A detailed view on the circumstellar environment of the M-type AGB star EP Aquarii I. High-resolution ALMA and SPHERE observations
| Autor: | Miguel Montargès, Anita M. S. Richards, Ward Homan, E. Cannon, Leen Decin, Tom J. Millar |
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| Přispěvatelé: | Cannon, Emily, Montarges, Miguel, Richards, Anita MS, Millar, Tom J, Decin, Leen |
| Rok vydání: | 2020 |
| Předmět: |
Brightness
FOS: Physical sciences High resolution Astrophysics::Cosmology and Extragalactic Astrophysics Astrophysics 01 natural sciences Computer Science::Digital Libraries 0103 physical sciences Astrophysics::Solar and Stellar Astrophysics Asymptotic giant branch 010303 astronomy & astrophysics Solar and Stellar Astrophysics (astro-ph.SR) Astrophysics::Galaxy Astrophysics Physics 010308 nuclear & particles physics Photodissociation Astrophysics::Instrumentation and Methods for Astrophysics White dwarf Astronomy and Astrophysics Astrophysics - Astrophysics of Galaxies Physics::History of Physics Interstellar medium Stars Astrophysics - Solar and Stellar Astrophysics 13. Climate action Space and Planetary Science Astrophysics of Galaxies (astro-ph.GA) Outflow Astrophysics::Earth and Planetary Astrophysics |
| Zdroj: | Astronomy & Astrophysics |
| Popis: | Cool evolved stars are known to be significant contributors to the enrichment of the interstellar medium through their dense and dusty stellar winds. High resolution observations of these outflows have shown them to possess high degrees of morphological complexity. We observed the asymptotic giant branch (AGB) star EP Aquarii with ALMA in band 6 and VLT/SPHERE/ZIMPOL in four filters the visible. Both instruments had an angular resolution of 0.025''. These are follow-up observations to the lower-resolution 2016 ALMA analysis of EP Aquarii, which revealed that its wind possesses a nearly face-on, spiral-harbouring equatorial density enhancement, with a nearly pole-on bi-conical outflow. At the base of the spiral, the SiO emission revealed a distinct emission void approximately 0.4'' to the west of the continuum brightness peak, which was proposed to be linked to the presence of a companion. The new ALMA data better resolve the inner wind and reveal that its morphology as observed in CO is consistent with hydrodynamical companion-induced perturbations. Assuming that photodissociation by the UV-field of the companion is responsible for the emission void in SiO, we deduced the spectral properties of the tentative companion from the size of the hole. We conclude that the most probable companion candidate is a white dwarf with a mass between 0.65 and 0.8 Msol , though a solar-like companion could not be definitively excluded. The radial SiO emission shows periodic, low-amplitude perturbations. We tentatively propose that they could be the consequence of the interaction of the AGB wind with another much closer low-mass companion. The polarised SPHERE/ZIMPOL data show a circular signal surrounding the AGB star with a radius of 0.1''... 24 pages, 25 Figures |
| Databáze: | OpenAIRE |
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