Astrophys. J., 750, 2 (2012/May-1)
Critical evaluation of magnetic field detections reported for pulsating b-type stars in light of ESPaDOnS, Narval, and reanalyzed FORS1/2 observations.
SHULTZ M., WADE G.A., GRUNHUT J., BAGNULO S., LANDSTREET J.D., NEINER C., ALECIAN E., HANES D. (The MiMeS Collaboration)
Abstract (from CDS):
Recent spectropolarimetric studies of seven slowly pulsating B (SPB) and β 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 (ε 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 3σ 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 α 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/β Cep stars than in the general population of B stars.
stars: early-type - stars: magnetic field - stars: massive - stars: oscillations - stars: variables: general
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