<p>NGC 2516 is somewhat richer and more massive than the Pleiades. A careful look at the mass function suggests there is about <span class="math-container">$1000 M_{\odot}$</span> in stars <span class="math-container">$\geq 0.3 M_{\odot}$</span>, within the central 0.9 square degrees (with about a 15% uncertainty), but there is probably a few hundred solar masses beyond this (<a href="https://arxiv.org/abs/astro-ph/0107097" rel="nofollow noreferrer">Jeffries et al. 2001</a>). This agrees with the figures of Dachs &amp; Kabus (1989), who essentially extrapolated from the numbers of high-mass stars using a typical cluster mass function.</p>
<p>New Gaia data will probably provide a more complete census in the halo of the cluster. There will also be some additional mass in lower mass stars and brown dwarfs, but this is unlikely to add more than 10% to the figure.</p>
<p>The lower masses quoted in your question are way too low. In an incomplete spectroscopic survey of the central square degree, a recent paper by
<a href="https://arxiv.org/abs/2006.09423" rel="nofollow noreferrer">Jackson et al. (2020)</a> found about 500 low-mass members (<span class="math-container">$0.4-1.2M_\odot$</span>), that alone would add up to about <span class="math-container">$400 M_\odot$</span>, before considering the many high-mass stars.</p>

CC BY-SA 4.0
2021-01-16T13:27:04.943Z
Thank you Rob, would you say that 1500 $M_{\odot}$ is a reasonable estimate for this cluster?
Gabriel
CC BY-SA 4.0
2021-01-16T13:53:42.227Z
@Gabriel My counter question would be out to what radius? Out to the tidal radius, that is probably about right. There are uncertainties associated with what you assume about binarity and about the masses you assign to young low mass stars based on their luminosity. And of course - the papers I've referred to are mine.  But I cannot understand why Jilinski et al. and Piskunov et al. think it could be so much lower - the Piskunov number is based on some automated calculation for 100s of clusters.
ProfRob
CC BY-SA 4.0
2021-01-16T14:07:59.133Z
My own analysis (using synthetic clusters) gives a mass in the range $2000-3000 M_{\odot}$ (members selected in a 6x6 deg area), but indeed it depends heavily on the binary fraction. Your analysis seems to be the most accurate so far, so the range 950-1560 should probably in the WP article.
Gabriel
CC BY-SA 4.0
2021-01-16T15:13:27.383Z
@Gabriel how do you use synthetic cluster to estimte a mass? The tidal radius would be about that sort of area.
ProfRob
CC BY-SA 4.0
2021-01-17T01:37:04.037Z
I use my own code [ASteCA](http://asteca.github.io/)
Gabriel
CC BY-SA 4.0
2021-01-17T08:34:42.327Z
@Gabriel are you using the code on Gaia data?  I guess I'm confused by "synthetic", which would usually require you to input the cluster mass.
ProfRob
CC BY-SA 4.0
2021-01-17T12:03:48.453Z
I am indeed using Gaia data. The code allows to fit the mass as a free parameter, just like the metallicity, age, extinction, distance, and binary fraction.
Gabriel
CC BY-SA 4.0
2021-01-17T13:14:31.257Z
@Gabriel I will check this out. It would be interesting for instance to compare your membership probabilities with those in Jackson et al. (2020) that only use the kinematics and don't use the CMD information. I guess your larger mass might imply that the cluster is more extended than found in Jeffries et al. (2001). I could believe that. Is the 2016 paper your most recent description of the code?
ProfRob
CC BY-SA 4.0
2021-01-18T00:30:26.840Z
Would it be ok if I sent you an email with the details? The comment section here is a bit restrictive.
Gabriel
CC BY-SA 4.0
2021-01-16T01:15:20.817Z
2021-01-16T01:31:52.683Z
2021-01-16T01:31:52.683Z
ProfRob
<p>The <a href="https://en.wikipedia.org/wiki/NGC_2516" rel="nofollow noreferrer">Wikipedia entry</a> on NGC2516 mentions a mass value in the range <span class="math-container">$[10^5 - 10^6]\; M_{\odot}$</span>. This seems like a rather enormous value for an open cluster.</p>
<p>In <a href="https://iopscience.iop.org/article/10.1088/0004-637X/691/1/212" rel="nofollow noreferrer">Jilinski et al. (2009)</a> the authors state that:</p>
<blockquote>
<p>The total mass of NGC 2516 is presently not well known. Values as low as 170 solar masses have been proposed by Pandey et al. (1987) and as high as about 1000 <span class="math-container">$M_{\odot}$</span> by Dachs &amp; Kabus (1989). More recently a mass of ∼250 <span class="math-container">$M_{\odot}$</span> for this cluster has been quoted by Piskunov et al. (2008)</p>
</blockquote>
<p>Anybody has a better/more recent estimate?</p>

CC BY-SA 4.0
2021-01-14T21:20:01.053Z
Looks like a bad value that has been there since 2006 and the first sub article. Suggest you just edit with the sources you have here.
James K
<mass><star-cluster>
Mass estimate for cluster NGC2516?
Gabriel
# Mass estimate for cluster NGC2516?

