Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Stars, Interstellar Medium and the Galaxy

1993

Articles 1 - 16 of 16

Full-Text Articles in Physical Sciences and Mathematics

Rotation Periods Of Open Cluster Stars, Ii, Charles F. Prosser, Matthew D. Shetrone, Ettore Marilli, Santo Catalano, Scott D. Williams, Dana E. Backman, Bentley D. Laaksonen, Vikram Adige, Laurence A. Marschall, John R. Stauffer Dec 1993

Rotation Periods Of Open Cluster Stars, Ii, Charles F. Prosser, Matthew D. Shetrone, Ettore Marilli, Santo Catalano, Scott D. Williams, Dana E. Backman, Bentley D. Laaksonen, Vikram Adige, Laurence A. Marschall, John R. Stauffer

Physics and Astronomy Faculty Publications

We present the results from a photometric monitoring program of 21 stars observed during 1992 in the Pleiades and Alpha Persei open clusters. Period determinations for 16 stars are given, 13 of which are the first periods reported for these stars. Brightness variations for an additional five cluster stars are also given. One K dwarf member of the a Per cluster is observed to have a period of rotation of only 4.39 hr, perhaps the shortest period currently known among BY Draconis variables. The individual photometric measurements have been deposited with the NSSDC. Combining current X-ray flux determinations with known …

Go to article

Chromospherically Active Stars. Xi. Giants With Compact Hot Companions And The Barium Star Scenario, Francis C. Fekel, Gregory W. Henry, Michael R. Busby, Joseph J. Eitter Dec 1993

Chromospherically Active Stars. Xi. Giants With Compact Hot Companions And The Barium Star Scenario, Francis C. Fekel, Gregory W. Henry, Michael R. Busby, Joseph J. Eitter

Information Systems and Engineering Management Research Publications

We have determined spectroscopic orbits for three chromsopherically active giants that have hot compact companions. They are HD 160538 (KO III + wd, P = 904 days), HD 165141 (G8 III + wd, P approximately 5200 days), and HD 185510 (KO III + sdB, P = 20.6619 days). By fitting an IUE spectrum with theoretical models, we find the white dwarf companion of HD 165141 has a temperature of about 35,000 K. Spectral types and rotational velocities have been determined for the three giants and distances have been estimated. These three systems and 39 Ceti are compared with the barium …

Go to article

Optical Spectroscopy Of The Dusty K5 V Star Hd 98800, Francis C. Fekel, Bernard W. Bopp Dec 1993

Optical Spectroscopy Of The Dusty K5 V Star Hd 98800, Francis C. Fekel, Bernard W. Bopp

Information Systems and Engineering Management Research Publications

High-resolution CCD spectra of the red region of the dusty K5 V star HD 98800, which may contain a protoplanetary disk, have been obtained at Kitt Peak National Observatory. The spectra verify the dwarf spectral type and show rotationally broadened photospheric lines, Hα emission, and a very strong Li Ι λ6707 absorption line, all of which confirm the star as a very young object. The overall spectrum of HD 98800 closely resembles that of the young, chromospherically active, single BY Dra star HD 82558 (=LQ Hya). The measured Li Ι equivalent width of 0.39 Å implies an abundance log N …

Go to article

Extremely Active Long-Period Rs Cvn Binary Hd 12545, Bernard W. Bopp, Francis C. Fekel, Jason P. Aufdenberg, Robert C. Dempsey, Virgiljus Dadonas Dec 1993

Extremely Active Long-Period Rs Cvn Binary Hd 12545, Bernard W. Bopp, Francis C. Fekel, Jason P. Aufdenberg, Robert C. Dempsey, Virgiljus Dadonas

Information Systems and Engineering Management Research Publications

The active-chromosphere giant HD 12545 is noteworthy for its remarkable 1990 photmetric amplitude of 0.6 mag in V, which implies that nearly half the visible hemisphere of the star was covered by cool spots. We report the results of a spectroscopic study of HD 12545, showing it to be an active-chromosphere binary with an orbital period of 23.97 days. We establish the spectral type as KO III, and measure v sin i = 17 +/- 2 km/s. The various indicators of activity in the optical and ultraviolet suggest that HD 12545 is one of the most active RS CVn systems …

