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

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.

References in corpus (6)

• The Magnetic Fields at the Surface of Active Single G-K Giants
• No Sun-like dynamo on the active star $\zeta$ Andromedae from starspot asymmetry
• ULTRASPEC: a high-speed imaging photometer on the 2.4-m Thai National Telescope
• Spot evolution on the red giant star XX Triangulum. A starspot-decay analysis based on time-series Doppler imaging
• Milliarcsecond angular resolution of reddened stellar sources in the vicinity of the Galactic Center
• First Lunar Occultation Results from the 2.4 m Thai National Telescope equipped with ULTRASPEC

Cited by in corpus (2)

• Three-dimensional hydrodynamical CO5BOLD model atmospheres of red giant stars VI. First chromosphere model of a late-type giant
• Further milliarcsecond resolution results on cool giants and binary stars from lunar occultations at Devashtal