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Articles 241 - 270 of 282
Full-Text Articles in Astrophysics and Astronomy
The Relative Age Of The Thin And Thick Galactic Disks, Wilson M. Liu, Brian Chaboyer
The Relative Age Of The Thin And Thick Galactic Disks, Wilson M. Liu, Brian Chaboyer
Dartmouth Scholarship
We determine the relative ages of the open cluster NGC 188 and selected Hipparcos field stars by isochrone fitting and compare them to the age of the thick-disk globular cluster 47 Tuc. The best-fit age for NGC 188 was determined to be 6.5 ± 1.0 Gyr. The solar-metallicity Hipparcos field stars yielded a slightly older thin-disk age, 7.5 ± 0.7 Gyr. Two slightly metal-poor ([Fe/H] = -0.22) field stars whose kinematic and orbital parameters indicate that they are members of the thin disk were found to have an age of 9.7 ± 0.6 Gyr. The age for 47 Tuc was …
The Infall Region Of Abell 576: Independent Mass And Light Profiles, Kenneth Rines, Margaret J. Geller, Antonaldo Diaferio, Joseph J. Mohr, Gary A. Wegner
The Infall Region Of Abell 576: Independent Mass And Light Profiles, Kenneth Rines, Margaret J. Geller, Antonaldo Diaferio, Joseph J. Mohr, Gary A. Wegner
Dartmouth Scholarship
We describe observations of the nearby (cz = 11,487 km s-1) cluster of galaxies Abell 576 beyond the virial radius and into the infall region where galaxies are on their first or second pass through the cluster. Using 1057 redshifts, we use the infall pattern in redshift space to determine the mass profile of A576 to a radius of ~4 h-1 Mpc. This mass estimation technique makes no assumptions about the equilibrium state of the cluster. Within ~1 h-1 Mpc, the mass profile we derive exceeds that determined from X-ray observations by a factor of …
Rosat Hri And Asca Observations Of The Spiral Galaxy Ngc 6946 And Its Northeast Complex Of Luminous Supernova Remnants, Eric M. Schlegel, William P. Blair, Robert A. Fesen
Rosat Hri And Asca Observations Of The Spiral Galaxy Ngc 6946 And Its Northeast Complex Of Luminous Supernova Remnants, Eric M. Schlegel, William P. Blair, Robert A. Fesen
Dartmouth Scholarship
Analysis of 80 ks ASCA and 60 ks ROSAT HRI observations of the face-on spiral galaxy NGC 6946 are presented. The ASCA image is the first observation of this galaxy above ~2 keV. Diffuse emission may be present in the inner ~4' extending to energies above ~2–3 keV. In the HRI data, 14 pointlike sources are detected, the brightest two being a source very close to the nucleus and a source to the northeast that corresponds to a luminous complex of interacting supernova remnants (SNRs). We detect a point source that lies ~30'' west of the SNR complex but with …
Enear Redshift-Distance Survey: Cosmological Constraints, Stefano Borgani, Mariangela Bernardi, Luiz N. Da Costa, Gary Wegner
Enear Redshift-Distance Survey: Cosmological Constraints, Stefano Borgani, Mariangela Bernardi, Luiz N. Da Costa, Gary Wegner
Dartmouth Scholarship
We present an analysis of the ENEAR sample of peculiar velocities of field and cluster elliptical galaxies, obtained with Dn-σ distances. We use the velocity correlation function ψ1(r) to analyze the statistics of the field object's velocities, while the analysis of the cluster data is based on the estimate of their rms peculiar velocity Vrms. The results are compared with predictions from cosmological models using linear theory. The statistics of the model velocity field is parameterized by the amplitude η8 = σ8Ω and by the shape parameter Γ of the cold dark matter-like power spectrum. …
Grb 991216 Joins The Jet Set: Discovery And Monitoring Of Its Optical Afterglow, J. P. Halpern, R. Uglesich, N. Mirabal, S. Kassin, J. Thorstenson, W. C. Keel, A. Diercks, J. S. Bloom, F. Harrison, J. Mattox, M. Eracleous
Grb 991216 Joins The Jet Set: Discovery And Monitoring Of Its Optical Afterglow, J. P. Halpern, R. Uglesich, N. Mirabal, S. Kassin, J. Thorstenson, W. C. Keel, A. Diercks, J. S. Bloom, F. Harrison, J. Mattox, M. Eracleous
Dartmouth Scholarship
