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Articles 31 - 35 of 35
Full-Text Articles in Stars, Interstellar Medium and the Galaxy
Hd 62454 And Hd 68192: Two New Γ Doradus Variables, Anthony B. Kaye, Gregory W. Henry, Francis C. Fekel, Richard O. Gray, Eloy Rodríguez, Susana Martín, Douglas R. Gies, William G. Bagnuolo, Douglas S. Hall
Hd 62454 And Hd 68192: Two New Γ Doradus Variables, Anthony B. Kaye, Gregory W. Henry, Francis C. Fekel, Richard O. Gray, Eloy Rodríguez, Susana Martín, Douglas R. Gies, William G. Bagnuolo, Douglas S. Hall
Information Systems and Engineering Management Research Publications
We present multilongitude, multicolor photometry and simultaneous high-resolution, high signal-to-noise spectroscopy of the newly discovered γ Doradus variables HD 62454 and HD 68192. From combined Johnson and Strömgren data, we are able to identify five independent periods in HD 62454 and two stable periods in HD 68192. The data presented are sufficient to rule out all physically meaningful types of variations, with the one exception of the high-order, low-degree, nonradial gravity-mode pulsations that are believed to be at work in γ Doradus stars. We also find that HD 62454 is a double-lined spectroscopic binary and we present an orbital solution.
Random Spots On Chromospherically Active Stars, Joel A. Eaton, Gregory W. Henry, Francis C. Fekel
Random Spots On Chromospherically Active Stars, Joel A. Eaton, Gregory W. Henry, Francis C. Fekel
Information Systems and Engineering Management Research Publications
We have investigated the effect of large numbers of moderately sized spots placed randomly on a differentially rotating star as the explanation of the rotational light curves of magnetically active cool stars. This hypothesis produces light variation very similar to observed light curves of RS CVn binaries, provided there are of order 10-40 spots at any time and provided individual spots have a finite lifetime.
Time-Series Photometric Spot Modeling. Ii. Fifteen Years Of Photometry Of The Bright Rs Cvn Binary Hr 7275., Klaus G. Strassmeier, Douglas S. Hall, Gregory W. Henry
Time-Series Photometric Spot Modeling. Ii. Fifteen Years Of Photometry Of The Bright Rs Cvn Binary Hr 7275., Klaus G. Strassmeier, Douglas S. Hall, Gregory W. Henry
Information Systems and Engineering Management Research Publications
We present a time-dependent spot modeling analysis of 15 consecutive years of V-band photometry of the long-period (Porb = 28.6 days) RS CVn binary HR 7275. This baseline in time is one of the longest, uninterrupted intervals a spotted star has been observed. The spot modeling analysis yields a total of 20 different spots throughout the time span of our observations. The distribution of the observed spot migration rates is consistent with solar-type differential rotation and suggests a lower limit of the differential-rotation coefficient of 0.022 +/-0.004. The observed, maximum lifetime of a single spot (or spot group) is 4.5 …
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 …
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.