Ca II H and K Measurements Made at MWO (Duncan+ 1991)

Details Ca II H and K Measurements Made at MWO (Duncan+ 1991) Ca II H and K Measurements Made at MWO (Duncan+ 1991)

Nov 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005ycat.3159....0d&link_type=abstract

VizieR On-line Data Catalog: III/159A. Originally published in: 1991ApJS...76..383D

Computer Science

Photometry: K-Line

Scientific paper

Summaries are presented of the photoelectric measurements of stellar CaII H and K line intensity made at Mount Wilson Observatory during the years 1966-1983. These results are derived from 65,263 individual observations of 1296 stars. For each star, for each observing season, the maximum, minimum, mean, and variation of the instrumental H and K index "S" are given, as well as a measurement of the accuracy of observation. A total of 3110 seasonal summaries are reported.
These observations were obtained with two instruments, HKP-1 and HKP-2. The HKP-2 instrument is a four-channel chopping spectrometer which records counts in 1.09{AA} FWHM triangular bandpasses centered in the H and K lines as well as in two 20{AA} reference bandpasses centered on 3901.067 and 4001.067{AA}. The stellar activity is expressed by the index S defined as
S = {alpha} (Nh+Nk)/(Nr+Nv)
where Nh and Nk are the counts (corrected from background) in the H and K lines, Nr and Nv those in the reference continuum bandpasses, and {alpha} is a constant of proportionality used to correct for night-to-night instrumental variations. Higher values of S generally correspond to higher levels of chromospehric activities.
Factors which effect the ability to detect stellar activity variations and accurately measure their amplitudes such as the accuracy of the H and K measurements and scattered light contamination are discussed. Relations are given which facilitate intercomparison of "S" values with residual intensities from ordinary spectrophotometry, and for converting measurements to absolute fluxes.
(1 data file).

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