The chromospheric emission of solar-type stars in the young open clusters IC 2391 and IC 2602 |
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| Authors: | S C Marsden B D Carter J-F Donati |
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| Institution: | Anglo-Australian Observatory, PO Box 296, Epping, NSW 1710, Australia;Faculty of Sciences, University of Southern Queensland, Toowoomba, QLD 4350, Australia;Laboratoire d'Astrophysique, Observatoire Midi-Pyrénées, F-31400 Toulouse, France |
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| Abstract: | In this paper we present chromospheric emission levels of the solar-type stars in the young open clusters IC 2391 and IC 2602. High-resolution spectroscopic data were obtained for over 50 F, G and K stars from these clusters over several observing campaigns using the University College London Echelle Spectrograph on the 3.9-m Anglo-Australian Telescope. Unlike older clusters, the majority (28/52) of the solar-type stars in the two clusters are rapid rotators ( v sin i > 20 km s?1) with five of the stars being classified as ultra-rapid rotators ( v sin i > 100 km s?1) . The emission levels in the calcium infrared triplet lines were then used as a measure of the chromospheric activity of the stars. When plotted against the Rossby number ( N R), the star's chromospheric emission levels show a plateau in the emission for log( N R) ??1.1 indicating chromospheric saturation similar to the coronal saturation seen in previously observed X-ray emission from the same stars. However, unlike the coronal emission, the chromospheric emission of the stars shows little evidence of a reduction in emission (i.e. supersaturation) for the ultra-rapid rotators in the clusters. Thus we believe that coronal supersaturation is not the result of an overall decrease in magnetic dynamo efficiency for ultra-rapid rotators. |
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| Keywords: | stars: activity stars: late-type stars: rotation open clusters and associations: individual: IC 2391 open clusters and associations: individual: IC 2602 |
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