Robust vetoes for gravitational-wave burst triggers using known instrumental couplings

The search for signatures of transient, unmodelled gravitational-wave (GW) bursts in the data of ground-based interferometric detectors typically uses `excess-power' search methods. One of the most challenging problems in the burst-data-analysis is to distinguish between actual GW bursts and spurious noise transients that trigger the detection algorithms. In this paper, we present a unique and robust strategy to `veto' the instrumental glitches. This method makes use of the phenomenological understanding of the coupling of different detector sub-systems to the main detector output. The main idea behind this method is that the noise at the detector output (channel H) can be projected into two orthogonal directions in the Fourier space -- along, and orthogonal to, the direction in which the noise in an instrumental channel X would couple into H. If a noise transient in the detector output originates from channel X, it leaves the statistics of the noise-component of H orthogonal to X unchanged, which can be verified by a statistical hypothesis testing. This strategy is demonstrated by doing software injections in simulated Gaussian noise. We also formulate a less-rigorous, but computationally inexpensive alternative to the above method. Here, the parameters of the triggers in channel X are compared to the parameters of the triggers in channel H to see whether a trigger in channel H can be `explained' by a trigger in channel X and the measured transfer function.Comment: 14 Pages, 8 Figures, To appear in Class. Quantum Gra

Thermodynamic Geometry of black hole in the deformed Horava-Lifshitz gravity

We investigate the thermodynamic geometry and phase transition of Kehagias-Sfetsos black hole in the deformed Horava-Lifshitz gravity with coupling constant $\lambda=1$. The phase transition in black hole thermodynamics is thought to be associated with the divergence of the capacities. And the structures of these divergent points are studied. We also find that the thermodynamic curvature produced by the Ruppeiner metric is positive definite for all $r_+ > r_-$ and is divergence at $\eta_2=0$ corresponded to the divergent points of $C_{\Phi}$ and $C_T$. These results suggest that the microstructure of the black hole has an effective repulsive interaction, which is very similar to the ideal gas of fermions. These may shine some light on the microstructure of the black hole.Comment: 5 pages, 3 figure

Initial operation of the International Gravitational Event Collaboration

The International Gravitational Event Collaboration, IGEC, is a coordinated effort by research groups operating gravitational wave detectors working towards the detection of millisecond bursts of gravitational waves. Here we report on the current IGEC resonant bar observatory, its data analysis procedures, the main properties of the first exchanged data set. Even though the available data set is not complete, in the years 1997 and 1998 up to four detectors were operating simultaneously. Preliminary results are mentioned.Comment: 8 pages, 2 figures, 3 tables; Proceeding of the GWDAW'99. Submitted to the International Journal of Modern Physic

Cone-beam CT reconstruction with gravity-induced motion.

Fixed-gantry cone-beam computed tomography (CBCT), where the imaging hardware is fixed while the subject is continuously rotated 360° in the horizontal position, has implications for building compact and affordable fixed-gantry linear accelerators (linacs). Fixed-gantry imaging with a rotating subject presents a challenging image reconstruction problem where the gravity-induced motion is coupled to the subject's rotation angle. This study is the first to investigate the feasibility of fixed-gantry CBCT using imaging data of three live rabbits in an ethics-approved study. A novel data-driven motion correction method that combines partial-view reconstruction and motion compensation was developed to overcome this challenge. Fixed-gantry CBCT scans of three live rabbits were acquired on a standard radiotherapy system with the imaging beam fixed and the rabbits continuously rotated using an in-house programmable rotation cradle. The reconstructed images of the thoracic region were validated against conventional CBCT scans acquired at different cradle rotation angles. Results showed that gravity-induced motion caused severe motion blur in all of the cases if unaccounted for. The proposed motion correction method yielded clinically usable image quality with  <1 mm gravity-induced motion blur for rabbits that were securely immobilized on the rotation cradle. Shapes of the anatomic structures were correctly reconstructed with  <0.5 mm accuracy. Translational motion accounted for the majority of gravity-induced motion. The motion-corrected reconstruction represented the time-averaged location of the thoracic region over a 360° rotation. The feasibility of fixed-gantry CBCT has been demonstrated. Future work involves the validation of imaging accuracy for human subjects, which will be useful for emerging compact fixed-gantry radiotherapy systems

Three-dimensional distribution of ejecta in Supernova 1987A at 10 000 days

Due to its proximity, SN 1987A offers a unique opportunity to directly observe the geometry of a stellar explosion as it unfolds. Here we present spectral and imaging observations of SN 1987A obtained ~10,000 days after the explosion with HST/STIS and VLT/SINFONI at optical and near-infrared wavelengths. These observations allow us to produce the most detailed 3D map of H-alpha to date, the first 3D maps for [Ca II] \lambda \lambda 7292, 7324, [O I] \lambda \lambda 6300, 6364 and Mg II \lambda \lambda 9218, 9244, as well as new maps for [Si I]+[Fe II] 1.644 \mu m and He I 2.058 \mu m. A comparison with previous observations shows that the [Si I]+[Fe II] flux and morphology have not changed significantly during the past ten years, providing evidence that it is powered by 44Ti. The time-evolution of H-alpha shows that it is predominantly powered by X-rays from the ring, in agreement with previous findings. All lines that have sufficient signal show a similar large-scale 3D structure, with a north-south asymmetry that resembles a broken dipole. This structure correlates with early observations of asymmetries, showing that there is a global asymmetry that extends from the inner core to the outer envelope. On smaller scales, the two brightest lines, H-alpha and [Si I]+[Fe II] 1.644 \mu m, show substructures at the level of ~ 200 - 1000 km/s and clear differences in their 3D geometries. We discuss these results in the context of explosion models and the properties of dust in the ejecta.Comment: Accepted for publication in Ap

