Related papers: X-ray Sources in Galactic Globular Clusters
We analyse a Chandra observation of the rich globular cluster NGC 362, finding 33 X-ray sources within 1' (1.2 half-mass radii) of the cluster center. Spectral analysis of the brightest source (X1) shows blackbody-like emission, indicating…
Low-mass X-ray binaries (LMXBs) are high-energy sources that require multi-wavelength follow up campaigns to be fully characterized. New transients associated to LMXBs are regularly discovered, and previously known systems are often…
Population synthesis is used to model the number of neutron stars in globular clusters that are observed as LMXBs and millisecond PSRs. The dynamical interaction between binary and single stars in a GC are assumed to take place with a…
Aims. We model the present-day population of 'classical' low-mass X-ray binaries (LMXBs) with neutron star accretors, which have hydrogen-rich donor stars. Their population is compared with that of hydrogen-deficient LMXBs, known as…
We present a study of the intra-cluster population of low-mass X-ray binaries (LMXB) residing in globular clusters (GC) in the central 1 $deg^2$ of the Fornax galaxy cluster. Differently from previous studies, which were restricted to the…
We summarize the x-ray properties of the complete samples of millisecond pulsars (MSPs) detected in our Chandra observations of the globular clusters 47 Tuc and NGC 6397. The 47 Tuc MSPs are predominantly soft sources suggestive of thermal…
We present the classification of 26 optical counterparts to X-ray sources discovered in the Galactic Bulge Survey. We use (time-resolved) photometric and spectroscopic observations to classify the X-ray sources based on their…
The $13.6\times 13.6$ arcmin$^{2}$ field covering the central part of the globular cluster NGC~6397 was surveyed in a search for short-period variable stars. We obtained light curves for 6 close binaries, 2 SX~Phe stars and 1 RR~Lyrae…
The presence of some X-ray sources in the Galactic Centre region which show variability, but do not show outbursts in over a decade of monitoring has been used to argue for the presence of a large population of stellar mass black holes in…
This paper reports the search for quiescent low-mass X-ray binaries (qLMXBs) in the globular cluster (GC) NGC 6553 using an XMM-Newton observation designed specifically for that purpose. We spectrally identify one candidate qLMXB in the…
We present Chandra X-ray Observatory ACIS-S3 X-ray imaging observations and VLT/FORS2 and Hubble Space Telescope optical observations of two low-density Galactic globular clusters; NGC 6366 and M55. We detect 16 X-ray sources with 0.5-6.0…
We report an observation by the Chandra X-ray Observatory of 4U2127+119, the X-ray source identified with the globular cluster M15. The Chandra observation reveals that 4U2127+119 is in fact two bright sources, separated by 2.7". One source…
We investigated for a possible connection between the types of X-ray binaries (XRBs) and the properties of compact star clusters in the nearby galaxy NGC 628. Using {\it Chandra} archival data covering the years 2001-2018, 75 X-ray sources…
Using the XMM-Newton Slew Survey, we construct a hard-band selected sample of low-luminosity Galactic X-ray sources. Two source populations are represented, namely coronally-active stars and binaries (ASBs) and cataclysmic variables (CVs),…
As part of our campaign to determine the nature of the various source populations of the low-luminosity globular cluster X-ray sources, we have obtained a Chandra X-ray Observatory ACIS-S3 image of the globular cluster NGC 6440. We detect…
We analyze photometry, spectra, and variability of over 100 faint X-ray sources in the globular cluster Terzan 5, using 737 ks of Chandra data. X-ray colors and spectral fitting allow clear separation of foreground sources (with less…
Globular clusters are dense stellar systems that have typical ages of ~13 billion years, implying that they formed at redshifts of z>~6. Massive stars in newly formed or primordial globular clusters could have played an important role…
We have discovered with XMM-Newton an X-ray source in the core of the globular cluster M13, whose X-ray spectral properties suggest that it is a quiescent neutron star X-ray binary. The spectrum can be well fitted with a pure hydrogen…
There have been several recent claims of black hole binaries in globular clusters. I show that these candidate systems could instead be ultracompact X-ray binaries (UCXBs) in which a neutron star accretes from a white dwarf. They would…
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…