Mass Outflow and Chromospheric Activity of Red Giant Stars in Globular Clusters. Ii. M13 and M92

Mészáros, Szabolcs; Dupree, A. K.; Szalai, T.

doi:10.1088/0004-6256/137/5/4282

Cited by 27 publications

(32 citation statements)

References 73 publications

(114 reference statements)

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“…Its blue shift remains constant at -71.8 km s −1 throughout our observations and also its strength remains fairly constant and is qualitatively comparable to the line profiles of mass-outflow giants, e.g. like the ones in low-metallicity globular clusters (Meszaros et al 2009). The asymmetry was already noticed by Fekel et al (1996).…”

Section: Balmer Lines Spectral Appearancesupporting

confidence: 80%

Evidence for enhanced mixing on the super-meteoritic Li-rich red giant HD 233517

Strassmeier

Carroll

Weber

et al. 2015

A&A

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Context. HD 233517 is among the most Li-rich stars in the sky. It is a rapidly rotating, single K giant thought to be on its first ascent on the red giant branch. The star has also the highest known infrared excess among any of the known first-ascent giants. Aims. We revisit the physical parameters of the system and aim to map its surface temperature distribution. Methods. New time-series photometry and high-resolution spectroscopy were obtained with our robotic facilities STELLA and Amadeus Automatic Photoelectric Telescope (APT) in 2007-2011. Inverse line-profile modelling is performed on a total of 167 échelle spectra and six Doppler images are presented.Results. Light and radial-velocity variations suggest a stellar rotation period of 47.6 ± 0.3 d. The atmospheric parameters agree with previous studies and verify a super-meteoritic log 7 Li abundance of 4.29 ± 0.10 with undetected 6 Li, while the metals are generally deficient by -0.4 dex with respect to the Sun. We determine a lower than normal isotopic carbon ratio of 12 C/ 13 C = 9 +4 −2 . Our Doppler images indicate warm and cool spots with an average temperature contrast of just ±65 K with respect to the effective temperature.Doppler maps from Li i 670.78 reveal practically identical surface morphology, with a higher average contrast of ±160 K and errors that are five times larger. Reconstructions with simultaneously 1617 and 3007 spectral lines showed both a signal degradation with respect to our 56-line final image. An error analysis indicates an average temperature error per surface pixel of just ±4 K. Conclusions. HD 233517 appears to be an old (≈10-Gyr) single 0.95-M giant currently undergoing mild mass loss in the form of a wind. The cool and warm photospheric features are interpreted to be merely locations of suppressed and enhanced convection, respectively, probably intermingled by a yet undetected weak magnetic field. The low carbon-isotope ratio is indicative of extra mixing rather than of an engulfing event. We tentatively conclude that HD 233517 operates an enhanced non-axisymmetric mixing process that leads to an inhomogeneous super-granulation pattern on the surface in form of large cool and warm features.

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Section: Balmer Lines Spectral Appearancesupporting

confidence: 80%

Evidence for enhanced mixing on the super-meteoritic Li-rich red giant HD 233517

Strassmeier

Carroll

Weber

et al. 2015

A&A

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“…7 Thus it is not surprising to find differing dynamical signatures in these line diagnostics, in addition to possible time variations. There may be a similarity here between the well-known changing asymmetries of Hα emission wings in metal-deficient giants (Smith & Dupree 1988;Cacciari et al 2004;Mészáros et al 2008Mészáros et al , 2009b) and the Mg ii emission.…”

Section: Line Profilessupporting

confidence: 56%

“…Mass flows can produce asymmetric profiles of Hα and Na D, as well as emission asymmetries and velocity shifts in the reversed absorption core of Ca ii and Mg ii. These features have been measured in red giants in many globular clusters (Cacciari et al 2004;McDonald & van Loon 2007;Mészáros et al 2008Mészáros et al , 2009b and in metal-poor field stars (Smith & Dupree 1988;Dupree & Smith 1995;Dupree et al 2007). However, the velocities inferred from the optical profiles are generally less than the escape velocity from the star, and cannot truly be identified as stellar winds.…”

Section: Spectroscopic Diagnostics Of Windsmentioning

confidence: 80%

“…The helium line profiles reported here overwhelmingly display a signature of outflowing gas in stars brighter than M V ∼ 0. Hα line cores show generally increasing outflowing velocities with luminosity (Mészáros et al 2008(Mészáros et al , 2009b. Even though some measured outflow velocities are less than the escape velocity, conservation of mass suggests that the velocities will yield meaningful mass loss rates.…”