Go to article

Spot On Rs Cvn From Spectroscopy And Photometry, Joel A. Eaton, Gregory W. Henry, Coretta Bell, Albert Okorogu Sep 1993

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 …

Go to article

The Spectroscopic Orbit Of Gamma Geminorum And A Search For Its Secondary, Francis C. Fekel, Jocelyn Tomkin Sep 1993

The Spectroscopic Orbit Of Gamma Geminorum And A Search For Its Secondary, Francis C. Fekel, Jocelyn Tomkin

Information Systems and Engineering Management Research Publications

New spectroscopic observations of Gamma Geminorum, a bright, 'normal' A1 IV star have resulted in an improved spectroscopic orbit. The orbital period is 12.632 +/- 0.002 yr, the eccentricity is 0.893 +/-0.002, and the orbital parallax is 0.0291 +/-0.0024 arcsec, or a distance of 34 pc. We determine a v sin i of 8 +/-1 km/s for the A star, which confirms that it is a slow rotator. Near-infrared spectroscopic observations at 8806 A, obtained through the brief nodal passage, have resulted in the probable detection of the secondary. The masses are 2.8 and 1.07 solar mass and the Delta …

Go to article

Radial-Velocity And Light Variations Of Ir Cephei, Laurence A. Marschall, Michael A. Seeds, Robert J. Davis Sep 1993

Radial-Velocity And Light Variations Of Ir Cephei, Laurence A. Marschall, Michael A. Seeds, Robert J. Davis

Physics and Astronomy Faculty Publications

Radical-velocity observations of the short-period Cepheid, IR Cephei, have been used to derive a complete radial-velocity versus phase curve for the variable, to investigate the presence of a possible binary companion, and to address the question of its membership in the Cepheus OB2 association. The observations are consistent with the absence of a close binary companion and shed doubt on its membership in the association. Photoelectric observations made with the Phoenix 10 Automated Photometric Telescope confirm the single nature of the star. We present simulations to show the effects of an equiluminous companion on the light curve of a Cepheid, …

Go to article

Ccd Photometry Of The Old Open Cluster M67, Kent A. Montgomery, Laurence A. Marschall, Kenneth A. Janes Jul 1993

Ccd Photometry Of The Old Open Cluster M67, Kent A. Montgomery, Laurence A. Marschall, Kenneth A. Janes

Physics and Astronomy Faculty Publications

We present a CCD photometric survey of the central one-half degree of the old open cluster, M67, in U, B, V, and I colors to magnitude V=20. Extensive comparison of our photometry with other published datasets shows excellent agreement, indicating that CCD photometry is capable of producing a uniform set of measurements consistent with the photometric system defined primarily by the Landolt standard sequence. The color-magnitude diagram of the cluster shows a well-defined main sequence extending at least to the limit of the photometry at Mv=10.55 and a substantial binary sequence. At least 38% of cluster stars are …

Go to article

Photometric And Spectroscopic Observations Of Sn 1990e In Ngc 1035: Observational Constraints For Models Of Type Ii Supernovae, Brian P. Schmidt, Robert P. Kirshner, Rudolph Schild, Bruno Leibundgut, David Jeffery, S. P. Willner, Reynier Peletier, Ann I. Zabludoff, Mark M. Phillips, Nicholas B. Suntzeff, Mario Hamuy, Lisa A. Wells, Chris Smith, Jack A. Baldwin, W. G. Weller, M. Navarette, L. Gonzalez, Alexei V. Filippenko, Joseph C. Shields, Charles C. Steidel, Saul Perlmutter, Carlton R. Pennypacker, Craig K. Smith, Alain C. Porter, Todd A. Boroson, Raylee Stathakis, Russell Cannon, J. Peters, E. Horine, Kenneth C. Freeman, Donna S. Womble, Remington P.S. Stone, Laurence A. Marschall, Andrew C. Phillips, A. Saha, Howard E. Bond Jun 1993

