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Astrophysics and Astronomy

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Tennessee State University

2007

Articles 1 - 19 of 19

Full-Text Articles in Physical Sciences and Mathematics

Starspots And Relativity: Applied Doppler Imaging For The Gravity Probe B Mission, Stephen C. Marsden, Svetlana V. Berdyugina, Jean-Francois Donati, Joel A. Eaton, Michael H. Williamson Dec 2007

Starspots And Relativity: Applied Doppler Imaging For The Gravity Probe B Mission, Stephen C. Marsden, Svetlana V. Berdyugina, Jean-Francois Donati, Joel A. Eaton, Michael H. Williamson

Information Systems and Engineering Management Research Publications

We present Doppler images and surface differential rotation measurements for the primary of the RS CVn binary IM Pegasi, the guide star for the Gravity Probe B experiment. The data used is a subset of that taken during optical support of the mission and was obtained almost nightly over a near three year period from the Automatic Spectroscopic Telescope operated by Tennessee State University. Using the technique of least-squares deconvolution to increase the signal-to-noise ratio of the data, we have reconstructed 31 maximum entropy Doppler images of the star. The images show that the spot features are relatively stable for …

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An Ab Initio Study Of The Structures, Vibrational Spectra, And Energetics Of Alshx (X = –1, 0, +1), Sujata Guha, Joseph S. Francisco Dec 2007

An Ab Initio Study Of The Structures, Vibrational Spectra, And Energetics Of Alshx (X = –1, 0, +1), Sujata Guha, Joseph S. Francisco

Chemistry Faculty Research

The ground state of aluminum hydrosulfide, AlSHX (where X = − 1,0, + 1), has been examined using high-level ab initio electronic structure calculations at the CCSD(T) level with an augmented correlation-consistent basis set. The geometries have been optimized up through the aug-cc-pV5Z level and vibrational frequencies calculated using the aug-cc-pV5Z basis set. The energetic properties of AlSH are also examined. The adiabatic ionization potential and electron affinity of AlSH are calculated to be 198.5 and 7.7 kcal mol−1, respectively. Dissociation of AlSH into AlS + H will require 78.2 kcal mol−1 of energy, and the Al-S bond energy is …

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Two Jovian-Mass Planets In Earthlike Orbits, Sarah E. Robinson, Gregory Laughlin, Steve Vogt, Debra A. Fischer, R. Paul Butler, Geoffrey W. Marcy, Gregory W. Henry, Peter Driscoll, Genya Takeda, John A. Johnson Dec 2007

Two Jovian-Mass Planets In Earthlike Orbits, Sarah E. Robinson, Gregory Laughlin, Steve Vogt, Debra A. Fischer, R. Paul Butler, Geoffrey W. Marcy, Gregory W. Henry, Peter Driscoll, Genya Takeda, John A. Johnson

Information Systems and Engineering Management Research Publications

We report the discovery of two new planets: a 1.94 MJup planet in a 1.8 yr orbit of HD 5319, and a 2.51 MJup planet in a 1.1 yr orbit of HD 75898. The measured eccentricities are 0.12 for HD 5319b and 0.10 for HD 75898b, and Markov chain Monte Carlo simulations based on the derived orbital parameters indicate that the radial velocities of both stars are consistent with circular planet orbits. With low eccentricity and 1 AU < a < 2 AU, our new planets have orbits similar to terrestrial planets in the solar system. The radial velocity residuals of both stars have significant trends, likely arising from substellar or low-mass stellar companions.

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The Rotation Period Of The Planet-Hosting Star Hd 189733, Gregory W. Henry, Joshua N. Winn Nov 2007

The Rotation Period Of The Planet-Hosting Star Hd 189733, Gregory W. Henry, Joshua N. Winn

Information Systems and Engineering Management Research Publications

We present synoptic optical photometry of HD 189733, the chromospherically active parent star of one of the most intensively studied exoplanets. We have significantly extended the timespan of our previously reported observations and refined the estimate of the stellar rotation period by more than an order of magnitude: P = 11.953 ± 0.009 days. We derive a lower limit on the inclination of the stellar rotation axis of 54° (with 95% confidence), corroborating earlier evidence that the stellar spin axis and planetary orbital axis are well aligned.

