Volume 447, Number 1, February III 2006
|Page(s)||199 - 203|
|Section||Galactic structure, stellar clusters, and populations|
|Published online||27 January 2006|
Chandra observations of the globular cluster M 54
Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK e-mail: firstname.lastname@example.org
Accepted: 8 October 2005
We have carried out a Chandra observation of the globular cluster M 54. We detected 7 sources located within the half-mass radius of M 54, at a flux limit of 1.5 10-15 erg s-1 cm-2 in the 0.3-8 keV energy band. The spatial distribution and the colour/spectral properties of the 7 sources suggest that they are likely to be cataclysmic variables or LMXBs in the globular cluster. M 54 shows the largest number of X-ray sources with luminosities greater than 1032 erg s-1 compared to other globular clusters observed using Chandra and XMM-Newton. We searched for a correlation between the number of sources above this luminosity level with globular cluster parameters. We found evidence that the number of sources peaks at a King concentration parameter c ~ 1.7–1.9, with globular clusters which are core-collapsed or have low-c values having a smaller number of sources. We speculate on possible reasons for this.
Key words: Galaxy: globular clusters: individual: M 54 / X-rays: binaries / stars: binaries: general / Galaxy: globular clusters: general
© ESO, 2006
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.