775 research outputs found

    The origin of variability of the intermediate-mass black-hole ULX system HLX-1 in ESO 243-49

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    The ultra-luminous intermediate-mass black-hole system HLX-1 in the ESO 243-49 galaxy exhibits variability with a possible recurrence time of a few hundred days. Finding the origin of this variability would constrain the still largely unknown properties of this extraordinary object. Since it exhibits an intensity-hardness behavior characteristic of black-hole X-ray transients, we have analyzed the variability of HLX-1 in the framework of the disk instability model that explains outbursts of such systems. We find that the long-term variability of HLX-1 is unlikely to be explained by a model in which outbursts are triggered by thermal-viscous instabilities in an accretion disc. Possible alternatives include the instability in a radiation-pressure dominated disk but we argue that a more likely explanation is a modulated mass-transfer due to tidal stripping of a star on an eccentric orbit around the intermediate-mass black hole. We consider an evolutionary scenario leading to the creation of such a system and estimate the probability of its observation. We conclude, using a simplified dynamical model of the post-collapse cluster, that no more than 1/100 to 1/10 of Mbh < 10^4 Msun IMBHs - formed by run-away stellar mergers in the dense collapsed cores of young clusters - could have a few times 1 Msun Main-Sequence star evolve to an AGB on an orbit eccentric enough for mass transfer at periapse, while avoiding collisional destruction or being scattered into the IMBH by 2-body encounters. The finite but low probability of this configuration is consistent with the uniqueness of HLX-1. We note, however, that the actual response of a standard accretion disk to bursts of mass transfer may be too slow to explain the observations unless the orbit is close to parabolic (and hence even rarer) and/or additional heating, presumably linked to the highly time-dependent gravitational potential, are invoked.Comment: 8 pages, 2 figures. Additional figure, extended discussion. To be published in ApJ, June 10, 2011, v734 -

    Applying an Anti-reflux Suture in the One Anastomosis Gastric Bypass to Prevent Biliary Reflux:a Long-Term Observational Study

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    INTRODUCTION: The one anastomosis gastric bypass (OAGB) is an effective treatment to induce sustained weight loss in morbidly obese patients. Concerns remain regarding the development of reflux. The aim of this study was to investigate the effect of an "anti-reflux suture" as anti-reflux modification to prevent reflux. METHOD: This is a single-center retrospective cohort study of patients who underwent a primary OAGB at the Center Obesity North-Netherlands (CON) between January 2015 and December 2016. Reflux was defined as symptoms of acid/bilious regurgitation or pyrosis. This was consequently asked and reported at each follow-up visit. Outcomes of patients with an anti-reflux suture were compared to those without. RESULTS: In 414 (59%) of the 703 included patients, an anti-reflux suture was applied. Follow-up at 3 years was 74%. The incidence of reflux did not differ between patients with or without an anti-reflux suture (57 versus 56%, respectively; P = 0.9). The presence of an anti-reflux suture was significantly associated with a lower incidence of conversion to Roux-en-Y gastric bypass (RYGB) for reflux (OR 0.56, 95%CI 0.34-0.91). Patients preoperatively diagnosed with gastroesophageal reflux disease (GERD) were 5.2 times more likely to need a conversion to RYGB for reflux (95%CI 2.7-10.1). CONCLUSION: The presence of preoperative GERD should be weighted heavily in the decision to perform an OAGB as this is a major risk factor for conversion surgery due to reflux. The anti-reflux suture might be a valuable addition to the procedure of the OAGB because it results in fewer conversion surgeries for reflux

    A Search for Charmless BVVB\to VV Decays

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    We have studied two-body charmless decays of the BB meson into the final states ρ0ρ0\rho^0 \rho^0, K0ρ0K^{*0} \rho^0, K0K0K^{*0} K^{*0}, K0K0ˉK^{*0} \bar{K^{*0}}, K+ρ0K^{*+} \rho^0, K+K0ˉK^{*+} \bar{K^{*0}}, and K+KK^{*+} K^{*-} using only decay modes with charged daughter particles. Using 9.7 million BBˉB \bar{B} pairs collected with the CLEO detector, we place 90% confidence level upper limits on the branching fractions, (0.467.0)×105(0.46-7.0)\times 10^{-5}, depending on final state and polarization.Comment: 8 pages postscript, also available through http://w4.lns.cornell.edu/public/CLN

