Hubble Space Telescope Constraints on the Winds and Astrospheres of Red Giant Stars*

Wood, Brian E.; Müller, Hans-Reinhard; Harper, G. M.

doi:10.3847/0004-637x/829/2/74

Cited by 19 publications

(15 citation statements)

References 66 publications

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“…Wind velocities are generally found to decrease with spectral type, from ∼40 km s −1 at K1.5 III to ∼20 km s −1 at M5 III. The power law index in the Wood et al (2016) empirical relation F M gII ∼ T 9.1 ef f is remarkably close to the index of a theoretical relation de-rived by Bohn (1984) linking the flux of acoustic power F acoustic and the effective temperature: F acoustic ∼ T 9.75 ef f . This makes it highly likely that the basal flux is indeed related to acoustic power, rather than magnetic effects (we thank the anonymous referee for pointing this out to us).…”

Section: Discussionsupporting

confidence: 84%

“…They further reported that their non-detection of a magnetic field on the post-RSG star ρ Cas suggests that the magnetic field disappears, or at least becomes undetectable with present methods, at later evolutionary stages and that their analysis of α 1 Her supports the proposed reclassification of the star as an M-type asymptotic giant branch star. Wood et al (2016) discuss constraints on the winds and astrospheres of Red Giant Stars provided by HST observations, focussing on spectra of the Mg II h and k lines near 2800Å. They studied stellar chromospheric emission, winds, and astrospheric absorption, concentrating on spectral types between K1.5 III and M5 III (noncoronal stars that possess strong, chromospheric winds).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

The Advanced Spectral Library (ASTRAL): Reference Spectra for Evolved M Stars^∗

Carpenter

Nielsen

Kober

et al. 2018

ApJ

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The HST Treasury Program "Advanced Spectral Library Project: Cool Stars" was designed to collect representative, high quality ultraviolet spectra of eight evolved F−M type cool stars. The Space Telescope Imaging Spectrograph (STIS) echelle spectra of these objects enable investigations of a broad range of topics including stellar and interstellar astrophysics. This paper provides a guide to the spectra of the two evolved M-stars, the M2Iab supergiant α Ori and the M3.4 giant γ Cru, with comparisons to the prototypical K1.5 giant α Boo. It includes identifications of the significant atomic and molecular emission and absorption features and discusses the character of the photospheric and chromospheric continua and line spectra. The fluorescent processes responsible for a large portion of the emission line spectrum, the characteristics of the stellar winds, and the available diagnostics for hot and cool plasmas are also summarized. This analysis will facilitate the future study of the spectra, outer atmospheres, and winds, not only of these objects, but for numerous other cool, low-gravity stars for years to come.

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Section: Discussionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 99%

The Advanced Spectral Library (ASTRAL): Reference Spectra for Evolved M Stars^∗

Carpenter

Nielsen

Kober

et al. 2018

ApJ

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“…In the red giant phase alone, the solar wind will likely be cooler (. 10 4 K), with lower velocities, but higher densities, leading to mass-loss rate that will be several magnitudes higher than today (Wood et al 2016). Solar rotation will change considerably due to its radius expansion.…”

Section: Final Remarks and Open Questionsmentioning

confidence: 96%

The evolution of the solar wind

Vidotto

2021

Living Rev Sol Phys

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How has the solar wind evolved to reach what it is today? In this review, I discuss the long-term evolution of the solar wind, including the evolution of observed properties that are intimately linked to the solar wind: rotation, magnetism and activity. Given that we cannot access data from the solar wind 4 billion years ago, this review relies on stellar data, in an effort to better place the Sun and the solar wind in a stellar context. I overview some clever detection methods of winds of solar-like stars, and derive from these an observed evolutionary sequence of solar wind mass-loss rates. I then link these observational properties (including, rotation, magnetism and activity) with stellar wind models. I conclude this review then by discussing implications of the evolution of the solar wind on the evolving Earth and other solar system planets. I argue that studying exoplanetary systems could open up new avenues for progress to be made in our understanding of the evolution of the solar wind.

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“…However, emission could be higher by about one order of magnitude (see their Fig. 2, as well as Wood et al 2016). We relied on these studies to estimate the effect of the Mg ii lines on photometry.…”

Section: Line Emissionmentioning

confidence: 99%

Impact of a companion and of chromospheric emission on the shape of chromosome maps for globular clusters

Martins

Morin

Charbonnel

et al. 2020

A&A

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Context. Globular clusters (GCs) host multiple populations of stars that are well-separated in a photometric diagram -the chromosome map -built from specific Hubble Space Telescope (HST) filters. Stars from different populations feature at various locations on this diagram due to peculiar chemical compositions. Stars of the first population, with field star-like abundances, sometimes show an unexpected extended distribution in the chromosome map. Aims. We aim to investigate the role of binaries and chromospheric emission on HST photometry of globular clusters' stars. We quantify their respective effects on the position of stars in the chromosome map, especially among the first population. Methods. We computed atmosphere models and synthetic spectra for stars of different chemical compositions, based on isochrones produced by stellar evolution calculations with abundance variations representative of first and second populations in globular clusters. From this we built synthetic chromosome maps for a mixture of stars of different chemical compositions. We subsequently replaced a fraction of stars with binaries, or stars with chromospheric emission, using synthetic spectroscopy. We studied how the position of stars is affected in the chromosome map. Results. Binaries can, in principle, explain the extension of the first population in the chromosome map. However, we find that given the binary fraction reported for globular clusters, the density of stars in the extended part is too small. Another difficulty of the binary explanation is that the shape of the distribution of the first population in the chromosome map is different in clusters with similar binary fractions. Also, the decrease of the binary fraction with radius is not mirrored in the shape of the chromosome map. Additionally, we find that the contribution of chromospheric emission lines to the HST photometry is too small to have an observable impact on the shape of the chromosome map. Continuum chromospheric emission has an effect qualitatively similar to binaries. Conclusions. We conclude that binaries do have an impact on the morphology of the chromosome map of globular clusters, but they are unlikely to explain entirely the shape of the extended distribution of the first population stars. Uncertainties in the properties of continuum chromospheric emission of stars in GCs prevent any quantitative conclusion. Therefore, the origin of the extended first population remains unexplained.

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Hubble Space Telescope Constraints on the Winds and Astrospheres of Red Giant Stars*

Cited by 19 publications

References 66 publications

The Advanced Spectral Library (ASTRAL): Reference Spectra for Evolved M Stars^∗

The Advanced Spectral Library (ASTRAL): Reference Spectra for Evolved M Stars^∗

The evolution of the solar wind

Impact of a companion and of chromospheric emission on the shape of chromosome maps for globular clusters

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Hubble Space Telescope Constraints on the Winds and Astrospheres of Red Giant Stars*

Cited by 19 publications

References 66 publications

The Advanced Spectral Library (ASTRAL): Reference Spectra for Evolved M Stars∗

The Advanced Spectral Library (ASTRAL): Reference Spectra for Evolved M Stars∗

The evolution of the solar wind

Impact of a companion and of chromospheric emission on the shape of chromosome maps for globular clusters

Contact Info

Product

Resources

About

The Advanced Spectral Library (ASTRAL): Reference Spectra for Evolved M Stars^∗

The Advanced Spectral Library (ASTRAL): Reference Spectra for Evolved M Stars^∗