J/A+A/633/A13 pi.01 Gru ALMA CO(3-2) data cube (Doan+, 2020)
The extended molecular envelope of the asymptotic giant branch star star
pi1 Gruis as seen by ALMA.
II. The spiral-outflow observed at high-angular resolution
Doan L., Ramstedt S., Vlemmings W.H.T., Mohamed S., Hoefner S., De Beck E.,
Kerschbaum F., Lindqvist M., Maercker M., Paladini C., Wittkowski M.
<Astron. Astrophys. 633, A13 (2020)>
=2020A&A...633A..13D 2020A&A...633A..13D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Radio sources
Keywords: stars: AGB and post-AGB - stars: mass-loss - radio lines: general -
binaries: general - stars: individual: pi1 Gru
Abstract:
This study follows up the previous analysis of lower-angular
resolution data in which the kinematics and structure of the
circumstellar envelope (CSE) around the S-type asymptotic giant branch
(AGB) star pi1 Gruis were investigated. The AGB star has a known
companion (at a separation of ∼400AU) which cannot explain the
strong deviations from spherical symmetry of the CSE. Recently,
hydrodynamic simulations of mass transfer in closer binary systems
have successfully reproduced the spiral-shaped CSEs found around a
handful of sources. There is growing evidence for an even closer,
undetected companion complicating the case of pi1 Gruis further.
The improved spatial resolution allows for the investigation of the
complex circumstellar morphology and the search for imprints on the
CSE of the third component.
We have observed the 12CO J=3-2 line emission from pi1 Gruis using
both the compact and extended array of Atacama Large
Millimeter/submillimeter Array (ALMA). The interferometric data has
furthermore been combined with data from the ALMA total power (TP)
array. The imaged brightness distribution has been used to constrain a
non-local, non-LTE 3D radiative transfer model of the CSE.
The high-angular resolution ALMA data have revealed the first example
of a source on the AGB where both a faster bipolar outflow and a
spiral pattern along the orbital plane can be seen in the gas
envelope. The spiral can be traced in the low- to intermediate velocity
(13-25km/s) equatorial torus. The largest spiral-arm separation is
∼5.5" and consistent with a companion with an orbital period of
∼330yrs and a separation of less than 70AU. The kinematics of the
bipolar outflow is consistent with it being created during a mass-loss
eruption where the mass-loss rate from the system increased by at
least a factor of 5 during 10-15yrs.
The spiral pattern is the result of an undetected companion. The
bipolar outflow is the result of a rather recent mass-loss eruption
event.
Description:
We have observed pi1 Gruis using both the compact array, ACA, and
the 12-m main array. ALMA total power (TP) observations were also
performed to complement the interferometric observations.
The reduced datacube of the CO(3-2) emission
Objects:
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RA (2000) DE Designation(s)
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22 22 44.21 -45 56 52.6 pi1 Gruis = V* pi.01 Gru
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 156 1 Information of fits datacube
fits/* . 1 Fits datacube
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 29 I2 --- Nz Number of pixels along Z-axis
31- 52 A22 "datime" Obs.date Observation date
54- 64 E11.6 Hz bFreq Lower value of frequency interval
66- 76 E11.6 Hz BFreq Upper value of frequency interval
78- 87 E10.5 Hz dFreq Frequency resolution
89- 93 I5 Kibyte size Size of FITS file
95-115 A21 --- FileName Name of FITS file, in subdirectory fits
117-156 A40 --- Title Title of the FITS file
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Acknowledgements:
Lam Doan, lam.doan(at)physics.uu.se
References:
Doan et al., Paper I 2017A&A...605A..28D 2017A&A...605A..28D
(End) Patricia Vannier [CDS] 28-Nov-2019