26 research outputs found
Low-latency gravitational wave alert products and their performance in anticipation of the fourth LIGO-Virgo-KAGRA observing run
Multi-messenger searches for binary neutron star (BNS) and neutron star-black
hole (NSBH) mergers are currently one of the most exciting areas of astronomy.
The search for joint electromagnetic and neutrino counterparts to gravitational
wave (GW)s has resumed with Advanced LIGO (aLIGO)'s, Advanced Virgo (AdVirgo)'s
and KAGRA's fourth observing run (O4). To support this effort, public
semi-automated data products are sent in near real-time and include
localization and source properties to guide complementary observations.
Subsequent refinements, as and when available, are also relayed as updates. In
preparation for O4, we have conducted a study using a simulated population of
compact binaries and a Mock Data Challenge (MDC) in the form of a real-time
replay to optimize and profile the software infrastructure and scientific
deliverables. End-to-end performance was tested, including data ingestion,
running online search pipelines, performing annotations, and issuing alerts to
the astrophysics community. In this paper, we present an overview of the
low-latency infrastructure as well as an overview of the performance of the
data products to be released during O4 based on a MDC. We report on expected
median latencies for the preliminary alert of full bandwidth searches (29.5 s)
and for the creation of early warning triggers (-3.1 s), and show consistency
and accuracy of released data products using the MDC. This paper provides a
performance overview for LVK low-latency alert structure and data products
using the MDC in anticipation of O4
Allocation, stress tolerance and carbon transport in plants: How does phloem physiology affect plant ecology?
Despite the crucial role of carbon transport in whole plant physiology and its impact on plant-environment interactions and ecosystem function, relatively little research has tried to examine how phloem physiology impacts plant ecology. In this review, we highlight several areas of active research where inquiry into phloem physiology has increased our understanding of whole plant function and ecological processes. We consider how xylem-phloem interactions impact plant drought tolerance and reproduction, how phloem transport influences carbon allocation in trees and carbon cycling in ecosystems, and how phloem function mediates plant relations with insects, pests, microbes and symbiotes. We argue that in spite of challenges that exist in studying phloem physiology, it is critical that we consider the role of this dynamic vascular system when examining the relationship between plants and their biotic and abiotic environment
Harmful Elements in Estuarine and Coastal Systems
Estuaries and coastal zones are dynamic transitional systems which provide many economic and ecological benefits to humans, but also are an ideal habitat for other organisms as well. These areas are becoming contaminated by various anthropogenic activities due to a quick economic growth and urbanization. This chapter explores the sources, chemical speciation, sediment accumulation and removal mechanisms of the harmful elements in estuarine and coastal seawaters. It also describes the effects of toxic elements on aquatic flora and fauna. Finally, the toxic element pollution of the Venice Lagoon, a transitional water body located in the northeastern part of Italy, is discussed as a case study, by presenting the procedures adopted to measure the extent of the pollution, the impacts on organisms and the restoration activities
Graphics processing unit implementation of the F-statistic for continuous gravitational wave searches
The -statistic is a detection statistic used widely in searches
for continuous gravitational waves with terrestrial, long-baseline
interferometers. A new implementation of the -statistic is
presented which accelerates the existing "resampling" algorithm using graphics
processing units (GPUs). The new implementation runs between 10 and 100 times
faster than the existing implementation on central processing units without
sacrificing numerical accuracy. The utility of the GPU implementation is
demonstrated on a pilot narrowband search for four newly discovered millisecond
pulsars in the globular cluster Omega Centauri using data from the second Laser
Interferometer Gravitational-Wave Observatory observing run. The computational
cost is GPU-hours using the new implementation, compared to 1092
core-hours with the existing implementation.Comment: Accepted for publication in Classical and Quantum Gravity. 19 pages,
4 figure
Validating continuous gravitational-wave candidates from a semicoherent search using Doppler modulation and an effective point spread function
Following up large numbers of candidates in continuous gravitational wave
searches presents a challenge, particularly in regard to computational power
and the time required to manually scrutinize each of the candidates. It is
important to design and test good follow-up procedures that are safe (i.e.,
minimize false dismissals) and computationally efficient across many search
configurations. We investigate two follow-up procedures, or "vetoes," both of
which exploit the Doppler modulation predicted in astrophysical signals. In
particular, we introduce the concept of using an effective point spread
function as part of our veto criteria. We take advantage of a well-established
semicoherent search algorithm based on a hidden Markov model to study various
search configurations and to generalize the veto criteria by considering the
overall veto performance in terms of efficiency and safety. The results can
serve as a guideline for follow-up studies in future continuous gravitational
wave searches using a hidden Markov model algorithm. The results also apply
qualitatively to other semicoherent search algorithms.Comment: 24 pages, 15 figure
First demonstration of early warning gravitational wave alerts
International audienceGravitational-wave observations became commonplace in Advanced LIGO-Virgo’s recently concluded third observing run. 56 nonretracted candidates were identified and publicly announced in near real time. Gravitational waves from binary neutron star mergers, however, remain of special interest since they can be precursors to high-energy astrophysical phenomena like γ-ray bursts and kilonovae. While late-time electromagnetic emissions provide important information about the astrophysical processes within, the prompt emission along with gravitational waves uniquely reveals the extreme matter and gravity during—and in the seconds following—merger. Rapid communication of source location and properties from the gravitational-wave data is crucial to facilitate multimessenger follow-up of such sources. This is especially enabled if the partner facilities are forewarned via an early warning (pre-merger) alert. Here we describe the commissioning and performance of such a low-latency infrastructure within LIGO-Virgo. We present results from an end-to-end mock data challenge that detects binary neutron star mergers and alerts partner facilities before merger. We set expectations for these alerts in future observing runs