The optical light curve of the energetic γ-ray burst GRB 991216 is consistent with jetlike behavior in which a power-law decay steepens from t-1.22+-0.04 at early times to t-1.53 +- 0.05 in a gradual transition at around 2 days. The derivation of the late-time decay slope takes into account the constant contribution of a host or intervening galaxy, which was measured 110 days after the event at R = 24.56 +- 0.14, although the light curve deviates from a single power law whether or not a constant term is included. The early-time spectral energy distribution of the afterglow …
The Age Of The Inner Halo Globular Cluster Ngc 6652, Brian Chaboyer, Ata Sarajedini, Taft E. Armandroff
The Age Of The Inner Halo Globular Cluster Ngc 6652, Brian Chaboyer, Ata Sarajedini, Taft E. Armandroff
Dartmouth Scholarship
Hubble Space Telescope (V, I) photometry has been obtained for the inner halo globular cluster NGC 6652. The photometry reaches ~4 mag below the turnoff and includes a well-populated horizontal branch. This cluster is located close to the Galactic center, at RGC 2.0 kpc, with a reddening of E(V-I) = 0.15 ± 0.02, and has a metallicity of [Fe/H] -0.85. Based upon ΔV, NGC 6652 is 11.7 ± 1.6 Gyr old. Using ΔV, precise differential ages for 47 Tuc (a thick disk globular cluster), M107, and NGC …
The Pulsation Properties Of Procyon A, Brian Chaboyer, P. Demarque, D. B. Guenther
The Pulsation Properties Of Procyon A, Brian Chaboyer, P. Demarque, D. B. Guenther
Dartmouth Scholarship
A grid of stellar evolution models for Procyon A has been calculated. These models include the best physics available to us (including the latest opacities and equation of state) and are based on the revised astrometric mass of Girard et al. Models were calculated with helium diffusion and with the combined effects of helium and heavy-element diffusion. Oscillation frequencies for l = 0, 1, 2, and 3 p-modes and the characteristic period spacing for the g-modes were calculated for these models. We find that g-modes are sensitive to model parameters that effect the structure of the core, …
Large‐Scale Power Spectrum And Cosmological Parameters From Sfi Peculiar Velocities, Wolfram Freudling, Idit Zehavi, Luiz N. Da Costa, Avishai Dekel, Amiram Eldar, Riccardo Giovanelli, Martha P. Haynes, John J. Salzer, Gary Wegner, Saleem Zaroubi
Large‐Scale Power Spectrum And Cosmological Parameters From Sfi Peculiar Velocities, Wolfram Freudling, Idit Zehavi, Luiz N. Da Costa, Avishai Dekel, Amiram Eldar, Riccardo Giovanelli, Martha P. Haynes, John J. Salzer, Gary Wegner, Saleem Zaroubi
Dartmouth Scholarship
We estimate the power spectrum of mass density fluctuations from peculiar velocities of galaxies by applying an improved maximum likelihood technique to the new all-sky SFI catalog. Parametric models are used for the power spectrum and the errors, and the free parameters are determined by assuming Gaussian velocity fields and errors and maximizing the probability of the data given the model. It has been applied to generalized cold dark matter (CDM) models with and without COBE normalization. The method has been carefully tested using artificial SFI catalogs. The most likely distance errors are found to be similar to the original …
Gravitational Waves From Collapsing Vacuum Domains, Marcelo Gleiser, Ronald Roberts
Gravitational Waves From Collapsing Vacuum Domains, Marcelo Gleiser, Ronald Roberts
Dartmouth Scholarship
The breaking of an approximate discrete symmetry, the final stages of a first order phase transition, or a postinflationary biased probability distribution for scalar fields are possible cosmological scenarios characterized by the presence of unstable domain wall networks. Combining analytical and numerical techniques, we show that the nonspherical collapse of these domains can be a powerful source of gravitational waves. We compute their contribution to the stochastic background of gravitational radiation and explore their observability by present and future gravitational wave detectors.
