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Extrasolar Giant Planets and X-ray Activity
Vinay L. Kashyap, Jeremy J. Drake, Steven H. Saar
We have carried out a survey of X-ray emission from stars with giant planets, combining both archival and targeted surveys. Over 230 stars have been currently identified as possess…
First Observation of Planet-Induced X-ray Emission: The System HD 179949
S. H. Saar, M. Cuntz, V. L. Kashyap +1
We present the first observation of planet-induced stellar X-ray activity, identified for the HD 179949 system, using Chandra / ACIS-S. The HD 179949 system consists of a close-in…
The Orbital Period of the Wolf-Rayet Binary IC 10 X-1; Dynamic Evidence that the Compact Object is a Black Hole
A. H. Prestwich, R. Kilgard, P. A. Crowther +6
IC 10 X-1 is a bright (Lx=10^38 ergs/s) variable X-ray source in the local group starburst galaxy IC 10. The most plausible optical counterpart is a luminous Wolf-Rayet star, makin…
Exoplanet-Induced Chromospheric Activity: Realistic Light Curves from Solar-type Magnetic Fields
Steven R. Cranmer, Steven H. Saar
There is growing observational evidence for some kind of interaction between stars and close-in extrasolar giant planets. Shkolnik et al. reported variability in the chromospheric…
Confirmation of the Planet Hypothesis for the Long-period Radial Velocity Variations of Beta Geminorum
A. P. Hatzes, W. D. Cochran, M. Endl E. W. Guenther +6
We present precise stellar radial velocity measurements for the K giant star Beta Gem spanning over 25 years. These data show that the long period low amplitude radial velocity var…
Spot patterns and differential rotation in the eclipsing pre-CV binary,V471 Tau
G. A. J. Hussain, C. Allende Prieto, S. H. Saar +1
We present surface spot maps of the K2V primary star in the pre-cataclysmic variable binary system, V471 Tau. The spot maps show the presence of large high latitude spots located a…
Testing the Reality of Strong Magnetic Fields on T Tauri Stars: The Naked T Tauri Star Hubble 4
Christopher M. Johns-Krull, Jeff A. Valenti, Steven H. Saar
High resolution optical and infrared (IR) echelle spectra of the naked (diskless) T Tauri star Hubble 4 are presented. The K band IR spectra include 4 Zeeman sensitive Ti I lines a…
Searching for Planets in the Hyades III: The Quest for Short-Period Planets
D. Paulson, S. Saar, W. Cochran +1
We have been using the Keck I High Resolution Spectrograph (HIRES) to search for planetary companions in the Hyades cluster. We selected four stars from this sample which showed si…
Uses of Linear Polarization as a Probe of Extrasolar Planet Atmospheres
S. Saar, S. Seager
We point out some advantages of making observations of extrasolar planets in linearly polarized (LP) light. Older cool stars have quite low levels (~ 10^-4 to 10^-5) of fractional…
The low-level radial velocity variability in Barnard's star (=GJ 699). Secular acceleration, indications for convective redshift, and planet mass limits
M. Kuerster, M. Endl, F. Rouesnel +6
We report results from 2 1/2 yr of high precision radial velocity (RV) monitoring of Barnard's star. The high RV measurement precision of the VLT-UT2+UVES of 2.65 m/s made the foll…
A new look at dynamo cycle amplitudes
Steven H. Saar, Axel Brandenburg
We explore the dependence of the amplitude of stellar dynamo cycle variability (as seen in the Mount Wilson Ca II HK timeseries data) on other stellar parameters. We find that the…
Searching for Planets in the Hyades II: Some Implications of Stellar Magnetic Activity
Diane B. Paulson, Steven H. Saar, William D. Cochran +1
The Hyades constitute a homogeneous sample of stars ideal for investigating the dependence of planet formation on the mass of the central star. Due to their youth, Hyades members a…
Further Analysis of Stellar Magnetic Cycle Periods
S. H. Saar, A. Brandenburg
We further investigate relationships between activity cycle periods in cool stars and rotation to include new cycle data, and explore different parameterizations of the problem. We…
Optical and UV observations of a strong flare in the young, single K2-dwarf LQ Hya
D. Montes, S. H. Saar, A. Collier Cameron +1
We present high resolution optical echelle spectra and IUE observations during a strong flare on 1993 December 22 in the very active, young, rapidly rotating, single K2 dwarf LQ Hy…