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Information Systems and Engineering Management Research Publications

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Infrared Spectroscopy Of Symbiotic Stars. I. Orbits For Well-Known S-Type Systems, Francis C. Fekel, Richard Joyce, Kenneth H. Hinkle, Michael F. Skrutskie Mar 2000

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

Information Systems and Engineering Management Research Publications

First results are reported for a program of monitoring symbiotic-star velocities in the 1.6 μm region with infrared-array technology. Infrared radial velocities have been used to determine single-lined spectroscopic orbits for six well-known symbiotic stars, EG And, T CrB, CI Cyg, BX Mon, RS Oph, and AG Peg. 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 six systems have been determined. Each of the orbital periods has been determined solely from the radial-velocity data. With the addition of our new velocities, the …

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Long‐Term Vri Photometry Of Ρ Cassiopeiae, John R. Percy, David L. Kolin, Gregory W. Henry Mar 2000

Long‐Term Vri Photometry Of Ρ Cassiopeiae, John R. Percy, David L. Kolin, Gregory W. Henry

Information Systems and Engineering Management Research Publications

We report over 5700 days (15 years) of VRI photometry of the yellow hypergiant variable star ρ Cassiopeiae. The V−I color curve is generally in phase with the V light curve on timescales of a few hundred days, but there is a 4000 day variation in V−I which is absent from the light curve. The approximate ratio of Δ(V−I)/ΔV is 0.46. The most conspicuous period in the light curve, in the autocorrelation diagram, and in the power spectrum is about 820 days. Less significant periods of 380, 510, and 645 days also appear in the power spectrum, …

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Photometric And Ca Ii H And K Spectroscopic Variations In Nearby Sun-Like Stars With Planets. Iii., Gregory W. Henry, Sallie L. Baliunas, Robert A. Donahue, Francis C. Fekel, Willie Soon Mar 2000

Photometric And Ca Ii H And K Spectroscopic Variations In Nearby Sun-Like Stars With Planets. Iii., Gregory W. Henry, Sallie L. Baliunas, Robert A. Donahue, Francis C. Fekel, Willie Soon

Information Systems and Engineering Management Research Publications

We present the results of an analysis of time-series photometry, Ca II H and K spectrophotometry, and high-dispersion visible spectra of nine nearby Sun-like stars recently identified as having planets. For the six stars whose presumed planets have orbital periods of less than 4 months (τ Boo, 51 Peg, υ And, ρ1 Cnc, ρ CrB, and 70 Vir), sine-curve fits to the photometric data show no variations with semiamplitude greater than 1 or 2 parts in 104. Photometric variations in 47 UMa are similarly small, although our photometric data of this star are slightly affected by variability …

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Planetary Companions To The Metal-Rich Stars Bd -10°3166 And Hd 52265, R. Paul Butler, Steve Vogt, Geoffrey W. Marcy, Debra A. Fischer, Gregory W. Henry, Kevin Apps Jan 2000

Planetary Companions To The Metal-Rich Stars Bd -10°3166 And Hd 52265, R. Paul Butler, Steve Vogt, Geoffrey W. Marcy, Debra A. Fischer, Gregory W. Henry, Kevin Apps

Information Systems and Engineering Management Research Publications

Precise Doppler measurements from the Keck/HIRES spectrometer reveal periodic Keplerian velocity variations in the stars BD -10°3166 and HD 52265. BD -10°3166 (K0 V) has a period of 3.487 days and a semiamplitude of 61 m s-1. An orbital fit yields a companion mass M sin i = 0.48 MJUP, a semimajor axis of a = 0.046 AU, and an eccentricity of e = 0.05 (consistent with zero). HD 52265 (G0 V) has a period of 119.0 days, a semiamplitude of 45 m s-1, an eccentricity of 0.29, a semimajor axis of a = …

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A Transiting "51 Peg-Like" Planet, Gregory W. Henry, Geoffrey W. Marcy, R. Paul Butler, Steve Vogt Dec 1999

