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Full-Text Articles in Stars, Interstellar Medium and the Galaxy
Patterns Of Photometric And Chromospheric Variation Among Sun-Like Stars: A 20 Year Perspective, G. Wesley Lockwood, Brian A. Skiff, Gregory W. Henry, Stephen M. Henry, Richard R. Radick, Sallie L. Baliunas, Robert A. Donahue, Willie Soon
Patterns Of Photometric And Chromospheric Variation Among Sun-Like Stars: A 20 Year Perspective, G. Wesley Lockwood, Brian A. Skiff, Gregory W. Henry, Stephen M. Henry, Richard R. Radick, Sallie L. Baliunas, Robert A. Donahue, Willie Soon
Information Systems and Engineering Management Research Publications
We examine patterns of variation of 32 primarily main-sequence Sun-like stars [selected at project onset as stars on or near the main sequence and color index 0.42 ≤ (B - V) ≤ 1.4], extending our previous 7-12 yr time series to 13-20 yr by combining Strömgren b, y photometry from Lowell Observatory with similar data from Fairborn Observatory. Parallel chromospheric Ca II H and K emission data from the Mount Wilson Observatory span the entire interval. The extended data strengthen the relationship between chromospheric and brightness variability at visible wavelengths derived previously. We show that the full range of photometric …
The Sun-Like Activity Of The Solar Twin 18 Scorpii, Jeffrey C. Hall, Gregory W. Henry, G. Wesley Lockwood
The Sun-Like Activity Of The Solar Twin 18 Scorpii, Jeffrey C. Hall, Gregory W. Henry, G. Wesley Lockwood
Information Systems and Engineering Management Research Publications
We present the results of 10 yr of complementary spectroscopic and photometric observations of the solar twin 18 Scorpii. We show that over the course of its ∼7 yr chromospheric activity cycle, 18 Sco's brightness varies in the same manner as the Sun's and with a likely total brightness variation of 0.09%, similar to the 0.1% decadal variation in the total solar irradiance.
Butterfly Diagram And Activity Cycles In Hr 1099, Svetlana Berdyugina, Gregory W. Henry
Butterfly Diagram And Activity Cycles In Hr 1099, Svetlana Berdyugina, Gregory W. Henry
Information Systems and Engineering Management Research Publications
We analyze photometric data of the active RS CVn-type star HR 1099 for the years 1975-2006 with an inversion technique and reveal the nature of two activity cycles of 15-16 yr and 5.3 ± 0.1 yr duration. The 16 yr cycle is related to variations of the total spot area and is coupled with the differential rotation, while the 5.3 yr cycle is caused by the symmetric redistribution of the spotted area between the opposite stellar hemispheres (flip-flop cycle). We recover long-lived active regions comprising two active longitudes that migrate in the orbital reference frame with a variable rate because …
Photospheric And Chromospheric Active Regions In Four Young Solar-Type Stars, Katia Biazzo, Antonio Frasca, Gregory W. Henry, S. Catalano, E. Marilli
Photospheric And Chromospheric Active Regions In Four Young Solar-Type Stars, Katia Biazzo, Antonio Frasca, Gregory W. Henry, S. Catalano, E. Marilli
Information Systems and Engineering Management Research Publications
We present a photometric and spectroscopic study of four G-K dwarfs, namely HD 166, epsilon Eri, χ1 Ori, and κ1 Cet. In three cases, we find a clear spatial association between photospheric and chromospheric active regions. For χ1 Ori we do not find appreciable variations of photospheric temperature or chromospheric Hα emission. We applied a spot/plage model to the observed rotational modulation of temperature and flux to derive spot/plage parameters and to reconstruct a rough "three-dimensional" map of the outer atmosphere of κ1 Cet, HD 166, and epsilon Eri.
