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Coronae of Stars with Supersolar Elemental AbundancesCoronal elemental abundances are known to deviate from the photospheric values of their parent star, with the degree of deviation depending on the first ionization potential (FIP). This study focuses on the coronal composition of stars with supersolar photospheric abundances. We present the coronal abundances of six such stars: 11 LMi, iota Hor, HR 7291, tau Boo, and alpha Cen A and B. These stars all have high-statistics X-ray spectra, three of which are presented for the first time. The abundances we measured were obtained using the line-resolved spectra of the Reflection Grating Spectrometer (RGS) in conjunction with the higher throughput EPIC-pn camera spectra onboard the XMM-Newton observatory. A collisionally ionized plasma model with two or three temperature components is found to represent the spectra well. All elements are found to be consistently depleted in the coronae compared to their respective photospheres. For 11 LMi and tau Boo no FIP effect is present, while iota Hor, HR 7291, and alpha Cen A and B show a clear FIP trend. These conclusions hold whether the comparison is made with solar abundances or the individual stellar abundances. Unlike the solar corona, where low-FIP elements are enriched, in these stars the FIP effect is consistently due to a depletion of high-FIP elements with respect to actual photospheric abundances. A comparison with solar (instead of stellar) abundances yields the same fractionation trend as on the Sun. In both cases, a similar FIP bias is inferred, but different fractionation mechanisms need to be invoked.
Document ID
20160010535
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Peretz, Uria
(Technion - Israel Inst. of Tech. Haifa, Israel)
Behar, Ehud
(Technion - Israel Inst. of Tech. Haifa, Israel)
Drake, Stephen A.
(Universities Space Research Association Greenbelt, MD, United States)
Date Acquired
August 23, 2016
Publication Date
May 8, 2015
Publication Information
Publication: Astronomy & Astrophysics
Publisher: EDP Sciences
Volume: 577
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN35011
Funding Number(s)
CONTRACT_GRANT: ISF-1937/12
CONTRACT_GRANT: NSF-PHYS-1066293
CONTRACT_GRANT: NNG06EO90A
CONTRACT_GRANT: ISF-1163/10
Distribution Limits
Public
Copyright
Other
Keywords
stars: abundances / stars: coronae / stars: general

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