Match Probability Statistics and Gamma Ray Burst Recurrences in the BATSE Catalog

We develop match probability statistics to test the recurrences of gamma ray bursts in the BATSE catalog 1B and 2B. We do not find a signal of repetitions at the match level of 1.e-3.Comment: 4 pages, LaTeX, two macros included (kluwer.sty, spacekap.sty) To appear in the proceedings of the Eslab29 symposium, ``gamma ray bursts: toward the source

The effect of gravitational-wave recoil on the demography of massive black holes

The coalescence of massive black hole (MBH) binaries following galaxy mergers is one of the main sources of low-frequency gravitational radiation. A higher-order relativistic phenomenon, the recoil as a result of the non-zero net linear momentum carried away by gravitational waves, may have interesting consequences for the demography of MBHs at the centers of galaxies. We study the dynamics of recoiling MBHs and its observational consequences. The ``gravitational rocket'' may: i) deplete MBHs from late-type spirals, dwarf galaxies, and stellar clusters; ii) produce off-nuclear quasars, including unusual radio morphologies during the recoil of a radio-loud source; and iii) give rise to a population of interstellar and intergalactic MBHs.Comment: emulateapj, 5 pages, 2 figures, to appear in the ApJ Letter

Reverberation Mapping and the Physics of Active Galactic Nuclei

Reverberation-mapping campaigns have revolutionized our understanding of AGN. They have allowed the direct determination of the broad-line region size, enabled mapping of the gas distribution around the central black hole, and are starting to resolve the continuum source structure. This review describes the recent and successful campaigns of the International AGN Watch consortium, outlines the theoretical background of reverberation mapping and the calculation of transfer functions, and addresses the fundamental difficulties of such experiments. It shows that such large-scale experiments have resulted in a ``new BLR'' which is considerably different from the one we knew just ten years ago. We discuss in some detail the more important new results, including the luminosity-size-mass relationship for AGN, and suggest ways to proceed in the near future.Comment: Review article to appear in Astronomical Time Series, Proceedings of the Wise Observatory 25th Ann. Symposium. 24 pages including 7 figure

Minisuperspace Quantization of "Bubbling AdS" and Free Fermion Droplets

We quantize the space of 1/2 BPS configurations of Type IIB SUGRA found by Lin, Lunin and Maldacena (hep-th/0409174), directly in supergravity. We use the Crnkovic-Witten-Zuckerman covariant quantization method to write down the expression for the symplectic structure on this entire space of solutions. We find the symplectic form explicitly around AdS_5 x S^5 and obtain a U(1) Kac-Moody algebra, in precise agreement with the quantization of a system of N free fermions in a harmonic oscillator potential, as expected from AdS/CFT. As a cross check, we also perform the quantization around AdS_5 x S^5 by another method, using the known spectrum of physical perturbations around this background and find precise agreement with our previous calculation.Comment: 22 Pages + 2 Appendices, JHEP3; v3: explanation of factor 2 mismatch added, references reordered, published versio

Variability and spectral energy distributions of low-luminosity active galactic nuclei: a simultaneous X-ray/UV look with Swift

We have observed four low-luminosity active galactic nuclei classified as Type 1 LINERs with the X-ray Telescope (XRT) and the UltraViolet-Optical Telescope (UVOT) onboard Swift, in an attempt to clarify the main powering mechanism of this class of nearby sources. Among our targets, we detect X-ray variability in NGC 3998 for the first time. The light curves of this object reveal variations of up to 30% amplitude in half a day, with no significant spectral variability on this time scale. We also observe a decrease of ~30% over 9 days, with significant spectral softening. Moreover, the X-ray flux is ~40% lower than observed in previous years. Variability is detected in M 81 as well, at levels comparable to those reported previously: a flux increase in the hard X-rays (1-10 keV) of 30% in ~3 hours and variations by up to a factor of 2 within a few years. This X-ray behaviour is similar to that of higher-luminosity, Seyfert-type, objects. Using previous high-angular-resolution imaging data from the Hubble Space Telescope (HST), we evaluate the diffuse UV emission due to the host galaxy and isolate the nuclear flux in our UVOT observations. All sources are detected in the UV band, at levels similar to those of the previous observations with HST. The XRT (0.2-10 keV) spectra are well described by single power-laws and the UV-to-X-ray flux ratios are again consistent with those of Seyferts and radio-loud AGNs of higher luminosity. The similarity in X-ray variability and broad-band energy distributions suggests the presence of similar accretion and radiation processes in low- and high-luminosity AGNs.Comment: 12 pages, 6 figures, in press in MNRA