The special point on the hybrid star mass–radius diagram and its multi–messenger implications

We show the existence and investigate the location of the special point (SP) in which hybrid neutron star mass-radius (M-R) curves have to cross each other when they belong to a class of hybrid equation of state (EoS) constructed with generic constant–speed–of–sound (CSS) quark matter models for which the onset deconfinement is varied. We demonstrate that for a three-parameter CSS model the position of the SP in the M-R diagram is largely independent of the choice of the hadronic EoS, but in dependence on the stiffness of the quark matter EoS it spans a region that we identify. We find that the difference between the maximum mass and the SP mass depends on the mass at the onset of deconfinement so that an upper limit of 0.19 M⊙ for this difference is obtained from which a lower limit on the radius of hybrid stars is deduced. Together with a lower limit on the radius of hadronic stars, derived from a class of reasonably soft hadronic EoS including hyperons, we identify a region in the M-R diagram which can be occupied only by hybrid stars. Accordingly, we suggest that a NICER radius measurement on the massive pulsar PSR J0740 + 6620 in the range of 8.6-11.9 km would indicate that this pulsar is a hybrid neutron star with deconfined quark matter in the inner core.

Comparative foliar epidermal morphology of Isolona Engl. (Annonaceae)

A qualitative micromorphological assessment of the seven species of Isolona occurring in Nigeria and the Cameroons was undertaken with the aid of light microscope. The stomatal cells are particularly useful, providing stable characters which can be reliably employed in distinguishing the species. Hypostomatic leaves and paracytic stomatal type are generic constant. Possession of only paracytic stomata is characteristic of I. dewevrei whereas other species may have in addition another type such as 1+2 laterocytic stomatal type found only in I. zenkeri and presence of brachyparacytic stomata which shows relatedness of I. campanulata, I. congolana, I. hexaloba, I. pleurocarpus and I. thonneri. The epidermal surfaces appeared glabrous but an indication of hairs is shown by the presence of a glandular trichome base only in I. hexaloba. The epidermal cell characters such as epidermal cell shapes and anticlinal wall patterns seem to intergrade and they are not as definite as the stomatal cells. However, a combination of these features will be helpful in defining the species better and their leaf fragments can be differentiated based on the various characters studied for effective utilization in herbal medicinal research.

Taxonomic significance of some leaf anatomical features of the species of Annona L. (annonaceae) from Nigeria

A comparative study of the some leaf anatomical features of four species of Annona occurring in Nigerian was undertaken with the aid of light microscope. The four foliar structures (epidermis, petiole, midrib and lamina architecture) studied revealed useful characters which support recognition of the species. A combination of these features has been used to prepare an artificial indented dichotomous key for identifying the species. The generic constant features encountered included hypostomata, paracytic stomatal type, linear nerves endings, uneven midrib outline, and centrally located vascular bundles in the petiole and midrib. However, the most reliable distinguishing characters found across the species included presence of brachyparacytic stomata in A. reticulata, presence of trichomes on the midrib in A. senegalensis, absence of druses on the abaxial surface in A. muricata and A. squamosa, a thick pitted anticlinal walls on the surfaces of A. muricata and consistent polygonal areola shape in A. squamosa. The overlapping characters which also justify the closeness of the species and their grouping in a genus were recorded in both the qualitative and quantitative features. Prominent among them are the mean stomatal width which is about 1.0 μm in all species, nerve endings within the areole which varies between 1-2, U- or V-shaped midrib on the adaxial surface and straight to curved anticlinal wall pattern. The significance of these observations is discussed in updating the existing data in the genus. Keywords: Epidermis, Microscopy, Midrib, Petiole, Systematic