Period -- mass-loss rate relation of Miras with and without technetium

Abstract

Aims: We report the discovery that Mira variables with and without absorption lines of the element technetium (Tc) occupy two different regions in a diagram of near- to mid-infrared colour versus pulsation period. Tc is an indicator of a recent or ongoing mixing event called the third dredge-up (3DUP), and the near- to mid-IR colour, such as the (K-[22]) colour where [22] is the the 22 micron band of the WISE space observatory, is an indicator of the dust mass-loss rate of a star. Methods: We collected data from the literature about the Tc content, pulsation period, and near- and mid-infrared magnitudes of more than 190 variable stars on the asymptotic giant branch (AGB) to which Miras belong. The sample is naturally biased towards optical AGB stars, which have low to intermediate (dust) mass-loss rates. Results: We show that a clear relation between dust mass-loss rate and pulsation period exists if a distinction is made between Tc-poor and Tc-rich Miras. Surprisingly, at a given period, Tc-poor Miras are redder in (K-[22]) than are Tc-rich Miras; i.e. they have higher mass-loss rates than the Tc-rich Miras. A few stars deviate from this trend; physical explanations are given for these exceptions, such as binarity or high mass. Conclusions: We put forward two hypotheses to explain this dichotomy and conclude that the two sequences formed by Tc-poor and Tc-rich Miras are probably due to the different masses of the two groups. The pulsation period has a strong correlation with the dust-mass loss rate, indicating that the pulsations are indeed triggering a dust-driven wind. The location in the (K-[22]) vs. period diagram can be used to distinguish between pre- and post-3DUP Miras, which we apply to a sample of Galactic bulge AGB stars. We find that 3DUP is probably not common in AGB stars in the inner bulge.

Accepted for publication in A&A (5 pages, 2 figures, 1 on-line table); final version (language corrected)

References in corpus (9)

• Too little radiation pressure on dust in the winds of oxygen-rich AGB stars
• A close halo of large transparent grains around extreme red giant stars
• Near-Infrared Photometry of Carbon Stars
• Lithium and zirconium abundances in massive Galactic O-rich AGB stars
• Constraining the structure and formation of the Galactic bulge from a field in its outskirts. FLAMES-GIRAFFE spectra of about 400 red giants around (l,b)=(0°,-10°)
• Exploring wind-driving dust species in cool luminous giants I. Basic criteria and dynamical models of M-type AGB stars
• Technetium and the third dredge up in AGB stars II. Bulge stars
• Large-scale environments of binary AGB stars probed by Herschel - I. Morphology statistics and case studies of R Aquarii and W Aquilae
• The AGB stars of the intermediate-age LMC cluster NGC 1846 Variability and age determination

Cited by in corpus (12)

• Evolution, nucleosynthesis and yields of AGB stars at different metallicities (III): intermediate mass models, revised low mass models and the ph-FRUITY interface
• A census of symbiotic stars in the 2MASS, WISE and Gaia surveys
• Pulsation-triggered mass loss from AGB stars: the 60-day critical period
• Characterisation of Galactic carbon stars and related stars from Gaia-EDR3
• Stellar Evolution in Real Time: Models Consistent with Direct Observation of Thermal Pulse in T Ursae Minoris
• Interplay between pulsation, mass loss, and third dredge-up: More about Miras with and without technetium
• Understanding AGB evolution in Galactic bulge stars from high-resolution infrared spectroscopy
• Molecular line study of the S-type AGB star W Aquilae. ALMA observations of CS, SiS, SiO and HCN
• Determination of pulsation periods and other parameters of 2875 stars classified as MIRA in the All Sky Automated Survey (ASAS)
• The impact of third dredge-up on the mass loss of Mira variables
• Millimetre observations of the S-type AGB star $\chi$ Cygni: variability of the emission of the inner envelope
• The Nearby Evolved Stars Survey II: Constructing a volume-limited sample and first results from the James Clerk Maxwell Telescope