The mass distribution of stellar mergers: A new scenario for several FS CMa stars

Abstract

(Abreviated) FS CMa stars belong to a diverse group of stars exhibiting the B[e] phenomenon, which is manifested mainly by the presence of forbidden emission lines and a~strong infrared (IR) excess in their spectra. Recently, a strong magnetic field has been discovered in the FS CMa star IRAS 17449+2320. Its strength and an unusually high space velocity point to a post-merger nature. Stellar mergers may provide an explanation for the complex and sometimes chaotic behaviour of some of the FS CMa stars. We did a statistical study of numerical simulations using Aarseth's NBODY6 code. We show the importance of stellar mergers of low- to intermediate-mass stars (from $\approx$ 1.4 to $\approx$ 8 ${\text{M}}_{\odot }$) and for B-type stars in particular. We analysed two sets of N-body simulations with different initial orbital period distributions. In the simulations, more massive binaries are treated differently than less massive binaries and the mass limit usually used is 5 ${\text{M}}_{\odot }$. We also used the value of 2 ${\text{M}}_{\odot }$ to test the influence of this ambiguous limit on the results. Looking at mass, distance from their birth cluster, and velocity distributions, we investigated the statistical significance of individual spectral types in terms of merger dynamics and how merger events affect the stellar evolution. We found that around 50 \% of stars in the simulated open clusters involved in the formation of mergers are B-type stars. As a result, more than 50 \% of the merger products end up as a B-type star as well. Between 12.54 \% and 23.24 \% of all B-type stars are mergers. These results are a natural consequence of the initial mass function, initial distribution of the binary star parameters, and large range of masses for B-type stars. We present a comparison of the W component and the space velocity of the simulated mergers with a sample of observed FS CMa stars.

15 pages, 12 figures including appendix, version after language correction, before the production stage

References in corpus (12)

• Binary interaction dominates the evolution of massive stars
• Toward Complete Statistics of Massive Binary Stars: Penultimate Results from the Cygnus OB2 Radial Velocity Survey
• On the structure of tidal tails
• An evolutionary catalogue of Galactic post-AGB and related objects
• Dependency of dynamical ejections of O stars on the masses of very young star clusters
• The possible role of stellar mergers for the formation of multiple stellar populations in globular clusters
• Long-term evolution of a magnetic massive merger product
• On the initial binary population for star cluster simulations
• The most massive stars in very young star clusters with a limited mass: Evidence favours significant self-regulation in the star formation processes
• A new method to create initially mass segregated star clusters in virial equilibrium
• Tidal tails of open star clusters as probes to early gas expulsion II: Predictions for Gaia
• First detection of a magnetic field in low-luminosity B[e] stars: New scenarios for the nature and evolutionary stages of FS CMa stars

Cited by in corpus (2)

• Intermediate-Mass Mergers: A New Scenario for Several FS CMa Stars
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