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Full-Text Articles in Physical Sciences and Mathematics
An Automated Search For Variability In Chromospherically Active Stars, Gregory W. Henry, Francis C. Fekel, Douglas S. Hall
An Automated Search For Variability In Chromospherically Active Stars, Gregory W. Henry, Francis C. Fekel, Douglas S. Hall
Information Systems and Engineering Management Research Publications
We have completed an automated photometric survey of 66 potential or known chromospherically active late-type stars with the 0.4 m Vanderbilt/Tennessee State robotic telescope. The precision of the observations from this telescope matches that predicted from photon and scintillation noise alone and represents a significant improvement in the precision of previous robotic telescope surveys of chromospherically active stars. Light variability has been detected and its period has been determined for 47 stars, 41 of which are newly discovered variables. The primary mechanism of variability is rotational modulation of a spotted surface. In addition we have detected eclipses in HD 62668 …
Binary Star Orbits From Speckle Interferometry. Vi. The Nearby Solar-Type Speckle-Spectroscopic Binary Hr 6697, Harold Mcalister, William I. Hartkopf, Brian D. Mason, Francis C. Fekel, Philip A. Ianna, Andrei A. Tokovinin, Roger F. Griffin, Roger B. Culver
Binary Star Orbits From Speckle Interferometry. Vi. The Nearby Solar-Type Speckle-Spectroscopic Binary Hr 6697, Harold Mcalister, William I. Hartkopf, Brian D. Mason, Francis C. Fekel, Philip A. Ianna, Andrei A. Tokovinin, Roger F. Griffin, Roger B. Culver
Information Systems and Engineering Management Research Publications
Interferometric, spectroscopic, astrometric, and photometric observations are presented for the nearby solar-type binary HR 6697. The system consists of a G0-2 V primary and a K2-S V secondary. From a combined solution of the speckle and spectroscopic data the orbital period is 881 days or 2.41 yr, the semimajor axis is 2.1 A.U., the eccentricity is 0.42, and the inclination is 68°. The masses and luminosities are 1.16±0.12 Msun, 0.77±0.05 Msun, 1.61±0.15 Lsun, and 0.17±0.05 Lsun. Two independent determinations of the parallax, a trigonometric parallax of 0".0379±0".0030, and an orbital parallax of 0".0375±0".0014, are in excellent agreement and give a …
Chromospherically Active Stars. Xiv. A Rediscussion Of The Properties And Evolutionary State Of Hd 181943, Francis C. Fekel, Gregory W. Henry, Douglas S. Hall
Chromospherically Active Stars. Xiv. A Rediscussion Of The Properties And Evolutionary State Of Hd 181943, Francis C. Fekel, Gregory W. Henry, Douglas S. Hall
Information Systems and Engineering Management Research Publications
The chromospherically active single star HD 181943 was previously proposed as either a pre-main-sequence star seen pole-on or a post-main-sequence subgiant that evolved from an Ap star similar to 53 Cam. It also was found to be a variable star with a 385 day period. We have used new spectroscopic and photometric observations to reevaluate the properties and evolutionary state of this unusual system. We conclude that HD 181943 is a single K1 V star that has recently arrived on the ZAMS. Its emission line fluxes are nearly identical to those of HD 82558= LQ Hya, while its log lithium …
Starspot Evolution, Differential Rotation, And Magnetic Cycles In The Chromospherically Active Binaries Lambda Andromedae, Sigma Geminorum, Ii Pegasi, And V711 Tauri, Gregory W. Henry, Joel A. Eaton, Jamesia Hamer, Douglas S. Hall
Starspot Evolution, Differential Rotation, And Magnetic Cycles In The Chromospherically Active Binaries Lambda Andromedae, Sigma Geminorum, Ii Pegasi, And V711 Tauri, Gregory W. Henry, Joel A. Eaton, Jamesia Hamer, Douglas S. Hall
Information Systems and Engineering Management Research Publications
We have analyzed 15-19 yr of photoelectric photometry, obtained manually and with automated telescopes, of the chromospherically active binaries lambda And, sigma Gem, II Peg, and V711 Tau. These observations let us identify individual dark starspots on the stellar surfaces from periodic dimming of the starlight, follow the evolution of these spots, and search for long-term cyclic changes in the properties of these starspots that might reveal magnetic cycles analogous to the Sun's 11 yr sunspot cycle. We developed a computer code to fit a simple two-spot model to our observed light curves that allows us to extract the most …
A Spectroscopic And Photometric Study Of 12 Bm Camelopardalis, Douglas S. Hall, Francis C. Fekel, Gregory W. Henry, Joel A. Eaton, William S. Barksdale, Virgiljus Dadonas, Zeki Eker, Peep Kalv, Carlson R. Chambliss, Robert E. Fried, George L. Fortier, Howard J. Landis, Howard P. Louth, Harry D. Powell, Thomas G. Mcfaul, Richard Miles, Paul Nielsen, Thomas R. Renner, Stephen P. Robb, Douglas M. Slauson, Harold J. Stelzer, Rick Wasson, James E. Wood
A Spectroscopic And Photometric Study Of 12 Bm Camelopardalis, Douglas S. Hall, Francis C. Fekel, Gregory W. Henry, Joel A. Eaton, William S. Barksdale, Virgiljus Dadonas, Zeki Eker, Peep Kalv, Carlson R. Chambliss, Robert E. Fried, George L. Fortier, Howard J. Landis, Howard P. Louth, Harry D. Powell, Thomas G. Mcfaul, Richard Miles, Paul Nielsen, Thomas R. Renner, Stephen P. Robb, Douglas M. Slauson, Harold J. Stelzer, Rick Wasson, James E. Wood
Information Systems and Engineering Management Research Publications
Radial velocities from 1916.95 to 1991.95 and photometry from l979.25, both published and new in this paper, are presented and analyzed. A new solution of the radial velocity curve reveals a new period of 80.90 days and an eccentricity of e = 0.05 +/- 0.02, both very different from the 80.17 days and 0.35 found by Abt et al. (1969). An alternative solution with e = 0 is given because we cannot decide firmly whether or not the small eccentricity is real. We find V sin i = 11.3 +/- 0.3 km/s from Maidanak and 10 unequal depth. 0.048 mins …
Starspots Found On The Ellipsoidal Variable V350 Lacertae = Hr 8575, Lionel J. Crews, Douglas S. Hall, Gregory W. Henry, Richard D. Lines, Helen C. Lines, Robert E. Fried
Starspots Found On The Ellipsoidal Variable V350 Lacertae = Hr 8575, Lionel J. Crews, Douglas S. Hall, Gregory W. Henry, Richard D. Lines, Helen C. Lines, Robert E. Fried
Information Systems and Engineering Management Research Publications
It has been a puzzle why this chromospherically active, strong-dynamo K2 IV-III star is not known to have the large starspots characteristic of other such stars. Published individual radial velocities, which had never been analyzed, are used to derive an orbital solution. Combined with the one older existing orbital solution, this yields an improved orbital ephemeris: time of conjunction (K star behind) = JD 2445255.47 +/- 0.11 days and period = 17.75346 +/- 0.00016 days. All available photoelectric photometry, from 1970.9 to 1992.5, is collected A cos 2 theta fit of the ellipticity effect yields JD 2445255.60 +/- 0.06 days …