SUMMARY – An ActiveX component to calculate temperature and vapour fraction in a geothermal reservoir using the quartz solubility geothermometry was written in Visual Basic. The approach is based on the conservation of mass and energy (enthalpy). Four representative types of regression equations for quartz solubility: (i) a quadratic regression equation of 1/T and pressure P, (ii) a linear equa...

Recent X-ray surveys by Chandra and XMM-Newton have revealed a population of X-ray bright, optically normal galaxies (XBONGs) at moderate redshifts. By analogy with nearby low-luminosity active galactic nuclei, we propose that many XBONGs are powered by an inner radiatively inefficient accretion flow (RIAF) plus an outer standard thin accretion disk. The absence of optical/UV activity in XBONGs...

We describe in detail how one can extract space-time geometry in an exactly solvable model of quantum dilaton gravity of the type proposed by Callan, Giddings, Harvey and Strominger ( CGHS ). Based on our previous work, in which a model with 24 massless matter scalars was quantized rigorously in BRST operator formalism, we compute, without approximation, mean values of the matter stress-energy ...

We study numerically the fully nonlinear gravitational collapse of a self-gravitating, minimallycoupled, massless scalar field in spherical symmetry. Our numerical code is based on double-null coordinates and on free evolution of the metric functions: The evolution equations are integrated numerically, whereas the constraint equations are only monitored. The numerical code is stable (unlike rec...

Self-adjoint extensions of elliptic operators are used to model the solution of a partial differential equation defined in a singularly perturbed domain. The asymptotic expansion of the solution of a Laplacian with respect to a small parameter ε is first performed in a domain perturbed by the creation of a small hole. The resulting singular perturbation is approximated by choosing an appropriat...

We report the rst detection of a hard power-law tail in the X-ray spectrum of the black hole candidate (BHC) binary X1755-338, which was observed in 1989 March-September during the TTM Galactic Centre survey. In addition, an ultrasoft thermal component with a temperature of 1:1 1:4 keV was also detected. We demonstrate that the soft and hard X-ray components of X1755-338 vary independently, as ...

Understanding the properties of the hot corona is very important for studying the accretion disks in black hole X-ray binary systems. Using the Monte-Carlo technique to simulate the inverse Compton scattering process between disk photons and electrons in the hot corona, we have produced two table models in the XSPEC package. Applying the models to the broad-band BeppoSAX observations of the bla...

Centrifugal pressure of matter spiralling onto black holes, have long been known to produce standing or oscillating shocks. The post-shock disc puffs up in the form of a torus, which intercepts soft photons from the outer Keplerian disc and inverse Comptonizes them to produce hard photons. The post-shock region also produces jets. We study the interaction of both hard photons and soft photons, ...

We calculate the spin correlation function and the magnetic longitudinal and transverse susceptibilities of a two-dimensional antiferromagnet doped with a small concentration of holes, in the t-J model. We find that the motion of holes generates spin fluctuations which add to the quantum fluctuations, the spin correlations decaying with the inverse of the spin distance, while increasing with do...

We fit the broad-band X/γ-ray spectrum (0.8–1000 keV) of the accreting black hole XTE J1550–564 in the very high state. The quasi-simultaneous data from ASCA, RXTE and OSSE show that the disc is strongly Comptonized, with a high energy tail extending out to several hundreds keV. However, inverse Compton scattering by a purely thermal or purely power-law electron distribution cannot explain the ...