Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Institution
- Keyword
-
- Spectroscopic binaries (6)
- White dwarfs (6)
- Eclipsing binaries (4)
- X-rays (4)
- Binaries (3)
-
- Globular clusters (3)
- Individual (3)
- Physics and Astronomy (3)
- Stars (3)
- Stars: evolution (3)
- Supernovae (3)
- Astronomy (2)
- Fundamental stellar parameters (2)
- Late-type stars (2)
- Mass function (2)
- Microlensing (2)
- Neutron (2)
- Red giant stars (2)
- Star evolution (2)
- Star interiors (2)
- Stellar evolution (2)
- Supernova remnants (2)
- AX J1811.2-1828 (1)
- Accretion (1)
- Accretion discs (1)
- Astrometry (1)
- Atmospheres (1)
- Axisymmetric Stellar Winds (1)
- Bar (1)
- Brown dwarfs (1)
- Publication
-
- Dartmouth Scholarship (10)
- Information Systems and Engineering Management Research Publications (7)
- Publications (7)
- ETSU Faculty Works (3)
- Physics and Astronomy Faculty Research Publications (3)
-
- Richard Ignace (3)
- Faculty Articles (2)
- Branch Mathematics and Statistics Faculty and Staff Publications (1)
- C. Martin Gaskell Publications (1)
- Faculty and Staff Publications (1)
- Hidden in Plain Sight Projects (1)
- Physics Faculty Publications (1)
- Physics and Astronomy Faculty Publications (1)
- Publications and Research (1)
- WKU Archives Records (1)
- Publication Type
Articles 1 - 30 of 43
Full-Text Articles in Physical Sciences and Mathematics
Discovery Of Extensive Optical Emission Associated With The X-Ray Bright, Radio Faint Galactic Snr G156.2+5.7, Christopher L. Gerardy, Robert A. Fesen
Discovery Of Extensive Optical Emission Associated With The X-Ray Bright, Radio Faint Galactic Snr G156.2+5.7, Christopher L. Gerardy, Robert A. Fesen
Dartmouth Scholarship
We present wide‐field Hα images of the Galactic supernova remnant (SNR) G156.2+5.7 which reveal the presence of considerable faint Hα line emission coincident with the remnant's X‐ray emission. We also present low‐resolution optical spectra for a few representative emission regions. The outermost Hα emission consists largely of long and thin (unresolved), smoothly curved filaments of Balmer‐dominated emission presumably associated with the remnant's forward shock front. Patches of brighter Hα emission along the western, south‐central, and north‐eastern regions appear to be radiative shocked interstellar medium filaments like those commonly seen in SNRs, with relatively strong [O i]λλ6300, 6364 and [S ii]λλ6716, …
Optical Variability Of The Three Brightest Nearby Quasars, C. Martin Gaskell, Andrew J. Benker, Jeffrey S. Campbell, Thomas A. George, Cecilia H. Hedrick, Mary E. Hiller, Elizabeth S. Klimek, Joseph P. Leonard, Shoji Masatoshi, Bradley W. Peterson, Kelly S. Peterson, Kelly M. Sanders
Optical Variability Of The Three Brightest Nearby Quasars, C. Martin Gaskell, Andrew J. Benker, Jeffrey S. Campbell, Thomas A. George, Cecilia H. Hedrick, Mary E. Hiller, Elizabeth S. Klimek, Joseph P. Leonard, Shoji Masatoshi, Bradley W. Peterson, Kelly S. Peterson, Kelly M. Sanders
C. Martin Gaskell Publications
We report on the relative optical variability of the three brightest nearby quasars, 3C 273, PDS 456, and PHL 1811. All three have comparable absolute magnitudes, but PDS 456 and PHL 1811 are radio quiet. PDS 456 is a broadline object, but PHL 1811 could be classified as a high-luminosity Narrow-Line Seyfert 1 (NLS1). Both of the radio-quiet quasars show significant variability on a timescale of a few days. The seasonal rms V-band variability amplitudes of 3C 273 and PDS 456 are indistinguishable, and the seasonal rms variability amplitude of PHL 1811 was only exceeded by 3C 273 once in …
Faint X‐Ray Structure In The Crab Pulsar Wind Nebula, F. D. Seward, W. H. Tucker, R. A. Fesen
Faint X‐Ray Structure In The Crab Pulsar Wind Nebula, F. D. Seward, W. H. Tucker, R. A. Fesen
Dartmouth Scholarship
We report on a Chandra observation of the Crab Nebula that gives the first clear view of the faint boundary of the Crab's X-ray-emitting pulsar wind nebula. There is structure in all directions. Fingers, loops, bays, and the south pulsar jet all indicate that either filamentary material or the magnetic field is controlling the relativistic electrons. In general, spectra soften as distance from the pulsar increases but do not change rapidly along linear features. This is particularly true for the pulsar jet. The termination of the jet is abrupt; the east side is close to an [O III] optical filament, …
Ua1b1/7 Wku Centennial Mosaic Dedication, Western Kentucky University
Ua1b1/7 Wku Centennial Mosaic Dedication, Western Kentucky University
WKU Archives Records
Dedication program for the WKU Centennial Mosaic and fountain, includes sky map for Founders Day, November 16, 2006.
