Thumbnail
Access Restriction
Open

Author Stift, Martin J. ♦ Leone, Francesco
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ♦ ABUNDANCE ♦ DIFFUSION ♦ ENTROPY ♦ MAGNETIC FIELDS ♦ MAGNETIC STARS ♦ MAPPING ♦ MATHEMATICAL SOLUTIONS ♦ NOISE ♦ SIGNAL-TO-NOISE RATIO ♦ STELLAR ATMOSPHERES ♦ STOKES PARAMETERS ♦ THREE-DIMENSIONAL CALCULATIONS ♦ ZEEMAN EFFECT
Abstract Numerical models of atomic diffusion in magnetic atmospheres of ApBp stars predict abundance structures that differ from the empirical maps derived with (Zeeman) Doppler mapping (ZDM). An in-depth analysis of this apparent disagreement investigates the detectability by means of ZDM of a variety of abundance structures, including (warped) rings predicted by theory, but also complex spot-like structures. Even when spectra of high signal-to-noise ratio are available, it can prove difficult or altogether impossible to correctly recover shapes, positions, and abundances of a mere handful of spots, notwithstanding the use of all four Stokes parameters and an exactly known field geometry; the recovery of (warped) rings can be equally challenging. Inversions of complex abundance maps that are based on just one or two spectral lines usually permit multiple solutions. It turns out that it can by no means be guaranteed that any of the regularization functions in general use for ZDM (maximum entropy or Tikhonov) will lead to a true abundance map instead of some spurious one. Attention is drawn to the need for a study that would elucidate the relation between the stratified, field-dependent abundance structures predicted by diffusion theory on the one hand, and empirical maps obtained by means of “canonical” ZDM, i.e., with mean atmospheres and unstratified abundances, on the other hand. Finally, we point out difficulties arising from the three-dimensional nature of the atomic diffusion process in magnetic ApBp star atmospheres.
ISSN 0004637X
Educational Use Research
Learning Resource Type Article
Publisher Date 2017-01-01
Publisher Place United States
Journal Astrophysical Journal
Volume Number 834
Issue Number 1


Open content in new tab

   Open content in new tab