Photometric And Spectroscopic Observations Of Sn 1990e In Ngc 1035: Observational Constraints For Models Of Type Ii Supernovae, Brian P. Schmidt, Robert P. Kirshner, Rudolph Schild, Bruno Leibundgut, David Jeffery, S. P. Willner, Reynier Peletier, Ann I. Zabludoff, Mark M. Phillips, Nicholas B. Suntzeff, Mario Hamuy, Lisa A. Wells, Chris Smith, Jack A. Baldwin, W. G. Weller, M. Navarette, L. Gonzalez, Alexei V. Filippenko, Joseph C. Shields, Charles C. Steidel, Saul Perlmutter, Carlton R. Pennypacker, Craig K. Smith, Alain C. Porter, Todd A. Boroson, Raylee Stathakis, Russell Cannon, J. Peters, E. Horine, Kenneth C. Freeman, Donna S. Womble, Remington P.S. Stone, Laurence A. Marschall, Andrew C. Phillips, A. Saha, Howard E. Bond

Physics and Astronomy Faculty Publications

We present 126 photometric and 30 spectral observation of SN 1990E spanning from 12 days before B maximum to 600 days past discovery. These observations show that SN 1990E was of type II-P, displaying hydrogen in its spectrum, and the characteristic plateau in its light curve. SN 1990E is one of the few SNe II which has been well observed before maximum light, and we present evidence that this SN was discovered very soon after its explosion. In the earliest spectra we identify, for the first time, several N II lines. We present a new technique for measuring extinction to …

Go to article

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 Jun 1993

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 …

Go to article

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 May 1993

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 …

Go to article

The Triple Symbiotic System Ch Cygni, Kenneth H. Hinkle, Francis C. Fekel, Diana S. Johnson, Werner W.G. Scharlach Mar 1993

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 …

Go to article

Lithium And Rapid Rotation In Chromospherically Active Single Giants, Francis C. Fekel, Suchitra C. Balachandran Feb 1993

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.

Go to article

Oscillator Strengths Of The Si Ii 181 Nanometer Resonance Multiplet, Scott D. Bergeson, J. E. Lawler Jan 1993

Oscillator Strengths Of The Si Ii 181 Nanometer Resonance Multiplet, Scott D. Bergeson, J. E. Lawler

Faculty Publications

We report Si II experimental log (gf)-values of –2.38(4) for the 180.801 nm line, of –2.18(4) for the 181.693 nm line, and of –3.29(5) for the 181.745 nm line, where the number in parenthesis is the uncertainty in the last digit. The overall uncertainties (~10%) include the 1 σ random uncertainty (~6%) and an estimate of the systematic uncertainty. The oscillator strengths are determined by combining branching fractions and radiative lifetimes. The branching fractions are measured using standard spectroradiometry on an optically thin source; the radiative lifetimes are measured using time-resolved laser-induced fluorescence.

Go to article

Extended Variability Of The Symbiotic Star Ag Draconis, Menas Kafatos, S. R. Meier Jan 1993

Extended Variability Of The Symbiotic Star Ag Draconis, Menas Kafatos, S. R. Meier

Mathematics, Physics, and Computer Science Faculty Articles and Research

We have analyzed the complete set of available IUE (International Ultraviolet Explorer) spectra for the symbiotic star AG Draconis covering the period from 1979 to 1989. All absolute line fluxes and wavelengths have been obtained for the prominent emission lines in the λλ1200-3200 wavelength range. These spectra contain observations which were taken before, during and after the two extended outbursts which occurred on 1980 November to 1981 November and 1985 February to 1986 January. These two outburst events have two maxima that are separated by ~1600 days, a time scale not known to be associated with the star, but which …

Go to article

Radiative Lifetimes, Branching Ratios, And Absolute Transition Probabilities In Cr Ii And Zn Ii, Scott D. Bergeson, J. E. Lawler Jan 1993

Radiative Lifetimes, Branching Ratios, And Absolute Transition Probabilities In Cr Ii And Zn Ii, Scott D. Bergeson, J. E. Lawler

Faculty Publications

New absolute atomic transition probability measurements are reported for 12 transitions in Cr II and two transitions in Zn II. These transition probabilities are determined by combining branching ratios measured by classical techniques and radiative lifetimes measured by time-resolved laser-induced fluorescence. The measurements are compared with branching fractions, radiative lifetimes, and transition probabilities in the literature. The 206 nm resonance multiplets in Cr II and Zn II are included in this work. These multiplets are very useful in determining the distribution of the elements in the gas versus grain phases in the interstellar medium.

Go to article