Upper limits on the central black hole masses of 47Tuc and NGC6397 (preprint)

[NGC104, NGC6397] New preprint:

S. De Rijcke, P. Buyle, H. Dejonghe

"Upper limits on the central black hole masses of 47Tuc and NGC6397"

4 pages, 1 figure, accepted for publication by MNRAS

"We present upper-limits on the masses of the putative central intermediate-mass black holes in two nearby Galactic globular clusters: 47Tuc (NGC104), the second brightest Galactic globular cluster, and NGC6397, a core-collapse globular cluster and, with a distance of 2.7 kpc, quite possibly the nearest globular cluster, using a technique suggested by T. Maccarone. These mass estimates have been derived from 3sigma upper limits on the radio continuum flux at 1.4 GHz, assuming that the putative central black hole accretes the surrounding matter at a rate between 0.1% and 1% of the Bondi accretion rate. For 47Tuc, we find a 3sigma upper limit of 2060 - 670 solar masses, depending on the actual accretion rate of the black hole and the distance to 47Tuc. For NGC6397, which is closer to us, we derive a 3sigma upper limit of 1290 - 390 solar masses..."

http://arxiv.org/abs/astro-ph/0601450