    Correlated /\c-/\cbar production in e+e- annihilations at sqrt{s}~10.5 GeV

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    Using 13.6/fb of continuum two-jet e+e- -> ccbar events collected with the CLEO detector, we have searched for baryon number correlations at the primary quark level. We have measured the likelihood for a /\c+ charmed baryon to be produced in the hemisphere opposite a /\c- relative to the likelihood for a /\c+ charmed baryon to be produced opposite an anticharmed meson Dbar; in all cases, the reconstructed hadrons must have momentum greater than 2.3 GeV/c. We find that, given a /\c- (reconstructed in five different decay modes), a /\c+ is observed in the opposite hemisphere (0.72+/-0.11)% of the time (not corrected for efficiency). By contrast, given a Dbar in one hemisphere, a /\c+ is observed in the opposite hemisphere only (0.21+/-0.02)% of the time. Normalized to the total number of either /\c- or Dbar ``tags'', it is therefore 3.52+/-0.45+/-0.42 times more likely to find a /\c+ opposite a /\c- than a Dbar meson. This enhancement is not observed in the JETSET 7.3 e+e- -> ccbar Monte Carlo simulation.Comment: 19 pages, Latex, one figure separat

    Extreme Mass Ratio Inspirals: LISA's unique probe of black hole gravity

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    In this review article I attempt to summarise past and present-ongoing-work on the problem of the inspiral of a small body in the gravitational field of a much more massive Kerr black hole. Such extreme mass ratio systems, expected to occur in galactic nuclei, will constitute prime sources of gravitational radiation for the future LISA gravitational radiation detector. The article's main goal is to provide a survey of basic celestial mechanics in Kerr spacetime and calculations of gravitational waveforms and backreaction on the small body's orbital motion, based on the traditional `flux-balance' method and the Teukolsky black hole perturbation formalism.Comment: Invited review article, 45 pages, 23 figure

    Hadronic Structure in the Decay τππ0ντ\tau^{-}\to \pi^{-}\pi^{0}\nu_{\tau}

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    We report on a study of the invariant mass spectrum of the hadronic system in the decay tau- -> pi- pi0 nu_tau. This study was performed with data obtained with the CLEO II detector operating at the CESR e+ e- collider. We present fits to phenomenological models in which resonance parameters associated with the rho(770) and rho(1450) mesons are determined. The pi- pi0 spectral function inferred from the invariant mass spectrum is compared with data on e+ e- -> pi+ pi- as a test of the Conserved Vector Current theorem. We also discuss the implications of our data with regard to estimates of the hadronic contribution to the muon anomalous magnetic moment.Comment: 39 pages postscript, also available through http://w4.lns.cornell.edu/public/CLN

    Search for a Scalar Bottom Quark with Mass 3.5-4.5 GeV/c2c^{2}

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    We report on a search for a supersymmetric B~\tilde{B} meson with mass between 3.5 and 4.5 GeV/c2c^2 using 4.52 fb1{\rm fb}^{-1} of integrated luminosity produced at s=10.52\sqrt{s}=10.52 GeV, just below the e+eBBˉe^+e^-\to B\bar{B} threshold, and collected with the CLEO detector. We find no evidence for a light scalar bottom quark.Comment: 10 pages postscript, also available through http://w4.lns.cornell.edu/public/CLN

    Measurement of Charge Asymmetries in Charmless Hadronic in B Meson Decays

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    We search for CP-violating asymmetries (Acp) in the B meson decays to K+- pi-+, K+- pi0, Ks pi+-, K+- eta', and omega pi+-. Using 9.66 million Upsilon(4S) decays collected with the CLEO detector, the statistical precision on Acp is in the range of \pm 0.12 to \pm 0.25 depending on decay mode. While CP-violating asymmetries of up to \pm 0.5 are possible within the Standard Model, the measured asymmetries are consistent with zero in all five decay modes studied.Comment: 10 pages, 3 figure
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