A Transiting "51 Peg-Like" Planet, Gregory W. Henry, Geoffrey W. Marcy, R. Paul Butler, Steve Vogt

Information Systems and Engineering Management Research Publications

Doppler measurements from Keck exhibit a sinusoidal periodicity in the velocities of the G0 dwarf HD 209458, having a semiamplitude of 81 m s-1 and a period of 3.5239 days, which is indicative of a "51 Peg-like" planet with a minimum mass (M sin i) of 0.62 MJup and a semimajor axis of 0.046 AU. Follow-up photometry reveals a drop of 0.017 mag at the predicted time (within the errors) of transit by the companion based on the velocities. This is the first extrasolar planet observed to transit its star. The radius of the planet derived …

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Simultaneous Photometry And Spectroscopy Of The Newly Discovered Γ Doradus Variable Hr 8330=Hd 207223, Anthony B. Kaye, Gregory W. Henry, Francis C. Fekel, Douglas S. Hall Oct 1999

Simultaneous Photometry And Spectroscopy Of The Newly Discovered Γ Doradus Variable Hr 8330=Hd 207223, Anthony B. Kaye, Gregory W. Henry, Francis C. Fekel, Douglas S. Hall

Information Systems and Engineering Management Research Publications

We present BV photometry and simultaneous high-resolution, high signal-to-noise ratio spectroscopy of the newly-discovered γ Doradus variable HR 8330 taken during the 1997 and 1998 observing seasons. We calculate power spectra for the B- and V-band data sets and for the time series defined throughout the observing season at each point across the Fe iiλ4508.289 and the Ti iiλ4501.278 line profiles to search for periodic variability. Period analysis reveals a single, 2.6-d period in both the photometric and the spectroscopic data, with a 237° phase lag between them. Based on the location of HR 8330 in the HR diagram and …

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Techniques For Automated High‐Precision Photometry Of Sun‐Like Stars, Gregory W. Henry Jul 1999

Techniques For Automated High‐Precision Photometry Of Sun‐Like Stars, Gregory W. Henry

Information Systems and Engineering Management Research Publications

Tennessee State University operates several Automatic Photoelectric Telescopes (APTs) located at Fairborn Observatory in the Patagonia Mountains of southern Arizona. The APTs are dedicated to photometric monitoring programs that would be difficult and expensive to accomplish without the advantages provided by automation. I describe the operation of two of the telescopes (0.75 and 0.80 m APTs) and the quality‐control techniques that result in their routine acquisition of single‐star differential photometry with a precision of 0.001 mag for single observations and 0.0001–0.0002 mag for seasonal means. I show that a primary obstacle to photometry at this level of precision is intrinsic …

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Orbital Elements And Physical Parameters Of Ten Chromospherically Active Binary Stars, Francis C. Fekel, Klaus G. Strassmeier, Michael Weber, A. Washuettl Jun 1999

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.

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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 Jan 1999

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 …

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The Visual Orbit Of Ι Pegasi, Andrew F. Boden, Christopher D. Koresko, Gerard T. Van Belle, Mark M. Colavita, Philip J. Dumont, Joseph Gubler, Shrinivas R. Kulkarni, Benjamin F. Lane, Dasia Mobley, Michael Shao, James K. Wallace, The Pti Collaboration, Gregory W. Henry Jan 1999

The Visual Orbit Of Ι Pegasi, Andrew F. Boden, Christopher D. Koresko, Gerard T. Van Belle, Mark M. Colavita, Philip J. Dumont, Joseph Gubler, Shrinivas R. Kulkarni, Benjamin F. Lane, Dasia Mobley, Michael Shao, James K. Wallace, The Pti Collaboration, Gregory W. Henry

Information Systems and Engineering Management Research Publications

We have determined the visual orbit for the spectroscopic binary ι Pegasi with interferometric visibility data obtained by the Palomar Testbed Interferometer in 1997. ι Peg is a double-lined binary system whose minimum masses and spectral typing suggests the possibility of eclipses. Our orbital and component diameter determinations do not favor the eclipse hypothesis: the limb-to-limb separation of the two components is 0.151±0.069 mas at conjunction. Our conclusion that the ι Peg system does not eclipse is supported by high-precision photometric observations. The physical parameters implied by our visual orbit and the spectroscopic orbit of Fekel & Tomkin are in …

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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 Jan 1999

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.

