scholarly journals Using X-Rays to Probe the Compact Binary Content of Globular Clusters

2004 ◽  
Vol 194 ◽  
pp. 75-76
Author(s):  
N. A. Webb ◽  
B. Gendre ◽  
D. Barret
Keyword(s):  
Globular Clusters ◽  
Cataclysmic Variables ◽  
Close Binaries ◽  
X Rays ◽  
X Ray ◽  
Compact Binaries ◽  
Compact Binary ◽  
Low Mass ◽  
Evolutionary Paths ◽  
New Generation

AbstractGlobular clusters (GCs) harbour a large number of close binaries which are hard to identify optically due to high stellar densities. Observing these GCs in X-rays, in which the compact binaries are bright, diminishes the over-crowding problem. Using the new generation of X-ray observatories, it is possible to identify populations of neutron star low mass X-ray binaries, cataclysmic variables and millisecond pulsars as well as other types of binaries. We present the spectra of a variety of binaries that we have identified in four GCs observed by XMM-Newton. We show that through population studies we can begin to understand the formation of individual classes of binaries in GCs and hence start to unfold the complex evolutionary paths of these systems.

scholarly journals X-ray sources in Galactic globular clusters and old open clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 367-376
Author(s):  
Maureen van den Berg
Keyword(s):  
Globular Clusters ◽  
Cataclysmic Variables ◽  
Star Clusters ◽  
Open Clusters ◽  
Encounter Rate ◽  
X Ray ◽  
Low Mass ◽  
New Perspective ◽  
X Ray Binaries ◽  
Cluster Age

AbstractThe features and make up of the population of X-ray sources in Galactic star clusters reflect the properties of the underlying stellar environment. Cluster age, mass, stellar encounter rate, binary frequency, metallicity, and maybe other properties as well, determine to what extent we can expect a contribution to the cluster X-ray emission from low-mass X-ray binaries, millisecond pulsars, cataclysmic variables, and magnetically active binaries. Sensitive X-ray observations withXMM-Newton and certainlyChandra have yielded new insights into the nature of individual sources and the effects of dynamical encounters. They have also provided a new perspective on the collective X-ray properties of clusters, in which the X-ray emissivities of globular clusters and old open clusters can be compared to each other and to those of other environments. I will review our current understanding of cluster X-ray sources, focusing on star clusters older than about 1 Gyr, illustrated with recent results.

scholarly journals Observational Evidence for the Origin of X-ray Sources in Globular Clusters

2007 ◽  
Vol 3 (S246) ◽  
pp. 301-310 ◽  
Author(s):  
Frank Verbunt ◽  
Dave Pooley ◽  
Cees Bassa
Keyword(s):  
Statistical Method ◽  
Globular Clusters ◽  
Cataclysmic Variables ◽  
Observational Evidence ◽  
X Ray ◽  
Cluster Mass ◽  
Low Mass ◽  
Optical Identifications ◽  
X Ray Binaries

AbstractLow-mass X-ray binaries, recycled pulsars, cataclysmic variables and magnetically active binaries are observed as X-ray sources in globular clusters. We discuss the classification of these systems, and find that some presumed active binaries are brighter than expected. We discuss a new statistical method to determine from observations how the formation of X-ray sources depends on the number of stellar encounters and/or on the cluster mass. We show that cluster mass is not a proxy for the encounter number, and that optical identifications are essential in proving the presence of primordial binaries among the low-luminosity X-ray sources.

scholarly journals X-Ray Binaries in Globular Clusters

1988 ◽  
Vol 126 ◽  
pp. 347-366
Author(s):  
Jonathan E. Grindlay
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Cataclysmic Variables ◽  
Line Emission ◽  
Brightness Distribution ◽  
Burst Source ◽  
X Ray ◽  
Compact Binaries ◽  
Central Surface ◽  
X Ray Binaries

