<p>No, the two limits are not the same - there is some range of masses that both white dwarfs (WDs) and neutron stars (NSs) can have.</p>

<p>The <a href="https://en.wikipedia.org/wiki/Chandrasekhar_limit" rel="noreferrer">Chandrasekhar mass limit</a> suggests that WDs cannot be more massive than about $1.4\,M_\odot$.  However, this is true for <em>non-rotating</em> WDs.  Rapidly rotating WDs might be <a href="http://esoads.eso.org/abs/2004A%26A...419..623Y" rel="noreferrer">as massive as $2\,M_\odot$</a>.  Accretion in a binary system could both spin up a WD and increase its mass.</p>

<p>NSs that have not undergone accretion are regularly observed with <a href="http://adsabs.harvard.edu/abs/2012ApJ...757...55O" rel="noreferrer">masses around $1.3\,M_\odot$</a>, while NSs who have 'recycled pulsars' have an observed mean mass of $\sim 1.5\,M_\odot$ according to the same paper.</p>

CC BY-SA 3.0
2016-07-15T15:23:47.023Z
2016-07-15T15:23:47.023Z
AstroFloyd
<p>The smallest, precisely measured mass for a neutron star is now $1.174 \pm 0.004 M_{\odot}$ - <a href="http://arxiv.org/abs/1509.08805" rel="nofollow noreferrer">Martinez et al. (2015)</a>. The theoretical lower limit is more like $0.1M_{\odot}$, but there are no obvious formation channels to produce such an object. See  <a href="https://physics.stackexchange.com/questions/143166/what-is-the-theoretical-lower-mass-limit-for-a-gravitationally-stable-neutron-st">https://physics.stackexchange.com/questions/143166/what-is-the-theoretical-lower-mass-limit-for-a-gravitationally-stable-neutron-st</a></p>

<p>The highest mass for a stable white dwarf (commonly called the Chandrasekhar mass) is theoretically about $1.39 M_{\odot}$ for a helium or carbon white dwarf (and a little bit lower for oxygen or neon white dwarfs), but can be increased somewhat by rotation. The observation of type Ia supernovae is strong circumstantial evidence that this limit is reached and then exceeded, probably by mass transfer onto a smaller white dwarf. The most massive, probably single, white dwarf known/measured is "WD 33" in the cluster NGC 2099 and has a mass of $1.28^{+0.05}_{-0.08}\ M_{\odot}$ (<a href="http://arxiv.org/abs/1603.00471" rel="nofollow noreferrer">Cummings et al. 2016)</a>.</p>

<p>So, both observationally and theoretically, the maximum mass of a white dwarf is higher than the minimum mass for a neutron star.</p>

CC BY-SA 3.0
2016-07-15T16:24:55.243Z
2016-07-15T16:32:25.263Z
2017-04-13T12:40:15.377Z
ProfRob
<p>If not, when can a white dwarf be more massive than a neutron star?</p>

CC BY-SA 3.0
2016-07-07T09:55:43.680Z
There has already been a question related to this on the http://physics.stackexchange.com/questions/143166/what-is-the-theoretical-lower-mass-limit-for-a-gravitationally-stable-neutron-st with a very detailed answer by Rob Jeffries
Dean
<neutron-star><white-dwarf>
Is the lower mass limit of a neutron star the same as the upper mass limit of a white dwarf?
Gstestso
# Is the lower mass limit of a neutron star the same as the upper mass limit of a white dwarf?

(Asked by: username_0 on 2016-07-07)

If not, when can a white dwarf be more massive than a neutron star?

**Tags:** neutron-star, white-dwarf
> **Comments:**
> **username_1**: There has already been a question related to this on the http://physics.stackexchange.com/questions/143166/what-is-the-theoretical-lower-mass-limit-for-a-gravitationally-stable-neutron-st with a very detailed answer by Rob Jeffries  

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## 2 answers

### Answer by username_3 on 2016-07-15. Score: 5 | Accepted answer

The smallest, precisely measured mass for a neutron star is now $1.174 \pm 0.004 M\_{\odot}$ - [Martinez et al. (2015)](http://arxiv.org/abs/1509.08805). The theoretical lower limit is more like $0.1M\_{\odot}$, but there are no obvious formation channels to produce such an object. See <https://physics.stackexchange.com/questions/143166/what-is-the-theoretical-lower-mass-limit-for-a-gravitationally-stable-neutron-st>

The highest mass for a stable white dwarf (commonly called the Chandrasekhar mass) is theoretically about $1.39 M\_{\odot}$ for a helium or carbon white dwarf (and a little bit lower for oxygen or neon white dwarfs), but can be increased somewhat by rotation. The observation of type Ia supernovae is strong circumstantial evidence that this limit is reached and then exceeded, probably by mass transfer onto a smaller white dwarf. The most massive, probably single, white dwarf known/measured is "WD 33" in the cluster NGC 2099 and has a mass of $1.28^{+0.05}\_{-0.08}\ M\_{\odot}$ ([Cummings et al. 2016)](http://arxiv.org/abs/1603.00471).

So, both observationally and theoretically, the maximum mass of a white dwarf is higher than the minimum mass for a neutron star.


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### Answer by username_2 on 2016-07-15. Score: 5

No, the two limits are not the same - there is some range of masses that both white dwarfs (WDs) and neutron stars (NSs) can have.

The [Chandrasekhar mass limit](https://en.wikipedia.org/wiki/Chandrasekhar_limit) suggests that WDs cannot be more massive than about $1.4\,M\_\odot$. However, this is true for *non-rotating* WDs. Rapidly rotating WDs might be [as massive as $2\,M\_\odot$](http://esoads.eso.org/abs/2004A%26A...419..623Y). Accretion in a binary system could both spin up a WD and increase its mass.

NSs that have not undergone accretion are regularly observed with [masses around $1.3\,M\_\odot$](http://adsabs.harvard.edu/abs/2012ApJ...757...55O), while NSs who have 'recycled pulsars' have an observed mean mass of $\sim 1.5\,M\_\odot$ according to the same paper.


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