Protostars and Planets VI, Heidelberg, July 15-20, 2013

Poster 1K097

Wilson-Bappu Effect: Extended to Surface Gravity

Park, Sunkyung (Kyung Hee University)
Lee, Jeong-Eun (Kyung Hee University)
Kang, Wonseok (Kyung Hee University)
Lee, Sang-Gak (Seoul National University)

Wilson and Bappu found a tight correlation between the stellar absolute visual magnitude (Mv) and the width of the Ca II K emission line for late-type stars in 1957. Here, we revisit the Wilson-Bappu relation (hereafter, WBR) to claim that WBR can be an excellent indicator of stellar surface gravity of late-type stars as well as a distance indicator. We have measured the width of the Ca II K emission line (log W) in high resolution spectra of 125 late-type stars, which were obtained with Bohyunsan Optical Echelle Spectrograph (BOES) and adopted from the UVES archive. Based on our measurement of the emission line width (log W), we have obtained a WBR of Mv = 33.76 – 18.08 log W. In order to extend the WBR to be a surface gravity indicator, the stellar atmospheric parameters such as effective temperature (Teff), surface gravity (log g), metallicity ([Fe/H]), and micro-turbulence („ītur) have been derived from the self-consistent detailed analysis using the Kurucz stellar atmospheric model and the abundance analysis code, MOOG. Using these stellar parameters and log W, we found that log g = - 5.85 log W + 9.97 log Teff - 23.48 for late-type stars.

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