X-ray binaries in globular clusters provide a powerful tool for the exploration of the evolution of compact binaries and their host globular clusters. Recent x-ray and optical studies of these systems have yielded long-sought binary periods and fundamental properties for two sources (in NGC 6624 and M 15). It appears that tidal capture formation of compact binaries in globular clusters can proceed by several different routes and lead to exotic systems such as the white dwarf-neutron star binary with an 11-minute period recently discovered in NGC 6624. Combined with previously reported long-term periods for several globular cluster (and field) x-ray sources, this suggests again that many of these systems may in fact be hierarchical triple systems. The prospects for forming these in the dense cores of clusters undergoing core collapse is discussed, and searches for color gradients in the cores of globular clusters showing cusps in their central surface brightness distribution are presented. A program to test for the high central density of binaries (and triples) expected in cusp clusters by searching for diffuse line emission from their constituent cataclysmic variables is briefly described. Finally, the case for globular cluster disruption and the formation of galactic x-ray burst source is reviewed in light of recent developments.

scholarly journals The Cyclotron Lines in the Optical Spectra of the Stars of AM Herculis Group: Observations and Interpretation

1980 ◽  
Vol 88 ◽  
pp. 453-465 ◽  
Author(s):  
I. G. Mitrofanov
Keyword(s):  
Magnetic Field ◽  
Cataclysmic Variables ◽  
Magnetized Plasma ◽  
Close Binaries ◽  
X Rays ◽  
Observational Method ◽  
Ultraviolet Continuum ◽  
X Ray ◽  
Optical Continuum ◽  
Basic Prediction

The stars of the AM Herculis group (AM Her, VV Pup, AN UMa and 2A 0311-227) are close binaries containing a mass losing, nondegenerate star and an accreting degenerate dwarf. Their main properties are: the large linear and circular polarization of the optical light, high and low luminosity states, the variable emission line, spectra of H, He and other elements and the identification of these objects with X-ray sources. It is generally accepted that the strong magnetic field of the degenerate dwarf is responsible for these peculiar properties and for the distinction between these objects and the cataclysmic variables (Mitrofanov 1978, 1979a). The polarized optical continuum may be emitted by the accreted magnetized plasma (e.g. Chanmugam and Wagner, 1979), by the magnetized photosphere of the degenerate dwarf (Mitrofanov et al. 1977), or by both sources (Mitrofanov, 1979b). To explain the observed X-rays, Lamb and Masters (1979) showed that a magnetic field about 108 gs is necessary. Unfortunately, the basic prediction of their model - the strong ultraviolet continuum in the spectrum of AM Herculis - appears to be absent (Raymond et al. 1979). Chanmugam and Wagner (1979) proposed a rather different estimate for B of 2 · 108/m*gs (m* = 5 ÷ 25). For further investigations of the AM Herculis-type stars it seems useful to find a direct observational method for measuring the dwarfs′ magnetic fields.

scholarly journals Birth of the ELMs: a ZTF survey for evolved cataclysmic variables turning into extremely low-mass white dwarfs

2021 ◽  
Author(s):  
Kareem El-Badry ◽  
Hans-Walter Rix ◽  
Eliot Quataert ◽  
Thomas Kupfer ◽  
Ken J Shen
Keyword(s):  
Mass Transfer ◽  
White Dwarfs ◽  
Main Sequence ◽  
Cataclysmic Variables ◽  
Close Binaries ◽  
Convective Envelope ◽  
Compact Binary ◽  
Show Evidence ◽  
Low Mass ◽  
Hubble Time

