Vaughan–Preston gap

In astronomy, the Vaughan–Preston gap is an observed absence of F-, G- and K-type stars with intermediate levels of magnetic activity. In 1980, Vaughan and Preston noted there were two populations of stars of these classifications, with either high or low levels of activity, separated by an apparent gap.{{Citation | last1 = Vaughan | first1 = A. H. | last2 = Preston | first2 = G. W. | title = A survey of chromospheric CA II H and K emission in field stars of the solar neighborhood | year = 1980 | journal = Publications of the Astronomical Society of the Pacific| volume = 92 | pages = 385| bibcode = 1980PASP...92..385V|doi = 10.1086/130683 | doi-access = free }} There remains no consensus on the cause of the gap.{{Citation | last1 = McQuillan | first1 = A. | last2 = Aigrain | first2 = S. | last3 = Mazeh | first3 = T. | title = Measuring the rotation period distribution of field M dwarfs with Kepler | year = 2013 | journal = Monthly Notices of the Royal Astronomical Society| volume = 432 | issue = 2 | pages = 1203–1216| arxiv = 1303.6787 | bibcode = 2013MNRAS.432.1203M|doi = 10.1093/mnras/stt536 | doi-access = free | s2cid = 118468125 }}