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Five Intermediate-Period Planets From The N2k Sample, Debra A. Fischer, Steve Vogt, Geoffrey W. Marcy, R. Paul Butler, Bun'ei Sato, Gregory W. Henry, Sarah E. Robinson, Gregory Laughlin, Shigeru Ida, Eri Toyota, Masashi Omiya, Peter Driscoll, Genya Takeda, Jason T. Wright, John A. Johnson Nov 2007

Five Intermediate-Period Planets From The N2k Sample, Debra A. Fischer, Steve Vogt, Geoffrey W. Marcy, R. Paul Butler, Bun'ei Sato, Gregory W. Henry, Sarah E. Robinson, Gregory Laughlin, Shigeru Ida, Eri Toyota, Masashi Omiya, Peter Driscoll, Genya Takeda, Jason T. Wright, John A. Johnson

Information Systems and Engineering Management Research Publications

We report the detection of five Jovian-mass planets orbiting high-metallicity stars. Four of these stars were first observed as part of the N2K program, and exhibited low rms velocity scatter after three consecutive observations. However, follow-up observations over the last 3 years now reveal the presence of longer period planets with orbital periods ranging from 21 days to a few years. HD 11506 is a G0 V star with a planet of M sin i = 4.74 MJup in a 3.85 yr orbit. HD 17156 is a G0 V star with a 3.12 MJup planet in a 21.2 day orbit. …

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The Orbits Of The Quadruple Star System 88 Tauri A From Phases Differential Astrometry And Radial Velocity, Benjamin F. Lane, Matthew W. Muterspaugh, Francis C. Fekel, Michael H. Williamson, Stanley Browne, Maciej Konacki, Bernard F. Burke, Mark M. Colavita, Shrinivas R. Kulkarni, Michael Shao Nov 2007

The Orbits Of The Quadruple Star System 88 Tauri A From Phases Differential Astrometry And Radial Velocity, Benjamin F. Lane, Matthew W. Muterspaugh, Francis C. Fekel, Michael H. Williamson, Stanley Browne, Maciej Konacki, Bernard F. Burke, Mark M. Colavita, Shrinivas R. Kulkarni, Michael Shao

Information Systems and Engineering Management Research Publications

We have used high-precision differential astrometry from the Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES) project and radial velocity measurements covering a time span of 20 years to determine the orbital parameters of the 88 Tau A system. 88 Tau is a complex hierarchical multiple system comprising a total of six stars; we have studied the brightest four, consisting of two short-period pairs orbiting each other with an ~18 yr period. We present the first orbital solution for one of the short-period pairs, and determine the masses of the components and distance to the system to the level of …

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Chromospherically Active Stars. Xxvi. The Double-Lined Late-Type Binary Hd 19485 = Wz Arietis, Francis C. Fekel, Charles Thomas Bolton Oct 2007

Chromospherically Active Stars. Xxvi. The Double-Lined Late-Type Binary Hd 19485 = Wz Arietis, Francis C. Fekel, Charles Thomas Bolton

Information Systems and Engineering Management Research Publications

We have used spectroscopic observations to determine the orbital elements and some basic properties of the double-lined spectroscopic binary HD 19485 = WZ Ari. The orbital period is 6.247854 days, and the orbit is circular. The G5 V primary and K0 V secondary are chromospherically active. One star or possibly both are synchronously rotating. Based on the Hipparcos parallax and the magnitude differences derived in this work, we find that both components are approximately 1 mag above the zero-age main sequence, a result that is inconsistent with the assumption that the components are coeval. We discuss some possible solutions to …

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A Determination Of The Spin-Orbit Alignment Of The Anomalously Dense Planet Orbiting Hd 149026, Aaron S. Wolf, Gregory Laughlin, Gregory W. Henry, Debra A. Fischer, Geoffrey W. Marcy, R. Paul Butler, Steve Vogt Sep 2007

A Determination Of The Spin-Orbit Alignment Of The Anomalously Dense Planet Orbiting Hd 149026, Aaron S. Wolf, Gregory Laughlin, Gregory W. Henry, Debra A. Fischer, Geoffrey W. Marcy, R. Paul Butler, Steve Vogt

