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Information Systems and Engineering Management Research Publications

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Full-Text Articles in Astrophysics and Astronomy

Seven New Keck Planets Orbiting G And K Dwarfs, R. Paul Butler, Geoffrey W. Marcy, Steve S. Vogt, Debra A. Fischer, Gregory W. Henry, Gregory Laughlin, Jason Wright Jan 2003

Seven New Keck Planets Orbiting G And K Dwarfs, R. Paul Butler, Geoffrey W. Marcy, Steve S. Vogt, Debra A. Fischer, Gregory W. Henry, Gregory Laughlin, Jason Wright

Information Systems and Engineering Management Research Publications

Planetary mass companions orbiting seven nearby G and K dwarfs have been found from the Keck Precision Doppler Survey. A "51 Peg-like" planet orbiting HD 49674 has the smallest mass yet found, M sin i = 0.12 MJ. This system does not transit. A double-planet system orbits HD 37124, with periods of 153 days and 6 yr and minimum masses of 0.91 and 1.70 MJ. Single companions with moderate eccentricity have been found orbiting HD 108874, HD 72659, HD 114729, and HD 145675 with orbital periods ranging from 1.09 to 5.98 yr, yielding minimum masses ranging …

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Multiperiodicity In Five Small‐Amplitude Pulsating Red Giants, John R. Percy, Gurtina Besla, Vince Velocci, Gregory W. Henry Jan 2003

Multiperiodicity In Five Small‐Amplitude Pulsating Red Giants, John R. Percy, Gurtina Besla, Vince Velocci, Gregory W. Henry

Information Systems and Engineering Management Research Publications

We report multiperiodicity in five small‐amplitude pulsating red giants: RZ Ari, V523 Mon, BC CMi, UX Lyn, and FS Com. For each of these stars, two or three periods recur in each season of our 5000 day database of V observations. The periods and their ratios are consistent with low‐order radial pulsation modes. The amplitudes of the modes change significantly on timescales of 1–5 yr; specifically, the amplitudes of the dominant periods vary on timescales of 2000–3500 days. Most often, the amplitudes of the modes in a given star rise and fall in unison.

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A Sub-Saturn Mass Planet Orbiting Hd 3651, Debra A. Fischer, R. Paul Butler, Geoffrey W. Marcy, Steve Vogt, Gregory W. Henry Jan 2003

A Sub-Saturn Mass Planet Orbiting Hd 3651, Debra A. Fischer, R. Paul Butler, Geoffrey W. Marcy, Steve Vogt, Gregory W. Henry

Information Systems and Engineering Management Research Publications

We report precise Doppler velocities of HD 3651 obtained at Lick and Keck Observatories. The velocities reveal evidence of a planetary companion with an orbital period of 62.23 ± 0.03 days, an eccentricity of 0.63 ± 0.04, and a velocity semiamplitude of 15.9 ± 1.7 m s-1. With an assumed mass of 0.79 M☉ for this K0 V star, we derive M sin i = 0.20MJ and a semimajor axis of 0.284 AU. The star is chromospherically inactive, with log R = -5.01, and 10 years of observations at Fairborn Observatory show it to be …

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A Dozen New Γ Doradus Stars, Gregory W. Henry, Francis C. Fekel Jan 2003

A Dozen New Γ Doradus Stars, Gregory W. Henry, Francis C. Fekel

Information Systems and Engineering Management Research Publications

We use new high-dispersion spectroscopic and precise photometric observations to identify 12 new γ Doradus stars. Two of the 12 systems are double-lined binaries that show obvious velocity variability. Five other stars have metallic lines with composite profiles characterized by a narrow feature near the center of each broad component. Spectrograms of the Hα line indicate that all five stars are binaries rather than shell stars. The remaining five stars in our sample are probably single. All 12 stars are photometrically variable with amplitudes between 6 and 87 mmag in Johnson B and periods between 0.3 and 1.2 days. Four …

