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Abstract We present timing solutions spanning nearly two decades for five redback (RB) systems found in globular clusters (GCs), created using a novel technique that effectively “isolates” the pulsar. By accurately measuring the time of passage through periastron (T₀) at points over the timing baseline, we use a piecewise-continuous binary model to get local solutions of the orbital variations that we pair with long-term orbital information to remove the orbital timing delays. The isolated pulse times of arrival can then be fit to describe the spin behavior of the millisecond pulsar (MSP). The results of our timing analyses via this method are consistent with those of conventional timing methods for binaries in GCs as demonstrated by analyses of NGC 6440D. We also investigate the observed orbital phase variations for these systems. Quasiperiodic oscillations in Terzan 5P’s orbit may be the result of changes to the gravitational quadruple moment of the companion as prescribed by the Applegate model. We find a striking correlation between the standard deviation of the phase variations as a fraction of a system’s orbit ( ${\sigma }_{\mathrm{\Delta }{T}_0}$) and the MSP’s spin frequency, as well as a potential correlation between ${\sigma }_{\mathrm{\Delta }{T}_0}$and the binary’s projected semimajor axis. While long-term RB timing is fraught with large systematics, our work provides a needed alternative for studying systems with significant orbital variations, especially when high-cadence monitoring observations are unavailable. 

Abstract We explore possible advantages of cyclic spectroscopy for observations of pulsars in instances where full cyclic deconvolution is not possible. We compute cyclic merits and full-deconvolution regime boundaries for pulsars observed by NANOGrav and discuss which sources stand to benefit the most from using cyclic spectroscopy when observed with the Green Bank Telescope and DSA-2000 in a given frequency range. We compare data products, namely the wavefield, in both full-deconvolution and partial-deconvolution regimes to demonstrate what can be accomplished with incomplete phase retrieval. Additionally, we show how some phase retrieval can still be achieved in the partial-deconvolution regime and how this allows for additional information in scintillation-based data products, like the dynamic wavefield power, compared to what can be found in traditional dynamic spectra. An examination of dynamic wavefield phase as a function of observing frequency reveals more complete phase retrieval is achieved the closer one gets to the full-deconvolution regime, agreeing with the expectations of cyclic merit. While we demonstrate that fragmentary recovery of the secondary wavefield can be accomplished in the partial-deconvolution regime, we advocate for a synergistic approach with phase retrieval methods like theθ−θtransform, although we also provide discussion about shortcomings of this strategy. Finally, we use the combination of modest cyclic merit and lack of discernible results for PSR J1903+0327 to motivate the creation of an updated “cyclic merit 2.0,” which relies on scintillation bandwidth instead of observing bandwidth. 

Abstract The amphibian chytrid fungusBatrachochytrium dendrobatidis(Bd) is a cosmopolitan pathogen with numerous distinct lineages. The global panzootic lineage (Bd-GPL) is the most widespread and virulent lineage and is responsible for many recorded amphibian declines. Mapping the extent ofBd-GPL and other more established lineages is important for predicting disease dynamics in amphibian communities. Ecuador is the most biodiverse country per unit area for amphibian taxa and, thus, a priority for studies on genotypic diversity ofBd. In this study, we tested skin swab samples collected from 464 individual amphibians across coastal, Andean montane, and Amazonian forests, for the presence of twoBdlineages known to be present in South America: the globally-distributedBd-GPL and the Brazilian-endemicBd-Asia2/Brazil lineage. By using a discriminatory qPCR SNP assay, we found widespread prevalence ofBd-GPL in Ecuador in diverse host taxa. Genotyping efficiency was 36% in this study, meaning that one in every three swabs that tested positive forBdin infection assays were successfully genotyped. Through this study, we provide further support for the presence of a singleBdlineage in this neotropical biodiversity hotspot. 

We present a 34 yr timing solution of the redback pulsar system Terzan 5A (Ter5A). Ter5A, also known as B1744−24A or J1748−2446A, has a 11.56 ms pulse period, a ~0.1 Msun dwarf companion star, and an orbital period of 1.82 hr. Ter5A displays highly variable eclipses and orbital perturbations. Using new timing techniques, we have determined a phase-connected timing solution for this system over 34 yr. This is the longest ever published for a redback pulsar. We find that the pulsar’s spin variability is much larger than most globular cluster pulsars. In fact, of the nine redback pulsars with published or in-preparation long-term timing solutions, Ter5A is by far the noisiest. We see no evidence of strong correlations between orbital and spin variability of the pulsar. We also find that long-term astrometric timing measurements are likely too contaminated by this variability to be usable, and therefore they require careful short-term timing to determine reasonable positions. Finally, we measure an orbital period contraction of  −2.5(3) x 10^-13, which is likely dominated by the general relativistic orbital decay of the system. The effects of the orbital variability due to the redback nature of the pulsar are not needed to explain the observed orbital period derivative, but they are constrained to less than ~30% of the observed value. 