Stochastic Background Search Correlating ALLEGRO with LIGO Engineering Data

We describe the role of correlation measurements between the LIGO interferometer in Livingston, LA, and the ALLEGRO resonant bar detector in Baton Rouge, LA, in searches for a stochastic background of gravitational waves. Such measurements provide a valuable complement to correlations between interferometers at the two LIGO sites, since they are sensitive in a different, higher, frequency band. Additionally, the variable orientation of the ALLEGRO detector provides a means to distinguish gravitational wave correlations from correlated environmental noise. We describe the analysis underway to set a limit on the strength of a stochastic background at frequencies near 900 Hz using ALLEGRO data and data from LIGO's E7 Engineering Run.Comment: 8 pages, 2 encapsulated PostScript figures, uses IOP class files, submitted to the proceedings of the 7th Gravitational Wave Data Analysis Workshop (which will be published in Classical and Quantum Gravity

A spectral survey of an ultra-hot Jupiter: Detection of metals in the transmission spectrum of KELT-9 b

Context: KELT-9 b exemplifies a newly emerging class of short-period gaseous exoplanets that tend to orbit hot, early type stars - termed ultra-hot Jupiters. The severe stellar irradiation heats their atmospheres to temperatures of $\sim 4,000$ K, similar to the photospheres of dwarf stars. Due to the absence of aerosols and complex molecular chemistry at such temperatures, these planets offer the potential of detailed chemical characterisation through transit and day-side spectroscopy. Studies of their chemical inventories may provide crucial constraints on their formation process and evolution history. Aims: To search the optical transmission spectrum of KELT-9 b for absorption lines by metals using the cross-correlation technique. Methods: We analyse 2 transits observed with the HARPS-N spectrograph. We use an isothermal equilibrium chemistry model to predict the transmission spectrum for each of the neutral and singly-ionized atoms with atomic numbers between 3 and 78. Of these, we identify the elements that are expected to have spectral lines in the visible wavelength range and use those as cross-correlation templates. Results: We detect absorption of Na I, Cr II, Sc II and Y II, and confirm previous detections of Mg I, Fe I, Fe II and Ti II. In addition, we find evidence of Ca I, Cr I, Co I, and Sr II that will require further observations to verify. The detected absorption lines are significantly deeper than model predictions, suggesting that material is transported to higher altitudes where the density is enhanced compared to a hydrostatic profile. There appears to be no significant blue-shift of the absorption spectrum due to a net day-to-night side wind. In particular, the strong Fe II feature is shifted by $0.18 \pm 0.27$ km~s$^{-1}$, consistent with zero. Using the orbital velocity of the planet we revise the steller and planetary masses and radii.Comment: Submitted to Astronomy and Astrophysics on January 18, 2019. Accepted on May 3, 2019. 26 pages, 11 figure

Advanced heart failure in adult congenital heart disease: the role of renal dysfunction in management and outcomes

Aims Previous studies in adult congenital heart disease (CHD) have demonstrated a link between renal dysfunction and mortality. However, the prognostic significance of renal dysfunction in CHD and decompensated heart failure (HF) remains unclear. We sought to assess the association between renal dysfunction and outcomes in adults with CHD presenting to our centre with acute HF between 2010 and 2021. Methods and results This retrospective analysis focused on the association between renal dysfunction, pre-existing and on admission, and outcomes during and after the index hospitalization. Chronic kidney disease (CKD) was defined as an estimated glomerular filtration rate <60 mL/min/1.73 m2. Cox regression analysis was used to identify the predictors of death post-discharge. In total, 176 HF admissions were included (mean age 47.7 ± 14.5 years, 43.2% females). One-half of patients had a CHD of great complexity, 22.2% had a systemic right ventricle, and 18.8% had Eisenmenger syndrome. Chronic kidney disease was present in one-quarter of patients. The median length of intravenous diuretic therapy was 7 (4–12) days, with a maximum dose of 120 (80–160) mg furosemide equivalents/day, and 15.3% required inotropic support. The in-hospital mortality rate was 4.5%. The 1- and 5-year survival rates free of transplant or ventricular assist device (VAD) post-discharge were 75.4% [95% confidence interval (CI): 69.2–82.3%] and 43.3% (95% CI: 36–52%), respectively. On multivariable Cox analysis, CKD was the strongest predictor of mortality or transplantation/VAD. Highly complex CHD and inpatient requirement of inotropes also remained predictive of an adverse outcome. Conclusion Adult patients with CHD admitted with acute HF are a high-risk cohort. CKD is common and triples the risk of death/transplantation/VAD. An expert multidisciplinary approach is essential for optimizing outcomes

Towards the fabrication of phosphorus qubits for a silicon quantum computer

The quest to build a quantum computer has been inspired by the recognition of the formidable computational power such a device could offer. In particular silicon-based proposals, using the nuclear or electron spin of dopants as qubits, are attractive due to the long spin relaxation times involved, their scalability, and the ease of integration with existing silicon technology. Fabrication of such devices however requires atomic scale manipulation - an immense technological challenge. We demonstrate that it is possible to fabricate an atomically-precise linear array of single phosphorus bearing molecules on a silicon surface with the required dimensions for the fabrication of a silicon-based quantum computer. We also discuss strategies for the encapsulation of these phosphorus atoms by subsequent silicon crystal growth.Comment: To Appear in Phys. Rev. B Rapid Comm. 5 pages, 5 color figure