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A Planetary Companion To Hd 40979 And Additional Planets Orbiting Hd 12661 And Hd 38529, Debra A. Fischer, Geoffrey W. Marcy, R. Paul Butler, Steve Vogt, Gregory W. Henry, Dimitri Pourbaix, Bernard Walp, Anthony A. Misch, Jason T. Wright Jan 2003

A Planetary Companion To Hd 40979 And Additional Planets Orbiting Hd 12661 And Hd 38529, Debra A. Fischer, Geoffrey W. Marcy, R. Paul Butler, Steve Vogt, Gregory W. Henry, Dimitri Pourbaix, Bernard Walp, Anthony A. Misch, Jason T. Wright

Information Systems and Engineering Management Research Publications

We report the detection of three extrasolar planets from the Lick and Keck observatories. The F8 V star HD 40979 has a companion with orbital period P = 263.1 ± 3 days, eccentricity e = 0.25 ± 0.05, and velocity semiamplitude K = 101.2 ± 5.6 m s-1. The inferred semimajor axis is 0.83 AU and M sin i = 3.28MJup. Observations of planetary companions orbiting the G6 V star HD 12661 and the G4 IV star HD 38529 have already been published, and here we report additional, longer period companions for both of these stars. The outer companion to …

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A Planet At 5 Au Around 55 Cancri, Geoffrey W. Marcy, R. Paul Butler, Debra A. Fischer, Greg Laughlin, Steve S. Vogt, Gregory W. Henry, Dimitri Pourbaix Dec 2002

A Planet At 5 Au Around 55 Cancri, Geoffrey W. Marcy, R. Paul Butler, Debra A. Fischer, Greg Laughlin, Steve S. Vogt, Gregory W. Henry, Dimitri Pourbaix

Information Systems and Engineering Management Research Publications

We report precise Doppler-shift measurements of 55 Cancri (G8 V) obtained from 1989 to 2002 at Lick Observatory. The velocities reveal evidence for an outer planetary companion to 55 Cancri orbiting at 5.5 AU. The velocities also confirm a second, inner planet at 0.11 AU. The outer planet is the first extrasolar planet found that orbits near or beyond the orbit of Jupiter. It was drawn from a sample of ~50 stars observed with sufficient duration and quality to detect a giant planet at 5 AU, implying that such planets are not rare. The properties of this Jupiter analog may …

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Six New Γ Doradus Stars, Gregory W. Henry, Francis C. Fekel Sep 2002

Six New Γ Doradus Stars, Gregory W. Henry, Francis C. Fekel

Information Systems and Engineering Management Research Publications

We present high‐resolution spectroscopy and precision photometry of six new γ Doradus stars, one of which was independently discovered by another group. This brings the total number of confirmed γ Doradus variables to 30. All six of these variables fall in the spectral class range F0–F2; all but one are subgiants. The six stars have between one and five photometric periods in the range 0.3–1.2 days. We find no evidence for higher frequency δ Scuti pulsations in any of these six stars. Our spectroscopic observations reveal HD 108100 to be the first confirmed γ Doradus variable with composite broad and …

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A False Planet Around Hd 192263, Gregory W. Henry, Robert A. Donahue, Sallie L. Baliunas Aug 2002

A False Planet Around Hd 192263, Gregory W. Henry, Robert A. Donahue, Sallie L. Baliunas

Information Systems and Engineering Management Research Publications

We present new high-precision Strömgren photometry and Ca II H and K spectrophotometry of HD 192263. Based on radial velocity variations detected previously by two groups, this K2 V star was thought to host a 0.75 MJup (minimum mass) planetary companion in a 24 day orbit. Our photometric observations reveal periodic variations that match the purported planetary orbital period, while the Ca II H and K emission fluxes are modulated on half the planetary period. This suggests that rotational modulation of the visibility of stellar surface activity is the source of the observed radial velocity variations. Therefore, HD 192263 should …

