DEATHSTAR: Nearby AGB stars with the Atacama Compact Array II. CO envelope sizes and asymmetriesCitation formats

  • External authors:
  • M Andriantsaralaza
  • W H T Vlemmings
  • T Danilovich
  • E De Beck
  • M A T Groenewegen
  • F Kerschbaum
  • T Khouri
  • M Lindqvist
  • M Maercker
  • H Olofsson
  • G Quintana-Lacaci
  • R Sahai

Standard

DEATHSTAR: Nearby AGB stars with the Atacama Compact Array II. CO envelope sizes and asymmetries : The S-type stars. / Andriantsaralaza, M; Vlemmings, W H T; Danilovich, T ; De Beck, E ; Groenewegen, M A T ; Kerschbaum, F; Khouri, T ; Lindqvist, M ; Maercker, M ; Olofsson, H; Quintana-Lacaci, G; Sahai, R; Zijlstra, Albert.

In: Astronomy & Astrophysics, 04.06.2021.

Research output: Contribution to journalArticlepeer-review

Harvard

Andriantsaralaza, M, Vlemmings, WHT, Danilovich, T, De Beck, E, Groenewegen, MAT, Kerschbaum, F, Khouri, T, Lindqvist, M, Maercker, M, Olofsson, H, Quintana-Lacaci, G, Sahai, R & Zijlstra, A 2021, 'DEATHSTAR: Nearby AGB stars with the Atacama Compact Array II. CO envelope sizes and asymmetries: The S-type stars', Astronomy & Astrophysics.

APA

Andriantsaralaza, M., Vlemmings, W. H. T., Danilovich, T., De Beck, E., Groenewegen, M. A. T., Kerschbaum, F., Khouri, T., Lindqvist, M., Maercker, M., Olofsson, H., Quintana-Lacaci, G., Sahai, R., & Zijlstra, A. (Accepted/In press). DEATHSTAR: Nearby AGB stars with the Atacama Compact Array II. CO envelope sizes and asymmetries: The S-type stars. Astronomy & Astrophysics.

Vancouver

Andriantsaralaza M, Vlemmings WHT, Danilovich T, De Beck E, Groenewegen MAT, Kerschbaum F et al. DEATHSTAR: Nearby AGB stars with the Atacama Compact Array II. CO envelope sizes and asymmetries: The S-type stars. Astronomy & Astrophysics. 2021 Jun 4.

Author

Andriantsaralaza, M ; Vlemmings, W H T ; Danilovich, T ; De Beck, E ; Groenewegen, M A T ; Kerschbaum, F ; Khouri, T ; Lindqvist, M ; Maercker, M ; Olofsson, H ; Quintana-Lacaci, G ; Sahai, R ; Zijlstra, Albert. / DEATHSTAR: Nearby AGB stars with the Atacama Compact Array II. CO envelope sizes and asymmetries : The S-type stars. In: Astronomy & Astrophysics. 2021.

Bibtex

@article{be4a813e8966445aab4b2961dedf9a02,
title = "DEATHSTAR: Nearby AGB stars with the Atacama Compact Array II. CO envelope sizes and asymmetries: The S-type stars",
abstract = "Aims.We aim to constrain the sizes of, and investigate deviations from spherical symmetry in, the CO circumstellar envelopes (CSEs)of 16 S-type stars, along with an additional 7 and 4 CSEs of C-type and M-type AGB stars, respectively.Methods. We map the emission from the CO J = 2–1 and 3–2 lines observed with the Atacama Compact Array (ACA) and its totalpower (TP) antennas, and fit with a Gaussian distribution in the uv- and image planes for ACA-only and TP observations, respectively.The major axis of the fitted Gaussian for the CO(2–1) line data gives a first estimate of the size of the CO-line-emitting CSE. Weinvestigate possible signs of deviation from spherical symmetry by analysing the line profiles, the minor/major axes ratio obtainedfrom visibility fitting, and by investigating the deconvolved images.Results. The sizes of the CO-line-emitting CSEs of low-mass-loss-rate (low-MLR) S-type stars fall between the sizes of C-stars,which are larger, and M-stars, which are smaller, as expected due to the dierences in their respective CO abundances and thedependence of the photodissociation rate on this quantity. The sizes of the low-MLR S-type stars show no dependence on circumstellardensity, as measured by the ratio of the MLR to terminal outflow velocity, irrespective of variability type. The density dependencesteepens for S-stars with higher MLRs. While the CO(2–1) brightness distribution size of the low-density S-stars is in general smallerthan the predicted photodissociation radius (assuming the standard interstellar radiation field), the measured size of a few of the highdensitysources are of the same order as the expected photodissociation radius. Furthermore, our results show that the CO CSEs ofmost of the S-stars in our sample are consistent with a spherically symmetric and smooth outflow. For some of the sources, clear andprominent asymmetric features are observed which are indicative of intrinsic circumstellar anisotropy.Conclusions. As the majority of the S-type CSEs of the stars in our sample are consistent with a spherical geometry, the CO envelopesizes obtained in this paper will be used to constrain detailed radiative transfer modelling to directly determine more accurate MLRestimates for the stars in our sample. For several of our sources that present signs of deviation from spherical symmetry, further highresolution observations would be necessary to investigate the nature and the physical processes behind these asymmetrical structures.This will provide further insight into the mass-loss process and its related chemistry of S-type AGB stars.",
author = "M Andriantsaralaza and Vlemmings, {W H T} and T Danilovich and {De Beck}, E and Groenewegen, {M A T} and F Kerschbaum and T Khouri and M Lindqvist and M Maercker and H Olofsson and G Quintana-Lacaci and R Sahai and Albert Zijlstra",
year = "2021",
month = jun,
day = "4",
language = "English",
journal = "Astronomy & Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",

