Resolving the stellar activity of the Mira AB binary with ALMA - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Astronomy and Astrophysics Supplement Series Année : 2015

Resolving the stellar activity of the Mira AB binary with ALMA

W. H. T., Vlemmings
  • Fonction : Auteur
S., Ramstedt
  • Fonction : Auteur
E. M. L., Humphreys
  • Fonction : Auteur
Alain Baudry
  • Fonction : Auteur
  • PersonId : 853057
M., Karovska
  • Fonction : Auteur

Résumé

We present the size, shape and flux densities at millimeter continuum wavelengths, based on ALMA science verification observations in Band 3 (~94.6 GHz) and Band 6 (~228.7 GHz), from the binary Mira A (o Ceti) and Mira B. The Mira AB system has been observed with ALMA at a spatial resolution of down to ~25 mas. The extended atmosphere of Mira A and the wind around Mira B sources are resolved and we derive the size of Mira A and of the ionized region around Mira B. The spectral indices within Band 3 (between 89-100 GHz) and between Band 3 and Band 6 are also derived. The spectral index of Mira A is found to change from 1.71+-0.05 within Band 3 to 1.54+-0.04 between Band 3 and 6. The spectral index of Mira B is 1.3+-0.2 in Band 3, in good agreement with measurements at longer wavelengths. However it rises to 1.72+-0.11 between the bands. For the first time the extended atmosphere of a star is resolved at these frequencies and for Mira A the diameter is ~3.7x2.9 AU in Band 3 (with brightness temperature Tb~6000 K) and ~4.0x3.6 AU in Band 6 (Tb~2500 K). Additionally, a bright hotspot of ~0.4 AU and with Tb~10000 K is found on the stellar disc of Mira A. The size of the ionized region around the accretion disk of Mira B is found to be ~2.4 AU. The emission around Mira B is consistent with that from a partially ionized wind of gravitationally bound material from Mira A close to the accretion disk of Mira B. The Mira A atmosphere does not fully match predictions, with brightness temperatures in Band 3 significantly higher than expected, potentially due to shock heating. The hotspot is likely due to magnetic activity and could be related to the previously observed X-ray flare of Mira A.

Dates et versions

hal-01136924 , version 1 (30-03-2015)

Identifiants

Citer

W. H. T., Vlemmings, S., Ramstedt, E., O'Gorman, E. M. L., Humphreys, M., Wittkowski, et al.. Resolving the stellar activity of the Mira AB binary with ALMA. Astronomy and Astrophysics Supplement Series, 2015, 577, pp.id.L4. ⟨10.1051/0004-6361/201526186⟩. ⟨hal-01136924⟩

Collections

INSU CNRS L3AB
47 Consultations
0 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More