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X-Ray And Optical Variations In The Classical Be Star Γ Cassiopeia: The Discovery Of A Possible Magnetic Dynamo, Richard D. Robinson, Myron A. Smith, Gregory W. Henry Aug 2002

X-Ray And Optical Variations In The Classical Be Star Γ Cassiopeia: The Discovery Of A Possible Magnetic Dynamo, Richard D. Robinson, Myron A. Smith, Gregory W. Henry

Information Systems and Engineering Management Research Publications

The classical B0.5e star γ Cassiopeia is known to be a unique X-ray source by virtue of its moderate LX (1033 ergs s-1), hard X-ray spectrum, and light curve punctuated by ubiquitous flares and slow undulations. The peculiarities of this star have led to a controversy concerning the origin of these emissions: whether they are from wind infall onto a putative degenerate companion, as in the case of normal Be/X-ray binaries, or from the Be star itself. Recently, much progress has been made to resolve this question: (1) the discovery that γ Cas is a moderately eccentric binary system (P …

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Chromospherically Active Stars. Xxi. The Giant, Single-Lined Binaries Hd 89546 And Hd 113816, Francis C. Fekel, Gregory W. Henry, Joel A. Eaton, Julius Sperauskas, Douglas S. Hall Aug 2002

Chromospherically Active Stars. Xxi. The Giant, Single-Lined Binaries Hd 89546 And Hd 113816, Francis C. Fekel, Gregory W. Henry, Joel A. Eaton, Julius Sperauskas, Douglas S. Hall

Information Systems and Engineering Management Research Publications

We have obtained spectroscopy and photometry of the chromospherically active, single-lined spectroscopic binaries HD 89546 and HD 113816. HD 89546 has a circular orbit with a period of 21.3596 days. Its primary has a spectral type of G9 III and is somewhat metal-poor with [Fe/H]~-0.5. HD 113816 has an orbit with a period of 23.6546 and a low eccentricity of 0.022. Its mass function is extremely small, 0.0007 Msolar, consistent with a very low inclination. The primary is a slightly metal-poor K2 III. A decade or more of photometric monitoring with an automatic telescope demonstrates that both systems display brightness …

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The Quadruple System Μ Orionis: Three-Dimensional Orbit And Physical Parameters, Francis C. Fekel, Colin D. Scarfe, David J. Barlow, William I. Hartkopf, Brian D. Mason, Harold Mcalister Mar 2002

The Quadruple System Μ Orionis: Three-Dimensional Orbit And Physical Parameters, Francis C. Fekel, Colin D. Scarfe, David J. Barlow, William I. Hartkopf, Brian D. Mason, Harold Mcalister

Information Systems and Engineering Management Research Publications

The star μ Orionis is a spectroscopic visual quadruple system in which each visual component is a short-period spectroscopic binary. The visual orbit has a period of 18.644 yr, a high eccentricity of 0.7426, and a high inclination of 962. The visual primary consists of an Am star and probably a G or early K dwarf that orbit each other in a nearly circular orbit with a period of 4.4475858 days. The visual secondary consists of a pair of F5: V stars in a circular orbit with a period of 4.7835361 days. While the masses of the two stars are …

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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 Feb 2002

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.

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Velocity Observations Of Multiple-Mode Asymptotic Giant Branch Variable Stars, Kenneth H. Hinkle, Thomas Lebzelter, Richard R. Joyce, Francis C. Fekel Feb 2002

Velocity Observations Of Multiple-Mode Asymptotic Giant Branch Variable Stars, Kenneth H. Hinkle, Thomas Lebzelter, Richard R. Joyce, Francis C. Fekel

Information Systems and Engineering Management Research Publications

Numerous infrared spectroscopic observations were obtained of nine asymptotic giant branch (AGB) field M giants that have multiple periods of light variability. Each star has a short period of several months, which is typical of low amplitude pulsation for stars on the AGB, as well as a long period of 1–3 yr, which is significantly longer than the predicted fundamental-mode pulsations for these stars. The location of these stars in the AGB period-luminosity relation is discussed. For six of the nine giants we found radial-velocity periods that confirm the long-period light variability. Although we considered the possibility that the velocity …