Information Systems and Engineering Management Research Publications

We report 35 radial velocity measurements of HD 149026 taken with the Keck Telescope. Of these measurements, 15 were made during the transit of the companion planet HD 149026b, which occurred on 2005 June 25. These velocities provide a high-cadence observation of the Rossiter-McLaughlin effect, the shifting of photospheric line profiles that occurs when a planet occults a portion of the rotating stellar surface. We combine these radial velocities with previously published radial velocity and photometric data sets and derive a composite best-fit model for the star-planet system. This model confirms and improves previously published orbital parameters, including the remarkably …

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The Tennessee State University Automatic Spectroscopic Telescope: Data Processing And Velocity Variation Of Cool Giants, Joel A. Eaton, Michael H. Williamson Aug 2007

The Tennessee State University Automatic Spectroscopic Telescope: Data Processing And Velocity Variation Of Cool Giants, Joel A. Eaton, Michael H. Williamson

Information Systems and Engineering Management Research Publications

This paper discusses data reduction for an echelle spectrograph we have developed for an automatic telescope at Tennessee State University and are using to monitor radial velocities and line profiles of cool giant and supergiant stars. Although our approach to data reduction is rather conventional, we discuss flat‐fielding and extraction of velocities in ways that should be of general interest, establish a transformation to the IAU radial velocity system (+0.35 ± 0.09 km s−1), and determine the external precision for measured velocities (0.10–0.11 km s−1). Also, we present results of the first 2–3 years of monitoring radial velocities in about …

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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 Jul 2007

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 …

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The Spectroscopic And Astrometric Orbits Of Hr 672, Francis C. Fekel, Michael H. Williamson, Dimitri Pourbaix Apr 2007

The Spectroscopic And Astrometric Orbits Of Hr 672, Francis C. Fekel, Michael H. Williamson, Dimitri Pourbaix

Information Systems and Engineering Management Research Publications

From a very extensive set of radial velocities obtained at Fairborn Observatory we have computed a new spectroscopic orbit for HR 672. This binary has an orbital period of 93.290 days and an eccentricity of 0.5249. The greatly improved orbital elements have been incorporated into a new astrometric orbit, which has an inclination of 110°, from Hipparcos data. The primary is a slowly rotating early G star that is situated nearly 1 mag above the main sequence and is likely pseudosynchronously rotating. It has an iron abundance that is greater than that of the Sun. Lines of the secondary were …

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The Sun-Like Activity Of The Solar Twin 18 Scorpii, Jeffrey C. Hall, Gregory W. Henry, G. Wesley Lockwood Apr 2007

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.

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Butterfly Diagram And Activity Cycles In Hr 1099, Svetlana Berdyugina, Gregory W. Henry Mar 2007

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 …

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The Distribution Of Activity On The Rs Cvn–Type Star Sz Piscium, Joel A. Eaton, Gregory W. Henry Mar 2007

The Distribution Of Activity On The Rs Cvn–Type Star Sz Piscium, Joel A. Eaton, Gregory W. Henry

Information Systems and Engineering Management Research Publications

We use contemporaneous spectra and BV light curves to derive a model of the distribution of spots and active regions on the cooler component of SZ Psc for the 1993–1994 season. For that epoch, both spots and active regions were visible at all rotational phases of this chromospherically active star. The lack of large distortions of Doppler profiles of optical lines argues for ≳15 spots with angular radii of ≲8°–10°. Transition region emission was constant to within ±12% over the orbit, nor was it eclipsed appreciably. This leads us to estimate that there are at least 20 active regions, perhaps …

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The Transit Light Curve Project. V. System Parameters And Stellar Rotation Period Of Hd 189733, Joshua N. Winn, Matthew J. Holman, Gregory W. Henry, Anna Roussanova, Keigo Enya, Yuzuru Yoshii, Avi Shporer, Tsevi Mazeh, John Asher Johnson, Norio Narita Mar 2007

The Transit Light Curve Project. V. System Parameters And Stellar Rotation Period Of Hd 189733, Joshua N. Winn, Matthew J. Holman, Gregory W. Henry, Anna Roussanova, Keigo Enya, Yuzuru Yoshii, Avi Shporer, Tsevi Mazeh, John Asher Johnson, Norio Narita

Information Systems and Engineering Management Research Publications

We present photometry of HD 189733 during eight transits of its close-in giant planet, and out-of-transit photometry spanning 2 yr. Using the transit photometry, we determine the stellar and planetary radii and the photometric ephemeris. Outside of transits, there are quasi-periodic flux variations with a 13.4 day period that we attribute to stellar rotation. In combination with previous results, we derive upper limits on the orbital eccentricity and on the true angle between the stellar rotation axis and planetary orbit (as opposed to the angle between the projections of those axes on the sky).

