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

A METHOD TO TEST THE EXISTENCE OF REGULAR BLACK HOLES

Illustration of a black hole. Image Credit & Copyright: Alain Riazuelo The existence of the singularity is an intrinsic problem of the General Relativity (GR). At the fundamentally level, the resolution of the problem of the singularity lies with the expectation that under situations where quantum effects become strong, the behavior of gravity could possibly greatly deviate from that predicted by the classical theory of GR. Regular black hole solution are proposed with the same spacetime geometry outside the horizon as the traditional black hole, but bears no singularity inside. Whether or not black hole singularities should exist, they would be covered by the black hole horizon. The black hole horizon serves as an information curtain hindering outside observers from directly observing the interior structure of the black hole, and determining that whether or not the black hole singularity does really exist. A method is needed to check the correctness of the new constructions ...

Dark Neutron Stars

Illustration of a neutron star. Credit: NASA/Dana Berry There is good evidence that electron-positron pair formation is not present in that section of the pulsar open magnetosphere which is the source of coherent radio emission, but the possibility of two-photon pair creation in an outer gap remains. Calculation of transition rates for this process based on measured whole-surface temperatures, combined with a survey of gamma-ray, X-ray and optical luminosities, expressed per primary beam lepton, shows that few Fermi LAT pulsars have significant outer-gap pair creation. For radio-loud pulsars with positive polar-cap corotational charge density and an ion-proton plasma there must be an outward flow of electrons from some other part of the magnetosphere to maintain a constant net charge on the star. In the absence of pair creation, it is likely that this current is the source of GeV gamma-emission observed by the Fermi LAT and its origin is in the region of the outer gap. With n...

THE HITCHCHIKER'S GUIDE TO THE LOCAL SUPERCLUSTER

Image: Virgo Supercluster. Credit: Andrew Z. Colvin The Virgo Supercluster is a region with a diameter of 33 megaparsecs (~1000 times larger the Milky Way's diameter) containing at least 100 galaxy groups and clusters.

SpaceTime

Search This Blog