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

Abstract

High resolution spectra of 123 red giant stars in the globular cluster M13 and 64 red giant stars in M92 were obtained with Hectochelle at the MMT telescope. Emission and line asymmetries in Halpha, and Ca K are identified, characterizing motions in the extended atmospheres and seeking differences attributable to metallicity in these clusters and M15. On the red giant branch, emission in Halpha generally appears in stars with T_eff < 4500 K and log L/L_sun > 2.75. Fainter stars showing emission are asymptotic giant branch (AGB) stars or perhaps binary stars. The line-bisector for Halpha reveals the onset of chromospheric expansion in stars more luminous than log L/L_sun ~ 2.5 in all clusters, and this outflow velocity increases with stellar luminosity. However, the coolest giants in the metal-rich M13 show greatly reduced outflow in Halpha most probably due to decreased T_eff and changing atmospheric structure. The Ca K_3 outflow velocities are larger than shown by Halpha at the same luminosity and signal accelerating outflows in the chromospheres. Stars clearly on the AGB show faster chromospheric outflows in Halpha than RGB objects. While the Halpha velocities on the RGB are similar for all metallicities, the AGB stars in the metal-poor M15 and M92 have higher outflow velocities than in the metal-rich M13. Comparison of these chromospheric line profiles in the paired metal-poor clusters, M15 and M92 shows remarkable similarities in the presence of emission and dynamical signatures, and does not reveal a source of the `second-parameter' effect.

41 pages, 14 figures, 11 tables, Accepted in Astronomical Journal

References in corpus (9)

• The fraction of second generation stars in Globular Clusters from the analysis of the Horizontal Branch
• High resolution spectroscopy for Cepheids distance determination. I. Line asymmetry
• Giants in the globular cluster omega Centauri: dust production, mass loss and distance
• Dust-driven Winds and Mass Loss of C-rich AGB Stars with subsolar Metallicities
• Dust, pulsation, chromospheres and their role in driving mass loss from red giants in Galactic globular clusters
• A Spitzer Space Telescope Atlas of omega Centauri: The Stellar Population, Mass Loss, and the Intracluster Medium
• Stellar Populations and Mass-Loss in M15: A Spitzer Detection of Dust in the Intra-Cluster Medium
• Mass Outflow and Chromospheric Activity of Red Giant Stars in Globular Clusters I: M15
• The Global Kinematics of the Globular Cluster M92

Cited by in corpus (7)

• N-body modeling of globular clusters: Masses, mass-to-light ratios and intermediate-mass black holes
• Near-Infrared Photometry of Globular Clusters Towards the Galactic Bulge: Observations and Photometric Metallicity Indicators
• Mass Outflow from Red Giant Stars in M13, M15, and M92
• The central dynamics of M3, M13, and M92: Stringent limits on the masses of intermediate-mass black holes
• High-resolution spectroscopic analysis of a large sample of Li-rich giants found by LAMOST
• Carbon Abundance Inhomogeneities and Deep Mixing Rates in Galactic Globular Clusters
• Search for Exoplanets around Northern Circumpolar Stars V. Three likely planetary companions to the giant stars HD 19615, HD 150010, and HD 174205