Lower mass limit for neutron stars?

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Discussion Overview

The discussion centers on the lower mass limit for neutron stars, exploring whether there is a fundamental physics threshold below which a neutron star could not exist without undergoing catastrophic collapse. Participants consider various aspects of neutron star formation, stability, and the implications of the Chandrasekhar limit.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions the existence of a lower mass limit for neutron stars, suggesting that smaller neutron stars might be stable if created under specific conditions.
  • Another participant asserts that neutron stars do not explode but can collapse into black holes if they gain enough mass.
  • Several participants emphasize the significance of the Chandrasekhar limit, arguing that it represents a stability threshold, and propose that any mass below this limit would lead to the formation of a white dwarf instead of a neutron star.
  • A reference to a paper discussing the minimum mass of neutron stars is provided, indicating that the minimum mass is estimated to be between 0.88 and 1.28 solar masses, and that this limit is largely unaffected by the presence of hyperons.
  • One participant reiterates the importance of the progenitor star's core mass, noting that most known neutron stars are below the Chandrasekhar limit, with the lowest known mass around one solar mass.

Areas of Agreement / Disagreement

Participants express differing views on the existence and implications of a lower mass limit for neutron stars. While some argue that the Chandrasekhar limit is definitive, others propose that smaller neutron stars could theoretically exist under certain conditions. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Some claims depend on specific definitions and assumptions regarding stellar evolution and the nature of neutron stars. The discussion includes references to theoretical models and empirical observations that may not be universally accepted.

Reedbeta
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I was wondering, does anyone know of a lower limit on the mass of a neutron star from fundamental physics? That is, the smallest it could be before its pressure would make it explode.

I don't mean the Chandrasekhar limit, as that's the upper limit for a white dwarf. Neutron stars occurring "in the wild" probably can't be too much smaller than this, as they would never have collapsed to a neutron star in the first place, but ignoring that fact, might much-smaller neutron stars be stable if they could somehow be created?
 
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The funny thing about neutron stars is they don't explode. If a neutron star accretes enough mass after formation, it will collapse into a black hole.
 
I think the Chandrasekhar limit is the limit. The Chandrasekhar limit isn't based on stellar evolution or detailed mechanisms of collapse. It's based on stability. If you could initially form a ball of neutrons with a mass under the Chandrasekhar limit, I think it would do n\rightarrow p+e^-+\bar{\nu} and turn into a white dwarf.
 
bcrowell said:
I think the Chandrasekhar limit is the limit. The Chandrasekhar limit isn't based on stellar evolution or detailed mechanisms of collapse. It's based on stability. If you could initially form a ball of neutrons with a mass under the Chandrasekhar limit, I think it would do n\rightarrow p+e^-+\bar{\nu} and turn into a white dwarf.

Intriguing thought! I suspect you are right. Nothing else seems to make sense.
 
See http://arxiv.org/abs/astro-ph/0012321
On the minimum and maximum mass of neutron stars and the delayed collapse
Authors: Klaus Strobel, Manfred K. Weigel (University of Munich)
(Submitted on 14 Dec 2000)
Abstract: The minimum and maximum mass of protoneutron stars and neutron stars are investigated. The hot dense matter is described by relativistic (including hyperons) and non-relativistic equations of state. We show that the minimum mass ($\sim$ 0.88 - 1.28 $M_{\sun}$) of a neutron star is determined by the earliest stage of its evolution and is nearly unaffected by the presence of hyperons. The maximum mass of a neutron star is limited by the protoneutron star or hot neutron star stage. Further we find that the delayed collapse of a neutron star into a black hole during deleptonization is not only possible for equations of state with softening components, as for instance, hyperons, meson condensates etc., but also for neutron stars with a pure nucleonic-leptonic equation of state.
Comments: 6 pages, 4 figures, using EDP Siences Latex A&A style, to be published in A&A
Subjects: Astrophysics (astro-ph); Nuclear Theory (nucl-th)
Journal reference: Astron.Astrophys.367:582,2001
DOI: 10.1051/0004-6361:20000428
Cite as: arXiv:astro-ph/0012321v1
 
bcrowell said:
I think the Chandrasekhar limit is the limit. The Chandrasekhar limit isn't based on stellar evolution or detailed mechanisms of collapse. It's based on stability. If you could initially form a ball of neutrons with a mass under the Chandrasekhar limit, I think it would do n\rightarrow p+e^-+\bar{\nu} and turn into a white dwarf.

The key factor is the core mass of the progenitor star. The supernova event that births a neutron star expels a large fraction of the progenitor star mass. Most known neutron stars fall below the Chandrasekhar mass limit. The lowest known neutron star mass is around 1 solar.
 
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