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Five New Δ Scuti Stars, Gregory W. Henry, Francis C. Fekel Jan 2002

Five New Δ Scuti Stars, Gregory W. Henry, Francis C. Fekel

Information Systems and Engineering Management Research Publications

We present high‐resolution spectroscopy and precision photometry of five new, relatively bright δ Scuti stars. They were originally chosen as photometric comparison stars in our program of automated, high‐precision photometry of solar‐type stars and subsequently recognized as new variable stars. We conducted follow‐up spectroscopic and photometric observations to determine the properties of the stars and their types of variability. All five of the stars presented here belong to the most common subgroup of low‐amplitude, Population I δ Scuti variables. One of the stars, HD 10502, is the third example of a δ Scuti variable with composite broad and narrow spectroscopic …

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Chromospherically Active Stars. Xx. The Giant Single-Lined Binary Hd 161570, Francis C. Fekel, Gregory W. Henry, Stephen M. Henry Dec 2001

Chromospherically Active Stars. Xx. The Giant Single-Lined Binary Hd 161570, Francis C. Fekel, Gregory W. Henry, Stephen M. Henry

Information Systems and Engineering Management Research Publications

Spectroscopy of HD 161570 shows it to be a single-lined spectroscopic binary with a period of 45.623 days and a nearly circular orbit. The primary star has spectral type G7 III, and the secondary is most likely a G or K dwarf. A high-resolution spectrum of the 3950 Å region confirms that the primary has Ca II H and K emission lines. The logarithm of the giant's lithium abundance is less than 0.9, indicating that it is not lithium-rich. From photometric observations covering six seasons, we detected periodic short-term light variability with an amplitude ranging from 0.02 to 0.04 mag. …

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No Planet For Hd 166435, Didier Queloz, Gregory W. Henry, Jean-Pierre Sivan, Sallie L. Baliunas, Jean-Luc Beuzit, Robert A. Donahue, Michel Mayor, Dominique Naef, Christian Perrier, Stephane Udry Nov 2001

No Planet For Hd 166435, Didier Queloz, Gregory W. Henry, Jean-Pierre Sivan, Sallie L. Baliunas, Jean-Luc Beuzit, Robert A. Donahue, Michel Mayor, Dominique Naef, Christian Perrier, Stephane Udry

Information Systems and Engineering Management Research Publications

The G0 V star HD 166435 has been observed by the fiber-fed spectrograph ELODIE as one of the targets in the large extra-solar planet survey that we are conducting at the Observatory of Haute-Provence. We detected coherent, low-amplitude, radial-velocity variations with a period of 3.7987 days, suggesting a possible close-in planetary companion. Subsequently, we initiated a series of high-precision photometric observations to search for possible planetary transits and an additional series of Ca II H and K observations to measure the level of surface magnetic activity and to look for possible rotational modulation. Surprisingly, we found the star to be …

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Chromospherically Active Stars. Xix. A Reexamination Of The Variability Of Hd 10909=Uv Fornacis, Francis C. Fekel, Gregory W. Henry, Keinon Brooks, Douglas S. Hall Aug 2001

Chromospherically Active Stars. Xix. A Reexamination Of The Variability Of Hd 10909=Uv Fornacis, Francis C. Fekel, Gregory W. Henry, Keinon Brooks, Douglas S. Hall

Information Systems and Engineering Management Research Publications

We have obtained new spectroscopy and photometry of the K0 IV, chromospherically active, single-lined spectroscopic binary HD 10909. Those observations show that the previously reported orbital and light variability periods are incorrect. HD 10909 has an orbital period of 30.1067 days and an eccentricity of 0.499. Its rotation period of 64.1 days is more than twice as long as its orbital period. The primary is situated near the base of the first-ascent red giant branch. Thus, its asynchronous rotation is likely the result of its recent evolution through the Hertzsprung gap, combined with its relatively long orbital period and high …

