Skip to main content

NEWBORN PULSARS WITH A HIDDEN MAGNETIC FIELD


Image: Crab nebula as seen by Chandra. Credit: NASA/CXC/SAO/F. Seward et al.

In the center of several supernova remnants there are pulsars with significantly lower values of the dipolar magnetic field than the average radio-pulsar population (10^{12}G). A possible explanation requires the slow rotation of the proto-neutron star at birth, which is unable to amplify its magnetic field to typical pulsar levels.


However, recent studies have shown that, even in the absence of rapid rotation, magnetic fields in pulsars can be amplified by other mechanisms such as convection and the standing accretion shock instability.
An alternative possibility, the hidden magnetic field scenario, considers the accretion of the fallback of the supernova debris onto the neutron star as responsible for the submergence (or screening) of the field and its apparently low value. A high accretion rate can compress the magnetic field of the NS which can eventually be buried into the neutron star crust. As a result, the value of the external magnetic field would be significantly lower than the internal 'hidden' magnetic field.

Credit: Torres-Forné et al. 2016
 Once  the  accretion  process  stops,  the  magnetic  field  might eventually reemerge.
The main conclusion of a recent paper (Torres-Forné et al. 2016) is that typical magnetic fields of a few times 10^{12}G can be buried by accreting only 0.001-0.01 solar masses, a relatively modest amount of mass. The field would  only  reemerge  after a few thousand years.
On the contrary, magnetar-like field strengths are much harder to screen and the required accreted mass is very large,  in  some  cases  so  large that the neutron star would collapse to a black hole. The anomalously weak magnetic fields should be common in very young neutron stars.

Read more>>
http://arxiv.org/pdf/1511.03823v2.pdf
http://mnras.oxfordjournals.org/content/456/4/3813.abstract

Etichette:

Comments

Post a Comment

Popular posts from this blog

ABOUT THE FORMATION OF THE COLD CLASSICAL KUIPER BELT

Image: The Kuiper Belt. Credit: NASA . The Kuiper belt is a circumstellar disc in the Solar System beyond the planets, extending from the orbit of Neptune (at 30 AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt (the circumstellar disc located roughly between the orbits of the planets Mars and Jupiter), but it is far larger-20 times as wide and 20 to 200 times as massive.
2 comments
Read more

ORIGIN OF RADIO EMISSION IN RADIO-QUIET QUASARS

Image Credit: NASA/Goddard Space Flight Center Radio emission of radio-quiet quasars may be due to stars formation in the quasar host galaxy, to a jet launched by the supermassive black hole, or to relativistic particles accelerated in a wide-angle radiatively-driven outflow.
Post a Comment
Read more

VISTA Gazes Into Carina Nebula In Infrared

This spectacular image of the Carina nebula reveals the dynamic cloud of interstellar matter and thinly spread gas and dust as never before.  Credit:  ESO/J. Emerson/M. Irwin/J. Lewis About 7500 light-years away, in the constellation of  Carina , lies a nebula within which stars form and perish side-by-side. Shaped by these dramatic  events, the  Carina Nebula  is a dynamic, evolving cloud of thinly sprea d interstellar gas and dust. Spanning over 300 light-years, the Carina Nebula is one of the Milky Way's largest star-forming regions and is easily visible to the unaided eye under dark skies. Unfortunately for those of us living in the north, it lies 60 degrees below the celestial equator, so is visible only from the Southern Hemisphere. The massive stars in the interior of this cosmic bubble emit intense radiation that causes the surrounding gas to glow. By contrast, other regions of the nebula contain dark pillars of dust cloak...
Post a Comment
Read more