The Motions Of Clusters Of Galaxies And The Dipoles Of The Peculiar Velocity Field, Riccardo Giovanelli, Martha P. Haynes, John J. Salzer, Gary Wegner
The Motions Of Clusters Of Galaxies And The Dipoles Of The Peculiar Velocity Field, Riccardo Giovanelli, Martha P. Haynes, John J. Salzer, Gary Wegner
Dartmouth Scholarship
In preceding papers of this series, TF relations for galaxies in 24 clusters with radial velocities between 1000 and 9200 km s-1 (SCI sample) were obtained, a Tully-Fisher (TF) template relation was constructed, and mean offsets of each cluster with respect to the template were obtained. Here, an estimate of the line-of-sight peculiar velocities of the clusters and their associated errors are given. It is found that cluster peculiar velocities in the cosmic microwave background reference frame do not exceed 600 km s-1 and that their distribution has a line-of-sight dispersion of 300 km s-1, suggesting …
Cluster Versus Field Elliptical Galaxies And Clues On Their Formation, Mariangela Bernardi, Alvio Renzini, Luiz N. Da Costa, Gary Wegner
Cluster Versus Field Elliptical Galaxies And Clues On Their Formation, Mariangela Bernardi, Alvio Renzini, Luiz N. Da Costa, Gary Wegner
Dartmouth Scholarship
Using new observations for a sample of 931 early-type galaxies, we investigate whether the Mg2-σ0 relation shows any dependence on the local environment. The galaxies have been assigned to three different environments depending on the local overdensity (clusters, groups, and field); we used our complete redshift database to guide the assignment of galaxies. It is found that cluster, group, and field early-type galaxies follow almost identical Mg2-σ0 relations, with the largest Mg2 zero-point difference (clusters minus field) being only 0.007±0.002 mag. No correlation of the residuals is found with the morphological type or …
Flows On Scales Of 150 Mpc?, K. R. Müller, W. Freudling, R. Watkins, G. Wegner
Flows On Scales Of 150 Mpc?, K. R. Müller, W. Freudling, R. Watkins, G. Wegner
Dartmouth Scholarship
In order to investigate the reality of large-scale streaming motion on scales of up to 150 Mpc, we have studied the peculiar motions of ~200 early-type galaxies in three directions of the South Equatorial Strip at distances out to ~20,000 km s-1. The new Automatic Plate Measuring Facility South Equatorial Strip Catalog (-175<δ<+25) was used to select the sample of field galaxies in three directions: (1) 15h10m-16h10m; (2) 20h30m-21h50m; (3) 00h10m-01h30m. New R-band CCD photometry and spectroscopic data for the galaxies are used. The fundamental plane distance-indicator …
Peculiar Velocity Dipoles Of Field Galaxies, Riccardo Giovanelli, Martha P. Haynes, Wolfram Freudling, Luiz N. Da Costa, John J. Salzer, Gary Wegner
Peculiar Velocity Dipoles Of Field Galaxies, Riccardo Giovanelli, Martha P. Haynes, Wolfram Freudling, Luiz N. Da Costa, John J. Salzer, Gary Wegner
Dartmouth Scholarship
The Tully-Fisher (TF) relation is applied to obtain peculiar velocities of field spiral galaxies and to calculate dipoles of the peculiar velocity field to cz8000 km s-1. The field galaxy sample is spatially coextensive with and completely independent of a cluster sample, for which dipole characteristics are given in a separate paper. Dipoles of the peculiar velocity field are obtained separately by applying (1) an inverse version of the TF relation and selecting galaxies by redshift windowing and (2) a direct TF relation, with velocities corrected for the inhomogeneous Malmquist bias and windowing galaxies by TF distance. …
The Century Survey: A Deeper Slice Of The Universe, Margaret J. Geller, Michael J. Kurtz, Gary Wegner, John R. Thorstensen