}

RIS

TY - JOUR

T1 - DEATHSTAR: Nearby AGB stars with the Atacama Compact Array II. CO envelope sizes and asymmetries

T2 - The S-type stars

AU - Andriantsaralaza, M

AU - Vlemmings, W H T

AU - Danilovich, T

AU - De Beck, E

AU - Groenewegen, M A T

AU - Kerschbaum, F

AU - Khouri, T

AU - Lindqvist, M

AU - Maercker, M

AU - Olofsson, H

AU - Quintana-Lacaci, G

AU - Sahai, R

AU - Zijlstra, Albert

PY - 2021/6/4

Y1 - 2021/6/4

N2 - Aims.We aim to constrain the sizes of, and investigate deviations from spherical symmetry in, the CO circumstellar envelopes (CSEs)of 16 S-type stars, along with an additional 7 and 4 CSEs of C-type and M-type AGB stars, respectively.Methods. We map the emission from the CO J = 2–1 and 3–2 lines observed with the Atacama Compact Array (ACA) and its totalpower (TP) antennas, and fit with a Gaussian distribution in the uv- and image planes for ACA-only and TP observations, respectively.The major axis of the fitted Gaussian for the CO(2–1) line data gives a first estimate of the size of the CO-line-emitting CSE. Weinvestigate possible signs of deviation from spherical symmetry by analysing the line profiles, the minor/major axes ratio obtainedfrom visibility fitting, and by investigating the deconvolved images.Results. The sizes of the CO-line-emitting CSEs of low-mass-loss-rate (low-MLR) S-type stars fall between the sizes of C-stars,which are larger, and M-stars, which are smaller, as expected due to the dierences in their respective CO abundances and thedependence of the photodissociation rate on this quantity. The sizes of the low-MLR S-type stars show no dependence on circumstellardensity, as measured by the ratio of the MLR to terminal outflow velocity, irrespective of variability type. The density dependencesteepens for S-stars with higher MLRs. While the CO(2–1) brightness distribution size of the low-density S-stars is in general smallerthan the predicted photodissociation radius (assuming the standard interstellar radiation field), the measured size of a few of the highdensitysources are of the same order as the expected photodissociation radius. Furthermore, our results show that the CO CSEs ofmost of the S-stars in our sample are consistent with a spherically symmetric and smooth outflow. For some of the sources, clear andprominent asymmetric features are observed which are indicative of intrinsic circumstellar anisotropy.Conclusions. As the majority of the S-type CSEs of the stars in our sample are consistent with a spherical geometry, the CO envelopesizes obtained in this paper will be used to constrain detailed radiative transfer modelling to directly determine more accurate MLRestimates for the stars in our sample. For several of our sources that present signs of deviation from spherical symmetry, further highresolution observations would be necessary to investigate the nature and the physical processes behind these asymmetrical structures.This will provide further insight into the mass-loss process and its related chemistry of S-type AGB stars.

AB - Aims.We aim to constrain the sizes of, and investigate deviations from spherical symmetry in, the CO circumstellar envelopes (CSEs)of 16 S-type stars, along with an additional 7 and 4 CSEs of C-type and M-type AGB stars, respectively.Methods. We map the emission from the CO J = 2–1 and 3–2 lines observed with the Atacama Compact Array (ACA) and its totalpower (TP) antennas, and fit with a Gaussian distribution in the uv- and image planes for ACA-only and TP observations, respectively.The major axis of the fitted Gaussian for the CO(2–1) line data gives a first estimate of the size of the CO-line-emitting CSE. Weinvestigate possible signs of deviation from spherical symmetry by analysing the line profiles, the minor/major axes ratio obtainedfrom visibility fitting, and by investigating the deconvolved images.Results. The sizes of the CO-line-emitting CSEs of low-mass-loss-rate (low-MLR) S-type stars fall between the sizes of C-stars,which are larger, and M-stars, which are smaller, as expected due to the dierences in their respective CO abundances and thedependence of the photodissociation rate on this quantity. The sizes of the low-MLR S-type stars show no dependence on circumstellardensity, as measured by the ratio of the MLR to terminal outflow velocity, irrespective of variability type. The density dependencesteepens for S-stars with higher MLRs. While the CO(2–1) brightness distribution size of the low-density S-stars is in general smallerthan the predicted photodissociation radius (assuming the standard interstellar radiation field), the measured size of a few of the highdensitysources are of the same order as the expected photodissociation radius. Furthermore, our results show that the CO CSEs ofmost of the S-stars in our sample are consistent with a spherically symmetric and smooth outflow. For some of the sources, clear andprominent asymmetric features are observed which are indicative of intrinsic circumstellar anisotropy.Conclusions. As the majority of the S-type CSEs of the stars in our sample are consistent with a spherical geometry, the CO envelopesizes obtained in this paper will be used to constrain detailed radiative transfer modelling to directly determine more accurate MLRestimates for the stars in our sample. For several of our sources that present signs of deviation from spherical symmetry, further highresolution observations would be necessary to investigate the nature and the physical processes behind these asymmetrical structures.This will provide further insight into the mass-loss process and its related chemistry of S-type AGB stars.

M3 - Article

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

SN - 0004-6361

ER -