The PyCBC search for gravitational waves from compact binary coalescence

We describe the PyCBC search for gravitational waves from compact-object binary coalescences in advanced gravitational-wave detector data. The search was used in the first Advanced LIGO observing run and unambiguously identified two black hole binary mergers, GW150914 and GW151226. At its core, the PyCBC search performs a matched-filter search for binary merger signals using a bank of gravitational-wave template waveforms. We provide a complete description of the search pipeline including the steps used to mitigate the effects of noise transients in the data, identify candidate events and measure their statistical significance. The analysis is able to measure false-alarm rates as low as one per million years, required for confident detection of signals. Using data from initial LIGO's sixth science run, we show that the new analysis reduces the background noise in the search, giving a 30% increase in sensitive volume for binary neutron star systems over previous searches.Comment: 29 pages, 7 figures, accepted by Classical and Quantum Gravit

Discovery and characterization of small molecules that target the Ral GTPase

The Ras-like GTPases RalA and B are important drivers of tumor growth and metastasis. Chemicals that block Ral function would be valuable as research tools and for cancer therapeutics. Here, we used protein structure analysis and virtual screening to identify drug-like molecules that bind a site on the GDP-form of Ral. Compounds RBC6, RBC8 and RBC10 inhibited Ral binding to its effector RalBP1, Ral-mediated cell spreading in murine fibroblasts and anchorage-independent growth of human cancer cell lines. Binding of RBC8 derivative BQU57 to RalB was confirmed by isothermal titration calorimetry, surface plasma resonance and 15N-HSQC NMR. RBC8 and BQU57 show selectivity for Ral relative to Ras or Rho and inhibit xenograft tumor growth similar to depletion of Ral by siRNA. Our results show the utility of structure-based discovery for development of therapeutics for Ral-dependent cancers

Characterizing Gravitational Wave Detector Networks: From A♯^\sharp to Cosmic Explorer

Gravitational-wave observations by the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo have provided us a new tool to explore the universe on all scales from nuclear physics to the cosmos and have the massive potential to further impact fundamental physics, astrophysics, and cosmology for decades to come. In this paper we have studied the science capabilities of a network of LIGO detectors when they reach their best possible sensitivity, called A#, and a new generation of observatories that are factor of 10 to 100 times more sensitive (depending on the frequency), in particular a pair of L-shaped Cosmic Explorer observatories (one 40 km and one 20 km arm length) in the US and the triangular Einstein Telescope with 10 km arms in Europe. We use a set of science metrics derived from the top priorities of several funding agencies to characterize the science capabilities of different networks. The presence of one or two A# observatories in a network containing two or one next generation observatories, respectively, will provide good localization capabilities for facilitating multimessenger astronomy and precision measurement of the Hubble parameter. A network of two Cosmic Explorer observatories and the Einstein Telescope is critical for accomplishing all the identified science metrics including the nuclear equation of state, cosmological parameters, growth of black holes through cosmic history, and make new discoveries such as the presence of dark matter within or around neutron stars and black holes, continuous gravitational waves from rotating neutron stars, transient signals from supernovae, and the production of stellar-mass black holes in the early universe. For most metrics the triple network of next generation terrestrial observatories are a factor 100 better than what can be accomplished by a network of three A# observatories.Comment: 45 pages, 20 figure

Search of the Orion spur for continuous gravitational waves using a loosely coherent algorithm on data from LIGO interferometers

We report results of a wideband search for periodic gravitational waves from isolated neutron stars within the Orion spur towards both the inner and outer regions of our Galaxy. As gravitational waves interact very weakly with matter, the search is unimpeded by dust and concentrations of stars. One search disk (A) is 6.87° in diameter and centered on 20h10m54.71s+33°33′25.29′′, and the other (B) is 7.45° in diameter and centered on 8h35m20.61s-46°49′25.151′′. We explored the frequency range of 50-1500 Hz and frequency derivative from 0 to -5×10-9 Hz/s. A multistage, loosely coherent search program allowed probing more deeply than before in these two regions, while increasing coherence length with every stage. Rigorous follow-up parameters have winnowed the initial coincidence set to only 70 candidates, to be examined manually. None of those 70 candidates proved to be consistent with an isolated gravitational-wave emitter, and 95% confidence level upper limits were placed on continuous-wave strain amplitudes. Near 169 Hz we achieve our lowest 95% C.L. upper limit on the worst-case linearly polarized strain amplitude h0 of 6.3×10-25, while at the high end of our frequency range we achieve a worst-case upper limit of 3.4×10-24 for all polarizations and sky locations. © 2016 American Physical Society

Improving the photon sensitivity of the Pierre Auger Observatory with the AugerPrime Radio Detector