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A Search For Lithium-Rich Giants Among Stars With Infrared Excesses, Francis C. Fekel, Lyndon C. Watson Nov 1998

A Search For Lithium-Rich Giants Among Stars With Infrared Excesses, Francis C. Fekel, Lyndon C. Watson

Information Systems and Engineering Management Research Publications

The unusual nature of the single, rapidly rotating, lithium-rich K giant HDE 233517, which is currently undergoing significant mass loss, prompted a search for giants with similar properties. High-dispersion spectroscopic observations were obtained of HD 219025, a known lithium-rich infrared-excess giant, plus 39 stars from a list of G and K giants with excess far-infrared emission. The projected rotational velocities of the vast majority of infrared-excess giants appear to be similar to those of normal G and K giants. Six giants have lithium abundances at or above theoretical upper envelope values. The percentage of such stars in the sample of …

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Physical Properties Of The Binary Star 12 Persei, David J. Barlow, Colin D. Scarfe, Francis C. Fekel Jun 1998

Physical Properties Of The Binary Star 12 Persei, David J. Barlow, Colin D. Scarfe, Francis C. Fekel

Information Systems and Engineering Management Research Publications

We have obtained new radial velocities of the double-lined spectroscopic binary star 12 Persei, whose period is 331 days, and which has been resolved in recent years by speckle interferometry. We derive a solution for the orbital elements from the speckle and radial velocity data simultaneously, and find from that solution masses of 1.306 ± 0.035 and 1.172 ± 0.030 M☉ for the components, and an orbital parallax of 0farcs04224 ± 0farcs00056. We also determine spectroscopically the difference in magnitude between the components and, hence, their absolute magnitudes. We estimate their spectral types and individual colors by fitting standard-star colors …

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Chromospherically Active Stars. Xvii. The Double-Lined Binary 54 Camelopardalis (Ae Lyncis), Francis C. Fekel, Joseph J. Eitter, José-Renan De Medeiros, J. Davy Kirkpatrick Mar 1998

Chromospherically Active Stars. Xvii. The Double-Lined Binary 54 Camelopardalis (Ae Lyncis), Francis C. Fekel, Joseph J. Eitter, José-Renan De Medeiros, J. Davy Kirkpatrick

Information Systems and Engineering Management Research Publications

New spectroscopic observations of the double-lined chromospherically active binary 54 Camelopardalis (=AE Lyncis) have been obtained, resulting in improved orbital elements and the determination of the fundamental properties of the system. 54 Cam has a period of 11.06794 days, an eccentricity of 0.125, and a mass ratio of 0.9945. The spectral types are F8 IV-V and G5 IV, positioning the components on opposite sides of the Hertzsprung gap. From a comparison with theoretical evolutionary tracks, the masses are estimated to be 1.60 and 1.59 M_⊙ for the G and F stars, respectively, while the radii are 3.7 and 3.2 R_⊙. …

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Chromospherically Active Stars. Xvi. The Double-Lined Binary 42 Capricorni, Francis C. Fekel Dec 1997

Chromospherically Active Stars. Xvi. The Double-Lined Binary 42 Capricorni, Francis C. Fekel

Information Systems and Engineering Management Research Publications

New spectroscopic observations of the chromospherically active binary, 42 Capricorni, have resulted in the detection of lines of the secondary, improved orbital elements, and the determination of fundamental properties of the components. 42 Cap has an orbital period of 13.174004 d, an eccentricity of 0.176, and a mass ratio A/B of 1.375. No evidence for a variation of the center-of-mass velocity, suggested by earlier investigators, has been found. Spectral types of the primary and secondary are G1 IV and G2 V, respectively. The V mag difference of 1.94 and HIPPARCOS parallax result in MV = 2.79 mag for A and …