Abstract The mergers of double neutron star (DNS) systems are believed to drive the majority of shortγ-ray bursts (SGRBs), while also serving as production sites of heavyr-process elements. Despite being key to (i) confirming the nature of the extragalactic SGRBs, (ii) addressing the poorly understoodr-process enrichment in the ultrafaint dwarf galaxies (UFDGs), and (iii) probing the formation process of DNS systems, the space velocity distribution of DNSs is still poorly constrained, due to the small number of DNSs with well-determined astrometry. In this work, we determine new proper motions and parallaxes of two Galactic DNSs, PSR J0509+3801 and PSR J1930−1852, using the Very Long Baseline Array, and we estimate the transverse velocitiesv_⊥of all 11 isolated Galactic DNSs having proper-motion measurements in a consistent manner. Our correlation analysis reveals that the DNSv_⊥is tentatively correlated with three parameters: spin period, orbital eccentricity, and companion mass. With the preliminaryv_⊥distribution, we obtain the following findings. First, the refinedv_⊥distribution is confirmed to agree with the observed displacements of the localized SGRBs from their host galaxy birth sites. Second, we estimate that around 11% and 25% of DNSs remain gravitationally bound to UFDGs with escape velocities of 15 and 25 km s⁻¹, respectively. Hence, the retained DNSs might indeed be responsible for ther-process enrichment confirmed so far in a few UFDGs. Finally, we discuss how a future ensemble of astrometrically determined DNSs may probe the multimodality of thev_⊥distribution. 

Abstract The binary pulsar J0348+0432 was previously shown to have a mass of approximately 2M_⊙, based on the combination of radial-velocity and model-dependent mass parameters derived from high-resolution optical spectroscopy of its white-dwarf companion. We present follow-up timing observations that combine archival observations with data acquired by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) pulsar instrument. We find that the inclusion of CHIME/Pulsar data yields an improved measurement of the variation of the orbital period ( ${\dot{P}}_b$) that is 1.2σconsistent with the original values published by J. Antoniadis et al. while being roughly 6 times more precise due to the extended baseline. Assuming that this $\dot{P_b}$is due to gravitational wave damping, and that the latter is as predicted by general relativity, we obtain new constraints on the mass of the pulsar and companion. When combined with the mass ratio determined from phase-resolved optical spectroscopy we determine a pulsar mass of 1.806(37)M_⊙. For the first time for this pulsar, timing alone significantly constrains the pulsar mass. If confirmed, our mass estimates indicate that the original analysis of the optical data has overestimated the mass of the companion (and by extension the mass of the pulsar) by about 10%. 

Abstract Cannabis sativais a globally important seed oil, fibre and drug-producing plant species. However, a century of prohibition has severely restricted development of breeding and germplasm resources, leaving potential hemp-based nutritional and fibre applications unrealized. Here we present a cannabis pangenome, constructed with 181 new and 12 previously released genomes from a total of 144 biological samples including both male (XY) and female (XX) plants. We identified widespread regions of the cannabis pangenome that are surprisingly diverse for a single species, with high levels of genetic and structural variation, and propose a novel population structure and hybridization history. Across the ancient heteromorphic X and Y sex chromosomes, we observed a variable boundary at the sex-determining and pseudoautosomal regions as well as genes that exhibit male-biased expression, including genes encoding several key flowering regulators. Conversely, the cannabinoid synthase genes, which are responsible for producing cannabidiol acid and delta-9-tetrahydrocannabinolic acid, contained very low levels of diversity, despite being embedded within a variable region with multiple pseudogenized paralogues, structural variation and distinct transposable element arrangements. Additionally, we identified variants of acyl-lipid thioesterase genes that were associated with fatty acid chain length variation and the production of the rare cannabinoids, tetrahydrocannabivarin and cannabidivarin. We conclude that theC. sativagene pool remains only partially characterized, the existence of wild relatives in Asia is likely and its potential as a crop species remains largely unrealized. 

Abstract The diverse and heterogeneous terrains in the Arctic, consisting of snow, melting ice, permafrost, ice-covered lakes, sea ice and open ocean, pose serious challenges to locomotion and autonomous navigation capabilities of rovers deployed in the region for data collection and experimentation. The Multi-terrain Amphibious ARCtic explOrer or MAARCO rover is a proposed screw-propelled vehicle that uses helical drives (similar to Archimedes’ screws) to move seamlessly across the diverse terrains in the Arctic. The motion of a pair of helical drives operating in soft or fluid terrain is dictated by the response of the surrounding substrate to the stresses exerted by the rotating helical drives. If the substrate under the rover does not fail when it is moving in a straight line, the linear displacement of the rover (x) and the number of rotations of the helical drives (n) are related through x = P · n, where P is the pitch length of the helical drives. However, when the substrate fails, the linear displacement of the rover is less than P · n, i.e., x < P · n. Thus, “x = P · n” motion represents the optimal mode of operation for the rover when moving in a straight line. This paper represents the first ever attempt, to the best of author’s knowledge, to derive the conditions necessary for the application of the holonomic constraint x = P · n to the dynamics of a helical drives-based rover.