Perturbed disks get shocked. Binary black hole merger effects on accretion disks

The merger process of a binary black hole system can have a strong impact on a circumbinary disk. In the present work we study the effect of both central mass reduction (due to the energy loss through gravitational waves) and a possible black hole recoil (due to asymmetric emission of gravitational radiation). For the mass reduction case and recoil directed along the disk's angular momentum, oscillations are induced in the disk which then modulate the internal energy and bremsstrahlung luminosities. On the other hand, when the recoil direction has a component orthogonal to the disk's angular momentum, the disk's dynamics are strongly impacted, giving rise to relativistic shocks. The shock heating leaves its signature in our proxies for radiation, the total internal energy and bremsstrahlung luminosity. Interestingly, for cases where the kick velocity is below the smallest orbital velocity in the disk (a likely scenario in real AGN), we observe a common, characteristic pattern in the internal energy of the disk. Variations in kick velocity simply provide a phase offset in the characteristic pattern implying that observations of such a signature could yield a measure of the kick velocity through electromagnetic signals alone.Comment: 10 pages, 13 figures. v2: Minor changes, version to be published in PR

The HARPS search for southern extra-solar planets I. HD330075 b: a new 'hot Jupiter'

We report on the first extra-solar planet discovered with the brand new HARPS instrument. The planet is a typical 'hot Jupiter' with m2sini = 0.62 MJup and an orbital period of 3.39 days, but from the photometric follow-up of its parent star HD330075 we can exclude the presence of a transit. The induced radial-velocity variations exceed 100 m/s in semi-amplitude and are easily detected by state-of-the-art spectro-velocimeters. Nevertheless, the faint magnitude of the parent star (V = 9.36) benefits from the efficient instrument: With HARPS less than 10 observing nights and 3 hours of total integration time were needed to discover the planet and characterize its orbit. The orbital parameters determined from the observations made during the first HARPS run in July 2003 have been confirmed by 7 additional observations carried out in February 2004. The bisector analysis and a photometric follow-up give no hint for activity-induced radial-velocity variations, indicating that the velocity curve is best explained by the presence of a low-mass companion to the star. In this paper we present a set of 21 measurements of excellent quality with weighted rms as low as 2.0 m/s. These measurements lead to a well defined orbit and consequently to the precise orbital parameters determination of the extra-solar planet HD330075b.Comment: 5 pages, 2 figures, accepted for publication by Astronomy and Astrophysics, see also http://obswww.unige.ch/~udry/planet/planet.htm

Response of a circumbinary accretion disc to black hole mass loss

We investigate the evolution of the surface density of a circumbinary accretion disc after the mass loss induced by the merger of two supermassive black holes. We first introduce an analytical model, under the assumption of a disc composed of test particles, to derive the surface density evolution of the disc following the mass loss. The model predicts the formation of sharp density peaks in the disc; the model also allows us to compute the typical timescale for the formation of these peaks. To test and validate the model, we run numerical simulations of the process using the Smoothed Particle Hydrodynamics (SPH) code PHANTOM, taking fluid effects into account. We find good agreement in the shape and position of the peaks between the model and the simulations. In a fluid disc, however, the epicyclic oscillations induced by the mass loss can dissipate, and only some of the predicted peaks form in the simulation. To quantify how fast this dissipation proceeds, we introduce an appropriate parameter, and we show that it is effective in explaining the differences between the analytical, collisionless model and a real fluid disc.Comment: 10 pages, 11 figures, accepted by MNRAS; added reference in v2. Animations of the simulations are available at http://db.tt/ceqkpmF

Fermion scattering off electroweak phase transition kink walls with hypermagnetic fields

We study the scattering of fermions off a finite width kink wall during the electroweak phase transition in the presence of a background hypermagnetic field. We derive and solve the Dirac equation for such fermions and compute the reflection and transmission coefficients for the case when the fermions move from the symmetric to the broken symmetry phase. We show that the chiral nature of the fermion coupling with the background field in the symmetric phase generates an axial asymmetry in the scattering processes. We discuss possible implications of such axial charge segregation for baryon number generation.Comment: 9 pages, 3 Postscript figures, uses RevTeX4. Expanded discussion, published versio

Black hole mergers: the first light

The coalescence of supermassive black hole binaries occurs via the emission of gravitational waves, that can impart a substantial recoil to the merged black hole. We consider the energy dissipation, that results if the recoiling black hole is surrounded by a thin circumbinary disc. Our results differ significantly from those of previous investigations. We show analytically that the dominant source of energy is often potential energy, released as gas in the outer disc attempts to circularize at smaller radii. Thus, dimensional estimates, that include only the kinetic energy gained by the disc gas, underestimate the real energy loss. This underestimate can exceed an order of magnitude, if the recoil is directed close to the disc plane. We use three dimensional Smooth Particle Hydrodynamics (SPH) simulations and two dimensional finite difference simulations to verify our analytic estimates. We also compute the bolometric light curve, which is found to vary strongly depending upon the kick angle. A prompt emission signature due to this mechanism may be observable for low mass (10^6 Solar mass) black holes whose recoil velocities exceed about 1000 km/s. Emission at earlier times can mainly result from the response of the disc to the loss of mass, as the black holes merge. We derive analytically the condition for this to happen.Comment: 16 pages, accepted by MNRAS. Animations of the simulations are available at http://jilawww.colorado.edu/~pja/recoil.htm

