Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 15 of 15
Full-Text Articles in Physical Sciences and Mathematics
Establishing Α Oph As A Prototype Rotator: Precision Orbit With New Keck, Chara, And Rv Observations, Tyler Gardner, John D. Monnier, Francis C. Fekel, Michael H. Williamson, Fabien Baron, Sasha Hinkley, Michael Ireland, Adam L. Kraus, Stefan Kraus, Rachael M. Roettenbacher, Gail Schaefer, Judit Sturmann, Laszlo Sturmann, Theo A. Ten Brummelaar
Establishing Α Oph As A Prototype Rotator: Precision Orbit With New Keck, Chara, And Rv Observations, Tyler Gardner, John D. Monnier, Francis C. Fekel, Michael H. Williamson, Fabien Baron, Sasha Hinkley, Michael Ireland, Adam L. Kraus, Stefan Kraus, Rachael M. Roettenbacher, Gail Schaefer, Judit Sturmann, Laszlo Sturmann, Theo A. Ten Brummelaar
Information Systems and Engineering Management Research Publications
Alpha Ophiuchi (Rasalhague) is a nearby rapidly rotating A5IV star that has been imaged by infrared interferometry. α Oph is also part of a known binary system, with a companion semimajor axis of ∼430 mas and a high eccentricity of 0.92. The binary companion provides the unique opportunity to measure the dynamical mass to compare with the results of rapid rotator evolution models. The lack of data near periastron passage limited the precision of mass measurements in previous work. We add new interferometric data from the MIRC combiner at the CHARA Array as well as new Keck adaptive optics imaging …
Spectroscopy Of Early F Stars: Γ Doradus Candidates And Possible Metallic Shell Stars, Francis C. Fekel, Phillip B. Warner, Anthony B. Kaye
Spectroscopy Of Early F Stars: Γ Doradus Candidates And Possible Metallic Shell Stars, Francis C. Fekel, Phillip B. Warner, Anthony B. Kaye
Information Systems and Engineering Management Research Publications
We obtained high-resolution spectroscopic observations of 34 γ Doradus candidates. From the red-wavelength spectra, we determined spectral classes, radial velocities, and projected rotational velocities. The spectra of seven late A or early F stars show metallic lines that have composite profiles consisting of a narrow component near the center of a broad line, indicating that they may be shell stars or binaries. Several stars, including HD 152896, HD 173977, HD 175337, and HD 195068/9, show large line profile asymmetries. Two stars, HD 11443 (=α Trianguli) and HD 149420, are ellipsoidal variables and not γ Doradus stars. The percentage of binary …
Chromospherically Active Stars. Xiii. Hd 30957: A Double Lined K Dwarf Binary, Francis C. Fekel, Virgiljus Dadonas, Julius Sperauskas, Todd R. Vaccaro, L. Ronald Patterson
Chromospherically Active Stars. Xiii. Hd 30957: A Double Lined K Dwarf Binary, Francis C. Fekel, Virgiljus Dadonas, Julius Sperauskas, Todd R. Vaccaro, L. Ronald Patterson
Information Systems and Engineering Management Research Publications
HD 30957 is a double-lined spectroscopic binary with a period of 44.395 days and a modest eccentricity of 0.09. The spectral types of the components are K2-3 V and K5 V. The measured v sin i for both components is less than or equal to 3 km/s and the orbital inclination is estimated to be 69 deg. The system is relatively nearby with a parallax of 0.025 sec or a distance of 40 pc. Space motions of the system indicate that it does not belong to any of the known moving groups. Absolute surface fluxes of the Ca II H …
Extremely Active Long-Period Rs Cvn Binary Hd 12545, Bernard W. Bopp, Francis C. Fekel, Jason P. Aufdenberg, Robert C. Dempsey, Virgiljus Dadonas
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 …
The Spectroscopic Orbit Of Gamma Geminorum And A Search For Its Secondary, Francis C. Fekel, Jocelyn Tomkin
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 …
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 …
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-, …
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 …
Chromospheric Ca Ii H And K And H Alpha Emission In Single And Binary Stars Of Spectra Types F6--M2, Klaus G. Strassmeier, Francis C. Fekel, Bernard W. Bopp, Robert C. Dempsey, Gregory W. Henry
Chromospheric Ca Ii H And K And H Alpha Emission In Single And Binary Stars Of Spectra Types F6--M2, Klaus G. Strassmeier, Francis C. Fekel, Bernard W. Bopp, Robert C. Dempsey, Gregory W. Henry
Information Systems and Engineering Management Research Publications
New observations of the Ca II H and K and H-epsilon region and/or the Balmer H-alpha line are presented for 100 mostly very active stars but also for weak or inactive stars with suspected activity. Correlations between chromospheric activity at Ca II H and K and H-alpha and effective surface temperature and rotation are identified, and several new stars with chromospheric Ca II H and K emission are discovered. No single activity-rotation relation can be derived for all luminosity classes, and there is clear evidence that evolved stars are generally more active than main-sequence stars of the same rotation period. …
