G. Wesley Lockwood

Publications (3)4.03 Total impact

• Source

  Available from: Steven H. Saar

  Article: The Activity and Variability of the Sun and Sun-Like Stars. II. Contemporaneous Photometry and Spectroscopy of Bright Solar Analogs

  Jeffrey C. Hall, Gregory W. Henry, G. Wesley Lockwood, Brian A. Skiff, and Steven H. Saar
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  ABSTRACT: We present 14 years of contemporaneous photometric and spectroscopic observations of 28 solar analog stars, taken with the Tennessee State University Automatic Photometric Telescopes at Fairborn Observatory and the Solar-Stellar Spectrograph at Lowell Observatory. These are the best observed and most nearly Sun-like of the targets in our magnitude-limited (V ≤ 7.5) sample. The correlations between luminosity and activity reveal the expected inverse activity-brightness correlations for active stars. Strong direct correlations between activity and brightness are not prevalent for the less active solar age stars, but are precision limited. The Sun does not appear to have unusually low photometric variability when compared with the most Sun-like inactive solar analogs. We present evidence that the activity index R'HK is not a good discriminant of Maunder Minimum candidate stars. On the basis of a star that appears to have transitioned from a low-variability state to a cycling state, we investigate the regime in which stars might switch from faculae-dominated to spot-dominated variations.
  The Astronomical Journal 06/2009; 138(1):312. · 4.03 Impact Factor
• Source

  Available from: arxiv.org

  Article: The Sun-like activity of the solar twin 18 Scorpii

  Jeffrey C. Hall, Gregory W. Henry, G. Wesley Lockwood
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  ABSTRACT: 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 year chromospheric activity cycle, 18 Sco's brightness varies in the same manner as the Sun's and with a likely brightness variation of 0.09%, similar to the 0.1% decadal variation in the total solar irradiance.
  04/2007;
• Source

  Available from: adsabs.harvard.edu

  Article: Precise automatic differential stellar photometry

  Andrew T. Young, Russell M. Genet, Louis J. Boyd, William J. Borucki, G. Wesley Lockwood
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  ABSTRACT: The factors limiting the precision of differential stellar photometry are reviewed. Errors due to variable atmospheric extinction can be reduced to below 0.001 mag at good sites by utilizing the speed of robotic telescopes. Existing photometric systems produce aliasing errors, which are several millimagnitudes in general but may be reduced to about a millimagnitude in special circumstances. Conventional differential photometry neglects several other important effects, which are discussed in detail. If all of these are properly handled, it appears possible to do differential photometry of variable stars with an overall precision of 0.001 mag with ground based robotic telescopes.
  03/1991;