Hd 71636, A Newly Discovered Eclipsing Binary, Gregory W. Henry, Francis C. Fekel, James R. Sowell, Joel S. Gearhart
Hd 71636, A Newly Discovered Eclipsing Binary, Gregory W. Henry, Francis C. Fekel, James R. Sowell, Joel S. Gearhart
Information Systems and Engineering Management Research Publications
Our differential BV photometric observations, acquired with an automated telescope at Fairborn Observatory, show that HD 71636 is an eclipsing binary. From follow-up red-wavelength spectroscopic observations we classify the primary and secondary as an F2 dwarf and an F5 dwarf, respectively. The system has a period of 5.01329 days and a circular orbit. We used the Wilson-Devinney program to simultaneously solve our BV light curves and radial velocities and determined a number of fundamental properties of the system. Comparison with evolutionary tracks indicates that both stars are well ensconced on the main sequence. The age of the system is about …
Spitzer White Dwarf Planet Limits, F. Mullally, Ted Von Hippel, D. E. Winget
Spitzer White Dwarf Planet Limits, F. Mullally, Ted Von Hippel, D. E. Winget
Publications
We present preliminary limits on the presence of planets around white dwarf stars using the IRAC photometer on the Spitzer space telescope. Planets emit strongly in the mid-infrared which allows their presence to be detected as an excess at these wavelengths. We place limits of 5 MJ for 8 stars assuming ages of 1 Gyr, and 10 MJ for 23 stars.We describe our survey, present our results and comment on approaches to improve our methodology.
Cooling Of The Quasi-Persistent Neutron Star X-Ray Transients Ks 1731-260 And Mxb 1659-29, Edward M. Cackett, Rudy Wijnands, Manuel Linares, Jon M. Miller, Jeroen Homan, Walter H. G. Lewin
Cooling Of The Quasi-Persistent Neutron Star X-Ray Transients Ks 1731-260 And Mxb 1659-29, Edward M. Cackett, Rudy Wijnands, Manuel Linares, Jon M. Miller, Jeroen Homan, Walter H. G. Lewin
Physics and Astronomy Faculty Research Publications
We present Chandra and XMM-Newton X-ray observations that monitor the neutron star cooling of the quasi-persistent neutron star X-ray transients KS 1731-260 and MXB 1659-29 for approximately 4 yr after these sources returned to quiescence from prolonged outbursts. In both sources the outbursts were long enough to significantly heat the neutron star crust out of thermal equilibrium with the core. We analyse the X-ray spectra by fitting absorbed neutron star atmosphere models to the observations. The results of our analysis strengthen the preliminary findings of Wijnands et al. that in both sources the neutron star crust cools down very rapidly …
Random Flows And Diagnostics Of Turbulence In The High Latitude Cirrus, Steven N. Shore, Ted N. Larosa, Raymond J. Chastain, Loris Magnani
Random Flows And Diagnostics Of Turbulence In The High Latitude Cirrus, Steven N. Shore, Ted N. Larosa, Raymond J. Chastain, Loris Magnani
Faculty Articles
Aims: We present an analysis of the exceptionally turbulent velocity field in the high Galactic latitude cirrus cloud MBM 3. As in the other translucent clouds in our study (MBM 16 and MBM 40), there is no evidence for internal star formation. However, the large scale velocity variation in this cloud is more pronounced. Methods: We have mapped the cloud in 12CO and 13CO (1-0) at high spatial (0.03 pc) and velocity (0.06 km s-1) resolution. We constructed several velocity probability density functions (PDFs), estimated the turbulent transfer rate, and analyzed the linewidths as a function of the size of …