The Century Survey: A Deeper Slice Of The Universe, Margaret J. Geller, Michael J. Kurtz, Gary Wegner, John R. Thorstensen
Dartmouth Scholarship
The "Century Survey" (CS hereafter) is a complete redshift survey of a 1° wide strip. It covers 0.03 steradians to a limiting mR = 16.13. The survey is 98.4% complete and contains 1762 galaxies. Large-scale features in the survey are qualitatively similar to those in other surveys: there are large voids surrounded or nearly surrounded by thin dense regions which are sections of structures like (and including) the Great Wall. The survey crosses the classical Corona Borealis supercluster. The galaxy density enhancement associated with this system extends for <˜100h-1 Mpc-1 (the Hubble constant is H0 = 100h …
The I Band Tully-Fisher Relation For Cluster Galaxies: Data Presentation., Riccardo Giovanelli, Martha P. Haynes, Terry Herter, Nicole P. Vogt, Gary Wegner, John J. Salzer, Luiz N. Da Costa, Wolfram Freudling
The I Band Tully-Fisher Relation For Cluster Galaxies: Data Presentation., Riccardo Giovanelli, Martha P. Haynes, Terry Herter, Nicole P. Vogt, Gary Wegner, John J. Salzer, Luiz N. Da Costa, Wolfram Freudling
Dartmouth Scholarship
Observational parameters which can be used for redshift-independent distance determination using the Tully-Fisher (TF) technique are given for 782 spiral galaxies in the fields of 24 clusters or groups. I band photometry for the full sample was either obtained by us or compiled from published literature. Rotational velocities are derived either from 21 cm spectra or optical emission line long--slit spectra, and converted to a homogeneous scale. In addition to presenting the data, a discussion of the various sources of error on TF parameters is introduced, and the criteria for the assignment of membership to each cluster are given.
Far-Ultraviolet Absorption Lines In The Remnant Of Sn 1006, Chi-Chao Wu, D. Michael Crenshaw, Andrew J. S. Hamilton, Robert A. Fesen
Far-Ultraviolet Absorption Lines In The Remnant Of Sn 1006, Chi-Chao Wu, D. Michael Crenshaw, Andrew J. S. Hamilton, Robert A. Fesen
Dartmouth Scholarship
We have obtained a far-ultraviolet spectrum (1150-1600 Å) of a hot subdwarf star behind the remnant of supernova 1006 with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope. The high-quality spectrum is used to test previous identifications of the strong absorption features discovered with the International Ultraviolet Explorer. These features have FWHM = 4000 (±300) km s-1 and are not at the rest wavelengths of known interstellar lines, as opposed to the broader (~8000 km s-1 FWHM) Fe II lines from the remnant centered at 0 km s-1 in near-UV FOS spectra. We …
The Mass Distribution In The Nearby Universe, Luiz N. Da Costa, Wolfram Freudling, Gary Wegner, Riccardo Giovanelli
The Mass Distribution In The Nearby Universe, Luiz N. Da Costa, Wolfram Freudling, Gary Wegner, Riccardo Giovanelli
Dartmouth Scholarship
We present a new reconstruction of the mass density and the peculiar velocity fields in the nearby universe using recent measurements of Tully-Fisher distances for a sample of late spirals. We find significant differences between our reconstructed fields and those obtained in earlier work: overdensities tend to be more compact while underdense regions, consisting of individual voids, are more abundant. Our results suggest that voids observed in redshift surveys of galaxies represent real voids in the underlying matter distribution. While we detect a bulk velocity of ~300 km s-1, within a top-hat window 6000 km s-1 in …
A Test Of The Lauer-Postman Bulk Flow, Riccardo Giovanelli, Martha P. Haynes, Gary Wegner, Luiz N. Da Costa
