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arXiv · 1712.00345

A search for the presence of magnetic fields in the two Supergiant Fast X-ray Transients IGR J08408-4503 and IGR J11215-5952

S. Hubrig·L. Sidoli·K. Postnov·M. Schöller·A. F. Kholtygin·S. P. Jarvinen·P. Steinbrunner
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Abstract

A significant fraction of high-mass X-ray binaries are supergiant fast X-ray transients (SFXTs). The prime model for the physics governing their X-ray behaviour suggests that the winds of donor OB supergiants are magnetized. To investigate if magnetic fields are indeed present in the optical counterparts of such systems, we acquired low-resolution spectropolarimetric observations of the two optically brightest SFXTs, IGR J08408-4503 and IGR J11215-5952 with the ESO FORS2 instrument during two different observing runs. No field detection at a significance level of 3sigma was achieved for IGR J08408-4503. For IGR J11215-5952, we obtain 3.2sigma and 3.8sigma detections ( _hydr = -978+-308G and _hydr = 416+-110G) on two different nights in 2016. These results indicate that the model involving the interaction of a magnetized stellar wind with the neutron star magnetosphere can indeed be considered to characterize the behaviour of SFXTs. We detected long-term spectral variability in IGR J11215-5952, while for IGR J08408-4503 we find an indication of the presence of short-term variability on a time scale of minutes.

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S. Hubrig, L. Sidoli, K. Postnov, M. Schöller, A. F. Kholtygin, S. P. Jarvinen, P. Steinbrunner. 2017-12-01. A search for the presence of magnetic fields in the two Supergiant Fast X-ray Transients IGR J08408-4503 and IGR J11215-5952. https://doi.org/10.1093/mnrasl/slx187

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