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

Physical Sciences and Mathematics Commons™

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

Astrophysics and Astronomy

2002

Information Systems and Engineering Management Research Publications

Articles 1 - 9 of 9

Full-Text Articles in Physical Sciences and Mathematics

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 …

Go to article

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 …

Go to article

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 …

Go to article

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 …

Go to article

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 …

Go to article

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 …

Go to article

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.

Go to article

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 …

Go to article

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 …

Go to article