MG11 
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Abstract

The Properties of the Supermassive-Black-Hole Sources, including Sgr A*

After more than 30 years of intense study, the proposed SBHs still face us with a number of hard-to-comeby problems: (1) The missing birth events: Their formations have defied identification. The best birth-site candidates - the centers of massive galaxies - have been found undercritical in density by factors > 30. (2) The nuclear burning hurdle: Long before reaching the critical density for collapse, explosive nuclear burning is expected to disintegrate a large mass concentration. (3) The missing mass: The integrated power of the AGN phenomenon predicts present-day BH masses of 10^(10.5 /pm 1.5)M(sun), instead of the observed 10^(6.5 /pm 1.5)M(sun). (4) Their excessive temperatures: The AGN spectra often peak above TeV energies, instead of the expected keV(M(sun)/M)^1/4 for a BH. (5) Their strong metal enrichment: Their spectra are >10^2-fold metal enriched over solar, looking like the ashes of nuclear burning. (6) Their powerful winds: with ejection rates through the BLR equalling the inferred infall rates. (7) Their high gamma-ray compactness: inconsistent with the escape of the relativistic pair plasma which feeds the jets of the radio-loud subclass. (8) The inverted evolution of the AGN phenomenon: whose Eddington power would grow with cosmic time whilst its observed power decreases rapidly. (9) The universality of the jet phenomenon: which involves (all) newborn stars as central engines, nowadays even brown dwarfs.

The proposed Astrophysical Black Holes

BH sources are discussed abundantly in the literature: as the supermassive central engines of the AGN phenomenon, as stellar-mass X-ray sources, gamma-ray bursters, perhaps even SN cores, jet engines, and CR generators. This talk will be restricted to the stellar-mass subclass, whose members are often called BHCs because they are difficult to distinguish from neutron-star (n*) sources surrounded by massive accretion disks. Indeed, n** are superior to BHs in all emission processes because of their (i) hard surfaces, (ii) strong, inclined, corotating magnetospheres, (iii) high transient surface temperatures during clumpy accretion, and (iv) extended binary windzones. For a discrimination, I will consider their (1) spectra, (2) lightcurves, (3) the indistinguishability of the BHCs within the class of compact accretors, and (4) the expected evolutionary place of the BHCs as the intermediate-mass compact binaries. This discussion will cover hard gamma-rays through hard & soft X-rays, visible light, and radio flares, broad emission lines, polarizations, precession periods, bimodalities, dipping, flickering, QPO variability, super-Eddington bursting, jet formation, and offset orbital periods during superhumps.

Neutron-Star Atmospheres and X-ray Spectra

Neutron Stars are thought to be good conductors, anchoring strong, corotating magnetospheres and radiating at (patchy) surface temperatures below 10^7 K. Even if their far fields are dipolar, stability (inside a fluid star) requires a `toroidal bandage´ - most likely acquired during the progenitor star's core collapse - so that their fields can be described by odd-order multipole expansions: `dipole + octupole + + 2^5-pole + ...´. A rotating magnet generates unipolar-induction E-fields which accelerate electrons and positrons to Lorentz factors e beta B h^2/m_e c^2 R > (h/cm)^2 >> 1 for transient vacuum gaps of height h, both `upward´ and `downward´ from its surface. Most of them will escape to infinity, along the `open´ B-lines, but some minority at least will bombard the star's surface, achieving a surface tempera- ture T_s = 10^6.5 K for typical n* values and a small assumed downward power fraction (of a few %), as a balance between bombardment and blackbody radiation. At this high T_s, the pair corona has a scale height H = kT/m_e g =10^4 cm T_7, and saturates when it gets opaque to pair annihilation, at an estimated opacity of tau = sigma_T/sigma_ann of order 10 for Thompson scattering, so that it is optically thick to the star's cooling radiation (at soft X-rays), resulting in the observed blackbody spectra.