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Resolving the stellar activity of the Mira AB binary with ALMA
| dc.contributor.author | VLEMMINGS, W. H. T., | |
| dc.contributor.author | RAMSTEDT, S., | |
| hal.structure.identifier | Department of Biology | |
| dc.contributor.author | O'GORMAN, E., | |
| dc.contributor.author | HUMPHREYS, E. M. L., | |
| hal.structure.identifier | European Southern Observatory [ESO] | |
| dc.contributor.author | WITTKOWSKI, M., | |
| hal.structure.identifier | FORMATION STELLAIRE 2015 | |
| dc.contributor.author | BAUDRY, Alain | |
| dc.contributor.author | KAROVSKA, M., | |
| dc.date.issued | 2015 | |
| dc.identifier.issn | 0365-0138 | |
| dc.description.abstractEn | 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. | |
| dc.language.iso | en | |
| dc.publisher | EDP Sciences | |
| dc.subject.en | stars: AGB and post-AGB | |
| dc.subject.en | stars: atmospheres | |
| dc.subject.en | binaries: close | |
| dc.subject.en | stars: individual: Mira AB | |
| dc.title.en | Resolving the stellar activity of the Mira AB binary with ALMA | |
| dc.type | Article de revue | |
| dc.identifier.doi | 10.1051/0004-6361/201526186 | |
| dc.subject.hal | Planète et Univers [physics]/Astrophysique [astro-ph]/Astrophysique galactique [astro-ph.GA] | |
| dc.identifier.arxiv | 1503.07647 | |
| bordeaux.journal | Astronomy and Astrophysics Supplement Series | |
| bordeaux.page | id.L4 | |
| bordeaux.volume | 577 | |
| bordeaux.peerReviewed | oui | |
| hal.identifier | hal-01136924 | |
| hal.version | 1 | |
| hal.popular | non | |
| hal.audience | Internationale | |
| hal.origin.link | https://hal.archives-ouvertes.fr//hal-01136924v1 | |
| bordeaux.COinS | ctx_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.jtitle=Astronomy%20and%20Astrophysics%20Supplement%20Series&rft.date=2015&rft.volume=577&rft.spage=id.L4&rft.epage=id.L4&rft.eissn=0365-0138&rft.issn=0365-0138&rft.au=VLEMMINGS,%20W.%20H.%20T.,&RAMSTEDT,%20S.,&O'GORMAN,%20E.,&HUMPHREYS,%20E.%20M.%20L.,&WITTKOWSKI,%20M.,&rft.genre=article |
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