The importance of non-photon noise in stellar spectropolarimetry. The spurious detection of a non-existing magnetic field in the A0 supergiant HD 92207

@article{Bagnulo2013TheIO,
  title={The importance of non-photon noise in stellar spectropolarimetry. The spurious detection of a non-existing magnetic field in the A0 supergiant HD 92207},
  author={Stefano Bagnulo and Luca Fossati and Oleg Kochukhov and John D. Landstreet},
  journal={arXiv: Instrumentation and Methods for Astrophysics},
  year={2013}
}
The low-resolution, Cassegrain mounted, FORS spectropolarimeter of the ESO Very Large Telescope is being extensively used for magnetic field surveys. Some of the new discoveries suggest that relatively strong magnetic fields may play an important role in numerous physical phenomena observed in the atmospheres as well as in the circumstellar environments of certain kinds of stars. We show in detail how small instabilities or data-reduction inaccuracies represent an alternative explanation for… 

Short time-scale spectral variability in the A0 supergiant HD 92207 and the importance of line profile variations for the interpretation of FORS 2 spectropolarimetric observations

Our recent search for the presence of a magnetic field in the bright early A-type supergiant HD92207 using FORS2 in spectropolarimetric mode indicated the presence of a longitudinal magnetic field of

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