On the detection of CO and mass-loss of bulge OH/IR stars
Journal article, 2018

We report on the successful search forCO(2-1) and (3-2) emission associated with OH/IR stars in the Galactic bulge. We observed a sample of eight extremely red asymptotic giant branch stars with the Atacama Pathfinder EXperiment telescope and detected seven. The sources were selected at a sufficiently high galactic latitude to avoid interference by interstellar CO, which hampered previous studies of inner galaxy stars. To study the nature of our sample and the mass-loss, we constructed the spectral energy distribution (SEDs) from photometric data and Spitzer IRS spectroscopy. In a first step, we apply radiative transfer modelling to fit the SEDs and obtain luminosities and dust mass-loss rates (MLRs). Through dynamical modelling, we then retrieve the total MLR and the gas-to-dust ratios. We derived variability periods of our stars. The luminosities range between approximately 4000 and 5500 L⊙and periods are shorter than 700 d. The total MLR ranges between 10-5and 10-4M⊙yr-1. Comparison with evolutionary models shows that the progenitor mass ≈ 1.5 M⊙, similar to the bulge Miras of intermediate age (3 Gyr). The gas-to-dust ratios are between 100 and 400 and are similar to what is found for OH/IR stars in the galactic disc. One star, IRAS 17347-2319, has a very short period of approximately 300 d that may be decreasing further. It may belong to a class of Mira variables with a sudden change in period as observed in some Galactic objects. It would be the first example of an OH/IR star in this class and deserves further follow-up observations.

Stars: mass-loss

Stars: AGB and post-AGB

Radio lines: stars

Circumstellar matter

Galaxy: bulge


Jadl Blommaert

Vrije Universiteit Brussel (VUB)

M. A. T. Groenewegen

Royal Observatory of Belgium

Kay Justtanont

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

L. Decin

KU Leuven

Monthly Notices of the Royal Astronomical Society

0035-8711 (ISSN) 1365-2966 (eISSN)

Vol. 479 3 3545-3562

Subject Categories

Meteorology and Atmospheric Sciences

Astronomy, Astrophysics and Cosmology

Probability Theory and Statistics



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