Spot distribution and fast surface evolution on Vega

TL;DR

This study uses Doppler Imaging over five nights to map Vega's surface spots, revealing complex, evolving patterns and potential rapid changes within days, hinting at dynamic magnetic activity.

Contribution

First detailed surface maps of Vega's spots showing their complex distribution and short-term evolution, advancing understanding of stellar surface dynamics.

Findings

Complex spot distribution covering most of Vega's surface

Evidence of rapid spot emergence and disappearance

Possible zonal flows with differential rotation

Abstract

Spectral signatures of surface spots were recently discovered from high cadence observations of the A star Vega. We aim at constraining the surface distribution of these photospheric inhomogeneities, and investigating a possible short term evolution of the spot pattern. Using data collected over five consecutive nights, we employ the Doppler Imaging method to reconstruct three different maps of the stellar surface, from three consecutive subsets of the whole time-series. The surface maps display a complex distribution of dark and bright spots, covering most of the visible fraction of the stellar surface. A number of surface features are consistently recovered in all three maps, but other features seem to evolve over the time span of observations, suggesting that fast changes can affect the surface of Vega within a few days at most. The short-term evolution is observed as emergence or disappearance of individual spots, and may also show up as zonal flows, with low-latitude and high latitude belts rotating faster than intermediate latitudes. It is tempting to relate the surface brightness activity to the complex magnetic field topology previously reconstructed for Vega, although strictly simultaneous brightness and magnetic maps will be necessary to assess this potential link.