<p>All type II supernovae are associated with the core collapse of a massive star and are thought to produce some sort of compact star. Supernovae should also always produce an expanding supernova remnant. Almost all massive stars are part of multiple systems.</p>

<p>These three facts might lead you to believe that most, if not all, supernova remnants should contain an observable compact star in a multiple system.</p>

<p>There are two classes of reason why this is not the case - observational issues and physical mechanisms.</p>

<p>Observationally, we do not see compact multiple systems unless one of the stars is a pulsar, which requires a correct orientation to see it, or if the compact star is accreting mass from its companion. The latter requires a close binary system that thas survived the supernova. Also note that isolated black holes may exist in supernovae remnants but would be unobservable.</p>

<p>Physically, the supernova explosion may disrupt the binary system. Pulsars are typically travelling at hundreds of km/s thanks to the "kick" they received from their supernova. Supernova remnants are not visible for long ($\sim$ a million years or less), so pulsars that have been kicked out of a binary can still be found within the supernova remnant.</p>

<p>The short-lived nature of supernovae remnants also biases against finding compact, X-ray accreting binaries. Typically, the compact star's companion must evolve to either fill its Roche lobe (for a low-mass X-ray binary) or to develop high mass loss rates (for a high-mass X-ray binary). This would not normally happen within the short life of the visible supernova remnant.</p>

<p>So examples of <em>observable</em> compact binary systems in supernova remnants are rare. But there are at least two examples known in our Galaxy and several in others. The (at least) two in our Galaxy are <a href="https://arxiv.org/abs/1312.0632" rel="nofollow noreferrer">Circinus X-1</a> and 
<a href="https://arxiv.org/abs/1101.3486" rel="nofollow noreferrer">SS433</a>.</p>

CC BY-SA 3.0
2016-11-06T14:12:58.253Z
ss433 is an X-ray binary, not in a SNR, although there is a SNR nearby.
questionhang
CC BY-SA 3.0
2016-11-06T16:55:05.483Z
Why do you say this? Have you looked at the paper I referenced? SS433 is at the centre of the SNR W50. @questionhang
ProfRob
CC BY-SA 3.0
2016-11-10T12:33:21.330Z
you are right. Why do not we mention SS433 is in a SNR much? W50 is not famous at all.
questionhang
CC BY-SA 3.0
2016-11-06T09:58:55.187Z
2016-11-06T09:58:55.187Z
ProfRob
<p>There are plenty of hard-x-ray binaries that involve a compact object with a companion.  Some should be in supernova remnants, but I don't know how many.  Are you sure there is a problem?</p>

CC BY-SA 3.0
2016-11-06T02:02:19.543Z
`Some should be in supernova remnants`, could you give an example?
questionhang
CC BY-SA 3.0
2016-11-06T03:57:13.147Z
Here are the first two google hits: https://arxiv.org/abs/1110.6404 and http://adsabs.harvard.edu/abs/2003MNRAS.341L..49R,
Ken G
CC BY-SA 3.0
2016-11-06T09:25:38.847Z
Or this https://astronomynow.com/2016/09/30/record-breaking-extragalactic-gamma-ray-binary-found/ or this http://www.nasa.gov/mission_pages/chandra/news/binary-star-system-clues.html
ProfRob
CC BY-SA 3.0
2016-11-05T15:43:54.967Z
2016-11-05T15:43:54.967Z
Ken G
<p>It seems all the central compact objects correlated with supernova remnant(SNRs) are isolated, not in binaries, right? </p>

<p>I find only one exception. A source is claimed to be a compact binary which correlates with SNR G308.3-1.4.<a href="http://adsabs.harvard.edu/abs/2012ApJ...750....7H" rel="nofollow noreferrer">ads link</a></p>

<p>My question is, generally, are the compact objects in SNR always isolated? 
And <strong>observationally</strong>, are the compact objects in SNRs neutron stars?</p>

CC BY-SA 3.0
2016-11-05T16:09:47.500Z
I'm not quite clear, since you have phrased your questions as statements. Do you mean "Are the compact objects in SNR always isolated?" and "Are the compact objects in SNRs neutron stars?"
James K
CC BY-SA 3.0
2016-11-06T01:45:41.860Z
@james  your summary is correct.
questionhang
<supernova>
Are the compact objects in supernova remnants isolated neutron stars?
questionhang
# Are the compact objects in supernova remnants isolated neutron stars?

