User talk:Aua/Archive5

Image:Graphics.gif listed for deletion
An image or media file that you uploaded or altered, Image:Graphics.gif, has been listed at Images and media for deletion. Please see the to see why this is (you may have to search for the title of the image to find its entry), if you are interested in it not being deleted. Nv8200p talk 02:27, 4 April 2008 (UTC)

April GA Newsletter
The April issue of the WikiProject Good Articles Newsletter is now available. Dr. Cash (talk) 03:45, 7 April 2008 (UTC)

WikiProject Good Articles May Newsletter
The May Newsletter for WikiProject Good Articles has now been published. Dr. Cash (talk) 22:16, 2 May 2008 (UTC)

black holes in globular clusters
Hey Timothy --

I'm new to trying to affect the content on Wikipedia entries, but I noticed an error and update that should be made to the Black Hole article - in particular, to the section on "Intermediate-mass black holes in globular clusters."

The final paragraph there mentions the likely discovery of a black hole in a globular cluster orbiting NGC 4472, and cites that the black hole mass could be about 400 solar masses. In fact, that paper really only claims the (first highly reliable) discovery of a black hole in a globular cluster, but is pretty clear that they're unable to make strong claims on the mass of this black hole. It could be a black hole of approximately 10 solar masses accreting at the Eddington limit (the maximum accretion rate of a black hole), or it could be a larger (e.g., intermediate-mass) black hole with sub-Eddington accretion.

I'm part of the team which has done follow-up work on that black hole (working with the team which made the original discovery). The paper was recently submitted to the Astrophysical Journal Letters and is available at:

http://xxx.lanl.gov/abs/0805.2952

The basic result is that based on a spectrum obtained at Keck Observatory, we're pretty certain that the black hole has a mass of only 10 solar masses (accreting at the Eddington limit).

One unsettling implication of this result is that, based on stellar dynamics work from the early 90's, any globular cluster hosting a stellar mass black hole (e.g., something small like the 10 solar mass black hole we found) would be *extremely unlikely* to host an intermediate mass black hole. Based on statistics of one, this suggests that, in fact, *globular clusters don't host intermediate-mass black holes*!

Cheers,

Danielstern (talk) 17:06, 1 June 2008 (UTC)danielstern