Patterns of Photometric and Chromospheric Variation among Sun-like Stars: A 20 Year Perspective

By G. Lockwood, B. Skiff, G. Henry, Stephen M. Henry, R. Radick, S. Baliunas, R. Donahue, Willie Soon. 2007

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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 variation has probably now been observed for a majority of the program stars. Twenty-seven stars are deemed variable according to an objective statistical criterion. On a year-to-year timescale, young active stars become fainter when their Ca II emission increases, while older less active stars such as the Sun become brighter when their Ca II emission increases. The Sun's total irradiance variation, scaled to the b and y stellar filter photometry, still appears to be somewhat smaller than stars in our limited sample with similar mean chromospheric activity, but we now regard this discrepancy as probably due mainly to our limited stellar sample.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

View Paper: https://www.semanticscholar.org/paper/f4fd4eab10f3cb4b7ea0f16ad6f99b11b45053d4

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Citations in the corpus

Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system (2013, background): “Indeed, according to Lockwood et al. (2007), faculae become less important (relative to spots) in stars more active than the Sun.”
THE LICK–CARNEGIE EXOPLANET SURVEY: A 3.1 M⊕ PLANET IN THE HABITABLE ZONE OF THE NEARBY M3V STAR GLIESE 581 (2010, background): “Long-term brightness monitoring of these stars enabled by our automatic telescopes can detect brightness changes due to the growth and decay of individual active regions as well as brightness variations associated with stellar magnetic cycles (Henry 1999; Lockwood et al. 2007; Hall et al. 2009).”
DIRECT IMAGING OF A COLD JOVIAN EXOPLANET IN ORBIT AROUND THE SUN-LIKE STAR GJ 504 (2013, methodology): “Other studies using data from Mt. Wilson Observatory have measured R′HK values of –4.443 (Baliunas et al. 1996) and –4.486 (Lockwood et al. 2007), which differ slightly from our adopted value of –4.45.”
Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics (2008, unknown): “Lockwood et al. (2007) and Hall et al. (2007) also provide recent syn- opses.”
Multiple and changing cycles of active stars - II. Results (2009, background): “Lockwood et al. (2007) studied the magneticcycle patterns seen in the photospheres and chromospheres of 32 stars primarily on or near the lower main-sequence.”
Magnetic activity in the photosphere of CoRoT-Exo-2a. Active longitudes and short-term spot cycle in (2008, background): “Therefore, we expect that its light variations are dominated by cool spots, as suggested by Radick et al. (1998) and Lockwood et al. (2007).”
KEPLER MISSION STELLAR AND INSTRUMENT NOISE PROPERTIES (2011, background): “Data on RMS variations observed in solar-type stars and their relation to the observed R′HK are presented in Radick et al. (1998), Lockwood et al. (2007) and Hall et al. (2009).”
SOAP 2.0: A TOOL TO ESTIMATE THE PHOTOMETRIC AND RADIAL VELOCITY VARIATIONS INDUCED BY STELLAR SPOTS AND PLAGES (2014, background): “In conclusion, simulations only considering the flux effect can reproduce the observed variation induced by active regions for stars that are spot-dominated (Shapiro et al. 2014; Lockwood et al. 2007), which is the case for very active stars (e.g. HD166435, Boisse et al. 2012).”