Astrophysics collection (March 11, 2016)

Latest astrophysics news

Rotation curves of galaxies as a test of MOND?

Galaxies are rotating with such speed that the gravity generated by their observable matter could not possibly hold them together. In a recent paper (Haghi et al. 2016) the authors test the Modified Newtonian Dynamics (MOND). Read>>

A binary origin for a central compact object (CCO)?

Doroshenko et al. 2016 investigate the possible binary origin of the CCO XMMUJ173203.3-344518. Read>>

Rapidly rotating pulsars as possible sources of fast radio bursts (FRB)

In a recent paper (Lyutikov et al. 2016) the authors discuss possible association of fast radio bursts (FRBs) with supergiant pulses emitted by young pulsars. Read>>

Supernovae from WD-WD direct collisions

In recent years it was suggested that WD-WD direct collisions (probably extremely rare and occurring only in dense stellar clusters) provide an additional channel for supernova explosions. Read>>

Telescopes Combine to Push Frontier on Galaxy Clusters

Hubblesite news. Read>>

No correlation between Fermi GBM signal and GW150914.

The electromagnetic signal detected by Fermi GBM is likely unrelated to the BH merger detected by LIGO. Read>>

Comments

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.

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 ...

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