Hd 131861, A Double-Line Spectroscopic Triple System, Francis C. Fekel, Gregory W. Henry, David J. Barlow, Dimitri Pourbaix
Hd 131861, A Double-Line Spectroscopic Triple System, Francis C. Fekel, Gregory W. Henry, David J. Barlow, Dimitri Pourbaix
Information Systems and Engineering Management Research Publications
Our red-wavelength spectroscopic observations of HD 131861, a previously known single-line multiple system, span 20 years. Now lines of two components, the short-period F5 V primary and G8 V secondary, have been detected. The inner orbit is circular with a period of 3.5507439 days, while the outer orbit of the system has a period of 1642 days or 4.496 yr and a relatively low eccentricity of 0.10. Analysis of the Hipparcos data produces a well-determined astrometric orbit for the long-period system that has an inclination of 52°. Our photometric observations show shallow primary and secondary eclipses of the short-period pair, …
A Spitzer Space Telescope Study Of Sn 2002hh: An Infrared Echo From A Type Iip Supernova, W. P. S. Meikle, S. Mattila, C. L. Gerardy, R. Kotak, M. Pozzo, S. D. Van Dyk, D. Farrah, R. A. Fesen
A Spitzer Space Telescope Study Of Sn 2002hh: An Infrared Echo From A Type Iip Supernova, W. P. S. Meikle, S. Mattila, C. L. Gerardy, R. Kotak, M. Pozzo, S. D. Van Dyk, D. Farrah, R. A. Fesen
Dartmouth Scholarship
We present late-time (590-994 days) mid-IR photometry of the normal but highly reddened Type IIP supernova SN 2002hh. Bright, cool, slowly fading emission is detected from the direction of the supernova. Most of this flux appears not to be driven by the supernova event but instead probably originates in a cool, obscured star formation region or molecular cloud along the line of sight. We also show, however, that the declining component of the flux is consistent with an SN-powered IR echo from a dusty progenitor CSM. Mid-IR emission could also be coming from newly condensed dust and/or an ejecta/CSM impact, …
Models Of Forbidden Line Emission Profiles From Axisymmetric Stellar Winds., Richard Ignace, A. Brimeyer
Models Of Forbidden Line Emission Profiles From Axisymmetric Stellar Winds., Richard Ignace, A. Brimeyer
ETSU Faculty Works
A number of strong infrared forbidden lines have been observed in several evolved Wolf–Rayet (WR) star winds, and these are important for deriving metal abundances and testing stellar evolution models. In addition, because these optically thin lines form at large radius in the wind, their resolved profiles carry an imprint of the asymptotic structure of the wind flow. This work presents model forbidden line profile shapes formed in axisymmetric winds. It is well known that an optically thin emission line formed in a spherical wind expanding at constant velocity yields a flat-topped emission profile shape. Simulated forbidden lines are produced …
1021-0304_Mir_Irs, Michael C. Cushing
Models Of Forbidden Line Emission Profiles From Axisymmetric Stellar Winds., R. Ignace, A. Brimeyer
Models Of Forbidden Line Emission Profiles From Axisymmetric Stellar Winds., R. Ignace, A. Brimeyer
Richard Ignace
