  We have carried out a Chandra observation of the globular cluster M54. We
detected 7 sources located within the half-mass radius of M54, at a flux limit
of 1.5x10^-15 erg/s/cm 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. M54 shows
the largest number of X-ray sources with luminosities greater than 10^32 ergs/s
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.

Astrophysics