Is Mira B a low mass white dwarf?

TL;DR

This study uses photometric observations of Mira to analyze its flickering behavior, estimating that Mira B is a low mass white dwarf with specific accretion properties, contributing new insights into its nature.

Contribution

The paper provides the first detailed photometric analysis of Mira's flickering, estimating Mira B's low mass white dwarf status and accretion rate, which is novel compared to prior assumptions.

Findings

Mira exhibits flickering with amplitudes of 0.11-0.28 mag in B band.

Estimated luminosity of the flickering source is 0.10-0.46 L_sun.

Mira B is a low mass white dwarf with approximately 0.24 M_sun.

Abstract

We report photometric observations in Johnson B and V bands of the short term variability (flickering) of Mira (omicron Ceti). The observations were performed during 7 nights in the period August - October 2025, in the course of the last minimum of the Mira pulsations. The observed peak-to-peak amplitude of the flickering is 0.11-0.28 mag in B band. For the flickering source we find luminosity in the range 0.10-0.46 L_sun. Using the amplitude-flux relation, we estimate an average luminosity of the accretion disc L_d = 0.91 +/- 0.28 L_sun. Assuming that the white dwarf accretes material through Wind Roche Lobe Overflow (WRLOF), we find that Mira B is a low mass white dwarf with M_wd = 0.24 +/- 0.04 M_sun accreting at a rate 6.8x10^{-9} M_sun/yr. This value of the mass is in the range of the extremely low mass white dwarfs. The data are available on Zenodo: zenodo.org/records/18756532