Resumen

PASQUATO, M.. Further Properties of the Dynamical Clock A+ Indicator in a Toy Model of Pure Dynamical Friction. Rev. mex. astron. astrofis [online]. 2020, vol.56, n.1, pp.7-10.  Epub 19-Mar-2021. ISSN 0185-1101.  https://doi.org/10.22201/ia.01851101p.2020.56.01.02.

The Alessandrini A+ indicator is a measure of star cluster dynamical evolution based on the mass-segregation of blue straggler stars. A+ is defined as the integral of the cumulative distribution of blue stragglers over log radius, minus a term related to the reference population used. In a companion paper I introduced a model of dynamical friction and calculated the A+ indicator analytically. Here I show further properties of the time evolution of A+, focusing on the physical interpretation of its time derivative dA+/dt. I find that dA+/dt is the mean of the reciprocal dyamical friction timescale, weighted by the density of blue stragglers. I show that it is non-negative (as expected based on monotonicity) due to the density of blue-stragglers being non-negative and that, for a radially non-decreasing dynamical friction timescale, dA+/dt is also non-decreasing with time, making A+ a convex function.

Palabras llave : blue stragglers; globular clusters: general; methods: analytical.