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 Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We present the first multi-epoch study that includes concurrent mid-infraredand radio interferometry of an oxygen-rich Mira star. We obtained mid-infraredinterferometry of S Ori with VLTI/MIDI at four epochs between December 2004 andDecember 2005. We concurrently observed v=1, J=1-0 (43.1 GHz), and v=2, J=1-0(42.8 GHz) SiO maser emission toward S Ori with the VLBA at three epochs. TheMIDI data are analyzed using self-excited dynamic model atmospheres includingmolecular layers, complemented by a radiative transfer model of thecircumstellar dust shell. The VLBA data are reduced to the spatial structureand kinematics of the maser spots. The modeling of our MIDI data results inphase-dependent continuum photospheric angular diameters between about 7.9 mas(Phase 0.55) and 9.7 mas (Phase 1.16). The dust shell can best be modeled withAl2O3 grains using phase-dependent inner boundary radii between 1.8 and 2.4photospheric radii. The dust shell appears to be more compact with greateroptical depth near visual minimum, and more extended with lower optical depthafter visual maximum. The ratios of the SiO maser ring radii to thephotospheric radii are between about 1.9 and 2.4. The maser spots mark theregion of the molecular atmospheric layers just beyond the steepest decrease inthe mid-infrared model intensity profile. Their velocity structure indicates aradial gas expansion. Al2O3 dust grains and SiO maser spots form at relativelysmall radii of 1.8-2.4 photospheric radii. Our results suggest increased massloss and dust formation close to the surface near the minimum visual phase,when Al2O3 dust grains are co-located with the molecular gas and the SiO masershells, and a more expanded dust shell after visual maximum. Silicon does notappear to be bound in dust, as our data show no sign of silicate grains.

The Mira variable S Ori: Relationships between the photosphere, molecular layer, dust shell, and SiO maser shell at 4 epochs