Folsom, C. P. and Bagnulo, S. and Wade, G. A. and Alecian, E. and Landstreet, J. D. and Marsden, S. C. and Waite, I. A. (2012) Chemical abundances of magnetic and non-magnetic HerbigAe/Be stars. Monthly Notices of the Royal Astronomical Society, 422 (3). pp. 2072-2101. ISSN 0035-8711
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Identification Number or DOI: doi: 10.1111/j.1365-2966.2012.20718.x
The photospheres of about 10–20 per cent of main-sequence A-and B-type stars exhibit a wide range of chemical peculiarities, often associated with the presence of a magnetic field. It is not exactly known at which stage of stellar evolution these chemical peculiarities develop. To investigate this issue, in this paper we study the photospheric compositions of a sample of Herbig Ae and Be stars, which are considered to be the pre-main-sequence progenitors of A and B stars. We have performed a detailed abundance analysis of 20 Herbig stars (three of which have confirmed magnetic fields), and one dusty young star. We have found that half the stars in our sample show λ Bootis (λ Boo) chemical peculiarities to varying degrees, only one star shows weak Ap/Bp peculiarities and all the remaining stars are chemically normal. The incidence of λ Boo chemical peculiarities we find in Herbig stars is much higher than what is seen on the main sequence. We argue that a selective accretion model for λ Boo star formation is a natural explanation for the remarkably large number of λ Boo stars in our sample. We also find that the magnetic Herbig stars do not exhibit a range of chemical compositions remarkably different from the normal stars: one magnetic star displays λ Boo chemical peculiarities (HD101412), one displays weak Ap/Bp peculiarities (V380 Ori A) and one (HD 190073) is chemically normal. This is completely different from what is seen on the main sequence, where all magnetic A and cool B stars show Ap/Bp chemical peculiarities, and this is consistent with the idea that the magnetic field precedes the formation of the chemical peculiarities typical of Ap and Bp stars.
|Item Type:||Article (Commonwealth Reporting Category C)|
|Additional Information:||Permanent restricted access to published version due to the copyright policy of the publisher.|
|Uncontrolled Keywords:||stars; abundances; chemically peculiar; magnetic field; pre-main-sequence|
|Fields of Research (FOR2008):||04 Earth Sciences > 0401 Atmospheric Sciences > 040199 Atmospheric Sciences not elsewhere classified|
02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
01 Mathematical Sciences > 0105 Mathematical Physics > 010599 Mathematical Physics not elsewhere classified
|Socio-Economic Objective (SEO2008):||E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences|
|Deposited On:||07 Sep 2012 17:19|
|Last Modified:||16 Jan 2013 11:19|
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