A Test Of The Lauer-Postman Bulk Flow, Riccardo Giovanelli, Martha P. Haynes, Gary Wegner, Luiz N. Da Costa
Dartmouth Scholarship
We use Tully-Fisher distances for a sample of field late spiral galaxies to test the Lauer & Postman result suggestive of a bulk flow with respect to the cosmic microwave background reference frame, of amplitude of +689 km s-1 in the direction l = 343°, b = +52°. A total of 432 galaxies are used, subdivided between two cones, of 30° semiaperture each and pointed toward the apex and antapex of the LP motion, respectively. The peculiar velocities in the two data sets are inconsistent with a bulk flow of the amplitude claimed by Lauer & Postman. When combined …
Determination Of Malmquist Bias And Selection Effects From Monte Carlo Simulations, Wolfram Freudling, Luiz N. Da Costa, Gary Wegner, Riccardo Giovanelli
Determination Of Malmquist Bias And Selection Effects From Monte Carlo Simulations, Wolfram Freudling, Luiz N. Da Costa, Gary Wegner, Riccardo Giovanelli
Dartmouth Scholarship
Maps of the peculiar velocity field derived from distance relations are affected by Malmquist type bias and selection effects. Because of the large number of interdependent effects, they are in most cases difficult to treat analytically. Monte Carlo simulations are used to understand and evaluate these effects. In these simulations the "true" spatial distribution and relevant properties of galaxies as well as selection effects and observational uncertainties are realistically modeled. The results of the simulation can be directly applied to correct observed peculiar velocity maps. The simulation is used to investigate biases in samples of measured peculiar velocities by Lynden-Bell …
The Spectroscopic-Speckle Triple System Hr 6469, Colin D. Scarfe, David J. Barlow, Francis C. Fekel, Richard F. Rees, R. W. Lyons, Charles Thomas Bolton, Harold A. Mcalister, William I. Hartkopf
The Spectroscopic-Speckle Triple System Hr 6469, Colin D. Scarfe, David J. Barlow, Francis C. Fekel, Richard F. Rees, R. W. Lyons, Charles Thomas Bolton, Harold A. Mcalister, William I. Hartkopf
Information Systems and Engineering Management Research Publications
HR 6469 consists of an evolved G star and a close pair of stars, believed to be on the main sequence, the brighter of which is an early F star. Shallow eclipses have been detected in the close pair and the components of the wide system have been resolved over most of the orbit by speckle interferometry (McAlister & Hartkopf, Second Catalog of Interferometric Observations of Binary Stars, Center for High Angular Resolution Astronomy, Contribution No. 2 (CHARA), 1988). This paper presents radial velocities, obtained at the David Dunlap, McDonald, Kitt Peak and Dominion Astrophysical Observatories, for the G star …
Spot On Rs Cvn From Spectroscopy And Photometry, Joel A. Eaton, Gregory W. Henry, Coretta Bell, Albert Okorogu
Spot On Rs Cvn From Spectroscopy And Photometry, Joel A. Eaton, Gregory W. Henry, Coretta Bell, Albert Okorogu
Information Systems and Engineering Management Research Publications
We have used contemporaneous spectra and V light curves to form spot models for RS CVn in 1991 and 1992. More than two spots are needed to fit all the properties of the observations. In fact, moderately small spots (22 x 28 deg in latitude and longitude) having only a slight effect on the rotational light curve were eclipsed in both years, and we find that a collection of 6-8 such moderate spots is required to fit the line profiles in each year. These groups of spots also account naturally for a difference in level of light between the two …
Chromospherically Active Stars. X. Spectroscopy And Photometry Of Hd 212280, Francis C. Fekel, Jared C. Browning, Gregory W. Henry, Mary D. Morton, Douglas S. Hall
