Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

2000

Astrophysics and Astronomy

Tennessee State University

Articles 1 - 13 of 13

Full-Text Articles in Physical Sciences and Mathematics

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 …

Go to article

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 …

Go to article

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 …

Go to article

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 …

Go to article

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 …

Go to article

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.

Go to article

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 …

Go to article

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 …

Go to article

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 …

Go to article

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 …

Go to article

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, …

Go to article

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 …

Go to article

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 = …

Go to article