Multiwavelength survey of X-ray sources in the Sculptor Dwarf Spheroidal Galaxy

Abstract We present an unprecedented, deep study of the primordial low-mass X-ray binary population in an isolated, lower metallicity environment. We perform follow-up observations of previously identified X-ray binary candidates in the Sculptor Dwarf Galaxy by combining a second Chandra observation with Spitzer and Gemini photometry, as well as Gemini spectroscopy of selected targets. Of the original nine bright X-ray sources identified, we are able to classify all but one as quasars, active galactic nuclei, or background galaxies. We further discover four new X-ray sources in the second-epoch Chandra observation. Three of these new sources are background sources and one is a foreground flaring star. We have found that Sculptor is effectively devoid of X-ray sources above a few 1034 erg s−1. If Sculptor is able to retain primordial binaries at a similar rate to globular clusters, this implies that bright X-ray binaries observed in globular clusters in the present epoch are all formed dynamically.

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Theory of Accretion Disk Coronae

International Astronomical Union Colloquium ◽

10.1017/s025292110001232x ◽

1990 ◽

Vol 115 ◽

pp. 187-196

Author(s):

T. R. Kallman

Keyword(s):

Active Galactic Nuclei ◽

Accretion Disk ◽

Cataclysmic Variables ◽

Galactic Nuclei ◽

X Ray ◽

Spectral Signatures ◽

Low Mass ◽

X Ray Absorption ◽

X Ray Binaries ◽

Theoretical Issues

AbstractAccretion disk coronae are likely to be the dominant site for X-ray absorption and reprocessed emission in low mass X-ray binaries, and may be present in other classes of compact X-ray sources such as active galactic nuclei and cataclysmic variables. In spite of this fact, and in spite of the observational evidence for their existence, there remain many uncertainties about the structure of accretion disk coronae. This paper will discuss the coronal structure and dynamics, their X-ray spectral signatures including coupling to the variability behavior of compact X-ray sources, and the major unsolved theoretical issues surrounding them.

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Probing ultra-diffuse galaxies out to the virial radius of the Coma cluster with XMM–Newton

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab548 ◽

2021 ◽

Author(s):

M S Mirakhor ◽

S A Walker

Keyword(s):

Globular Clusters ◽

Galactic Nuclei ◽

Current Data ◽

Point Sources ◽

Dark Matter Halo ◽

Coma Cluster ◽

X Ray ◽

Hot Gas ◽

Low Mass ◽

X Ray Binaries

Abstract We probe the formation scenarios and the active galactic nuclei (AGN) occupation fraction of ultra-diffuse galaxies (UDGs) in the nearby Coma cluster by utilizing XMM−Newton observations of 779 out of 854 UDG candidates identified by Subaru survey. Their origin is probed by measuring the dark matter halo mass of the stacked sample of UDGs and the population of low-mass X-ray binaries residing in globular clusters. Our measurements suggest that the average UDG population does not have a substantial amount of hot gas or a large number of globular clusters. This supports the formation scenario, in which UDGs are puffed-up dwarf galaxies, agreeing with that obtained for 404 Coma cluster UDGs using Chandra. We also determine AGN occupation fraction of UDGs by cross-correlating the position of UDGs with the detected point sources in Coma. We detect three X-ray sources with detection significance σ ≥ 5 that could be off-centre AGN within 5 arcsec from the centre of the UDG 317, UDG 432, and UDG 535. We identify an optical counterpart for the X-ray source associated with the UDG 317, suggesting that this source is more likely an off-centre AGN. Based on the current data, however, we cannot conclusively constrain whether the detected AGN is residing in the Coma cluster or not.

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The Formation of Astrophysical Jets

International Astronomical Union Colloquium ◽

10.1017/s0252921100044298 ◽

1997 ◽

Vol 163 ◽

pp. 845-866 ◽

Cited By ~ 5

Author(s):

Mario Livio

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Young Stellar Objects ◽

Astrophysical Jets ◽

Stellar Objects ◽

X Ray ◽

Astrophysical Objects ◽

Low Mass ◽

Wind Source ◽

X Ray Binaries

AbstractIt is assumed that the acceleration and collimation mechanisms of jets are the same in all the classes of astrophysical objects which are observed to produce jets. These classes now include: active galactic nuclei, young stellar objects, massive x-ray binaries, low mass x-ray binaries, black hole x-ray transients, symbiotic systems, planetary nebulae, and supersoft x-ray sources.On the basis of this assumption, an attempt is made, to identify the necessary ingredients for the acceleration and collimation mechanism. It is argued that: (i) jets are produced at the center of accretion disks which are threaded by a vertical magnetic field, (ii) the production of powerful jets requires, in addition, an energy/wind source associated with the central object. Tentative explanations for the presence of jets in some classes of objects and absence in others are given. Some critical observation that can test the ideas presented in this paper are suggested.

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Polarization Variability of Active Galactic Nuclei and X‐Ray Binaries

The Astrophysical Journal ◽

10.1086/304575 ◽

1997 ◽

Vol 487 (1) ◽

pp. 142-152 ◽

Cited By ~ 9

Author(s):

Gang Bao ◽

Petr Hadrava ◽

Paul J. Wiita ◽

Ying Xiong

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

X Ray ◽

X Ray Binaries

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

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319007981 ◽

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.