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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 May 1997

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 …

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Rotational Velocities Of Late-Type Stars, Francis C. Fekel May 1997

Rotational Velocities Of Late-Type Stars, Francis C. Fekel

Information Systems and Engineering Management Research Publications

A calibration based on the results of Gray has been used to determine projected rotational velocities for 133 bright stars with spectral types of F, G, or K, most of which appear in {The Bright Star Catalogue}. The vast majority have {v} sin {i} ≤q 10 km s-1 and, thus, are slow rotators. With the new calibration, projected rotational velocities have been determined for a sample of 111 late-type stars, most of which are chromospherically active. Some of the stars have had their rotational velocities measured for the first time.

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Whole Earth Telescope Observations Of The Helium Interacting Binary Pg 1346+082 (Cr Bootis), Judith L. Provencal, Donald E. Winget, R. Edward Nather, Edward L. Robinson, J. Christopher Clemens, Paul A. Bradley, Charles F. Claver, Scot J. Kleinman, Albert D. Grauer, Butler P. Hine, Lilia Ferrario, Darragh O'Donoghue, Brian Warner, Gerard Vauclair, Michel Chevreton, Kepler De Souza Oliveira Filho, Matt A. Wood, Gregory W. Henry May 1997

Whole Earth Telescope Observations Of The Helium Interacting Binary Pg 1346+082 (Cr Bootis), Judith L. Provencal, Donald E. Winget, R. Edward Nather, Edward L. Robinson, J. Christopher Clemens, Paul A. Bradley, Charles F. Claver, Scot J. Kleinman, Albert D. Grauer, Butler P. Hine, Lilia Ferrario, Darragh O'Donoghue, Brian Warner, Gerard Vauclair, Michel Chevreton, Kepler De Souza Oliveira Filho, Matt A. Wood, Gregory W. Henry

Information Systems and Engineering Management Research Publications

We present our analysis of 240 hr of white-light, high-speed photometry of the dwarf nova-like helium variable PG 1346+082 (CR Boo). We identify two frequencies in the low-state power spectrum, at 679.670 ± 0.004 μHz and 669.887 ± 0.008 μHz. The 679.670 μHz variation is coherent over at least a 2 week time span, the first demonstration of a phase-coherent photometric variation in any dwarf nova-like interacting binary white dwarf system. The high-state power spectrum contains a complex fundamental with a frequency similar, but not identical, to the low-state spectrum, and a series of harmonics not detected in low state. …

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The Extremely Active Single Giant 1e 1751+7046 = Et Draconis: Revised Properties And A Reevaluation Of Its Evolutionary Status, Carol W. Ambruster, Francis C. Fekel, Edward F. Guinan, Bruce J. Hrivnak Apr 1997

The Extremely Active Single Giant 1e 1751+7046 = Et Draconis: Revised Properties And A Reevaluation Of Its Evolutionary Status, Carol W. Ambruster, Francis C. Fekel, Edward F. Guinan, Bruce J. Hrivnak

Information Systems and Engineering Management Research Publications

New spectroscopic observations have resulted in significant revisions to several of the orginally published properties of the X-ray bright, chromospherically active star 1E 1751+7046: the spectral classification has been revised from K5 IV to K0 III, v sin i from 30-40 km s-1 to 23 km s-1, and the reported nondetection of the Li I 6707 Å line to a significant log epsilon(Li) = 1.8. Chromospheric and transition region surface fluxes from IUE observations and the coronal surface flux from earlier Einstein data are close to saturation levels, and comparable only to very active binaries, pre-main-sequence stars, and FK Comae …

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The Spectroscopic Orbit Of Pi Ceti, Claud H.S. Lacy, Francis C. Fekel, Robert D. Mathieu, Nidia I. Morrell, J. A. Morse, Guillermo Torres, Daryl W. Willmarth Mar 1997