Horizontal partial laryngectomy for supraglottic squamous cell carcinoma

Between 1981-1999, 75 patients treated for supraglottic SCC with horizontal supraglottic laryngectomy (HSL) at the Otolaryngology Head and Neck Surgery Department of Lausanne University Hospital were retrospectively studied. There were 16 patients with T1, 46 with T2 and 13 with T3 tumors. Among these, 16 patients (21%) had clinical neck disease corresponding to stage I, II, III and IV in 12, 39, 18 and 6 patients, respectively. All patients had HSL. Most patients had either elective or therapeutic bilateral level II-IV selective neck dissection. Six patients (8%) with advanced neck disease had ipsilateral radical and controlateral elective II-IV selective neck dissections. Adjuvant radiotherapy was given to 25 patients (30%) for either positive surgical margins (n=8), pathological nodal status (n=14) or both (n=3). Median follow-up was 48 months (range, 24-199). Five-year disease-specific survival and locoregional and local control were 92, 90 and 92.5%, respectively. Among five patients who were diagnosed with local recurrence, one had a total laryngectomy (1.4%); the others were treated by endoscopic laser surgery. Two patients had both a local and regional recurrence. They were salvaged with combined surgery and radiotherapy, but eventually died of their disease. Cartilage infiltration seems to influence both local control (P=0.03) and disease-specific survival (P=0.06). There was a trend for worse survival with pathological node involvement (P=0.15) and extralaryngeal extension of the cancer (P=0.1). All patients except one recovered a close to normal function after the treatment. Aspiration was present in 16 patients (26%) in the early postoperative period. A median of 16 days (7-9) was necessary to recover a close to normal diet. Decannulation took a median of 17 days (8-93). Seven patients kept a tracheotomy tube for up to 3 months because of persistent aspiration. There was no permanent tracheostomy or total laryngectomy for functional purposes. Horizontal supraglottic laryngectomy remains an adequate therapeutic alternative for supraglottic squamous cell carcinoma, offering an excellent oncological outcome. The postoperative functional morbidity is substantial, indicating the need for careful patient selection, but good laryngeal function recovery is the rule. The surgical alternative is endoscopic laser surgery, which may offer comparable oncological results with less functional morbidity. Nevertheless, these two different techniques need to be compared prospectively

Method to estimate ISCO and ring-down frequencies in binary systems and consequences for gravitational wave data analysis

Recent advances in the description of compact binary systems have produced gravitational waveforms that include inspiral, merger and ring-down phases. Comparing results from numerical simulations with those of post-Newtonian (PN), and related, expansions has provided motivation for employing PN waveforms in near merger epochs when searching for gravitational waves and has encouraged the development of analytic fits to full numerical waveforms. The models and simulations do not yet cover the full binary coalescence parameter space. For these yet un-simulated regions, data analysts can still conduct separate inspiral, merger and ring-down searches. Improved knowledge about the end of the inspiral phase, the beginning of the merger, and the ring-down frequencies could increase the efficiency of both coherent inspiral-merger-ring-down (IMR) searches and searches over each phase separately. Insight can be gained for all three cases through a recently presented theoretical calculation, which, corroborated by the numerical results, provides an implicit formula for the final spin of the merged black holes, accurate to within 10% over a large parameter space. Knowledge of the final spin allows one to predict the end of the inspiral phase and the quasinormal mode ring-down frequencies, and in turn provides information about the bandwidth and duration of the merger. In this work we will discuss a few of the implications of this calculation for data analysis.Comment: Added references to section 3 14 pages 5 figures. Submitted to Classical and Quantum Gravit

Elliptic and hyperelliptic magnetohydrodynamic equilibria

The present study is a continuation of a previous one on "hyperelliptic" axisymmetric equilibria started in [Tasso and Throumoulopoulos, Phys. Plasmas 5, 2378 (1998)]. Specifically, some equilibria with incompressible flow nonaligned with the magnetic field and restricted by appropriate side conditions like "isothermal" magnetic surfaces, "isodynamicity" or P + B^2/2 constant on magnetic surfaces are found to be reducible to elliptic integrals. The third class recovers recent equilibria found in [Schief, Phys. Plasmas 10, 2677 (2003)]. In contrast to field aligned flows, all solutions found here have nonzero toroidal magnetic field on and elliptic surfaces near the magnetic axis.Comment: 9 page