Abstract We present a systematic survey for mass-transferring and recently-detached cataclysmic variables (CVs) with evolved secondaries, which are progenitors of extremely low mass white dwarfs (ELM WDs), AM CVn systems, and detached ultracompact binaries. We select targets below the main sequence in the Gaia colour-magnitude diagram with ZTF light curves showing large-amplitude ellipsoidal variability and orbital period Porb < 6 hr. This yields 51 candidates brighter than G = 18, of which we have obtained many-epoch spectra for 21. We confirm all 21 to be completely– or nearly–Roche lobe filling close binaries. 13 show evidence of ongoing mass transfer, which has likely just ceased in the other 8. Most of the secondaries are hotter than any previously known CV donors, with temperatures 4700 < Teff/K < 8000. Remarkably, all secondaries with $T_{\rm eff} \gtrsim 7000\, \rm K$ appear to be detached, while all cooler secondaries are still mass-transferring. This transition likely marks the temperature where magnetic braking becomes inefficient due to loss of the donor’s convective envelope. Most of the proto-WD secondaries have masses near 0.15 M⊙; their companions have masses near 0.8 M⊙. We infer a space density of $\sim 60\, \rm kpc^{-3}$, roughly 80 times lower than that of normal CVs and three times lower than that of ELM WDs. The implied Galactic birth rate, $\mathcal {R}\sim 60\, \rm Myr^{-1}$, is half that of AM CVn binaries. Most systems are well-described by MESA models for CVs in which mass transfer begins only as the donor leaves the main sequence. All are predicted to reach minimum periods 5 ≲ Porb/min ≲ 30 within a Hubble time, where they will become AM CVn binaries or merge. This sample triples the known evolved CV population and offers broad opportunities for improving understanding of the compact binary population.

scholarly journals Multi-epoch X-ray imaging of globular cluster M62 with Chandra

2020 ◽  
Vol 498 (1) ◽  
pp. 292-303
Author(s):  
Kwangmin Oh ◽  
C Y Hui ◽  
K L Li ◽  
A K H Kong
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Imaging Data ◽  
Short Term ◽  
Observation Window ◽  
X Ray ◽  
Compact Binaries ◽  
X Ray Imaging ◽  
Low Mass

ABSTRACT Using archival spectral-imaging data with a total exposure of ∼144 ks obtained by Chandra, 43 X-ray sources are detected within the half-light radius of globular cluster M62 (NGC 6266). Based on the X-ray colour–luminosity diagram or the positional coincidences with known sources, we have classified these sources into different groups of compact binaries including cataclysmic variable (CV), quiescent low-mass X-ray binary (qLMXB), millisecond pulsar, and black hole (BH). Candidates of the X-ray counterparts of 12 CVs, 4 qLMXBs, 2 MSPs, and 1 BH are identified in our analysis. The data used in our analysis consist of two frames separated by 12 yr, which enable us to search for the long-term variability as well as the short-term X-ray flux variability within each observation window. Evidence for the short-term variability and long-term variability have been found in 7 and 12 sources, respectively. For a number of bright sources with X-ray luminosities Lx ≳ 1032 erg s−1, we have characterized their spectral properties in further details. By comparing the X-ray population in M62 with those in several other prototypical globular clusters, we found the proportion of bright sources is larger in M62 that can possibly be a result of their active dynamical formation processes.

scholarly journals Ultraviolet and X-ray properties of Coma’s ultra-diffuse galaxies

2020 ◽  
Vol 497 (3) ◽  
pp. 2759-2770 ◽  
Author(s):  
Chris H Lee ◽  
Edmund Hodges-Kluck ◽  
Elena Gallo
Keyword(s):  
Star Formation ◽  
Globular Clusters ◽  
Large Population ◽  
Population Based ◽  
Optical Data ◽  
X Rays ◽  
Coma Cluster ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

ABSTRACT Many ultra-diffuse galaxies (UDGs) have been discovered in the Coma cluster, and there is evidence that some, notably Dragonfly 44, have Milky Way-like dynamical masses despite dwarf-like stellar masses. We used X-ray, ultraviolet (UV), and optical data to investigate the star formation and nuclear activity in the Coma UDGs, and we obtained deep UV and X-ray data (Swift and XMM–Newton) for Dragonfly 44 to search for low-level star formation, hot circumgalactic gas, and the integrated emission from X-ray binaries. Among the Coma UDGs, we find UV luminosities consistent with quiescence but NUV − r colours indicating star formation in the past Gyr. This indicates that the UDGs were recently quenched. The r-band luminosity declines with projected distance from the Coma core. The Dragonfly 44 UV luminosity is also consistent with quiescence, with SFR$\lt 6\times 10^{-4} \, \mathrm{M}_{\odot }$ yr−1, and no X-rays are detected down to a sensitivity of 1038 erg s−1. This rules out a hot corona with a $M \gt 10^8 \, \mathrm{M}_{\odot }$ within the virial radius, which would normally be expected for a dynamically massive galaxy. The absence of bright, low-mass X-ray binaries is consistent with the expectation from the Galaxy total stellar mass, but it is unlikely if most low-mass X-ray binaries form in globular clusters, as Dragonfly 44 has a very large population. Based on the UV and X-ray analysis, the Coma UDGs are consistent with quenched dwarf galaxies, although we cannot rule out a dynamically massive population.

