Multiline Zeeman signatures through line addition

Semel, M.; Ramírez Vélez, J. C.; Martínez González, M. J.; Asensio Ramos, A.; Stift, M. J.; López Ariste, A.; Leone, F.
Bibliographical reference

Astronomy and Astrophysics, Volume 504, Issue 3, 2009, pp.1003-1009

Advertised on:
9
2009
Number of authors
7
IAC number of authors
2
Citations
30
Refereed citations
25
Description
Context: To obtain a significant Zeeman signature in the polarised spectra of a magnetic star, we usually “add” the contributions of numerous spectral lines; the ultimate goal is to recover the spectropolarimetric prints of the magnetic field in these line additions. Aims: Here we want to clarify the meaning of these techniques of line addition; in particular, we try to interpret the meaning of the “pseudo-line” formed during this process and to find out why and how its Zeeman signature is still meaningful. Methods: We create a synthetic case of line addition and apply well tested standard solar methods routinely used in research on magnetism in the Sun. Results: The results are convincing and the Zeeman signatures well detected; Solar methods are found to be quite efficient for stellar observations. We statistically compare line addition with least-squares deconvolution and demonstrate that they both give very similar results, as a consequence of the special statistical properties of the weights. Conclusions: The Zeeman signatures are unequivocally detected in this multiline approach. We suggest that magnetic field detection is reliable well beyond the weak-field approximation. Linear polarisation in the spectra of solar type stars can be detected when the spectral resolution is sufficiently high.
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