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arXiv · 1609.06007

Evidence of asymmetries in the Aldebaran photosphere from multi-wavelength lunar occultations

A. Richichi·V. Dyachenko·A. K. Pandey·S. Sharma·O. Tasuya·Y. Balega·A. Beskakotov·D. Rastegaev·V. S. Dhillon
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Abstract

We have recorded three lunar occultations of Aldebaran (AlfTau) at different telescopes and using various band-passes, from the ultraviolet to the far red. The data have been analyzed using both model-dependent and model-independent methods. The derived uniform-disc angular diameter values have been converted to limb-darkened values using model atmosphere relations, and are found in broad agreement among themselves and with previous literature values. The limb-darkened diameter is about 20.3 milliarcseconds on average . However, we have found indications that the photospheric brightness profile of Aldebaran may have not been symmetric, a finding already reported by other authors for this and for similar late-type stars. At the sampling scale of our brightness profile, between one and two milliarcsecond, the uniform and limb-darkened disc models may not be a good description for Aldebaran. The asymmetries appear to differ with wavelength and over the 137 days time span of our measurements. Surface spots appear as a likely explanation for the differences between observations and the models.

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A. Richichi, V. Dyachenko, A. K. Pandey, S. Sharma, O. Tasuya, Y. Balega, A. Beskakotov, D. Rastegaev, V. S. Dhillon. 2016-09-20. Evidence of asymmetries in the Aldebaran photosphere from multi-wavelength lunar occultations. https://doi.org/10.1093/mnras%2Fstw2352

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