The chromospheric emission of solar-type stars in the young open clusters IC 2391 and IC 2602

Marsden, S.C., Carter, B.D., and Donati, J-F. (2009) The chromospheric emission of solar-type stars in the young open clusters IC 2391 and IC 2602. Monthly Notices of the Royal Astronomical Society, 399 (2). pp. 888-905.

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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 (NR), the star's chromospheric emission levels show a plateau in the emission for log(NR) ≲−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.

Item ID: 16628
Item Type: Article (Refereed Research - C1)
Keywords: stars: activity; stars: late-type; stars: rotation; open clusters and associations: individual: IC 2391; open clusters and associations: individual: IC 2602
ISSN: 1365-2966
Date Deposited: 13 Jul 2011 04:53
FoR Codes: 02 PHYSICAL SCIENCES > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970102 Expanding Knowledge in the Physical Sciences @ 100%
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