The Chandra Deep Field-North Survey: XVII. Evolution of magnetic activity in old late-type stars

The extremely sensitive Chandra Deep Field-North (CDF-N) pencil-beam X-ray survey is used to identify and characterize the X-ray emission from old high-latitude main sequence Galactic stars. Our principal goal is to investigate the expected long-term decay of magnetic activity of late-type stars due to the gradual spindown of stellar rotation from a magnetized stellar wind. Thirteen X-ray sources are associated with late-type stars; 11 of these constitute a well-defined sample for statistical analysis. This sample consists of 2 G, 2 K0−K4, and 7 M2−M5 stars with median V -band magnitude around 19 and median distance around 300 pc. X-ray luminosities are typically logLx ≃ 27 erg s Based in part on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Stanford University, Ludwig-MaximiliansUniversitt München, and Georg-August-Universitt Göttingen. Department of Astronomy & Astrophysics, 525 Davey Laboratory, Pennsylvania State University, University Park, PA 16802 Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation. Chandra Fellow, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218 INAF Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, United Kingdom Astrophysics Division, Space Science Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands