Late Stages of Stellar Evolution - Herschel's contributions

Abstract

Cool objects glow in the infrared. The gas and solid-state species that escape the stellar gravitational attraction of evolved late-type stars in the form of a stellar wind are cool, with temperatures typically $\la$1500\,K, and can be ideally studied in the infrared. These stellar winds create huge extended circumstellar envelopes with extents approaching $10^{19}$\,cm. In these envelopes, a complex kinematical, thermodynamical and chemical interplay determines the global and local structural parameters. Unraveling the wind acceleration mechanisms and deriving the complicated structure of the envelopes is important to understand the late stages of evolution of ~97% of stars in galaxies as our own Milky Way. That way, we can also assess the significant chemical enrichment of the interstellar medium by the mass loss of these evolved stars. The Herschel Space Observatory is uniquely placed to study evolved stars thanks to the excellent capabilities of the three infrared and sub-millimeter instruments on board: PACS, SPIRE and HIFI. In this review, I give an overview of a few important results obtained during the first two years of Herschel observations in the field of evolved low and intermediate mass stars, and I will show how the Herschel observations can solve some historical questions on these late stages of stellar evolution, but also add some new ones.

Review for Advances in Space Research

References in corpus (18)

• 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
• Oxygen Chemistry in the Circumstellar Envelope of the Carbon-Rich Star IRC+10216
• Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles I. Theoretical model -- Mass-loss history unravelled in VY CMa
• Atmospheric dynamics and the mass loss process in red supergiant stars
• Warm water vapour in the sooty outflow from a luminous carbon star
• The enigmatic nature of the circumstellar envelope and bow shock surrounding Betelgeuse as revealed by Herschel. I. Evidence of clumps, multiple arcs, and a linear bar-like structure
• Computing the dust distribution in the bowshock of a fast moving, evolved star
• A spectral line survey in the 2 mm and 1.3 mm windows toward the carbon rich envelope of IRC +10216
• Winds of M- and S-type AGB stars: an unorthodox suggestion for the driving mechanism
• The close circumstellar environment of Betelgeuse - II. Diffraction-limited spectro-imaging from 7.76 to 19.50 microns with VLT/VISIR
• The distribution of SiO in the circumstellar envelope around IRC+10216
• Discovery of multiple dust shells beyond 1 arcmin in the circumstellar envelope of IRC+10216 using Herschel/PACS
• Herschel's view into Mira's head
• Water in IRC+10216: a genuine formation process by shock-induced chemistry in the inner wind
• Detection of `parent' molecules from the inner wind of AGB stars as tracers of non-equilibrium chemistry
• The impact of the 18F(a,p)21Ne reaction on asymptotic giant branch nucleosynthesis
• H2O vapor excitation in dusty AGB envelopes. A PACS view of OH 127.8+0.0

Cited by in corpus (5)

• Models of the circumstellar medium of evolving, massive runaway stars moving through the Galactic plane
• Review of scientific topics for Millimetron space observatory
• Herschel/PACS observations of the 69 $\mu m$ band of crystalline olivine around evolved stars
• VLBI Astrometry of AGB Variables with VERA -- A Mira Type Variable T Lepus
• Model of the vibrationally excited H${}_2$O maser at 658 GHz in circumstellar envelopes around asymptotic giant branch stars