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The Wikipedia entry 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) 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?

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    $\begingroup$ 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. $\endgroup$
    – James K
    Commented Jan 14, 2021 at 21:20

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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). 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) 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.

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  • $\begingroup$ Thank you Rob, would you say that 1500 $M_{\odot}$ is a reasonable estimate for this cluster? $\endgroup$
    – Gabriel
    Commented Jan 16, 2021 at 13:27
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    $\begingroup$ @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. $\endgroup$
    – ProfRob
    Commented Jan 16, 2021 at 13:53
  • $\begingroup$ 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. $\endgroup$
    – Gabriel
    Commented Jan 16, 2021 at 14:07
  • $\begingroup$ @Gabriel how do you use synthetic cluster to estimte a mass? The tidal radius would be about that sort of area. $\endgroup$
    – ProfRob
    Commented Jan 16, 2021 at 15:13
  • $\begingroup$ I use my own code ASteCA $\endgroup$
    – Gabriel
    Commented Jan 17, 2021 at 1:37

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