A number of strong infrared forbidden lines have been observed in several evolved Wolf–Rayet (WR) star winds, and these are important for deriving metal abundances and testing stellar evolution models. In addition, because these optically thin lines form at large radius in the wind, their resolved profiles carry an imprint of the asymptotic structure of the wind flow. This work presents model forbidden line profile shapes formed in axisymmetric winds. It is well known that an optically thin emission line formed in a spherical wind expanding at constant velocity yields a flat-topped emission profile shape. Simulated forbidden lines are produced …
Hr 1613: A Slowly Rotating A Dwarf Spectroscopic Binary With Solar Abundances, Francis C. Fekel, Michael H. Williamson, Christiane Buggs, Gerald Onuoha, Brittany Smith
Hr 1613: A Slowly Rotating A Dwarf Spectroscopic Binary With Solar Abundances, Francis C. Fekel, Michael H. Williamson, Christiane Buggs, Gerald Onuoha, Brittany Smith
Information Systems and Engineering Management Research Publications
From two sets of radial velocities we have obtained the orbital elements of HR 1613. This single-lined binary has an orbital period of 8.11128 days and a nearly circular orbit. The primary has an A9 V spectral type and a v sin i value of 11 km s-1, while the unseen secondary is likely a K or M dwarf. Spectral classifications and spectrum synthesis analysis indicate that the abundances of the primary are normal. We reject the possibility that the primary of HR 1613 is seen nearly pole-on and instead argue that its rotational inclination is at least 20°, resulting …
Heliospheric Response To Different Possible Interstellar Environments, Hans-Reinhard Muller, Priscilla C. Frisch, Vladimir Florinski, Gary P. Zank
Heliospheric Response To Different Possible Interstellar Environments, Hans-Reinhard Muller, Priscilla C. Frisch, Vladimir Florinski, Gary P. Zank
Dartmouth Scholarship
At present, the heliosphere is embedded in a warm, low-density interstellar cloud that belongs to a cloud system flowing through the local standard of rest with a velocity near ~18 km s-1. The velocity structure of the nearest interstellar material (ISM), combined with theoretical models of the local interstellar cloud (LIC), suggest that the Sun passes through cloudlets on timescales of ≤103-104 yr, so the heliosphere has been, and will be, exposed to different interstellar environments over time. By means of a multifluid model that treats plasma and neutral hydrogen self-consistently, the interaction of the …
Debris Disks Around White Dwarfs: The Daz Connection, Mukremin Kilic, Ted Von Hippel, Et Al.
Debris Disks Around White Dwarfs: The Daz Connection, Mukremin Kilic, Ted Von Hippel, Et Al.
Publications
We present near-infrared spectroscopic observations of 20 previously known DAZ white dwarfs obtained at the NASA Infrared Telescope Facility. Two of these white dwarfs (G29-38 and GD 362) are known to display significant K-band excesses due to circumstellar debris disks. Here we report the discovery of excess K-band radiation from another DAZ white dwarf WD0408041 (GD56). Using spectroscopic observations, we show that the excess radiation cannot be explained by a stellar or substellar companion, and is likely to be caused by a warm debris disk. Our observations strengthen the connection between the debris disk phenomena and the observed …
Inverting Color-Magnitude Diagrams To Access Precise Star Cluster Parameters: A Bayesian Approach, Ted Von Hippel, Et Al.
Inverting Color-Magnitude Diagrams To Access Precise Star Cluster Parameters: A Bayesian Approach, Ted Von Hippel, Et Al.