(Asked by: username_0 on 2016-11-05)

It seems all the central compact objects correlated with supernova remnant(SNRs) are isolated, not in binaries, right?

I find only one exception. A source is claimed to be a compact binary which correlates with SNR G308.3-1.4.[ads link](http://adsabs.harvard.edu/abs/2012ApJ...750....7H)

My question is, generally, are the compact objects in SNR always isolated?
And **observationally**, are the compact objects in SNRs neutron stars?

**Tags:** supernova
> **Comments:**
> **username_1**: I'm not quite clear, since you have phrased your questions as statements. Do you mean "Are the compact objects in SNR always isolated?" and "Are the compact objects in SNRs neutron stars?"  
> **username_0**: @james  your summary is correct.  

---

## 2 answers

### Answer by username_2 on 2016-11-06. Score: 2 | Accepted answer

All type II supernovae are associated with the core collapse of a massive star and are thought to produce some sort of compact star. Supernovae should also always produce an expanding supernova remnant. Almost all massive stars are part of multiple systems.

These three facts might lead you to believe that most, if not all, supernova remnants should contain an observable compact star in a multiple system.

There are two classes of reason why this is not the case - observational issues and physical mechanisms.

Observationally, we do not see compact multiple systems unless one of the stars is a pulsar, which requires a correct orientation to see it, or if the compact star is accreting mass from its companion. The latter requires a close binary system that thas survived the supernova. Also note that isolated black holes may exist in supernovae remnants but would be unobservable.

Physically, the supernova explosion may disrupt the binary system. Pulsars are typically travelling at hundreds of km/s thanks to the "kick" they received from their supernova. Supernova remnants are not visible for long ($\sim$ a million years or less), so pulsars that have been kicked out of a binary can still be found within the supernova remnant.

The short-lived nature of supernovae remnants also biases against finding compact, X-ray accreting binaries. Typically, the compact star's companion must evolve to either fill its Roche lobe (for a low-mass X-ray binary) or to develop high mass loss rates (for a high-mass X-ray binary). This would not normally happen within the short life of the visible supernova remnant.

So examples of *observable* compact binary systems in supernova remnants are rare. But there are at least two examples known in our Galaxy and several in others. The (at least) two in our Galaxy are [Circinus X-1](https://arxiv.org/abs/1312.0632) and
[SS433](https://arxiv.org/abs/1101.3486).

> **Comments:**
> **username_0**: ss433 is an X-ray binary, not in a SNR, although there is a SNR nearby.  
> **username_2**: Why do you say this? Have you looked at the paper I referenced? SS433 is at the centre of the SNR W50. @questionhang  
> **username_0**: you are right. Why do not we mention SS433 is in a SNR much? W50 is not famous at all.  

---

### Answer by username_3 on 2016-11-05. Score: 2

There are plenty of hard-x-ray binaries that involve a compact object with a companion. Some should be in supernova remnants, but I don't know how many. Are you sure there is a problem?

> **Comments:**
> **username_0**: `Some should be in supernova remnants`, could you give an example?  
> **username_3**: Here are the first two google hits: https://arxiv.org/abs/1110.6404 and http://adsabs.harvard.edu/abs/2003MNRAS.341L..49R,  
> **username_2**: Or this https://astronomynow.com/2016/09/30/record-breaking-extragalactic-gamma-ray-binary-found/ or this http://www.nasa.gov/mission_pages/chandra/news/binary-star-system-clues.html  

---

