Predictions of a population of cataclysmic variables in globular clusters

Stefano, Rosanne Di; Rappaport, S.

doi:10.1086/173805

Cited by 77 publications

(90 citation statements)

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“…Simulations also show that a large number of close binaries (neutron star X-ray binaries and cataclysmic variables, CVs) should exist in GCs (e.g. Di Stefano & Rappaport 1994;Davies 1997;Ivanova et al 2006).…”

Section: Introductionmentioning

confidence: 98%

CV1 in the globular cluster M 22: confirming its nature through X-ray observations and optical spectroscopy

Webb¹,

Servillat²

2013

A&A

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Context. Observations of cataclysmic variables in globular clusters appear to show a dearth of outbursts compared to those observed in the field. A number of explanations have been proposed, including low mass-transfer rates and/or moderate magnetic fields implying higher mass white dwarfs than the average observed in the field. Alternatively this apparent dearth may be simply a selection bias. Aims. We examine multi-wavelength data of a new cataclysmic variable, CV1, in the globular cluster M 22 to try to constrain its period and magnetic nature, with an aim at understanding whether globular cluster cataclysmic variables are intrinsically different from those observed in the field. Methods. We use the sub-arcsecond resolution of the Chandra ACIS-S to identify the X-ray counterpart to CV1 and analyse the X-ray spectrum to determine the spectral model that best describes this source. We also examine the low resolution optical spectrum for emission lines typical of cataclysmic variables. Cross correlating the H α line in each individual spectrum also allows us to search for orbital motion. Results. The X-ray spectrum reveals a source best-fitted with a high-temperature bremsstrahlung model and an X-ray unabsorbed luminosity of 1.8 × 10 32 erg s −1 (0.3-8.0 keV), which are typical of cataclysmic variables. Optical spectra reveal Balmer emission lines, which are indicative of an accretion disc. Potential radial velocity in the H α emission line is detected and a period for CV1 is proposed. Conclusions. These observations support the CV identification. The radial velocity measurements suggest that CV1 may have an orbital period of ∼7 h, but further higher resolution optical spectroscopy of CV1 is needed to unequivocally establish the nature of this CV and its orbital period.

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Section: Introductionmentioning

confidence: 98%

CV1 in the globular cluster M 22: confirming its nature through X-ray observations and optical spectroscopy

Webb¹,

Servillat²

2013

A&A

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“…Of particular importance is the primordial binary star population (Heggie 1975;Hut et al 1992), which provides a crucial internal energy source for the cluster by virtue of inelastic scattering encounters. Some of the more dramatic products of these encounters include recycled pulsars (Rappaport, Putney, & Verbunt 1989;Phinney 1996), low-mass X-ray binaries (Verbunt & Johnston 1996), cataclysmic variables (CVs; Di Stefano & Rappaport 1994;Cool et al 1995;Grindlay et al 2001aGrindlay et al , 2001b, and blue stragglers (Sigurdsson, Davies, & Bolte 1994;Lombardi, Rasio, & Shapiro 1996). Cool et al (1998, hereafter CGC98) and Edmonds et al (1999, hereafter EGC99) have reported the detection of a new stellar population near the center of the core-collapsed globular cluster NGC 6397.…”

Section: Introductionmentioning

confidence: 99%

Helium Core White Dwarfs in Globular Clusters

Hansen

Kalogera

Rasio

2003

ApJ

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We examine the theoretical implications of a population of low-mass helium core white dwarfs in globular clusters. In particular, we focus on the observed population in the core of NGC 6397, where several low-mass white dwarf candidates have been identified as '' nonflickerers '' by Cool and collaborators. Age and mass estimates from cooling models, combined with dynamical and evolutionary considerations, lead us to infer that the dark binary companions are C/O white dwarfs rather than neutron stars. Furthermore, we find that the progenitor binaries very likely underwent an exchange interaction within the last 10 9 yr. We examine the prospects for detecting a similar population in other globular clusters, with particular attention to the case of 47 Tuc.

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“…Galactic Globular Cluster X-Ray Sources X-ray studies of Milky Way (MW) globular clusters (GCs) suggested that they be divided into '' bright '' (L X > 10 35 ergs s À1 ) and '' dim '' (L X < 10 34 ergs s À1 ) sources (see e.g., Hertz & Grindlay 1983;Verbunt et al 1985;Deutsch et al 2000). The majority of dim sources are thought to be accreting white dwarfs (Di Stefano & Rappaport 1994;Hakala et al 1997;Grindlay et al 2001). Chandra observations with realistic exposure times can see only evidence of large populations of dim sources in M31, not individual sources.…”

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confidence: 99%

Bright X‐Ray Sources in M31 Globular Clusters

Stefano

Kong

Garcia

et al. 2002

ApJ

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We have conducted Chandra observations of $2560 arcmin 2 ($131 kpc 2 ) of M31 and find that the most luminous X-ray sources in most of our fields are in globular clusters. Of the 28 globular cluster X-ray sources in our fields, 15 are newly discovered. Approximately one-third of all the sources have L X ([0.5-7] keV Þ > 10 37 ergs s À1 , and approximately one-tenth of all the sources have L X ([0.5-7] keV) close to or above 10 38 ergs s À1 . The most luminous source, in the globular cluster Bo 375, is consistently observed to have L X greater than 2 Â 10 38 ergs s À1 . (1) We present data on the spectra and/or light curves of the five most luminous M31 globular cluster sources. (2) We explore possible explanations for the high X-ray luminosities of the brightest sources. These include that the X-ray sources may be composites, the radiation we receive may be beamed, metallicity effects could be at work, or the sources may be accreting black holes. We weigh each of these possibilities against the data. In addition, we introduce a neutron star model in which mass transfer proceeds on the thermal timescale of the donor star. Our model can produce luminosities of several times 10 38 ergs s À1 and leads to a set of well-defined predictions. (3) We compute the X-ray luminosity function and the distribution of counts in wavebands that span the range of energies to which Chandra is sensitive. We find the peak X-ray luminosity is higher and that systems with L X > 10 37 ergs s À1 constitute a larger fraction of all GC sources than in our Galaxy. (4) We study the possible reasons for this difference between M31 and Galactic globular cluster X-ray sources and identify three promising explanations.

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Predictions of a population of cataclysmic variables in globular clusters

Cited by 77 publications

References 0 publications

CV1 in the globular cluster M 22: confirming its nature through X-ray observations and optical spectroscopy

CV1 in the globular cluster M 22: confirming its nature through X-ray observations and optical spectroscopy

Helium Core White Dwarfs in Globular Clusters

Bright X‐Ray Sources in M31 Globular Clusters

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