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Photometry And Spectroscopy Of 11 Γ Doradus Stars, Gregory W. Henry, Francis C. Fekel, Stephen M. Henry Feb 2007

Photometry And Spectroscopy Of 11 Γ Doradus Stars, Gregory W. Henry, Francis C. Fekel, Stephen M. Henry

Information Systems and Engineering Management Research Publications

We have used precise photometric and high-dispersion spectroscopic observations to study 11 γ Doradus stars, 10 of them newly confirmed. Only five of these 11 γ Doradus stars appear to be single; two are primaries of double-lined spectroscopic binaries, one is the secondary of a double-lined binary, two are primaries of visual binaries and, in the case of the double-lined binary (HD 86371), either or both components could be a pulsating γ Doradus star. We have determined a preliminary orbital period of 5.32 days for the double-lined binary HD 41547. Several of the stars show spectroscopic line-profile and low-amplitude radial …

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Photospheric And Chromospheric Active Regions In Four Young Solar-Type Stars, Katia Biazzo, Antonio Frasca, Gregory W. Henry, S. Catalano, E. Marilli Feb 2007

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.

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Infrared Spectroscopy Of Symbiotic Stars. V. First Orbits For Three S-Type Systems: Henize 2-173, Cl Scorpii, And As 270, Francis C. Fekel, Kenneth H. Hinkle, Richard R. Joyce, Peter R. Wood, Thomas Lebzelter Jan 2007

Infrared Spectroscopy Of Symbiotic Stars. V. First Orbits For Three S-Type Systems: Henize 2-173, Cl Scorpii, And As 270, Francis C. Fekel, Kenneth H. Hinkle, Richard R. Joyce, Peter R. Wood, Thomas Lebzelter

Information Systems and Engineering Management Research Publications

Infrared radial velocities have been used to compute first orbits of the M giants in three southern S-type symbiotic systems. Of the three, Hen 2-173 has the longest orbital period, 911 days, and also has a noncircular orbit with an eccentricity of 0.21. The large value of its mass function suggests that Hen 2-173 may be an eclipsing system. For CL Sco our spectroscopic orbital period of 626 days is essentially identical to the previously determined light variability period of 625 days, and we have adopted the latter. AS 270 has an orbital period of similar length, 671 days, and …

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The Record-Breaking Rotational Braking Of The He Strong Cp Star Hd 37776, Zdeněk Mikulášek, Jiří Krtička, Juraj Zverko, Gregory W. Henry, Jan Janik, Iosif I. Romanyuk, Jozef Ziznovsky, Hrvoje Božić, Miloslav Zejda, Thomas Graf, Martin Netolický Jan 2007

The Record-Breaking Rotational Braking Of The He Strong Cp Star Hd 37776, Zdeněk Mikulášek, Jiří Krtička, Juraj Zverko, Gregory W. Henry, Jan Janik, Iosif I. Romanyuk, Jozef Ziznovsky, Hrvoje Božić, Miloslav Zejda, Thomas Graf, Martin Netolický

Information Systems and Engineering Management Research Publications

We study the long-term light and spectral variations in the He-strong magnetic chemically peculiar star HD 37776 (V901 Ori) to search for changes of its 1.5387 d period in 1976-2007. We analyze all published photometric observations and spectrophotometry in the HeI 4026 A line. The data were supplmented with 506 new (U)VB observations obtained during the last 2 observing seasons, 66 estimates of HeI equivalent widths on 23 CFHT spectrograms and 35 of the 6-m Zeeman spectrograms. All the 1895 particular observations heve been processed simultaneously. We confirm the previously suspected increase of the period in HD 37776 which is …

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