Search for gravitational waves from Scorpius X-1 in the second Advanced LIGO observing run with an improved hidden Markov model

We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO's second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h095%=3.47×10-25 when marginalizing over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering. © 2019 American Physical Society

Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω0T<5.58×10-8, Ω0V<6.35×10-8, and Ω0S<1.08×10-7 at a reference frequency f0=25 Hz. © 2018 American Physical Society

On the progenitor of binary neutron star merger GW170817

On 2017 August 17 the merger of two compact objects with masses consistent with two neutron stars was discovered through gravitational-wave (GW170817), gamma-ray (GRB 170817A), and optical (SSS17a/AT 2017gfo) observations. The optical source was associated with the early-type galaxy NGC 4993 at a distance of just ∼40 Mpc, consistent with the gravitational-wave measurement, and the merger was localized to be at a projected distance of ∼2 kpc away from the galaxy's center. We use this minimal set of facts and the mass posteriors of the two neutron stars to derive the first constraints on the progenitor of GW170817 at the time of the second supernova (SN). We generate simulated progenitor populations and follow the three-dimensional kinematic evolution from binary neutron star (BNS) birth to the merger time, accounting for pre-SN galactic motion, for considerably different input distributions of the progenitor mass, pre-SN semimajor axis, and SN-kick velocity. Though not considerably tight, we find these constraints to be comparable to those for Galactic BNS progenitors. The derived constraints are very strongly influenced by the requirement of keeping the binary bound after the second SN and having the merger occur relatively close to the center of the galaxy. These constraints are insensitive to the galaxy's star formation history, provided the stellar populations are older than 1 Gyr

Measuring the perceived impact of facilitation on implementing recommendations from external assessment: lessons from the Dutch visitatie programme for medical specialists

Objective To evaluate the impact of facilitation by management consultants on implementing recommendations from external quality assessment (visitatie). Design Data collection through a postal survey amongst 205 medical specialists, representing 50 hospital-based specialist groups in the Netherlands. Setting Under the auspices of the specialty societies of surgeons, paediatricians and gynaecologists, 25 groups were offered similar to 20 h of management consulting to support the implementation of recommendations for quality improvement and were compared to 25 specialist groups not receiving the support. Intervention The Quality Consultation (QC) took a site-specific multifaceted implementation approach. Main measures Self-reported degree of implementation of recommendations, specialists' judgement of implementation result and process; experienced obstructing factors in implementing recommendations. Results The response rate was 54% (n = 110). The supported specialist groups were more successful in partially or fully implementing the recommendations from external peer assessment: 66.1% vs. 53.8%. The implementation result and process were also rated significantly higher for the supported groups. The supported groups reported significantly less (P <0.005) obstructing factors; in particular for the barriers 'expectation of implementation advantages', 'acceptance of the recommendations' and 'assessed self-efficacy'. The experienced obstructing factors are strongly related with the degree of implementation (spearman rho 0.57-32.5%). Conclusions This study suggests QC is a powerful implementation strategy. It also shows the limitations of merely quantitatively analysing multifaceted strategies: it does not offer any insight into the 'black box' of the QC. It is recommended that these limitations are met by also exploring multifaceted strategies qualitativel