On the progenitor of binary neutron star merger GW170817

On 2017 August 17 the merger of two compact objects with masses consistent with two neutron stars was discovered through gravitational-wave (GW170817), gamma-ray (GRB 170817A), and optical (SSS17a/AT 2017gfo) observations. The optical source was associated with the early-type galaxy NGC 4993 at a distance of just ∼40 Mpc, consistent with the gravitational-wave measurement, and the merger was localized to be at a projected distance of ∼2 kpc away from the galaxy's center. We use this minimal set of facts and the mass posteriors of the two neutron stars to derive the first constraints on the progenitor of GW170817 at the time of the second supernova (SN). We generate simulated progenitor populations and follow the three-dimensional kinematic evolution from binary neutron star (BNS) birth to the merger time, accounting for pre-SN galactic motion, for considerably different input distributions of the progenitor mass, pre-SN semimajor axis, and SN-kick velocity. Though not considerably tight, we find these constraints to be comparable to those for Galactic BNS progenitors. The derived constraints are very strongly influenced by the requirement of keeping the binary bound after the second SN and having the merger occur relatively close to the center of the galaxy. These constraints are insensitive to the galaxy's star formation history, provided the stellar populations are older than 1 Gyr

Critical slowing down and noise-induced intermittency in bistable perception: Bifurcation analysis

Coreopsis (Asteraceae) sect. Pseudoagarista is the largest section in the genus. It is disjunct between the high mountains of Mexico and high elevations in the Andes. Most species in the section are similar in floral and fruit characters, and are distinguished primarily by leaf characters. Despite the morphological similarity among all species, the monophyly of the section has been called into question by molecular data. Prior studies of tribe Coreopsideae have been equivocal with, cpDNA markers indicating monophyly but nrDNA ITS sequences have not resolved the section as monophyletic. Expanded cpDNA and nrDNA ITS datasets, and statistical (i.e., AU) tests of the ITS and cpDNA topologies provide support that sect. Pseudoagarista is not monophyletic. Both data partitions strongly support the Mexican and South American subclades as monophyletic. The low cpDNA sequence variation within each subclade provides no resolution, and thus patterns of evolution within each were examined using a phylogenetic framework estimated from ITS data. Sequences from ITS fail to provide high resolution of relationships among South American species, a likely result of a recent, rapid radiation, as is known in other Andean lineages. Divergence among species is generally higher in the Mexican species, resulting in better resolution of phylogenetic relationships compared to South American species. Three ploidy levels (diploid, tetraploid, hexaploid) are known in species from South America, and diploids and tetraploids have been documented in Mexico. Multiple origins of polyploidy are indicated for both geographic areas. " International Association for Plant Taxonomy (IAPT) 2014.",,,,,,"10.12705/635.31",,,"http://hdl.handle.net/20.500.12104/40376","http://www.scopus.com/inward/record.url?eid=2-s2.0-84908245555&partnerID=40&md5=3e1a6ca2861212b9ea6411bd57b79d7c",,,,,,"5",,"Taxon",,"109