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First Results From The Anglo-Australian Planet Search: A Brown Dwarf Candidate And A 51 Peg-Like Planet, Chris G. Tinney, R. Paul Butler, Geoffrey W. Marcy, Hugh R. A. Jones, Alan J. Penny, Steve S. Vogt, Kevin Apps, Gregory W. Henry Apr 2001

First Results From The Anglo-Australian Planet Search: A Brown Dwarf Candidate And A 51 Peg-Like Planet, Chris G. Tinney, R. Paul Butler, Geoffrey W. Marcy, Hugh R. A. Jones, Alan J. Penny, Steve S. Vogt, Kevin Apps, Gregory W. Henry

Information Systems and Engineering Management Research Publications

We report results from the Anglo-Australian Planet Search, a survey for planets around 200 solar-type stars in the southern hemisphere that is being carried out on the 3.9 m Anglo-Australian Telescope. Limiting Doppler precisions of 3 m s-1 have been demonstrated from the first 2.5 years of operation, making this the highest-precision planet search in the southern hemisphere. From these data we report results for two new substellar detections. The first is a 51 Peg-like planet around the star HD 179949 with M sin i = 0.84 MJUP. Photometric study reveals this is not a transiting system. The second is …

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Infrared Spectroscopy Of Symbiotic Stars. Iii. First Orbits For Three S-Type Systems, Francis C. Fekel, Kenneth H. Hinkle, Richard Joyce, Michael F. Skrutskie Apr 2001

Infrared Spectroscopy Of Symbiotic Stars. Iii. First Orbits For Three S-Type Systems, Francis C. Fekel, Kenneth H. Hinkle, Richard Joyce, Michael F. Skrutskie

Information Systems and Engineering Management Research Publications

Infrared radial velocities have been used to derive the first well-determined orbital elements for the cool giants of three symbiotic systems, BF Cyg, V1329 Cyg, and V343 Ser=AS 289. Periods found for BF Cyg and V1329 Cyg from the radial velocity data are in good agreement with periods previously determined for their light variations, and the orbits are circular. Masses for the components of BF Cyg and V1329 Cyg were determined by combining our orbital elements for the cool giants with elements for their hot stars. BF Cyg and V1329 Cyg are shown to be detached binary systems. The third …

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Long‐Term Vri Photometry Of Small‐Amplitude Red Variables. I. Light Curves And Periods, John R. Percy, Joseph B. Wilson, Gregory W. Henry Jan 2001

Long‐Term Vri Photometry Of Small‐Amplitude Red Variables. I. Light Curves And Periods, John R. Percy, Joseph B. Wilson, Gregory W. Henry

Information Systems and Engineering Management Research Publications

We report up to 5000 days of VRI photometry, from a robotic photometric telescope, of 34 pulsating red giants, namely, TV Psc, EG And, Z Psc, RZ And, 4 Ori, RX Lep, UW Lyn, η Gem, μ Gem, ψ1 Aur, V523 Mon, V614 Mon, HD 52690, Y Lyn, BC CMi, X Cnc, UX Lyn, RS Cnc, VY UMa, ST UMa, TU CVn, FS Com, SW Vir, 30 Her, α1 Her, V642 Her, R Lyr, V450 Aql, V1293 Aql, δ Sge, EU Del, V1070 Cyg, W Cyg, and μ Cep, as well as a few variable comparison stars. V …

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10 New Γ Doradus And Δ Scuti Stars, Gregory W. Henry, Francis C. Fekel, Anthony B. Kaye, Ann Kaul Jan 2001

10 New Γ Doradus And Δ Scuti Stars, Gregory W. Henry, Francis C. Fekel, Anthony B. Kaye, Ann Kaul

Information Systems and Engineering Management Research Publications

We present high-resolution spectroscopy and precision photometry of five new γ Doradus and five new δ Scuti variables. The five new γ Doradus variables substantially increase the number of confirmed stars of this class. All 10 stars fall in the spectral class range F0–F2, but they are cleanly separated into two groups by their luminosity and photometric periods. However, the period gap between the γ Doradus and δ Scuti stars is becoming very narrow since we confirm that HD 155154 is a γ Doradus star with the shortest periods reported to date (the shortest of its four periods is ∼0.312 …