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THE X-RAY LUMINOSITY FUNCTION OF LOW MASS X-RAY BINARIES IN EARLY-TYPE GALAXIES, THEIR METAL-RICH, AND METAL-POOR GLOBULAR CLUSTERS

The Astrophysical Journal ◽

10.3847/0004-637x/818/1/33 ◽

2016 ◽

Vol 818 (1) ◽

pp. 33 ◽

Cited By ~ 14

Author(s):

Mark B. Peacock ◽

Stephen E. Zepf

Keyword(s):

Globular Clusters ◽

Luminosity Function ◽

Early Type ◽

X Ray ◽

Low Mass ◽

X Ray Binaries

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Radiative efficiency of hot accretion flow and the radio/X-ray correlation in X-ray binaries

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315007723 ◽

2014 ◽

Vol 10 (S312) ◽

pp. 139-140

Author(s):

Fu-Guo Xie

Keyword(s):

Black Hole ◽

Active Galactic Nuclei ◽

Accretion Rate ◽

Galactic Nuclei ◽

X Ray ◽

Radiative Efficiency ◽

Accretion Flow ◽

Accretion Rates ◽

Distinctive Property ◽

X Ray Binaries

AbstractSignificant progresses have been made since the discovery of hot accretion flow, a theory successfully applied to the low-luminosity active galactic nuclei (LLAGNs) and black hole (BH) X-ray binaries (BHBs) in their hard states. Motivated by these updates, we re-investigate the radiative efficiency of hot accretion flow. We find that, the brightest regime of hot accretion flow shows a distinctive property, i.e. it has a constant efficiency independent of accretion rates, similar to the standard thin disk. For less bright regime, the efficiency has a steep positive correlation with the accretion rate, while for faint regime typical of advection-dominated accretion flow, the correlation is shadower. This result can naturally explain the observed two distinctive correlations between radio and X-ray luminosities in black hole X-ray binaries. The key difference in systems with distinctive correlations could be the viscous parameter, which determines the critical luminosity of different accretion modes.

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Commission N°48: High Energy Astrophysics (Astrophysique Des Hautes Energies)

Transactions of the International Astronomical Union ◽

10.1017/s0251107x00007549 ◽

1988 ◽

Vol 20 (1) ◽

pp. 671-675

Author(s):

C.J. Cesarsky ◽

R.A. Sunyaev ◽

G.W. Clark ◽

R. Giacconi ◽

Vin-Yue Qu ◽

...

Keyword(s):

Active Galactic Nuclei ◽

Supernova Remnants ◽

Cataclysmic Variables ◽

Galactic Nuclei ◽

High Energy ◽

Clusters Of Galaxies ◽

High Energy Astrophysics ◽

X Ray ◽

X Ray Binaries ◽

Imaging Telescopes

The european X-ray observatory (EXOSAT), which was launched in 1983 and which finished operations in April 1986, has brought a rich harvest of results in the period 1984-1987, surveyed here. The EXOSAT payload consisted of three sets of instruments: two low energy imaging telescopes (LE:E<2 KeV), a medium-energy experiment (ME:E=l-50KeV) and a gas scintillation proportional counter (GSPC:E=2-20KeV). Over most of the energy range covered, EXOSAT was not more sensitive than its predecessor, the american EINSTEIN satellite. But the EINSTEIN satellite is far from having exhausted the treasures of the X-ray sky. And EXOSAT, thanks to its elliptical 90-hour orbit, had the extra advantage of being able to make long, continuous observations of interesting objects, lasting up to 72 hours. Thus, EXOSAT was very well suited for variability studies, and many of its most important findings are in this area. EXOSAT observations sample a vide range of astrophysical sources: X-ray binaries, cataclysmic variables and active stars; supernova remnants and the interstellar medium; active galactic nuclei, and clusters of galaxies. Among the highlights, let us mention:

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Non-equilibrium chemistry and destruction of CO by X-ray flares

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz902 ◽

2019 ◽

Vol 486 (1) ◽

pp. 1094-1122 ◽

Cited By ~ 6

Author(s):

Jonathan Mackey ◽

Stefanie Walch ◽

Daniel Seifried ◽

Simon C O Glover ◽

Richard Wünsch ◽

...

Keyword(s):

Active Galactic Nuclei ◽

Thermal Evolution ◽

Galactic Nuclei ◽

Galactic Centre ◽

X Rays ◽

X Ray ◽

Uv Emission ◽

Sgr A ◽

X Ray Binaries ◽

Fractal Cloud

ABSTRACT Sources of X-rays such as active galactic nuclei and X-ray binaries are often variable by orders of magnitude in luminosity over time-scales of years. During and after these flares the surrounding gas is out of chemical and thermal equilibrium. We introduce a new implementation of X-ray radiative transfer coupled to a time-dependent chemical network for use in 3D magnetohydrodynamical simulations. A static fractal molecular cloud is irradiated with X-rays of different intensity, and the chemical and thermal evolution of the cloud are studied. For a simulated $10^5\, \mathrm{M}_\odot$ fractal cloud, an X-ray flux <0.01 erg cm−2 s−1 allows the cloud to remain molecular, whereas most of the CO and H2 are destroyed for a flux of ≥1 erg cm−2 s−1. The effects of an X-ray flare, which suddenly increases the X-ray flux by 105×, are then studied. A cloud exposed to a bright flare has 99 per cent of its CO destroyed in 10–20 yr, whereas it takes >103 yr for 99 per cent of the H2 to be destroyed. CO is primarily destroyed by locally generated far-UV emission from collisions between non-thermal electrons and H2; He+ only becomes an important destruction agent when the CO abundance is already very small. After the flare is over, CO re-forms and approaches its equilibrium abundance after 103–105 yr. This implies that molecular clouds close to Sgr A⋆ in the Galactic Centre may still be out of chemical equilibrium, and we predict the existence of clouds near flaring X-ray sources in which CO has been mostly destroyed but H is fully molecular.

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