Chromospherically Active Stars. Vii. 39 Ceti=Ay Ceti, Hd185151=V1764 Cygni, And Binary Synchronization, Francis C. Fekel, Joseph J. Eitter
Chromospherically Active Stars. Vii. 39 Ceti=Ay Ceti, Hd185151=V1764 Cygni, And Binary Synchronization, Francis C. Fekel, Joseph J. Eitter
Information Systems and Engineering Management Research Publications
Improved orbital elements have been determined for 39 Ceti and HD 185151.39 Cet has a circular orbit with an orbital period of 56.82 days, which differs substantially from its rotational period of 75-78 days. An observation of the lithium region of 39 Cet shows that the G5 III component has almost no lithium in its outer atmosphere. HD 185151 has a circular orbit with an orbital period of 40.142 days and has a nearly identical rotational period. The large mass function suggests that the secondary is a late A to mid F type star whose continuum should be visible at …
Chromospherically Active Stars. Vi. Hd 136901 = Uv Crb: A Massive Ellipsoidal K Giant Single-Lined Spectroscopic Binary, Francis C. Fekel, J. Davy Kirkpatrick, Xinxing Yang, Klaus G. Strassmeier
Chromospherically Active Stars. Vi. Hd 136901 = Uv Crb: A Massive Ellipsoidal K Giant Single-Lined Spectroscopic Binary, Francis C. Fekel, J. Davy Kirkpatrick, Xinxing Yang, Klaus G. Strassmeier
Information Systems and Engineering Management Research Publications
The variable star HD 136901 = UV CrB is a chromospherically active K2 III single-lined spectroscopic binary with an orbital period of 18.665 days. It has modest-strength Ca H and K emission and UV features, while H-alpha is a strong absorption feature containing little or no emission. The inclination of the system is 53 + or - 12 deg. The v sin i of the primary is 42 + or - 2 km/s, resulting in a minimum radius of 15.5 + or - 0.8 solar. When compared with the Roche lobe radius, this results in a mass ratio of 2.90 …
Chromospherically Active Stars. V. Hd 91816=Lr Hya: A Double-Lined By Draconis Type Binary, Francis C. Fekel, Kim Gillies, John L. Africano, Robert Quigley
Chromospherically Active Stars. V. Hd 91816=Lr Hya: A Double-Lined By Draconis Type Binary, Francis C. Fekel, Kim Gillies, John L. Africano, Robert Quigley
Information Systems and Engineering Management Research Publications
Observations of HD 91816=LR Hya obtained between 1982 and 1988 show it to consist of two nearly identical K0 dwarfs and to have an orbital period of 6.866 days and an orbital eccentricity of 0.014 + or - 0.003. The results suggest that the system has an age equal to or greater than that of the Hyades cluster. A spectroscopic parallax of 0.027 is obtained, and individual minimum masses of 0.55 solar masses each are found, implying an inclination of 61 + or - 3 deg.
Chromospherically Active Stars. Iv. Hd 178450=V478 Lyr: An Early-Type By Draconis Type Binary, Francis C. Fekel
Chromospherically Active Stars. Iv. Hd 178450=V478 Lyr: An Early-Type By Draconis Type Binary, Francis C. Fekel
Information Systems and Engineering Management Research Publications
The variable star HD 178450 = V478 Lyr is a chromospherically active G8 V single-lined spectroscopic binary with a period of 2.130514 days. This star has strong ultraviolet emission features and a filled-in Hα absorption line which is variable in strength. It is classified as an early-type BY Draconis system and is similar in many respects to the BY Dra star HD 175742 = V775 Her. The unseen secondary of HD 178450 has a mass of about 0.3 M_sun; and is probably an M2-M3 dwarf. The inclination of the system is 67°±12°. The lithium abundance of the G8 dwarf results …
Chromospherically Active Stars. I. Hd 136905., Francis C. Fekel, Douglas S. Hall, John L. Africano, Kim Gillies, Robert Quigley, Robert E. Fried
Chromospherically Active Stars. I. Hd 136905., Francis C. Fekel, Douglas S. Hall, John L. Africano, Kim Gillies, Robert Quigley, Robert E. Fried
Information Systems and Engineering Management Research Publications
The variable star HD 136905, recently designated GX Librae, is a chromospherically active K1 III single-lined spectroscopic binary with a period of 11.1345 days. It has moderate strength Ca II H and K and ultraviolet emission features, while Hα is strongly in absorption. The inclination of the systems is 58°±17° and the unseen secondary is most likely a G or K dwarf. The v sin i of the primary, 32±2 km s-1, results in a minimum radius of 7.0±0.4 R_sun;. Since the star fills a substantial fraction of its Roche lobe, the double-peaked light curve seen by photometric observers is …