2008A&A...480..397S -
Astronomy and Astrophysics, volume 480, 397-407 (2008/3-3)
XMM-Newton observations of the Galactic globular clusters NGC 2808 and NGC 4372.
SERVILLAT M., WEBB N.A. and BARRET D.
Abstract (from CDS):
Galactic globular clusters harbour binary systems that are detected as faint X-ray sources. These close binaries are thought to play an important role in the stability of the clusters by liberating energy and delaying the inevitable core collapse of globular clusters. The inventory of close binaries and their identification is therefore essential. We present XMM-Newton observations of two Galactic globular clusters:
NGC 2808 and
NGC 4372. We use X-ray spectral and variability analysis combined with ultra-violet observations made with the XMM-Newton optical monitor and published data from the Hubble Space Telescope to identify sources associated with the clusters. We compare the results of our observations with estimates from population synthesis models. Five sources out of 96 are likely to be related to
NGC 2808. Nine sources are found in the field of view of
NGC 4372, none being located inside its half-mass radius. We find one quiescent neutron star low mass X-ray binary candidate in the core of
NGC 2808, and propose that the majority of the central sources in
NGC 2808 are cataclysmic variables. An estimation leads to 20±10 cataclysmic variables with luminosity above 4.25x10
31erg/s. Millisecond pulsars could also be present in the core of
NGC 2808, and some sources outside the half-mass radius could possibly be linked to the cluster.
Abstract Copyright:
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Journal keyword(s):
Galaxy: globular clusters: individual: NGC 2808 - Galaxy: globular clusters: individual: NGC 4372 - X-rays: general - stars: binaries: close
VizieR on-line data:
<Available at CDS (J/A+A/480/397): table2.dat table3.dat>
Nomenclature:
Table 2: [SWB2008] NGC 2808 CN (Nos C1-C5), [SWB2008] NGC 2808 NN (Nos 1-92). Table 3: [SWB2008] NGC 4372 NN (Nos 1-10).
Status at CDS
:
All or part of tables of objects could be ingested in SIMBAD with priority 2.
Simbad objects:
41
View the references in ADS