Chromospherically Active Stars. X. Spectroscopy And Photometry Of Hd 212280, Francis C. Fekel, Jared C. Browning, Gregory W. Henry, Mary D. Morton, Douglas S. Hall
Information Systems and Engineering Management Research Publications
The system HD 212280 is a chromospherically active double lined spectroscopic binary with an orbital period of 45.284 days and an eccentricity of 0.50. The spectrum is composite with spectral types of G8 IV and F5-8 V for the components. An estimated inclination of 78 +/- 8 deg results in masses of 1.7 and 1.4 solar mass for the G subgiant and mid-F star, respectively. The distance to the system is estimated to be 112 pc. Photometric observations obtained between 1987 November and 1992 June reveal that HD 212280 is a newly identified variable star with a V amplitude of …
Observations Of The Ca Ii Infrared Triplet In Chromospherically Active Single And Binary Stars, Robert C. Dempsey, Bernard W. Bopp, Gregory W. Henry, Douglas S. Hall
Observations Of The Ca Ii Infrared Triplet In Chromospherically Active Single And Binary Stars, Robert C. Dempsey, Bernard W. Bopp, Gregory W. Henry, Douglas S. Hall
Information Systems and Engineering Management Research Publications
Spectroscopic observations of the Ca II infrared triplet (8498, 8542, 8662 A) have been obtained for 45 stars which are known or suspected to be chromospherically active. The sample includes both single and binary stars of spectral types from F2 to M5 spanning luminosity classes III, IV, and V. Several different types of activity diagnostics were measured, and their relative merits are discussed. Dependence of chromospheric emission upon rotation period, luminosity, temperature, and duplicity are analyzed. Synchronous binaries show a slight trend of increased emission with decreasing period while the asynchronous binaries show abnormally high activity levels for their rotation …
The Triple Symbiotic System Ch Cygni, Kenneth H. Hinkle, Francis C. Fekel, Diana S. Johnson, Werner W.G. Scharlach
The Triple Symbiotic System Ch Cygni, Kenneth H. Hinkle, Francis C. Fekel, Diana S. Johnson, Werner W.G. Scharlach
Information Systems and Engineering Management Research Publications
Analysis of high-resolution IR spectra of CH Cygni shows that the star is a triple system with a short period orbit of just over 2 yrs. The period ratio of seven for CH Cyg is the smallest known for a triple system. The symbiotic pair is the short-period system. An eccentric and a circular orbit solution are determined for the short-period pair, and the circular orbit solution is found to be more appropriate. The observed eccentricity appears to be due to phase-dependent line asymmetries resulting from the irradiation of the M giant by the white dwarf. The system does not …
Lithium And Rapid Rotation In Chromospherically Active Single Giants, Francis C. Fekel, Suchitra C. Balachandran
Lithium And Rapid Rotation In Chromospherically Active Single Giants, Francis C. Fekel, Suchitra C. Balachandran
Information Systems and Engineering Management Research Publications
The rotational velocities presently obtained via spectroscopic observations of a group of moderately rapidly rotating, chomospherically active single giants indicate that Gray's (1989) rotostat hypothesis requires modification. Their rapid rotation appears to be due to high Li abundances, and results in increased chromospheric activity. A scenario is projected in which the surface convection zone reaches the rapidly rotating core just as a star begins its first ascent of the giant branch, and dredges both high angular momentum material and freshly synthesized Li to the surface.