The Spectroscopic Orbit Of Pi Ceti, Claud H.S. Lacy, Francis C. Fekel, Robert D. Mathieu, Nidia I. Morrell, J. A. Morse, Guillermo Torres, Daryl W. Willmarth

Information Systems and Engineering Management Research Publications

π Ceti (HR 811, B7 V) has been known to be variable in its radial velocity for almost a century, but its relatively long period and small amplitude have conspired against a determination of its orbit. We have combined in an optimal fashion observations from early in this century with modern measurements to find the spectroscopic orbit with high accuracy. The orbit has a period of 7.45 years and a semiamplitude of 4.3 km/s. The measured eccentricity of e=0.00±0.07 is indistinguishable from circular, surprising for such a long period. The 76 radial velocity observations available extend over 12 cycles of …

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New And Improved Parameters Of Hd 202908=Ads 14839: A Spectroscopic-Visual Triple System, Francis C. Fekel, Colin D. Scarfe, David J. Barlow, Antoine Duquennoy, Harold A. Mcalister, William I. Hartkopf, Brian D. Mason, Andrei A. Tokovinin Mar 1997

New And Improved Parameters Of Hd 202908=Ads 14839: A Spectroscopic-Visual Triple System, Francis C. Fekel, Colin D. Scarfe, David J. Barlow, Antoine Duquennoy, Harold A. Mcalister, William I. Hartkopf, Brian D. Mason, Andrei A. Tokovinin

Information Systems and Engineering Management Research Publications

HD 202908=ADS 14839 is a spectroscopic-visual triple system consisting of three solar-type stars. Eighteen years of spectroscopic observations including coverage of the recent periastron of 1987 January plus visual and speckle observations, the latter covering roughly the same interval as the radial velocities, have been used to obtain a simultaneous three-dimensional orbital solution. The short-period pair, Aa and Ab, has an orbital period of 3.9660465 days and a small but real eccentricity of 0.0033. The visual pair, A and B, has an orbital period of 78.5 yr and an eccentricity of 0.865. The solution yields masses for all three stars …

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Properties Of Sun-Like Stars With Planets: 51 Pegasi, 47 Ursae Majoris, 70 Virginis, And Hd 114762, Gregory W. Henry, Sallie L. Baliunas, Robert A. Donahue, Willie H. Soon, Steven H. Saar Jan 1997

Properties Of Sun-Like Stars With Planets: 51 Pegasi, 47 Ursae Majoris, 70 Virginis, And Hd 114762, Gregory W. Henry, Sallie L. Baliunas, Robert A. Donahue, Willie H. Soon, Steven H. Saar

Information Systems and Engineering Management Research Publications

Radial velocity variations have revealed planets orbiting 51 Peg, 47 UMa, and 70 Vir, and a low-mass companion orbiting HD 114762. We analyze parallel records of photometric measurements in Strömgren b and y and Johnson V, R, and I passbands and Ca II H and K fluxes in those stars. In the case of 51 Peg, the high precision of the differential photometric measurements made by the 0.75 m Automatic Photoelectric Telescope and the nonvariability of the star would allow the detection of a transit of a planet as small as Earth (corresponding to an amplitude of 0.0001 mag) if …

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Properties Of Sun-Like Stars With Planets: Ρ1 Cancri, Τ Bootis, And Υ Andromedae, Sallie L. Baliunas, Gregory W. Henry, Robert A. Donahue, Francis C. Fekel, Willie Soon Jan 1997

Properties Of Sun-Like Stars With Planets: Ρ1 Cancri, Τ Bootis, And Υ Andromedae, Sallie L. Baliunas, Gregory W. Henry, Robert A. Donahue, Francis C. Fekel, Willie Soon

Information Systems and Engineering Management Research Publications

Planets have been reported orbiting the Sun-like stars ρ1 Cnc, τ Boo, and υ And based on low-amplitude radial velocity variations. We have derived information on the first two stars from analysis of spectra, as well as parallel records of high-precision Strömgren b and y photometry and Ca II H + K fluxes. In the case of ρ1 Cnc, the upper limit (peak to peak) of nondetection of photometric variability at the orbital period is Δy ~ 0.0004 mag. The possibility of a planetary transit cannot be ruled out completely from the photometric data. Variations of the …