Photospheric Temperature Measurements In Young Main Sequence Stars, Katia Biazzo, Antonio Frasca, Gregory W. Henry, S. Catalano, Ettore Marilli
Photospheric Temperature Measurements In Young Main Sequence Stars, Katia Biazzo, Antonio Frasca, Gregory W. Henry, S. Catalano, Ettore Marilli
Information Systems and Engineering Management Research Publications
As part of our program to study stellar photospheric and chromospheric activity, we have examined several young solar type stars with activity levels intermediate between the Sun and the very active RS CVn binaries. We have analysed contemporaneous spectroscopic data obtained at Catania Observatory (Serra La Nave station, Mt. Etna) and photometric data acquired in the Stromgren bands with an automatic photometric telescope (APT) at Fairborn Observatory (Arizona, USA). Surface inhomogeneities have been detected from the rotational modulation of stellar brightness as well as from the modulation of several photospheric line-depth ratios (LDRs). The presence of chromospheric plage-like regions has …
Why Do Some Spotted Stars Become Bluer As They Become Fainter?, Vidar Aarum-Ulvås, Gregory W. Henry
Why Do Some Spotted Stars Become Bluer As They Become Fainter?, Vidar Aarum-Ulvås, Gregory W. Henry
Information Systems and Engineering Management Research Publications
Chromospherically active, spotted stars generally become redder as well as fainter when large starspots rotate into view on the stellar disc. However, the RS CVn system UX Ari (a triple-lined system), becomes bluer as it gets fainter. One possible explanation is that hot, bright facular regions accompany the cool, dark photospheric spots of the active component. The bluer flux of the hotter, inactive component does not appear to be sufficient to explain the observed behaviour. We have begun a search for additional chromospherically active stars with a similar relation between colour and brightness, to investigate whether these relations can be …
Bv Photometry Of Ux Ari In The Period 1987–2002, Vidar Aarum Ulvås, Gregory W. Henry
Bv Photometry Of Ux Ari In The Period 1987–2002, Vidar Aarum Ulvås, Gregory W. Henry
Information Systems and Engineering Management Research Publications
We present 14.3 years of previously unpublished photometric observations of UX Ari. The observations were obtained between 1987.9 and 2002.2 using the T3 0.4-metre Automatic Photoelectric Telescope at Fairborn Observatory and consist of 1228 B band and 1213 V band measurements. The comparison star was 62 Ari. We have analyzed the new data together with previously published photometric observations. The V magnitude shows variations with dominant periods of about 12 and 25 years, where the longest period seems to correspond to an activity cycle. The previously reported anticorrelation between the colour and V magnitude variations is confirmed.
Time Series Analysis Of V511 Lyrae Photometry, J. Lyytinen, Peter Johansson, Lauri Jetsu, Eero Esko, Thomas Hackman, Douglas S. Hall, Gregory W. Henry, S. Kontinen, P. Könönen, S. Maisala, A. Palviainen, Kyösti Ryynänen
Time Series Analysis Of V511 Lyrae Photometry, J. Lyytinen, Peter Johansson, Lauri Jetsu, Eero Esko, Thomas Hackman, Douglas S. Hall, Gregory W. Henry, S. Kontinen, P. Könönen, S. Maisala, A. Palviainen, Kyösti Ryynänen
Information Systems and Engineering Management Research Publications
Our time series analysis of sixteen BV light curves of the chromospherically active binary V511 Lyr confirmed the rotation period uniquely. The seasonal periodicity changes of 3.8% indicated the presence of detectable surface differential rotation. The significant periodicity in the light curve minimum epochs suggested that the strongest starspot formation in V511 Lyr was concentrated on one stable active longitude.