Publications
We demonstrate a new Bayesian technique to invert color-magnitude diagrams of main-sequence and white dwarf stars to reveal the underlying cluster properties of age, distance, metallicity, and line-of-sight absorption, as well as individual stellar masses. The advantages our technique has over traditional analyses of color-magnitude diagrams are objectivity, precision, and explicit dependence on prior knowledge of cluster parameters. Within the confines of a given set of often-used models of stellar evolution, a single mapping of initial to final masses, and white dwarf cooling, and assuming photometric errors that one could reasonably achieve with the Hubble Space Telescope, our technique …
Xmm-Newton Discovery Of The X-Ray Transient Xmmu J181227.8-181234 In The Galactic Plane, Edward M. Cackett, Rudy Wijnands, Ron Remillard
Xmm-Newton Discovery Of The X-Ray Transient Xmmu J181227.8-181234 In The Galactic Plane, Edward M. Cackett, Rudy Wijnands, Ron Remillard
Physics and Astronomy Faculty Research Publications
We report the discovery of an X-ray transient, observed in outburst with XMM-Newton on 2003 March 20, and with position (J2000, approximate positional error 2arcsec). No known source is present at this position and the source was not detected during published ROSAT or ASCA observations of that region. However, the source may be associated with 1H1812-182 detected by HEAO 1, although the error bars on the HEAO 1 position are very large and the two sources could also be unrelated. Therefore, we name the source XMMU J181227.8-181234. Initially, the source was not detected using the All-Sky Monitor (ASM) on-board the …
Probing The Universe On Gigaparsec Scales With Remote Cosmic Microwave Background Quadrupole Measurements, Emory F. Bunn
Probing The Universe On Gigaparsec Scales With Remote Cosmic Microwave Background Quadrupole Measurements, Emory F. Bunn
Physics Faculty Publications
Scattering of cosmic microwave background (CMB) radiation in galaxy clusters induces a polarization signal proportional to the CMB quadrupole anisotropy at the cluster’s location and lookback time. A survey of such remote quadrupole measurements provides information about large-scale cosmological perturbations. This paper presents a formalism for calculating the correlation function of remote quadrupole measurements in spherical harmonic space. The number of independent modes probed by both single-redshift and volume-limited surveys is presented, along with the length scales probed by these modes. In a remote quadrupole survey sparsely covering a large area of sky, the largest-scale modes probe the same-length scales …
A Chandra X-Ray Observation Of The Globular Cluster Terzan 1, E. M. Cackett, R. Wijnands, C. O. Heinke, D. Pooley, W. H. G. Lewin, J. E. Grindlay, P. D. Edmonds, P. G. Jonker, J. M. Miller
A Chandra X-Ray Observation Of The Globular Cluster Terzan 1, E. M. Cackett, R. Wijnands, C. O. Heinke, D. Pooley, W. H. G. Lewin, J. E. Grindlay, P. D. Edmonds, P. G. Jonker, J. M. Miller
Physics and Astronomy Faculty Research Publications
We present a ~19-ks Chandra Advanced CCD Imaging Spectrometer (ACIS)-S observation of the globular cluster Terzan 1. 14 sources are detected within 1.4arcmin of the cluster centre with two of these sources predicted to be not associated with the cluster (background active galactic nuclei or foreground objects). The neutron star X-ray transient, X1732-304, has previously been observed in outburst within this globular cluster with the outburst seen to last for at least 12yr. Here, we find four sources that are consistent with the ROSAT position for this transient, but none of the sources are fully consistent with the position of …
Grb 060218/Sn 2006aj: A Gamma-Ray Burst And Prompt Supernova Atz= 0.0335, N. Mirabal, J. P. Halpern, D. An, J. R. Thorstensen, D. M. Terndrup
Grb 060218/Sn 2006aj: A Gamma-Ray Burst And Prompt Supernova Atz= 0.0335, N. Mirabal, J. P. Halpern, D. An, J. R. Thorstensen, D. M. Terndrup
Dartmouth Scholarship
We report the imaging and spectroscopic localization of GRB 060218 to a low-metallicity dwarf starburst galaxy at z = 0.03345 ± 0.00006. In addition to making it the second nearest gamma-ray burst known, optical spectroscopy reveals the earliest detection of weak, supernova-like Si II near 5720 Å (~0.1c), starting 1.95 days after the burst trigger. UBVRI photometry obtained between 1 and 26 days postburst confirms the early rise of supernova light, and suggests a short time delay between the gamma-ray burst and the onset of SN 2006aj if the early appearance of a soft component in the X-ray …
Lp 400-22, A Very Low Mass And High-Velocity White Dwarf, Adela Kawka, Stephane Vennes, Terry D. Oswalt, J. Allyn Smith, Nicole M. Silvestri
Lp 400-22, A Very Low Mass And High-Velocity White Dwarf, Adela Kawka, Stephane Vennes, Terry D. Oswalt, J. Allyn Smith, Nicole M. Silvestri
Publications
We report the identification of LP 400-22 (WD 2234 + 222) as a very low mass and high-velocity white dwarf. The ultraviolet GALEX and optical photometric colors and a spectral line analysis of LP 400-22 show this star to have an effective temperature of 11,080 ± 140 K and a surface gravity of log g p 6.32 ± 0.08. Therefore, this is a helium-core white dwarf with a mass of 0.17 MꙨ. The tangential velocity of this white dwarf is 414 ± 43 km s-1, making it one of the fastest moving white dwarfs known. We …
The Mystery Deepens: Spitzer Observations Of Cool White Dwarfs, Mukremin Kilic, Ted Von Hippel, Et Al.