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Chromospherically Active Stars. Xv. Hd 8357=Ar Piscium, An Extremely Active Rs Cvn System, Francis C. Fekel Jul 1996

Chromospherically Active Stars. Xv. Hd 8357=Ar Piscium, An Extremely Active Rs Cvn System, Francis C. Fekel

Information Systems and Engineering Management Research Publications

One of the first x-ray sources optically identified as a chromospherically active star, HD 8357=AR Piscium, is a double-lined binary consisting of a K1 IV primary and G7 V secondary. Careful examination of the Ca II H and K lines indicates that only the primary is active, having strong Ca II H and K, Hɛ, and Hα emission. The system has an orbital period of 14.3023 days and an eccentricity of 0.185. Such an eccentricity is not particularly unusual for chromospherically active stars with periods between 10 and 20 days. An assumed mass of 0.92Msun for the secondary results in …

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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 Jun 1996

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 …

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Random Spots On Chromospherically Active Stars, Joel A. Eaton, Gregory W. Henry, Francis C. Fekel May 1996

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.

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Hde 233517: Lithium And Excess Infrared Emission In Giant Stars, Francis C. Fekel, Richard A. Webb, Russel J. White, Benjamin Zuckerman May 1996

Hde 233517: Lithium And Excess Infrared Emission In Giant Stars, Francis C. Fekel, Richard A. Webb, Russel J. White, Benjamin Zuckerman

Information Systems and Engineering Management Research Publications

Recent studies have identified a small class of moderately rapidly rotating, chromospherically active, single giants, some of which are lithium rich. We present evidence suggesting the peculiar K-type star HDE 233517 is one such object. Previously, HDE 233517 has been suggested to be a young star, consistent with its large far-infrared excess and our log ε(Li) ~ 3.3. However, our high-resolution spectroscopic observations show it is likely a single, post-main-sequence K2 giant with v sin i = 15 km s-1 and modest Ca II H and K emission. The giant status of HDE 233517 is determined directly from luminosity-sensitive line …

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A Search For Optical Flares In Chromospherically Active Stars, Gregory W. Henry, M. S. Newsom Mar 1996

A Search For Optical Flares In Chromospherically Active Stars, Gregory W. Henry, M. S. Newsom

Information Systems and Engineering Management Research Publications

We have surveyed four years of archival UBV photometry of 69 chromospherically active stars obtained with the Phoenix-10 automatic photoelectric telescope in search of optical flares on these stars. We demonstrate taht, while flares can be detected in these data, the number of events observed on evolved stars remains very small. Flares were found only on UX Arietis, II Pegasi, and AR Piscium.

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Hd 12545, A Study In Spottedness, Melissa Hampton, Gregory W. Henry, Joel A. Eaton, Richard A. Nolthenius, Douglas S. Hall Jan 1996

Hd 12545, A Study In Spottedness, Melissa Hampton, Gregory W. Henry, Joel A. Eaton, Richard A. Nolthenius, Douglas S. Hall

Information Systems and Engineering Management Research Publications

We have solved two sets of light curves of HD 12545 at its epoch of extreme spottedness in 1990-91, one of which coincides with an independent set analyzed recently by Strassmeier and Olah. Even for the huge amplitudes observed, these light-curve solutions did not give reliable determinations of several important spot properties. Specifically, we find that we could obtain acceptable solutions for a wide range of inclination; that spot temperature depends on inclination assumed, falling in the range Delta-T = Tstar - Tspot = 650-1200 K for inclinations of 70-30 deg; that spot latitudes derived from the light curves are …

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An Automated Search For Variability In Chromospherically Active Stars, Gregory W. Henry, Francis C. Fekel, Douglas S. Hall Dec 1995

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 …

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