A study of polarized spectra of magnetic CP stars:: Predicted vs. observed Stokes iQUV profiles for β CrB and 53 Cam

被引:61
作者
Bagnulo, S
Wade, GA
Donati, JF
Landstreet, JD
Leone, F
Monin, DN
Stift, MJ
机构
[1] Univ Vienna, Inst Astron, A-1180 Vienna, Austria
[2] Univ Toronto, Dept Astron, Mississauga, ON L5L 1CS, Canada
[3] Observ Midi Pyrenees, F-31400 Toulouse, France
[4] Univ Western Ontario, Dept Phys & Astron, London, ON N6A 3K7, Canada
[5] Osserv Astrofis Catania, I-95125 Catania, Italy
[6] Russian Acad Sci, Special Astrophys Observ, Nizhnii Arkhyz 357147, Russia
来源
ASTRONOMY & ASTROPHYSICS | 2001年 / 369卷 / 03期
关键词
stars : magnetic fields; polarization; stars : chemically peculiar; stars : individual : beta CrB; stars : individual : 53 Cam;
D O I
10.1051/0004-6361:20010101
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present, a comparison of observed and calculated Stokes IQUV spectra of two well-known magnetic chemically peculiar stars, beta Coronae Borealis and 53 Camelopardalis. The observed Stokes spectra were recently described by Wade et al. (2000a), and have been complemented with additional circularly polarized spectra obtained at the Special Astrophysical Observatory. The calculated spectra represent the predictions of new and previously published magnetic field models derived from the analysis of some surface averaged field estimates (e.g., longitudinal field, magnetic field modulus, etc.). We find that these magnetic models are not sufficient to account fully for the observed Stokes profiles particularly remarkable is the disagreement between the predicted and observed Stokes Q and U profiles of 53 Cam. We suggest that this should be interpreted in terms of magnetic morphologies which are significantly more complex than the second-order multipolar expansions assumed in the models. However, it is clear that some of our inability to reproduce the detailed shapes of the Stokes IQUV profiles is unrelated to the magnetic models. For many metallic ions, for both stars, we found it impossible to account for the strengths and shapes of the observed spectral line profiles when we adopted a unique value for the individual ion abundance. We suggest that this results from strongly non-uniform distributions of these ions as a function of optical depth (i.e., chemical stratification), a hypothesis that is supported by comparison with simple chemically stratified models.
引用
收藏
页码:889 / 907
页数:19
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