Time Series Analysis Of V815 Herculis Photometry Between 1984 And 1998, Lauri Jetsu, Thomas Hackman, Douglas S. Hall, Gregory W. Henry, Mariitta Kokko, J. You
Time Series Analysis Of V815 Herculis Photometry Between 1984 And 1998, Lauri Jetsu, Thomas Hackman, Douglas S. Hall, Gregory W. Henry, Mariitta Kokko, J. You
Information Systems and Engineering Management Research Publications
As a case study of the solar-stellar connection, we have analysed a prolonged time series of BV photometry of the chromospherically active binary V815 Her . The surface differential rotation in the rapidly rotating G5{v} primary caused changes of 4.6% in the seasonal photometric rotation periods. This would imply a differential rotation coefficient of k = 0.184, if the rotation of the starspots follows the solar law of differential rotation and the activity is confined within the same latitudinal range as in the Sun, having k = 0.189 and the spectral-type of G2{v}. Our analysis of the primary and secondary …
Orbital Elements And Physical Parameters Of Ten Chromospherically Active Binary Stars, Francis C. Fekel, Klaus G. Strassmeier, Michael Weber, A. Washuettl
Orbital Elements And Physical Parameters Of Ten Chromospherically Active Binary Stars, Francis C. Fekel, Klaus G. Strassmeier, Michael Weber, A. Washuettl
Information Systems and Engineering Management Research Publications
Orbital elements have been determined for 10 chromospherically active binaries from a combination of new velocities and velocities in the literature. First orbits for three binaries, HD 33363, HD 152178, and HD 208472, are presented, as well as updated orbits for seven other binaries. Two of the latter systems, LN Peg and HD 106225 were discovered to be triple, and both short- and long-period orbits have been computed for each. Fundamental properties have been determined for the chromopherically active primary in each system.
Evolved, Single, Slowly Rotating . . . But Magnetically Active The G8-Giant Hr 1362 = Ek Eridani Revisited, Klaus G. Strassmeier, Kazimierz Stępień, Gregory W. Henry, Douglas S. Hall
Evolved, Single, Slowly Rotating . . . But Magnetically Active The G8-Giant Hr 1362 = Ek Eridani Revisited, Klaus G. Strassmeier, Kazimierz Stępień, Gregory W. Henry, Douglas S. Hall
Information Systems and Engineering Management Research Publications
We rediscuss the unusual case of the slowly rotating late-type giant HR 1362, which exhibits a very unusual high level of magnetic activity. New BVRI photometry from two robotic telescopes from 1991 through 1998 together with previously published photometric data gives a very precise photometric period of 306.9±0.4 days. With the aid of high-resolution (R=120,000) optical spectra and the Hipparcos parallax we redetermine the absolute parameters of HR 1362 and find it to be a single G8IV-III star of 14 L and a mass of 1.85 M with Teff=5125 K, log g=3.25, and solar abundances. Lithium is not significantly different …
Time-Series Photometric Spot Modeling. Iii. Thirty Years In The Life Of Hk Lacertae., Katalin Oláh, Zsolt Kővári, János Bartus, Klaus G. Strassmeier, Douglas S. Hall, Gregory W. Henry
Time-Series Photometric Spot Modeling. Iii. Thirty Years In The Life Of Hk Lacertae., Katalin Oláh, Zsolt Kővári, János Bartus, Klaus G. Strassmeier, Douglas S. Hall, Gregory W. Henry
Information Systems and Engineering Management Research Publications
We present a spot modeling analysis of the active late-type giant HK Lac using 30 years of photometry, including 600 new data points from the last six years. We have analyzed folded light curves and, when we had long continuous data sets, applied a new computer code for time-series modeling. The validity of the modeling results was tested as a function of the photometric noise. We have determined the unspotted brightness of HK Lac in the BV(RI)_C_ bandpasses and obtained a spot temperature of {DELTA}T=1200+/-100K. Polar active regions were recovered throughout the modeling because no other scenario was able to …
Flare Energetics: Analysis Of A Large Flare On Yz Canis Minoris Observed Simultaneously In The Ultraviolet, Optical And Radio., G. H. J. Van Den Oord, John G. Doyle, M. Rodono, D. E. Gary, Gregory W. Henry, Patrick B. Byrne, Jeffrey L. Linsky
Flare Energetics: Analysis Of A Large Flare On Yz Canis Minoris Observed Simultaneously In The Ultraviolet, Optical And Radio., G. H. J. Van Den Oord, John G. Doyle, M. Rodono, D. E. Gary, Gregory W. Henry, Patrick B. Byrne, Jeffrey L. Linsky
Information Systems and Engineering Management Research Publications
The results of coordinated observations of the dMe star YZ CMi at optical, UV and radio wavelengths during 3-7 February 1983 are presented. YZ CMi showed repeated optical flaring with the largest flare having a magnitude of 3.8 in the U-band. This flare coincided with an IUE exposure which permits a comparison of the emission measure curves of YZ CMi in its flaring and quiescent state. During the flare a downward shift of the transition zone is observed while the radiative losses in the range 10^4^-10^7^K strongly increase. The optical flare is accompanied with a radio flare at 6cm, while …
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.