Paucity of Dwarf Novae in Globular Clusters

2007 ◽  
Vol 3 (S246) ◽  
pp. 371-372
Author(s):  
P. Pietrukowicz ◽  
J. Kaluzny
Keyword(s):  
Globular Clusters ◽  
Cataclysmic Variables ◽  
Photometric Data ◽  
Light Curves ◽  
Artificial Light ◽  
X Ray ◽  
Compact Binaries ◽  
Dwarf Nova ◽  
The Rich ◽  
Internal Evolution

AbstractWe have conducted an extensive photometric search for dwarf nova (DN) outbursts in 16 Galactic globular clusters (GCs). The survey was based on the rich photometric data collected by the Cluster AgeS Experiment (CASE) team. We have identified two new DNe. Together with previously known systems this gives the total number of 12 known DNe in 7 Galactic GCs. Inserting artificial light curves of “DNe” into frames of investigated clusters allowed us to assess completeness of the search. Our results clearly show that outbursting cataclysmic variables (CVs) are very rare in GCs in comparison to field CVs where half of the systems belongs to DNe. Recent X-ray observations of GCs lead to identification of hundreds of compact binaries. Many of them are promising candidates for CVs. The theory also predicts that dozens of white/red dwarf binaries should form in the cores of GCs via dynamical processes or internal evolution of the binaries. Our results rises the question about possible causes of paucity of outbursts in GCs.

scholarly journals XMM-Newton and Chandra Observations of Neutron Stars and Cataclysmic Variables in the Globular Cluster NGC 2808

2007 ◽  
Vol 3 (S246) ◽  
pp. 373-374
Author(s):  
M. Servillat ◽  
N. A. Webb ◽  
D. Barret ◽  
R. Cornelisse ◽  
A. Dieball ◽  
...  
Keyword(s):  
Neutron Stars ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Cataclysmic Variables ◽  
Cataclysmic Variable ◽  
Specific Nature ◽  
X Ray ◽  
The Core ◽  
Show Evidence ◽  
Low Mass

AbstractWe report on XMM-Newton and Chandra observations of the globular cluster NGC 2808. We detect one quiescent low mass X-ray binary of the 3±1 expected, if these systems are formed through encounters, and we show evidence for the presence of 20±10 bright cataclysmic variables in the core with a luminosity above 4×1031 erg s−1. We also review the specific nature of cataclysmic variables in globular clusters with reference to recent VLT/FORS1 observations of a cataclysmic variable in M 22.

scholarly journals Magnetic Braking in Cataclysmic and Low-Mass X-Ray Binaries

1984 ◽  
Vol 80 ◽  
pp. 287-294
Author(s):  
O. Vilhu
Keyword(s):  
Mass Transfer ◽  
Binary Stars ◽  
Cataclysmic Variables ◽  
Turnover Time ◽  
Coronal Emission ◽  
X Ray ◽  
Compact Binaries ◽  
Gradual Loss ◽  
Low Mass ◽  
Magnetic Braking

AbstractThe chromospheric-coronal emission of lower Main-Sequence single and binary stars can be correlated with an activity parameter of type R = g(B-V)P-1 where P is the rotation or orbital period and g(B-V) a function of the color resembling the convective turnover time. Observations indicate that the active region area coverage filling factor grows as R2, and the whole stellar surface becomes filled with closed loop structures at R ≂ 3. A braking formula is proposed (Equation 4) to include all periods (0.d1 ≲ R ≳ 30d) and spectral types F-M. On the basis of this equation, the mass transfer rates in compact binaries (driven by the gradual loss of orbital angular momentum) are discussed. It is concluded that the magnetic braking has good chances of being that mechanism which drives the mass transfer in cataclysmic variables and galactic bulge X-ray sources.

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