Section: Estimate Of the Mass Loss Ratementioning

confidence: 95%

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Fast Winds and Mass Loss From Metal-Poor Field Giants

Dupree

Smith

Strader

2009

The Astronomical Journal

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Echelle spectra of the infrared He i λ10830 line were obtained with NIRSPEC on the Keck 2 telescope for 41 metal-deficient field giant stars including those on the red giant branch (RGB), asymptotic giant branch (AGB), and red horizontal branch (RHB). The presence of this He i line is ubiquitous in stars with T eff 4500 K and M V fainter than −1.5, and reveals the dynamics of the atmosphere. The line strength increases with effective temperature for T eff 5300 K in RHB stars. In AGB and RGB stars, the line strength increases with luminosity. Fast outflows ( 60 km s −1 ) are detected from the majority of the stars and about 40% of the outflows have sufficient speed as to allow escape of material from the star as well as from a globular cluster. Outflow speeds and line strengths do not depend on metallicity for our sample ([Fe/H]= −0.7 to −3.0), suggesting the driving mechanism for these winds derives from magnetic and/or hydrodynamic processes. Gas outflows are present in every luminous giant, but are not detected in all stars of lower luminosity indicating possible variability. Mass loss rates ranging from ∼3 × 10 −10 to ∼6 × 10 −8 M yr −1 estimated from the Sobolev approximation for line formation represent values with evolutionary significance for red giants and RHB stars. We estimate that 0.2 M will be lost on the RGB, and the torque of this wind can account for observations of slowly rotating RHB stars in the field. About 0.1-0.2 M will be lost on the RHB itself. This first empirical determination of mass loss on the RHB may contribute to the appearance of extended horizontal branches in globular clusters. The spectra appear to resolve the problem of missing intracluster material in globular clusters. Opportunities exist for "wind smothering" of dwarf stars by winds from the evolved population, possibly leading to surface pollution in regions of high stellar density.

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“…Qualitatively, the profiles resemble those of mass-outflow red giants, e.g. like the ones in lowmetallicity globular clusters (Meszaros et al 2009). Note .…”

Section: F-star Wind and Upper Atmospherementioning

confidence: 66%

Time‐series high‐resolution spectroscopy and photometry of ε Aurigae from 2006–2013: Another brick in the wall

et al. 2014

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We present continuous and time-resolved R = 55 000 opticaléchelle spectroscopy of Aurigae from [2006][2007][2008][2009][2010][2011][2012][2013] We conclude that Hα is contaminated by changes in the circumstellar environment while the Hβ and V I photometry stems predominantly from the non radial pulsations of the F0 supergiant. We isolate the disk-rotation profile from 61 absorption lines and found that low disk eccentricity generally relates to low disk rotational velocity (but not always) while high disk eccentricity always relates to high velocity. There is also the general trend that the disk-absorption in spectral lines with higher excitation potential comes from disk regions with higher eccentricity and thus also with higher rotational velocity. The dependency on transition probability is more complex and shows a bi-modal trend. The outskirts of the disk is distributed asymmetrically around the disk and appears to have been built up mostly in a tail along the orbit behind the secondary. Our data show that this tail continues to eclipse the F0 Iab primary star even two years after the end of the photometric eclipse. High-resolution spectra were also taken of the other, bona-fide, visual-binary components of Aur (ADS 3605BCDE). Only the C-component, a K3-4-giant, appears at the same distance than Aur but its radial velocity is in disagreement with a bound orbit. The other components are a nearby (≈ 7 pc) cool DA white dwarf, a G8 dwarf, and a B9 supergiant, and not related to Aur. The cool white dwarf shows strong DIB lines that suggest the existence of a debris disk around this star.

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Mass Outflow and Chromospheric Activity of Red Giant Stars in Globular Clusters. Ii. M13 and M92

Cited by 27 publications

References 73 publications

Evidence for enhanced mixing on the super-meteoritic Li-rich red giant HD 233517

Evidence for enhanced mixing on the super-meteoritic Li-rich red giant HD 233517

Fast Winds and Mass Loss From Metal-Poor Field Giants

Time‐series high‐resolution spectroscopy and photometry of ε Aurigae from 2006–2013: Another brick in the wall

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