STABLE CARBON PRODUCTION ON ACCRETING NEUTRON STARS AT THE ORIGIN OF SUPERBURSTS

Image Credit: David A. Hardy & PPARC

Accreting neutron stars exhibit bursts due to nuclear burning of hydrogen/helium and rarely even carbon. The carbon flashes generate the superbusts. The carbon is produced during the hydrogen/helium flashes. However the amount of carbon produced in hydrogen/helium flashes is insufficient to power the superbursts.

To produce the amount of carbon necessary to trigger the superbursts is required a "stable burning" of hydrogen/helium in addition to high accretion rates. But the accretion rates observed in superbursts (10^[- 9] solar masses/year) are too low to produce the amount of carbon necessary for superbursts.
In a recent paper (Keek, Heger 2016) the authors find that the hot CNO burning of hydrogen heats the neutron star envelope accelerating the burning of helium (and thus the production of carbon) before the conditions of a helium flash are reached. This acceleration of the production rate of carbon makes it possible superbursts even with growth rates lower, consistent as order of magnitude with those observed (10 ^ [- 9] solar masses / year).

Read more>>
http://arxiv.org/abs/1508.06630
http://mnrasl.oxfordjournals.org/content/456/1/L11.abstract

Comments

Fermi Bubbles

Image: A giant gamma-ray structure was discovered in 2010 by processing Fermi all-sky data at energies from 1 to 10 billion electron volts, shown here. The dumbbell-shaped feature (center) emerges from the galactic center and extends 50 degrees north and south from the plane of the Milky Way, spanning the sky from the constellation Virgo to the constellation Grus. Credits: NASA/DOE/Fermi LAT/D. Finkbeiner et al. At a time when our earliest human ancestors mastered walking upright the heart of our Milky Way galaxy underwent a titanic eruption, driving gases and other material outward at 2 million miles per hour.

CONTAMINATION BY SUPERNOVAE IN GLOBULAR CLUSTERS

Credit: ALMA (ESO/NAOJ/NRAO)/Alexandra Angelich (NRAO/AUI/NSF) Only a small amount of the supernovae products remains trapped within globular clusters and this "catch" only occurs in the most massive cases (mass cluster ≥ 10^6 solar masses).

New research looks at how ‘cosmic web’ of filaments alters star formation in galaxies

Cosmic Web. Credit: NASA Astronomer Gregory Rudnick sees the universe crisscrossed by something like an interstellar superhighway system. Filaments — the strands of aggregated matter that stretch millions of light years across the universe to connect galaxy clusters — are the freeways. “Galaxies will flow along filaments from less dense parts of the universe to more dense parts of the universe, kind of like cars flowing down a highway to the big city. In this case, they are going toward big clusters, being pulled by the gravity of those large concentrations of matter,” he said. “I’m interested in how galaxies are affected by the regions in which they live,” Rudnick said. “Filaments are the first place where galaxies come into contact with higher density regions of the universe. If a galaxy in a ‘rural’ part of the universe enters a dense part, I want to know how its properties change — for example, does it change the number of stars it forms, or does its shape get altered? Us...

SpaceTime

Search This Blog