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

GAMMA-RAY EMISSION FROM THE SNR HB3

Image: At a distance of about 20,000 light years, G292.0+1.8 is one of only three supernova remnants in the Milky Way known to contain large amounts of oxygen. These oxygen-rich supernovas are of great interest to astronomers because they are one of the primary sources of the heavy elements (that is, everything other than hydrogen and helium) necessary to form planets and people. The X-ray image from Chandra shows a rapidly expanding, intricately structured, debris field that contains, along with oxygen (yellow and orange), other elements such as magnesium (green) and silicon and sulfur (blue) that were forged in the star before it exploded. Credit: NASA/CXC/SAO The processes of particles acceleration to very high energies from the supernova shock region and diffusion in the interstellar medium of such particles has not been well understood so far. Gamma-ray observations in the GeV regime are a powerful probe of these mechanisms

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).

Boulevard of Broken Rings

Credit: ESO/Perrot This Picture illustrates the remarkable capabilities of SPHERE (the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument), a planet-hunting instrument mounted on ESO's Very Large Telescope (VLT) in Chile: It shows a series of broken rings of dust around a nearby star. These concentric rings are located in the inner region of the debris disc surrounding a young star named HD 141569A, which sits some 370 light-years away from us. In this image we see what is known as a transition disc, a short-lived stage between the protoplanetary phase, when planets have not yet formed, and a later time when planets have coalesced, leaving the disc populated only by any remaining - and predominantly dusty - debris. What we see here are structures formed of dust, revealed for the first time in near-infrared light by SPHERE - at a high enough resolution to capture remarkable detail! The area shown in this image has a diameter of just 200 times the Earth–Sun distan...

SpaceTime

Search This Blog