Spectra of Cosmic X-Ray Sources

Holt, S. S.; McCray, Richard

doi:10.1146/annurev.aa.20.090182.001543

Cited by 40 publications

(9 citation statements)

References 89 publications

(94 reference statements)

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“…Although estimates vary, the hot plasma has a temperature of some 10 7 -10 8 K. The upper end of this range is quite high, more akin to the temperatures found for intergalactic gas bound to clusters of galaxies than to the temperatures found for individual galactic nuclei or supernova remnants (Holt & McCray 1982, Pietsch 1994. At temperatures near 10 8 K, the gas would not be bound to the Galaxy at all (Yamauchi et al 1990, and a wind would expand from the center at a few thousand kilometers per second, implying a lifetime of ∼ 10 5 yr.…”

Section: The Hot Componentmentioning

confidence: 94%

The Galactic Center Environment

Morris

Serabyn

1996

Annu. Rev. Astron. Astrophys.

899

905

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The central half kiloparsec region of our Galaxy harbors a variety of phenomena unique to the central environment. This review discusses the observed structure and activity of the interstellar medium in this region in terms of its inevitable inflow toward the center of the Galactic gravitational potential well. A number of dissipative processes lead to a strong concentration of gas into a "Central Molecular Zone" of about 200-pc radius, in which the molecular medium is characterized by large densities, large velocity dispersions, high temperatures, and apparently strong magnetic fields. The physical state of the gas and the resultant star formation processes occurring in this environment are therefore quite unlike those occurring in the large-scale disk. Gas not consumed by star formation either enters a hot X ray-emitting halo and is lost as a thermally driven galactic wind or continues moving inward, probably discontinuously, through the domain of the few parsec-sized circumnuclear disks and eventually into the central parsec. There, the central radio source SgrA * currently accepts only a tiny fraction of the inflowing material, likely as a result of a limit cycle wherein the continual inflow of matter provokes star formation, which in turn can temporarily halt the inflow via mass-outflow winds.

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Section: The Hot Componentmentioning

confidence: 94%

The Galactic Center Environment

Morris

Serabyn

1996

Annu. Rev. Astron. Astrophys.

899

905

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“…Accordingly, the properties of the continuum spectra will first be reviewed, and then those of the line spectra. Reviews devoted primarily to the observations of the x-ray spectra of clusters have been given recently by Canizares (1981) and Mushotzky (1980Mushotzky ( ,1984, while Holt and McCray (1982) review all of x-ray spectroscopy.…”

Section: Iia)mentioning

confidence: 99%

“…Superclusters of galaxies are reviewed by Dort (1983). Some recent reviews which include the x-ray properties of clusters are Gursky and Schwartz (1977), Binney (1980), Cavaliere (1980), Cowie (1981), Canizares (1981), and Holt and McCray (1982). Fabian et al (1984) give an excellent review of cooling flows in x-ray clusters (see Sec.…”

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confidence: 99%

X-ray emission from clusters of galaxies

1986

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Clusters of galaxies are gravitationally bound configurations containing typically hundreds of galaxies in a region about 10 cm in size. They range from irregular clusters, with strong subclustering, no strong central concentration, and mainly spiral galaxies, to regular clusters, with smooth and centrally condensed galaxy distributions containing few spiral galaxies. Observations of these clusters of galaxies show that they are bright x-ray sources, with luminosities of 1043 45 ergs/sec. It is now established that the emission mechanism is thermal bremsstrahlung from hot (-10 K}, low-density (-10 atoms/cm ) gas. This intracluster gas has a distribution similar to that of the galaxies in the cluster and fills the space between the galaxies. Remarkably, the total mass of hot gas in a typical cluster is similar to the total mass in all the stars in all the galaxies in the cluster. The x-ray spectra of clusters show strong x-ray line emission from iron and other heavy elements; this indicates that a significant portion of the intracluster gas must have been ejected from galaxies in the cluster. Recent x-ray observations from the Einstein x-ray satellite show that intracluster gas is cooling in some clusters and being accreted ontc large, central galaxies. X-ray images from Einstein also suggest that the morphology of the gas mirrors the dynamical state of the cluster. In this paper the x-ray observations of clusters of galaxies are reviewed. Related optical and radio measurements of clusters are also summarized. Theories for the physical state, distribution, origin, and evolution of the intracluster medium are extensively discussed. Finally, the author comments. on the prospects for future x-ray observations.

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“…There is some tendency for the more complex dependences of the pulse profiles on energy to occur among the longer period pulsars. Representiative X-ray pulsar spectra from six sources are shown in Figure 4 [see Holt & McCray (1982) and White et al (1983) for extensive reviews of the subject]. Though these spectra differ in detail, the spectra of X-ray pulsars have the following general features: (a) broadband emission not dominated by sharp spectral features, (b) power mostly emitted in the range 2-20 ke V, (c) rapid falloff in flux for energies above � 20 keY, with the falloff often less abrupt for systems with lower X-ray luminosities, (d) no simple description in terms of a blackbody, thermal bremsstrahlung, or power-law shape, and (e) an iron K-shell emission fe ature near 7 keY in many, but not all, cases (see, for example, Becker et al 1978, White et al 1980.…”

mentioning

confidence: 99%