2018A&A...616A..34H


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.04CEST02:38:09

2018A&A...616A..34H - Astronomy and Astrophysics, volume 616A, 34-34 (2018/8-1)

An unusual face-on spiral in the wind of the M-type AGB star EP Aquarii.

HOMAN W., RICHARDS A., DECIN L., DE KOTER A. and KERVELLA P.

Abstract (from CDS):

High-resolution interferometric observations of the circumstellar environments of AGB stars show a variety of morphologies. Guided by the unusual carbon monoxide line profile of the AGB star EP Aquarii, we have observed its circumstellar environment with ALMA band 6 in cycle 4. We describe the morphological complexity of the CO, SiO, and SO2 molecular emission. The CO emission exhibits the characteristics of a bi-conical wind with a bright nearly face-on spiral feature around the systemic velocity. This is the first convincing detection of a spiral morphology in an O-rich wind. Based on the offsets of the centres of the two bi-conical wind hemispheres, we deduce the position angle of the inclination axis to be ∼150° measured anticlockwise from north. Based on the velocity width of the spiral signature, we estimate the inclination angle of the system to be between 4° and 18°. The central emission zone exhibits a morphology that resembles simulations modelling the spiral-inducing wind Roche-lobe overflow mechanism. Though the spiral may be a companion-induced density enhancement in the stellar outflow, the extremely narrow width of the spiral signature in velocity space suggests that it may be a hydrodynamical perturbation in a face-on differentially rotating disk. The SiO emission does not show the spiral, but exhibits a local emission void approximately 0.5'' west of the continuum brightness peak. We hypothesise that this may be a local environment caused by the presence of a stellar companion with a mass of at most 0.1M, based on its non-detection in the continuum. Finally, the SO2 emission remains confined to a 0.5'' radius, and does not show any obvious substructure, but it exhibits a clear rotation signature. Combined, the properties of the molecular emission favour the face-on rotating disk scenario. We observe unexpectedly large red- and blue-shifted wings in the spectral line of SiO, which could be explained by the potential non-local thermodynamic equilibrium (NLTE) nature of driven, mixed, partly granular fluids.

Abstract Copyright: © ESO 2018

Journal keyword(s): radiative transfer - stars: AGB and post-AGB - circumstellar matter - submillimeter: stars - molecular data

Errata: erratum vol. 632, art. C1 (2019)

Simbad objects: 12

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Number of rows : 12

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 * omi Cet A Mi* 02 19 20.792 -02 58 39.50   4.46 3.04     M5-9e 32 0
2 * omi Cet Mi* 02 19 20.79210 -02 58 39.4956   7.63 6.53 5.03   M5-9IIIe+DA 1434 0
3 * omi Cet B WD* 02 19 20.80 -02 58 40.0           DA 39 1
4 V* IK Tau Mi* 03 53 28.8884898148 +11 24 21.865959095 16.99 17.03 13.39 7.29 3.20 M7-11 570 0
5 V* R Dor AB* 04 36 45.59127 -62 04 37.7974 7.84 6.98 5.40 2.71 -0.44 M8III:e 282 0
6 * l Pup sg* 07 43 48.4687222 -28 57 17.372015 4.06 4.09 3.93 3.68 3.50 A4Iabe 175 0
7 4C -02.81 BLL 21 34 10.30959643 -01 53 17.2387909   18.6 19.0 18.87   ~ 328 1
8 V* EP Aqr AB* 21 46 31.8467491729 -02 12 45.901666975   7.93 6.78     M7-III: 209 0
9 4C 06.69 QSO 21 48 05.4585565234 +06 57 38.605396596   16.85 16.47 15.06   ~ 598 1
10 ICRF J215614.7-003704 BLL 21 56 14.75791251 -00 37 04.5943965   21.48 20.78 19.88   ~ 28 1
11 4C 11.69 QSO 22 32 36.40890517 +11 43 50.9040717   17.75 17.33     ~ 968 2
12 RAFGL 3068 C* 23 19 12.60744 +17 11 33.1332           C 249 0

    Equat.    Gal    SGal    Ecl

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2020.07.04-02:38:09

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