh, Benjamin F. Lane, Francis C. Fekel, Maciej Konacki, Bernard F. Burke, Shrinivas R. Kulkarni, Mark M. Colavita, Michael Shao, Sloane J. Wiktorowicz
Masses, Luminosities, And Orbital Coplanarities Of The Μ Orionis Quadruple-Star System From Phases Differential Astrometry, Matthew W. Muterspaugh, Benjamin F. Lane, Francis C. Fekel, Maciej Konacki, Bernard F. Burke, Shrinivas R. Kulkarni, Mark M. Colavita, Michael Shao, Sloane J. Wiktorowicz
Information Systems and Engineering Management Research Publications
μ Orionis was identified by spectroscopic studies as a quadruple-star system. Seventeen high-precision differential astrometry measurements of μ Ori have been collected by the Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES). These show both the motion of the long-period binary orbit and short-period perturbations superimposed on that caused by each of the components in the long-period system being themselves binaries. The new measurements enable the orientations of the long-period binary and short-period subsystems to be determined. Recent theoretical work predicts the distribution of relative inclinations between inner and outer orbits of hierarchical systems to peak near 40 and 140 …
The Extinction Toward The Galactic Bulge From Rr Lyrae Stars, Andrea Kunder, Piotr Popowski, Kem H. Cook, Brian Chaboyer
The Extinction Toward The Galactic Bulge From Rr Lyrae Stars, Andrea Kunder, Piotr Popowski, Kem H. Cook, Brian Chaboyer
Dartmouth Scholarship
We present mean reddenings toward 3525 RR0 Lyrae stars from the Galactic bulge fields of the MACHO Survey. These reddenings are determined using the color at minimum V-band light of the RR0 Lyrae stars themselves and are found to be in general agreement with extinction estimates at the same location obtained from other methods. Using 3256 stars located in the Galactic Bulge, we derive the selective extinction coefficient RV,VR = AV/E(V − R) = 4.3 ± 0.2. This value is what is expected for a standard extinction law with R …
New Precision Orbits Of Bright Double-Lined Spectroscopic Binaries. Ii. Hr 2962, Hd 214686, And 16 Psc, Jocelyn Tomkin, Francis C. Fekel
New Precision Orbits Of Bright Double-Lined Spectroscopic Binaries. Ii. Hr 2962, Hd 214686, And 16 Psc, Jocelyn Tomkin, Francis C. Fekel
Information Systems and Engineering Management Research Publications
Radial velocities from the 2.1 m telescope at McDonald Observatory and the coudé feed telescope at Kitt Peak National Observatory are used to determine new spectroscopic orbits for the double-lined spectroscopic binaries HR 2962 (F5V), HD 214686 (F8IV), and 16 Psc (F6Vb vw). The new orbital dimensions (a1sin i and a2sin i) and minimum masses (m1sin3i and m2sin3i) have accuracies of 0.1–1%. In the case of HD 214686, which has components of nearly the same mass (m1/m2 = 1.0080 ± 0.0013), we confirm that the component labeled as the primary in previous spectroscopic studies of this system is the slightly …
The Crab Nebula's Dynamical Age As Measured From Its Northern Filamentary Jet, G. C. Rudie, R. A. Fesen, T. Yamada
The Crab Nebula's Dynamical Age As Measured From Its Northern Filamentary Jet, G. C. Rudie, R. A. Fesen, T. Yamada
Dartmouth Scholarship
We present a deep [O III] 4959,5007 image of the northern filamentary jet in the Crab Nebula taken with the 8.2m Subaru telescope. Using this image and an image taken with the KPNO 4m in 1988 (Fesen & Staker 1993), we have computed proper motions for 35 locations in the jet. The results suggest that when compared to the main body of the remnant, the jet experienced less outward acceleration from the central pulsar's rapidly expanding synchrotron nebula. The jet's apparent expansion rate yields an undecelerated explosion date for the Crab Nebula of 1055 plus or minus 24 C.E., a …
Phase-Dependent X-Ray Observations Of The Beta Lyrae System: No Eclipse In The Soft Band., Richard Ignace, L. Oskinova, W. Waldron, J. Hoffman, W.-R. Hamann
Phase-Dependent X-Ray Observations Of The Beta Lyrae System: No Eclipse In The Soft Band., Richard Ignace, L. Oskinova, W. Waldron, J. Hoffman, W.-R. Hamann
ETSU Faculty Works
Aims.We report on observations of the eclipsing and interacting binary beta Lyrae from the Suzaku X-ray telescope. This system involves an early B star embedded in an optically and geometrically thick disk that is siphoning atmospheric gases from a less massive late B II companion. Methods.Motivated by an unpublished X-ray spectrum from the Einstein X-ray telescope suggesting unusually hard emission, we obtained time with Suzaku for pointings at three different phases within a single orbit. Results.From the XIS detectors, the softer X-ray emission appears typical of an early-type star. What is surprising is the remarkably unchanging character …
White Dwarf Luminosity And Mass Functions From Sloan Digital Sky Survey Spectra, Steven Degennaro, Ted Von Hippel, D. E. Winget, S. O. Kepler, Atsuko Nitta, Detlev Koester, Leandro Althaus
White Dwarf Luminosity And Mass Functions From Sloan Digital Sky Survey Spectra, Steven Degennaro, Ted Von Hippel, D. E. Winget, S. O. Kepler, Atsuko Nitta, Detlev Koester, Leandro Althaus
Publications
We present the first phase in our ongoing work to use Sloan Digital Sky Survey (SDSS) data to create separate white dwarf (WD) luminosity functions (LFs) for two or more different mass ranges. In this paper, we determine the completeness of the SDSS spectroscopic WD sample by comparing a proper-motion selected sample of WDs from SDSS imaging data with a large catalog of spectroscopically determined WDs. We derive a selection probability as a function of a single color (g − i) and apparent magnitude (g) that covers the range −1.0 < g − i < 0.2 and 15 < g < 19.5. We address the observed upturn in log g for WDs with Teff 12,000 K and offer arguments that the problem is limited to the line profiles and is not present in the continuum. We offer an empirical method of removing the upturn, recovering a reasonable mass function for WDs with Teff < 12,000 K. Finally we present a WD LF with nearly an order of magnitude (3358) more spectroscopically confirmed WDs than any previous work.