2008/02/19 by G. Beccari, B. Lanzoni, F. R. Ferraro +33 · 19 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Blue straggler #Cluster (spacecraft) #Globular cluster #Physics #Population #RADIUS #Star (game theory) #Star cluster #Stars #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/587689
published in The Astrophysical Journal 679(1), 712-719 (IOP Publishing) · 25 pages, 9 figures, accepted for publication on ApJ
arxiv created 2008/02/19 · openalex publication_date 2008/05/13 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
We used a proper combination of high-resolution and wide-field multiwavelength observations collected at three different telescopes ( HST , LBT, and CFHT) to probe the blue straggler star (BSS) population in the globular cluster M53. Almost 200 BSSs have been identified over the entire cluster extension. The radial distribution of these stars has been found to be bimodal (similar to that of several other clusters) with a prominent dip at ~60'' (~2 r c ) from the cluster center. This value turns out to be a factor of 2 smaller than the radius of avoidance ( r avoid , the radius within which all the stars of ~1.2 M ☉ have sunk to the core because of dynamical friction effects in a Hubble time). While in most of the clusters with a bimodal BSS radial distribution, r avoid has been found to be located in the region of the observed minimum, this is the second case (after NGC 6388) where this discrepancy is noted. This evidence suggests that in a few clusters the dynamical friction seems to be somehow less efficient than expected. We have also used this database to construct the radial star density profile of the cluster; this is the most extended and accurate radial profile ever published for this cluster, including detailed star counts in the very inner region. The star density profile is reproduced by a standard King Model with an extended core (~25'') and a modest value of the concentration parameter ( c = 1.58). A deviation from the model is noted in the most external region of the cluster (at r > 6.5' from the center). This feature needs to be further investigated in order to address the possible presence of a tidal tail in this cluster.