Colours of the flickering source of Mira

Abstract

We report photometric observations in Johnson UBV bands of the short term variability of Mira. The amplitude detected is 0.16 mag in B band. Adopting interstellar extinction E(B − V ) ≈ 0, we find for the flickering source colour B − V ≈ 1.3, temperature T ≈ 3400 K, and radius R ≈ 0.77 R⊙. The colour of the flickering source is considerably redder than the average B-V colour of cataclysmic variables.