The Mystery Deepens: Spitzer Observations Of Cool White Dwarfs, Mukremin Kilic, Ted Von Hippel, Et Al.
Publications
We present 4.5 and 8 µm photometric observations of 18 cool white dwarfs obtained with the Spitzer Space Telescope. Our observations demonstrate that four white dwarfs with Teᶠᶠ < 6000 K show slightly depressed mid-infrared fluxes relative to white dwarf models. In addition, another white dwarf with a peculiar optical and near-infrared spectral energy distribution (LHS 1126) is found to display significant flux deficits in Spitzer observations. These mid-infrared flux deficits are not predicted by the current white dwarf models including collision-induced absorption due to molecular hydrogen. We postulate that either the collision-induced absorption calculations are incomplete or there are other unrecognized physical processes occurring in cool white dwarf atmospheres. The spectral energy distribution of LHS 1126 surprisingly fits a Rayleigh-Jeans spectrum in the infrared, mimicking a hot white dwarf with effective temperature well in excess of 105 K. This implies that the source of this flux deficit is probably not molecular absorption but some other process.
New Precision Orbits Of Bright Double-Lined Spectroscopic Binaries. I. Rr Lyncis, 12 Bootis, And Hr 6169, Jocelyn Tomkin, Francis C. Fekel
New Precision Orbits Of Bright Double-Lined Spectroscopic Binaries. I. Rr Lyncis, 12 Bootis, And Hr 6169, Jocelyn Tomkin, Francis C. Fekel
Information Systems and Engineering Management Research Publications
Radial velocities from the 2.1 m telescope at McDonald Observatory supplemented with radial velocities from the coudé feed telescope at Kitt Peak National Observatory provide new precise orbits for the double-lined spectroscopic binaries RR Lyn (A3/A8/A6), 12 Boo (F8 IV), and HR 6169 (A2 V). We derive orbital dimensions (a1 sin i and a2 sin i) and minimum masses (m1 i and m2 i) with accuracies of 0.06%-0.9%. The three systems, which have V magnitudes of 5.53, 4.82, and 6.42, respectively, are all sufficiently bright that they are easily within the grasp of modern optical interferometers and so afford the …
Microlensing Of Circumstellar Envelopes Iii. Line Profiles From Stellar Winds In Homologous Expansion., M. Hendry, Richard Ignace, H. Bryce
Microlensing Of Circumstellar Envelopes Iii. Line Profiles From Stellar Winds In Homologous Expansion., M. Hendry, Richard Ignace, H. Bryce
ETSU Faculty Works
This paper examines line profile evolution due to the linear expansion of circumstellar material obsverved during a microlensing event. This work extends our previous papers on emission line profile evolution from radial and azimuthal flow during point mass lens events and fold caustic crossings. Both “flavours” of microlensing were shown to provide effective diagnostics of bulk motion in circumstellar envelopes. In this work a different genre of flow is studied, namely linear homologous expansion, for both point mass lenses and fold caustic crossings. Linear expansion is of particular relevance to the effects of microlensing on supernovae at cosmological distances. We …
Microlensing Of Circumstellar Envelopes Iii. Line Profiles From Stellar Winds In Homologous Expansion., M. A. Hendry, R. Ignace, H. M. Bryce
Microlensing Of Circumstellar Envelopes Iii. Line Profiles From Stellar Winds In Homologous Expansion., M. A. Hendry, R. Ignace, H. M. Bryce
Richard Ignace
This paper examines line profile evolution due to the linear expansion of circumstellar material obsverved during a microlensing event. This work extends our previous papers on emission line profile evolution from radial and azimuthal flow during point mass lens events and fold caustic crossings. Both “flavours” of microlensing were shown to provide effective diagnostics of bulk motion in circumstellar envelopes. In this work a different genre of flow is studied, namely linear homologous expansion, for both point mass lenses and fold caustic crossings. Linear expansion is of particular relevance to the effects of microlensing on supernovae at cosmological distances. We …
