English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Context: As is the case of several other Be stars, Achernar is surrounded byan envelope, recently detected by near-IR interferometry.  Aims: We search for the signature of circumstellar emission at distances of afew stellar radii from Achernar, in the thermal IR domain.  Methods: We obtained interferometric observations on three VLTI baselines inthe N band (8-13 mic), using the MIDI instrument.  Results: From the measured visibilities, we derive the angular extension andflux contribution of the N band circumstellar emission in the polar directionof Achernar. The interferometrically resolved polar envelope contributes 13.4+/- 2.5 % of the photospheric flux in the N band, with a full width at halfmaximum of 9.9 +/- 2.3 mas (~ 6 Rstar). This flux contribution is in goodagreement with the photometric IR excess of 10-20% measured by fitting thespectral energy distribution. Due to our limited azimuth coverage, we can onlyestablish an upper limit of 5-10% for the equatorial envelope. We compare theobserved properties of the envelope with an existing model of this starcomputed with the SIMECA code.  Conclusions: The observed extended emission in the thermal IR along the polardirection of Achernar is well reproduced by the existing SIMECA model. Alreadydetected at 2.2mic, this polar envelope is most probably an observationalsignature of the fast wind ejected by the hot polar caps of the star.

The environment of the fast rotating star Achernar - Thermal infrared interferometry with VLTI/MIDI and SIMECA modeling