7 research outputs found
Evolution and Asteroseismology of Pulsating Low-Mass White Dwarfs
The 21st European Workshop on White Dwarfs was held in Austin, TX from July 23rd to 27th of 2018Many low-mass white dwarfs are being discovered
in the field of our galaxy and some of them exhibit
g-mode pulsations, comprising the extremely
low-mass variable (ELMV) stars class. Although
it is generally believed that these stars are characterized
by thick H envelopes, the existence of
low-mass WDs with thin H envelopes is also possible
from stellar evolution considerations. We
have performed detailed asteroseismological fits to
all the known ELMVs to search for a representative
model by employing a set of fully evolutionary
models that are representative of low-mass
He-core white dwarf stars with a range of stellar
masses [0.1554-0.4352]M , effective temperatures
[6000 - 10000] K, and also with a range of H envelope
thicknesses -5:8 ~< log(MH/M*) ~< -1.7, hence
expanding the space of parameters. We found that
some of the stars under analysis are characterized
by thick H envelopes, but others are better represented
by models with a thin H envelope.Astronom
The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance
The past 2 years, during which waves of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants swept the globe, have starkly highlighted health disparities across nations. Tegally et al. show how the coordinated efforts of talented African scientists have in a short time made great contributions to pandemic surveillance and data gathering. Their efforts and initiatives have provided early warning that has likely benefited wealthier countries more than their own. Genomic surveillance identified the emergence of the highly transmissible Beta and Omicron variants and now the appearance of Omicron sublineages in Africa. However, it is imperative that technology transfer for diagnostics and vaccines, as well the logistic wherewithal to produce and deploy them, match the data-gathering effort