Line Profile Asymmetries In Chromospherically Active Stars, Robert C. Dempsey, Bernard W. Bopp, Klaus G. Strassmeier, Arno F. Granados, Gregory W. Henry, Douglas S. Hall
Line Profile Asymmetries In Chromospherically Active Stars, Robert C. Dempsey, Bernard W. Bopp, Klaus G. Strassmeier, Arno F. Granados, Gregory W. Henry, Douglas S. Hall
Information Systems and Engineering Management Research Publications
A powerful, new probe of chromospheric activity, cross-correlation, has been developed and applied to a variety of stars. In this particular application, an entire CCD spectrum of an active star is correlated with the spectrum of a narrow-line, inactive star of similar spectral type and luminosity class. Using a number of strong lines in this manner enables the detection of absorption profile asymmetries at moderate resolution (lambda/Delta lambda about 40,000) and S/N 150:1. This technique has been applied to 14 systems mostly RS CVn's, with 10 not greater than nu sin i not greater than 50 km/s and P not …
Speckle And Spectroscopic Orbits Of The Early A-Type Triple System In Virginis, William I. Hartkopf, Harold A. Mcalister, Xinxing Yang, Francis C. Fekel
Speckle And Spectroscopic Orbits Of The Early A-Type Triple System In Virginis, William I. Hartkopf, Harold A. Mcalister, Xinxing Yang, Francis C. Fekel
Information Systems and Engineering Management Research Publications
Eta Virginis is a bright (V = 3.89) triple system of composite spectral type A2 IV that has been observed for over a dozen years with both spectroscopy and speckle interferometry. Analysis of the speckle observations results in a long period of 13.1 yr. This period is also detected in residuals from the spectroscopic observations of the 71.7919 day short-period orbit. Elements of the long-period orbit were determined separately using the observations of both techniques. The more accurate elements from the speckle solution have been assumed in a simultaneous spectroscopic determination of the short- and long-period orbital elements. The magnitude …
Hr 266=Ads 784: An Early Type Spectroscopic, Speckle Astrometric Multiple System, Warren A. Cole, Francis C. Fekel, William I. Hartkopf, Harold A. Mcalister, Jocelyn Tomkin
Hr 266=Ads 784: An Early Type Spectroscopic, Speckle Astrometric Multiple System, Warren A. Cole, Francis C. Fekel, William I. Hartkopf, Harold A. Mcalister, Jocelyn Tomkin
Information Systems and Engineering Management Research Publications
The detection and nature of a 'speckle astrometric' system are reported with attention given to alternative interpretations of the system components. The HR 226 = ADS 784 system is described as a short-period binary (with a period of 4.241148 +/- 0.000008 d) orbiting an unseen companion (with a period of 1769 +/- 10 d), and the triple's visual orbit is 83.10 +/- 0.20 yr. The elements of the various orbits taken from spectroscopic data are employed to develop the model scenarios. The masses and spectral types of the components are developed and used to calculate the inclinations of the short-, …
Chromospherically Active Stars. Ix. Hd 33798 = V390 Aurigae: A Lithium-Rich Rapidly Rotating Single Giant., Francis C. Fekel, Laurence A. Marschall
Chromospherically Active Stars. Ix. Hd 33798 = V390 Aurigae: A Lithium-Rich Rapidly Rotating Single Giant., Francis C. Fekel, Laurence A. Marschall
Information Systems and Engineering Management Research Publications
Results are presented of spectroscopic observations of HD 33798 obtained to determine if this star is a short-period binary and to examine its evolutionary status. Analysis of 40 radial velocities indicates no periodic velocity variations, suggesting that the star is single, so its rapid rotation is highly unusual. This rotation is inconsistent with the rotational brake hypothesis advanced by Gray (1989). It is proposed that HD 33798 is in a post-main-sequence phase of evolution. Its space motion is similar to FK Com, suggesting that it is a coalesced binary in the process of spinning down. Scenarios are presented to explain …
The Extraordinary 1989 December 14/15 Optical Flare Events On V711 Tauri, Gregory W. Henry, Douglas S. Hall
The Extraordinary 1989 December 14/15 Optical Flare Events On V711 Tauri, Gregory W. Henry, Douglas S. Hall
Information Systems and Engineering Management Research Publications
Photometry in B and V taken with the Vanderbilt Tennessee State 16 inch (41 cm) robotic telescope confirms the intense broad-band optical continuum flare activity reported by Chinese observers on the active chromosphere binary V711 Tau on December 14/15, 1989. Twelve hours after the flare reported from China, there occurred a separate and more intense flare with B and V amplitudes of 0.69 and 0.42 mag, respectively. These amplitudes correspond to peak flare luminosities of approximately 2 x 10 to the 33rd ergs/s in B and 1 x 10 to the 33rd ergs/s in V. The observed color of its …