From Canonical To Enhanced Extra Mixing In Low‐Mass Red Giants: Tidally Locked Binaries, Pavel A. Denissenkov, Brian Chaboyer, Ke Li
From Canonical To Enhanced Extra Mixing In Low‐Mass Red Giants: Tidally Locked Binaries, Pavel A. Denissenkov, Brian Chaboyer, Ke Li
Dartmouth Scholarship
Stellar models that incorporate simple diffusion or shear-induced mixing are used to describe canonical extra mixing in low-mass red giants of low and solar metallicity. These models are able to simultaneously explain the observed Li and CN abundance changes along the upper red giant branch (RGB) in field low-metallicity stars and match photometry, rotation, and 12C/13C ratios for stars in the old open cluster M67. The shear mixing model requires that main-sequence (MS) progenitors of upper RGB stars possessed rapidly rotating radiative cores and that specific angular momentum was conserved in each of their mass shells during …
Theoretical Uncertainties In Red Giant Branch Evolution: The Red Giant Branch Bump, Stephan R. R. Bjork, Brian Chaboyer
Theoretical Uncertainties In Red Giant Branch Evolution: The Red Giant Branch Bump, Stephan R. R. Bjork, Brian Chaboyer
Dartmouth Scholarship
A Monte Carlo simulation exploring uncertainties in standard stellar evolution theory on the red giant branch of metal-poor globular clusters has been conducted. Confidence limits are derived on the absolute V-band magnitude of the bump in the red giant branch luminosity function (MV,b) and the excess number of stars in the bump, Rb. The analysis takes into account uncertainties in the primordial helium abundance, abundance of α-capture elements, radiative and conductive opacities, nuclear reaction rates, neutrino energy losses, the treatments of diffusion and convection, the surface boundary conditions, and color transformations. The uncertainty in …
Infrared Spectroscopy Of Symbiotic Stars. Iv. V2116 Ophiuchi/Gx 1+4, The Neutron Star Symbiotic, Kenneth H. Hinkle, Francis C. Fekel, Richard R. Joyce, Peter R. Wood, Verne V. Smith, Thomas Lebzelter
Infrared Spectroscopy Of Symbiotic Stars. Iv. V2116 Ophiuchi/Gx 1+4, The Neutron Star Symbiotic, Kenneth H. Hinkle, Francis C. Fekel, Richard R. Joyce, Peter R. Wood, Verne V. Smith, Thomas Lebzelter
Information Systems and Engineering Management Research Publications
We have computed, using 17 infrared radial velocities, the first set of orbital elements for the M giant in the symbiotic binary V2116 Ophiuchi. The giant's companion is a neutron star, the bright X-ray source GX 1+4. We rule out the previously proposed period of 304 days and instead find an orbital period of 1161 days, by far the longest of any known X-ray binary. The orbit has a modest eccentricity of 0.10, with an orbital circularization time of ≲5 × 106 yr. The large mass function of the orbit significantly restricts the mass of the M giant. Adopting a …
Absolute Magnitude Distributions And Light Curves Of Stripped-Envelope Supernovae, D. Richardson, D. Branch, E. Baron
Absolute Magnitude Distributions And Light Curves Of Stripped-Envelope Supernovae, D. Richardson, D. Branch, E. Baron
Faculty and Staff Publications
The absolute visual magnitudes of three Type IIb, 11 Type Ib, and 13 Type le supernovae (collectively known as stripped-envelope supernovae) are studied by collecting data on the apparent magnitude, distance, and interstellar extinction of each event. Weighted and unweighted mean absolute magnitudes of the combined sample, as well as various subsets of the sample, are reported. The limited sample size and the considerable uncertainties, especially those associated with extinction in the host galaxies, prevent firm conclusions regarding differences between the absolute magnitudes of supernovae of Types Ib and Ic, and regarding the existence of separate groups of over-luminous and …