(Asked by: username_0 on 2021-01-14)

The [Wikipedia entry](https://en.wikipedia.org/wiki/NGC_2516) on NGC2516 mentions a mass value in the range $[10^5 - 10^6]\; M\_{\odot}$. This seems like a rather enormous value for an open cluster.

In [Jilinski et al. (2009)](https://iopscience.iop.org/article/10.1088/0004-637X/691/1/212) the authors state that:

> The total mass of NGC 2516 is presently not well known. Values as low as 170 solar masses have been proposed by Pandey et al. (1987) and as high as about 1000 $M\_{\odot}$ by Dachs & Kabus (1989). More recently a mass of ∼250 $M\_{\odot}$ for this cluster has been quoted by Piskunov et al. (2008)

Anybody has a better/more recent estimate?

**Tags:** mass, star-cluster
> **Comments:**
> **username_1**: Looks like a bad value that has been there since 2006 and the first sub article. Suggest you just edit with the sources you have here.  

---

## 1 answers

### Answer by username_2 on 2021-01-16. Score: 1 | Accepted answer

NGC 2516 is somewhat richer and more massive than the Pleiades. A careful look at the mass function suggests there is about $1000 M\_{\odot}$ in stars $\geq 0.3 M\_{\odot}$, within the central 0.9 square degrees (with about a 15% uncertainty), but there is probably a few hundred solar masses beyond this ([Jeffries et al. 2001](https://arxiv.org/abs/astro-ph/0107097)). This agrees with the figures of Dachs & Kabus (1989), who essentially extrapolated from the numbers of high-mass stars using a typical cluster mass function.

New Gaia data will probably provide a more complete census in the halo of the cluster. There will also be some additional mass in lower mass stars and brown dwarfs, but this is unlikely to add more than 10% to the figure.

The lower masses quoted in your question are way too low. In an incomplete spectroscopic survey of the central square degree, a recent paper by
[Jackson et al. (2020)](https://arxiv.org/abs/2006.09423) found about 500 low-mass members ($0.4-1.2M\_\odot$), that alone would add up to about $400 M\_\odot$, before considering the many high-mass stars.

> **Comments:**
> **username_0**: Thank you Rob, would you say that 1500 $M_{\odot}$ is a reasonable estimate for this cluster?  
> **username_2**: @Gabriel My counter question would be out to what radius? Out to the tidal radius, that is probably about right. There are uncertainties associated with what you assume about binarity and about the masses you assign to young low mass stars based on their luminosity. And of course - the papers I've referred to are mine.  But I cannot understand why Jilinski et al. and Piskunov et al. think it could be so much lower - the Piskunov number is based on some automated calculation for 100s of clusters.  
> **username_0**: My own analysis (using synthetic clusters) gives a mass in the range $2000-3000 M_{\odot}$ (members selected in a 6x6 deg area), but indeed it depends heavily on the binary fraction. Your analysis seems to be the most accurate so far, so the range 950-1560 should probably in the WP article.  
> **username_2**: @Gabriel how do you use synthetic cluster to estimte a mass? The tidal radius would be about that sort of area.  
> **username_0**: I use my own code [ASteCA](http://asteca.github.io/)  
> **username_2**: @Gabriel are you using the code on Gaia data?  I guess I'm confused by "synthetic", which would usually require you to input the cluster mass.  
> **username_0**: I am indeed using Gaia data. The code allows to fit the mass as a free parameter, just like the metallicity, age, extinction, distance, and binary fraction.  
> **username_2**: @Gabriel I will check this out. It would be interesting for instance to compare your membership probabilities with those in Jackson et al. (2020) that only use the kinematics and don't use the CMD information. I guess your larger mass might imply that the cluster is more extended than found in Jeffries et al. (2001). I could believe that. Is the 2016 paper your most recent description of the code?  
> **username_0**: Would it be ok if I sent you an email with the details? The comment section here is a bit restrictive.  

---

