Open data from the third observing run of LIGO, Virgo, KAGRA, and GEO

The global network of gravitational-wave observatories now includes five detectors, namely LIGO Hanford, LIGO Livingston, Virgo, KAGRA, and GEO 600. These detectors collected data during their third observing run, O3, composed of three phases: O3a starting in 2019 April and lasting six months, O3b starting in 2019 November and lasting five months, and O3GK starting in 2020 April and lasting two weeks. In this paper we describe these data and various other science products that can be freely accessed through the Gravitational Wave Open Science Center at https://gwosc.org. The main data set, consisting of the gravitational-wave strain time series that contains the astrophysical signals, is released together with supporting data useful for their analysis and documentation, tutorials, as well as analysis software packages

SPEAR Coilgun

The SPEAR, a development in coilgun technology, passively launches a projectile with a solenoidally wound armature. This paper describes the SPEAR, its electromagnetic operation, its construction, and the tests performed to prove its principle. It describes the composite stator sections and the glass reinforced armature coils. It describes how engineers at CEM-UT overcame the problem of keeping solid state switch volume low by employing a modular switch design with a unique snubbing circuit that reduces required volume. Results of test #5, described in the paper, show how well the operation of the SPEAR matches the computer simulation predictions. Conceptually, the proximity of the approaching armature electromagnetically drives a stator coil's current through zero. At zero crossing the stator freewheel switch turns off, preventing reestablishment of stator current as the armature moves away. As originally designed, the gun was to accelerate a 2 kg package to 2000 m/s. The part built is expected to achieve 1000 m/s with a 0.75 kg package.Center for Electromechanic

It's not all black and white: Investigating colour polymorphism in manta rays across Indo-Pacific populations

Intraspecific colour polymorphisms have been the focus of numerous studies, yet processes affecting melanism in the marine environment remain poorly understood. Arguably, the most prominent example of melanism in marine species occurs in manta rays (Mobula birostris and Mobula alfredi). Here, we use long-term photo identification catalogues to document the frequency variation of melanism across Indo-Pacific manta ray populations and test for evidence of selection by predation acting on colour morph variants. We use mark–recapture modelling to compare survivorship of typical and melanistic colour morphs in three M. alfredi populations and assess the relationship between frequency variation and geographical distance. While there were large differences in melanism frequencies among populations of both species (0–40.70%), apparent survival estimates revealed no difference in survivorship between colour morphs. We found a significant association between phenotypic and geographical distance in M. birostris, but not in M. alfredi. Our results suggest that melanism is not under selection by predation in the tested M. alfredi populations, and that frequency differences across populations of both species are a consequence of neutral genetic processes. As genetic colour polymorphisms are often subjected to complex selection mechanisms, our findings only begin to elucidate the underlying evolutionary processes responsible for the maintenance and frequency variation of melanism in manta ray populations