Question--can a neutron star shed mass?

[Duane M]

Once the steller core of a massive star collapses into a neutron star, is there any known mechanism by which the neutron star can shed mass?

[Labguy]

Once the steller core of a massive star collapses into a neutron star, is there any known mechanism by which the neutron star can shed mass? Yes. When a neutron star is "new" with temperatures above ~ 109 K, there is strong heat-loss (therefore mass) by neutrino emission. At lower temperatures, there is "standard thermal photon cooling", which has a power proportional to T4 K. Another process is where an electron passes by a nucleus and, instead of emitting a single photon emits a neutrino-antineutrino pair. This has a power of about T6.

Either way, the heat loss translates to mass loss by emission of various particle types. There are more complicated processes which involve interaction of the (huge) magnetic field, but the bottom line is that any heat loss will also lead to a mass loss.

[meteor]

Yes. When a neutron star is "new"...

By "new" I think that you mean when is exactly what is called a protoneutron star. Then yes, it loses all its neutrinos by a process called deleptonization

[Labguy]

By "new" I think that you mean when is exactly what is called a protoneutron star. Then yes, it loses all its neutrinos by a process called deleptonization Even after the protoneutron star (PNS) stage, neutrino emissions dominate for ~100 years in the "standard" model and as much as 1 million years in certain cases depending on the state of the "superfluidity" of the degenerate matter.

100 to 1 million years certainly extends well beyond the PNS stage. Deleptonization is a description of the change in properties of the matter in a neutron star, neutron loss is called neutron diffusion. See at least pages 1-4 (out of 61) at:

http://arxiv.org/PS_cache/astro-ph/pdf/0012/0012136.pdf