CRITICAL EVALUATION OF MAGNETIC FIELD DETECTIONS REPORTED FOR PULSATING B-TYPE STARS IN LIGHT OF ESPaDOnS, NARVAL, AND REANALYZED FORS1/2 OBSERVATIONS

Recent spectropolarimetric studies of seven slowly pulsating B (SPB) and beta Cep stars have suggested that photospheric magnetic fields are more common in B-type pulsators than in the general population of B stars, suggesting a significant connection between magnetic and pulsational phenomena. We p...

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Bibliographic Details
Published in:The Astrophysical journal 2012-05, Vol.750 (1), p.1-10
Main Authors: SHULTZ, M, WADE, G. A, GRUNHUT, J, BAGNULO, S, LANDSTREET, J. D, NEINER, C, ALECIAN, E, HANES, D
Format: Article
Language:English
Subjects:
ASTRONOMY
ASTROPHYSICS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
B stars
DATA ANALYSIS
Earth, ocean, space
EMISSION SPECTRA
Exact sciences and technology
Fluid flow
GIANT STARS
MAGNETIC FIELDS
MAGNETISM
Mathematical models
OSCILLATIONS
Physics
POLARIMETRY
PULSATIONS
Reduction
Spectra
Stars
VARIABLE STARS
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Summary:Recent spectropolarimetric studies of seven slowly pulsating B (SPB) and beta Cep stars have suggested that photospheric magnetic fields are more common in B-type pulsators than in the general population of B stars, suggesting a significant connection between magnetic and pulsational phenomena. We present an analysis of new and previously published spectropolarimetric observations of these stars. New Stokes V observations obtained with the high-resolution ESPaDOnS and Narval instruments confirm the presence of a magnetic field in one of the stars ( epsilon Lup), but find no evidence of magnetism in five others. A re-analysis of the published longitudinal field measurements obtained with the low-resolution FORS1/2 spectropolarimeters finds that the measurements of all stars show more scatter from zero than can be attributed to Gaussian noise, suggesting the presence of a signal and/or systematic underestimation of error bars. Re-reduction and re-measurement of the FORS1/2 spectra from the ESO archive demonstrates that small changes in reduction procedure lead to substantial changes in the inferred longitudinal field, and substantially reduces the number of field detections at the 3[sigma] level. Furthermore, we find that the published periods are not unique solutions to the time series of either the original or the revised FORS1/2 data. We conclude that the reported field detections, proposed periods, and field geometry models for alpha Pyx, 15 CMa, 33 Eri, and V1449 Aql are artifacts of the data analysis and reduction procedures, and that magnetic fields at the reported strength are no more common in SPB/ beta Cep stars than in the general population of B stars.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/750/1/2