The AugerPrime upgrade represents a significant enhancement in the capability of the Pierre Auger Observatory to detect air showers. Central to this advancement is the installation of a radio antenna atop each existing Surface Detector station, constituting the Radio Detector (RD). The RD enhances the sensitivity of the Surface Detector to the electromagnetic component of air showers. Hence, the new detector presents an opportunity for the discovery of rare particles such as ultra-high-energy photons. This contribution shows the development efforts towards an RD trigger with focus on the detection of rare particles. The radio trigger designed for the detection of photon-induced events will be outlined, and the challenge of a radio background consisting of human-made noise is discussed. The trigger efficiency and reconstruction accuracy are studied with simulations. The presentation will conclude by summarizing the effectiveness of the new detector component

Anisotropy studies of ultra-high-energy cosmic rays measured at the Pierre Auger Observatory

Measurements of anisotropic arrival directions of ultra-high-energy cosmic rays provide important information for identifying their sources. On large scales, cosmic rays with energies above 8 EeV reveal a dipolar flux modulation in right ascension with a significance of 6.9σ, with the dipole direction pointing 113◦ away from the Galactic center. This observation is explained by extragalactic origins. Also, model-independent searches for small- and intermediate-scale overdensities have been performed in order to unveil astrophysically interesting regions. On these scales, no statistically significant features could be detected. However, intermediate-scale analyses comparing the measured arrival directions with potential source catalogs show indications for a coincidence of the measured arrival directions with catalogs of starburst galaxies and the Centaurus A region. In this contribution, an overview of the studies regarding anisotropies of the arrival directions of ultra-high-energy cosmic rays measured at the Pierre Auger Observatory on different angular scales is presented and the current results are discussed

Towards a Cosmic-Ray Energy Scale with the Auger Engineering Radio Array

Radio detection of cosmic-ray (CR) induced extensive air showers with digital antenna arrays is a matured technique by now. At the Pierre Auger Observatory, the Auger Engineering Radio Array (AERA) has been measuring air-shower signals in conjunction with the particle detectors of the surface detector (SD) for over ten years. For an absolute determination of the CR energy with the Auger baseline detectors, the shower size estimator from the SD is calibrated with the energy scale of the fluorescence detector (FD). However, AERA has an independent access to the energy scale through the reconstructed radio signals. The hybrid detectors at the Pierre Auger Observatory offer the unique opportunity to compare the two independent energy scales. In this contribution, we present our envisaged methodology for cross-checking the agreement between the energy scales of the FD and AERA using hybrid SD-AERA shower data and simulations. We show individual steps of our radio signal reconstruction and highlight the key ingredients for calibrated energy measurements

Drone-based calibration of AugerPrime radio antennas at the Pierre Auger Observatory

Radio emissions of extensive air showers can be observed at the Pierre Auger Observatory with the AugerPrime Radio Detector (RD). As part of the AugerPrime upgrade, RD is being installed on 1660 water-Cherenkov detectors on an area of about 3000 km2 and consists of dual-polarized Short Aperiodic Loaded Loop Antennas (SALLA). To achieve high measurement precision, RD needs to be well-calibrated, which requires the antenna response pattern to be well-known. We introduce a method to measure the directional response of the SALLA using a well-defined biconical antenna mounted to a drone. The drone-based setup possesses active stabilization and precise pointing with the use of a gimbal. Additionally, the drone’s position is tracked using differential GPS with O(cm) precision. This setup allows us to precisely extract the antenna response pattern from any direction in the frequency range of 30 − 80 MHz. In a recent in-situ campaign, calibration measurements of the AugerPrime radio detector have been performed. First results of these measurements are presented and compared to simulations

Astrophysical interpretation of energy spectrum and mass composition of cosmic rays as measured at the Pierre Auger Observatory

The combined interpretation of the spectrum and composition measurements plays a key role in the quest for the origin of ultra-high-energy cosmic rays (UHECRs). The Pierre Auger Observatory, thanks to its huge exposure, provides the most precise measurement of the energy spectrum of UHECRs and the most reliable information on their composition, exploiting the distributions of the depth of maximum of the showers in the atmosphere. A combined fit of a simple astrophysical model of UHECR sources to the spectrum and mass composition measurements is used to evaluate the constraining power of the data measured by the Pierre Auger Observatory on the source properties. We find that our data across the “ankle” feature are well reproduced if two extragalactic populations of sources are considered, one emitting a very soft spectrum which dominates the region below the ankle, and the other taking over at energies above the ankle, with an intermediate mixed composition, a hard spectrum and a low rigidity cutoff. Interestingly, similar results can also be obtained if the medium-mass contribution at lower energy is provided by an additional galactic component