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 …
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 …
Optical Variability In The Unusual K5 V Infrared-Excess Star Hd 98800, Gregory W. Henry, Douglas S. Hall
Optical Variability In The Unusual K5 V Infrared-Excess Star Hd 98800, Gregory W. Henry, Douglas S. Hall
Information Systems and Engineering Management Research Publications
The dusty infrared-excess star HD 98800 (K5 V) was observed for several weeks in the spring of 1993 by the Vanderbilt/Tennessee State 0.4 m automatic photoelectric telescope. It was found to be a variable star with an amplitude of 0.07 mag in V and a period of 14.7 days. We show, by comparison with other chromospherically active variable stars and constant stars with good observational histories, that the Rossby number for HD 98800, determined to be 0.30, places it well within the regime of stars whose convective envelopes and rotation rates combine to drive a magnetic dynamo strong enough to …
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 …
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 …
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 …
Chromospherically Active Stars. Viii. Hd 155683 = V972 Herculis: Observational Constraints On Evolutionary Theory, Francis C. Fekel
Chromospherically Active Stars. Viii. Hd 155683 = V972 Herculis: Observational Constraints On Evolutionary Theory, Francis C. Fekel
Information Systems and Engineering Management Research Publications
V792 Her is an eclipsing RS CVn binary with an orbital period of 27.54 days whose components have spectral types of K0 III and F2 IV. New spectroscopic observations combined with existing photometry have resulted in masses of 1.47 + or - 0.003 solar mass and 1.41 + or - 0.003 solar mass for the K giant and F star, respectively. Additional fundamental parameters are derived. Standard evolutionary models were specifically computed by VandenBerg (1990) for the two stars. The best fit occurs if the components are somewhat metal poor with Fe/H/ = - 0.46. Ages of about 2.3 x …
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. Iii. Hd 26337 = Ei Eri: An Rs Cvn Candidate For The Doppler-Imaging Technique, Francis C. Fekel, Robert Quigley, Kim Gillies, John L. Africano
Chromospherically Active Stars. Iii. Hd 26337 = Ei Eri: An Rs Cvn Candidate For The Doppler-Imaging Technique, Francis C. Fekel, Robert Quigley, Kim Gillies, John L. Africano
Information Systems and Engineering Management Research Publications
The variable star HD 26337 = EI Eri is a chromospherically active G5 IV single-lined spectroscopic binary with a period of 1.94722 days. It has moderate strength Ca II H and K emission and strong ultraviolet emission features, while Hα is a weak absorption feature that is variable in strength. The inclination of the system is 46°±12°, and the unseen secondary is most likely a late K or early M dwarf. The v sin i of the primary is 50±3 km s-1, resulting in a minimum radius of 1.9±0.1 R_sun;. A mass ratio of M1/M2 ≥ 2.6 and a mass …
Chromospherically Active Stars. Ii. Hd 82558, A Young Single By Draconis Variable., Francis C. Fekel, Bernard W. Bopp, John L. Africano, Bret D. Goodrich, Leigh Hunter Palmer, Robert Quingley, Theodore Simon
Chromospherically Active Stars. Ii. Hd 82558, A Young Single By Draconis Variable., Francis C. Fekel, Bernard W. Bopp, John L. Africano, Bret D. Goodrich, Leigh Hunter Palmer, Robert Quingley, Theodore Simon
Information Systems and Engineering Management Research Publications
It is presently noted that the HD 82558 chromospherically active star is a young and rapidly rotating K2 V single BY Draconis variable with very strong far-UV emission features and an H-alpha line filled to the continuum level by emission. HD 82558 has constant velocity and is not a member of the Hyades Supercluster. Its light curve behavior, which appears to have been stable for several hundred rotation cycles, is reminiscent of that of the young, rapidly rotating, single K V variable H II 1883 in the Pleiades; this stability may be characteristic of young, single, chromospherically active stars.