Effects of tidally enhanced stellar wind on the horizontal branch morphology of globular clusters

Abstract

Metallicity is the first parameter to influence the horizontal branch (HB) morphology of globular clusters (GCs). It has been found, however, that some other parameters may also play an important role in affecting the morphology. While the nature of these important parameters remains unclear, they are believed to be likely correlated with wind mass-loss of red giants, since this mass loss determines their subsequent locations on the HB. Unfortunately, the mass loss during the red giant stages of the stellar evolution is poorly understood at present. The stellar winds of red giants may be tidally enhanced by companion stars if they are in binary systems. We investigate evolutionary consequences of red giants in binaries by including tidally enhanced stellar winds, and examine the effects on the HB morphology of GCs. We find that red, blue, and extreme horizontal branch stars are all produced under the effects of tidally enhanced stellar wind without any additional assumptions on the mass-loss dispersion. Furthermore, the horizontal branch morphology is found to be insensitive to the tidal enhancement parameter, Bw. We compare our theoretical results with the observed horizontal branch morphology of globular cluster NGC 2808, and find that the basic morphology of the horizontal branch can be well reproduced. The number of blue horizontal branch stars in our calculations, however, is lower than that of NGC 2808.

7 pages, 4 figures, 2 tables, accepted for publication in Astronomy & Astrophysics

References in corpus (5)

• Modules for Experiments in Stellar Astrophysics (MESA)
• A binary model for the UV-upturn of elliptical galaxies (MNRAS version)
• The fraction of binary systems in the core of thirteen low-density Galactic globular clusters
• The fraction of second generation stars in Globular Clusters from the analysis of the Horizontal Branch
• Implementation of New OPAL Tables in Eggleton's Stellar Evolution Code

Cited by in corpus (20)

• Unresolved stellar companions with Gaia DR2 astrometry
• Hot subluminous stars
• The age of the Milky Way inner stellar spheroid from RR Lyrae population synthesis
• BayeSED: A General Approach to Fitting the Spectral Energy Distribution of Galaxies
• Hot Subdwarf Stars Observed in LAMOST DR1 - Atmospheric parameters from single-lined spectra
• Hot subdwarf Atmospheric parameters, Kinematics, and Origins -- Based on 1587 hot subdwarf stars observed in Gaia DR2 and LAMOST DR7
• Hot subdwarf stars observed in Gaia DR2 and LAMOST DR5
• RR Lyrae From Binary Evolution: Abundant, Young and Metal-Rich
• SHOTGLAS I: The ultimate spectroscopic census of extreme horizontal branch stars in $\omega$ Centauri
• A new Hyper-Runaway star discovered from LAMOST and GAIA: ejected almost in the galactic rotation direction
• Precise radial velocities of giant stars IX. HD 59686 Ab: a massive circumstellar planet orbiting a giant star in a ~13.6 au eccentric binary system
• A possible formation channel for blue hook stars in globular cluster
• Hot Subdwarf Stars Identified in Gaia DR2 with Spectra of LAMOST DR6 and DR7. II. Kinematics
• Level of helium enhancement among M3's horizontal-branch stars
• A possible formation channel for blue hook stars in globular cluster - II. Effects of metallicity, mass ratio, tidal enhancement efficiency and helium abundance
• Stellar-Encounter Driven Red-Giant Star Mass-Loss in Globular Clusters
• Synthetic horizontal branch morphology for different metallicities and ages under tidally enhanced stellar wind
• Core collapse and horizontal-branch morphology in galactic globular clusters
• Effect of Binary Fraction on Horizontal Branch Morphology under Tidally Enhanced Stellar Wind
• Evolving Low- and Intermediate-Mass Binaries: Departures from Classical Theory