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Infrared Spectroscopy Of Symbiotic Stars. Ii. Orbits For Five S-Type Systems With Two-Year Periods, Francis C. Fekel, Kenneth H. Hinkle, Richard Joyce, Michael F. Skrutskie Dec 2000

Infrared Spectroscopy Of Symbiotic Stars. Ii. Orbits For Five S-Type Systems With Two-Year Periods, Francis C. Fekel, Kenneth H. Hinkle, Richard Joyce, Michael F. Skrutskie

Information Systems and Engineering Management Research Publications

Infrared radial velocities have been used to determine orbital elements for the cool giants of five well-known symbiotic systems, Z And, AG Dra, V443 Her, AX Per, and FG Ser, all of which have orbital periods near the two-year mean period for S-type symbiotics. The new orbits are in general agreement with previous orbits derived from optical velocities. From the combined optical and infrared velocities, improved orbital elements for the five systems have been determined. Each of the orbital periods has been determined solely from the radial-velocity data. The orbits are circular and have quite small mass functions of 0.001–0.03 …

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Chromospherically Active Stars. Xviii. Sorting Out The Variability Of Hd 95559 And Gliese 410=Ds Leonis, Francis C. Fekel, Gregory W. Henry Dec 2000

Chromospherically Active Stars. Xviii. Sorting Out The Variability Of Hd 95559 And Gliese 410=Ds Leonis, Francis C. Fekel, Gregory W. Henry

Information Systems and Engineering Management Research Publications

We have obtained spectroscopy and photometry of HD 95559 and photometry of Gliese 410=DS Leonis. HD 95559 consists of a pair of essentially identical K1 V stars, whose orbital period we refine to 1.52599775+/-0.00000104 days. The system is photometrically variable with a mean period of 1.5264+/-0.0003 days. Despite minimum masses greater than 0.8 Msolar for each component, a search for eclipses proved negative. The lithium abundances of the components of HD 95559 indicate that the system is younger than the Hyades cluster, and its components may even have just arrived on the zero-age main sequence. Gl 410=DS Leo is also …

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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 Oct 2000

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 …

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Two K Giants With Supermeteoritic Lithium Abundances: Hde 233517 And Hd 9746, Suchitra C. Balachandran, Francis C. Fekel, Gregory W. Henry, Han Uitenbroek Oct 2000

Two K Giants With Supermeteoritic Lithium Abundances: Hde 233517 And Hd 9746, Suchitra C. Balachandran, Francis C. Fekel, Gregory W. Henry, Han Uitenbroek

Information Systems and Engineering Management Research Publications

Two unusual Li-rich K giants, HDE 233517 and HD 9746, have been studied. Optical spectroscopy and photometry have been obtained to determine the fundamental parameters of HDE 233517, a single K2 III with an extremely large infrared excess. The spectra yield Teff=4475 K, logg=2.25, [Fe/H]=-0.37, vsini=17.6 km s-1, and a non-LTE logɛ(7Li)=4.22. Photometric observations reveal low-amplitude light variability with a period of 47.9 days. Combined with other parameters, this results in a minimum radius of 16.7 Rsolar and minimum distance of 617 pc. Comparison of spectra obtained in 1994 and 1996 show profile variations in Hα and the Na D …

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Photometric Variability In A Sample Of 187 G And K Giants, Gregory W. Henry, Francis C. Fekel, Stephen M. Henry, Douglas S. Hall Sep 2000

Photometric Variability In A Sample Of 187 G And K Giants, Gregory W. Henry, Francis C. Fekel, Stephen M. Henry, Douglas S. Hall

