The recently discovered correlation between black hole mass and stellar velocity dispersion provides a new method to determine the masses of black holes in active galaxies. We have obtained optical spectra of Markarian 501, a nearby γ-ray blazar with emission extending to TeV energies. The stellar velocity dispersion of the host galaxy, measured from the calcium triplet lines in a 2× 3.7 apertu...

Most models for the central engine of gamma-ray bursts involve a stellar mass black hole surrounded by a thick disk formed after the merging of a system of compact objects or the collapse of a massive star. Energy released from the accretion of disk material by the black hole or from the rotation of the hole itself extracted by the Blandford-Znajek mechanism powers a relativistic wind along the...

Using high-resolution SPH numerical simulations, we investigate the effects of gas on the inspiral and merger of a massive black hole binary. This study is motivated by both observational and theoretical work that indicate the presence of large amounts of gas in the central regions of merging galaxies. N-body simulations have shown that the coalescence of a massive black hole binary eventually ...

Recent X–ray observations of intense high–speed outflows in quasars suggest that supercritical accretion on to the central black hole may have an important effect on a host galaxy. I revisit some ideas of Silk and Rees, and assume such flows occur in the final stages of building up the black hole mass. It is now possible to model explicitly the interaction between the outflow and the host galax...

The nucleus of the Seyfert galaxy NGC 1068 is believed to host a supermassive black hole. Evidence for the presence of a massive central object is provided by water maser emission, which displays a linear pattern in the sky, suggestive of a rotating disk. The rotating disk hypothesis is further strengthened by the declining shape of the derived rotation curve. Similar maser emission from NGC 42...

Recent X–ray observations of intense high–speed outflows in quasars suggest that supercritical accretion on to the central black hole may have an important effect on a host galaxy. I revisit some ideas of Silk and Rees, and assume such flows occur in the final stages of building up the black hole mass. It is now possible to model explicitly the interaction between the outflow and the host galax...

In the neighborhood of Sgr A*, several stars (S2, S12, S14, S1, S8, S13) enjoy an accurate determination of their orbital parameters. General Relativity predicts that the central black hole acts as a gravitational lens on these stars, generating a secondary image and two infinite series of relativistic images. For each of these six stars, we calculate the light curves for the secondary and the ...

We study theoretically the electronic structures of various group III acceptors in Ge under [001] stress, based on the effective-mass theory with a semi-empirical impurity potential which considers the q-dependent screening and the central-cell correction. An assignment is made for inter-level transition lines which were previously ignored or incorrectly assigned. In addition, our calculation c...

I report the detection of two X-ray sources of luminosities ∼ 10 36 ergs s −1 in the central region of 30 Doradus. These two sources appear point-like in images taken with the ROSAT HRI. One of the sources is most likely associated with a close spectroscopic binary R140a2 (WN6) with an orbital period of 2.76 days. The mass of the unknown binary component is likely in the range of 2.4 − 15 M ⊙. ...

New measurements of the stellar-mass deficits at the centers of luminous elliptical galaxies are presented. These were derived considering the following observational facts. Firstly, “core” galaxies, which are thought to have had their inner region depleted from the coalesence of supermassive black holes, show an abrupt downward deviation of their inner light-profile relative to their outer Sér...