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On the utility of low resolution IUE spectroscopy of the 2800 A Mg II lines as a stellar chromosphere indicatorLow resolution IUE spectroscopy of the 2800-A Mg II h and k lines is shown to provide a useful means for documenting chromospheric activity among relatively young dwarf stars. An index I(Mg II) has been defined which measures the integrated flux in the region 2784-2814 A relative to the flux interpolated from nearby comparison regions. Values of this index have been derived from low resolution IUE spectra for a sample of field dwarfs for which Ca II H and K line indices have been published as part of the Mount Wilson HK program. The large range in chromospheric activity among field dwarfs that is exhibited by the Mount Wilson Ca II S index is found to also be reflected by the lower resolution I(Mg II) index. Using an age calibration of Ca II emission line strengths derived by Barry, it is found that the value of I(Mg II) can be used to distinguish between dwarfs younger and older than 3 Gyr. The low resolution nature of the I(Mg II) index means that it holds potential for use as an age diagnostic for stellar population studies. Among dwarfs of age greater than 3 Gyr there is some evidence that this Mg II index is affected by line blanketing.
Document ID
19910039616
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Smith, Graeme H.
(Lick Observatory Santa Cruz, CA, United States)
Burstein, David
(Arizona State University Tempe, United States)
Fanelli, Michael N.
(Lick Observatory Santa Cruz, CA, United States)
O'Connell, Robert W.
(Virginia, University Charlottesville, United States)
Wu, C.-C.
(Space Telescope Science Institute; Computer Sciences Corp. Baltimore, MD, United States)
Date Acquired
August 15, 2013
Publication Date
February 1, 1991
Publication Information
Publication: Astronomical Journal
Volume: 101
ISSN: 0004-6256
Subject Category
Astronomy
Accession Number
91A24239
Funding Number(s)
CONTRACT_GRANT: NAG5-1265
CONTRACT_GRANT: NAS5-28749
CONTRACT_GRANT: NAG5-547
Distribution Limits
Public
Copyright
Other

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