Information Systems and Engineering Management Research Publications

We have used three automatic photoelectric telescopes to obtain photometric observations of 187 G, K, and (a few) M0 field giants. We find low-amplitude photometric variability on timescales of days to weeks on both sides of the coronal dividing line (CDL) in a total of 81 or 43% of the 187 giants. About one-third of the variables have amplitudes greater than 0.01 mag in V. In our sample the percentage of variable giants is a minimum for late-G spectral classes and increases for earlier and later classes; all K5 and M0 giants are variable. We also obtained high-resolution, red wavelength …

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Spectroscopy And Photometry Of Nearby Young Solar Analogs, Eric J. Gaidos, Gregory W. Henry, Stephen M. Henry Aug 2000

Spectroscopy And Photometry Of Nearby Young Solar Analogs, Eric J. Gaidos, Gregory W. Henry, Stephen M. Henry

Information Systems and Engineering Management Research Publications

We present new photometry and spectroscopy of 34 stars from a catalog of 38 nearby (d < 25 pc) G and K dwarfs selected as analogs to the early Sun. We report that the least active star in our sample is also slowly rotating and probably of solar age. Two other stars appear to be evolved objects that have recently acquired angular momentum. A fourth star may be a spectroscopic binary. Many of the other stars belong to previously identified common proper-motion groups. Space motions, lithium abundances, and Ca II emission of these stars suggest ages between 70 and 800 Myr.

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Search For Transits Of A Short-Period, Sub-Saturn Extrasolar Planet Orbiting Hd 46375, Gregory W. Henry Jun 2000

Search For Transits Of A Short-Period, Sub-Saturn Extrasolar Planet Orbiting Hd 46375, Gregory W. Henry

Information Systems and Engineering Management Research Publications

Precise brightness measurements of HD 46375 have been acquired with an automatic telescope to search for transits of its short-period, sub-Saturn extrasolar planet. Transits of the companion do not occur, indicating that the inclination of the orbit i is less than 83° and sin i is less than 0.992. This upper limit on sin i still preserves the possibility that the mass of the planet is less than Saturn's. Analysis of the photometry for HD 46375 reveals no photometric variability larger than 0.0001 ± 0.0002 mag at the orbital period of the planet. This effectively eliminates starspots and stellar pulsations …

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Long‐Term Vri Photometry Of 89 (V441) Herculis, John R. Percy, Akos G. Bakos, Gregory W. Henry Jun 2000

Long‐Term Vri Photometry Of 89 (V441) Herculis, John R. Percy, Akos G. Bakos, Gregory W. Henry

Information Systems and Engineering Management Research Publications

We report 4500 days of VRI photometry of the peculiar high‐latitude F2 Ibe star 89 (V441) Herculis, from a robotic photometric telescope, and the American Association of Variable Star Observers photoelectric photometry program. We detected the previously known photometric period of 65.2 days and also the 283 day period which was previously observed in radial velocity only and ascribed to binarity. We have determined the relative amplitudes and phases of light, color, and radial velocity for each period. The 65.2 day period appears to be due to pulsation—probably radial. The nature of the 283 day variations is unclear; we discuss …

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64 Orionis: Three-Dimensional Orbit And Physical Parameters, Colin D. Scarfe, David J. Barlow, Francis C. Fekel May 2000

64 Orionis: Three-Dimensional Orbit And Physical Parameters, Colin D. Scarfe, David J. Barlow, Francis C. Fekel

Information Systems and Engineering Management Research Publications

We have obtained radial velocities of the components of the short-period subsystem of the B-type triple star 64 Orionis, covering a full cycle of the long-period orbit since the date of our earlier paper by Fekel & Scarfe. We use all of our radial velocities, together with available speckle interferometry, to derive a three-dimensional orbit for the long-period system. The system has orbital periods of 14.57213 days and 12.98 yr. We also determine spectroscopically a magnitude difference at 4500 Å of 1.0 ± 0.1 between the components of the close pair. Although radial velocities of the third component continue to …

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