ABSTRACT
GRANDMA (Global Rapid Advanced Network Devoted to the Multi-messenger Addicts) is a network of 25 telescopes of different sizes, including both photometric and spectroscopic facilities. The ...network aims to coordinate follow-up observations of gravitational-wave (GW) candidate alerts, especially those with large localization uncertainties, to reduce the delay between the initial detection and the optical confirmation. In this paper, we detail GRANDMA’s observational performance during Advanced LIGO/Advanced Virgo Observing Run 3 (O3), focusing on the second part of O3; this includes summary statistics pertaining to coverage and possible astrophysical origin of the candidates. To do so, we quantify our observation efficiency in terms of delay between GW candidate trigger time, observations, and the total coverage. Using an optimized and robust coordination system, GRANDMA followed-up about 90 per cent of the GW candidate alerts, that is 49 out of 56 candidates. This led to coverage of over 9000 deg2 during O3. The delay between the GW candidate trigger and the first observation was below 1.5 h for 50 per cent of the alerts. We did not detect any electromagnetic counterparts to the GW candidates during O3, likely due to the very large localization areas (on average thousands of degrees squares) and relatively large distance of the candidates (above 200 Mpc for 60 per cent of binary neutron star, BNS candidates). We derive constraints on potential kilonova properties for two potential BNS coalescences (GW190425 and S200213t), assuming that the events’ locations were imaged.
We derive a Bayesian criterion for assessing whether signals observed in two separate data sets originate from a common source. The Bayes factor for a common versus unrelated origin of signals ...includes an overlap integral of the posterior distributions over the common-source parameters. Focusing on multimessenger gravitational-wave astronomy, we apply the method to the spatial and temporal association of independent gravitational-wave and electromagnetic (or neutrino) observations. As an example, we consider the coincidence between the recently discovered gravitational-wave signal GW170817 from a binary neutron star merger and the gamma-ray burst GRB 170817A: we find that the common-source model is enormously favored over a model describing them as unrelated signals.
The behavior of Ba1-xSrxTiO3 ceramics (x = 0, 0.3, 0.4 and 0.45) in both unpoled and poled states was studied using XRD, SEM, DSC and dielectric methods. The ceramics exhibit pure perovskite ...structure with tetragonal symmetry for x = 0, 0.3 and 0.4 and pseudocubic for x = 0.45. It was found that the substitution of SrTiO3 to BaTiO3 significantly influences the properties under investigation, leading to a shift of phase transitions and weakness of the dielectric and ferroelectric properties. This suggests that the effects are mainly due to the differences in ionic size between dopant and host ions and to the more covalent nature of the A–O bond following Sr2+ addition and that the former effect is predominant. It was shown that prior electric field poling decreases the disorder introduced by Sr modification through reinforced domains/polar regions ordering.
Beam alignment is an important practical aspect of the application of squeezed states of light. Misalignments in the detection of squeezed light result in a reduction of the observable squeezing ...level. In the case of squeezed vacuum fields that contain only very few photons, special measures must be taken in order to sense and control the alignment of the essentially dark beam. The GEO 600 gravitational wave detector employs a squeezed vacuum source to improve its detection sensitivity beyond the limits set by classical quantum shot noise. Here, we present our design and implementation of an alignment sensing and control scheme that ensures continuous optimal alignment of the squeezed vacuum field at GEO 600 on long time scales in the presence of free-swinging optics. This first demonstration of a squeezed light automatic alignment system will be of particular interest for future long-term applications of squeezed vacuum states of light.
An object's mental representation includes not just visible attributes but also its nonvisible history. The present studies tested whether preschoolers seek subtle indicators of an object's history, ...such as a mark acquired during its handling. Five studies with 169 children 3–5 years of age and 97 college students found that children (like adults) searched for concealed traces of object history, invisible traces of object history, and the absence of traces of object history, to successfully identify an owned object. Controls demonstrated that children (like adults) appropriately limit their search for hidden indicators when an owned object is visibly distinct. Altogether, these results demonstrate that concealed and invisible indicators of history are an important component of preschool children's object concepts.
•Does exploration prior to instruction impact what preschoolers teach a naïve learner?•No exploration leads to faithful transmission of what was taught.•Exploration reduces the transmission of taught ...information that is easy to discover.•Thus, children favor teaching what they could not discover on their own.
Across three studies (N=100), we explored whether and, if so, under what circumstances children’s self-discovered knowledge impacts their transmission of taught information. All participants were taught one of several methods for extracting rewards from a box. Half of the participants were also given an opportunity to discover their own method prior to receiving such instruction. Across studies, we varied the transparency of the taught method relative to the method children could discover on their own. When asked to teach a naive pupil about the box, children who did not explore the box always transmitted what they were taught. Children in the Exploration+Instruction condition were also likely to transmit what they had been taught, but they were especially likely to do so when the taught method was more opaque than the method they had discovered for themselves. Thus, children faithfully transmit what they have been taught, but only when that information is difficult to discover.
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