Paper: astro-ph/0509359
Date: Tue, 13 Sep 2005 20:15:35 GMT (71kb)

Title: All quiet in Globular Clusters

Authors: Andrej Dobrotka (Slovak Univ. of Technology, IAP), Jean-Pierre Lasota
(IAP), Kristen Menou (Columbia Univ.)

Comments: 10 pages, 6 figures
\\
Cataclysmic Variables (CVs) should be present in large numbers in Globular
Clusters (GCs). Numerous low-luminosity X-ray sources identified over the past
few years as candidate CVs in GCs support this notion. Yet, very few
"cataclysms," the characteristic feature of this class of objects in the field,
have been observed in GCs. We address this discrepancy here, within the
framework of the standard Disk Instability Model for CV outbursts. We argue
that the paucity of outbursts in GCs is probably not a direct consequence of
the donors' low metallicities. We present diagnostics based on outburst
properties allowing tests of the hypothesis that rare cataclysms are entirely
due to lower mass transfer rates in GCs relative to the field, and we argue
against this explanation. Instead, we propose that a combination of low mass
transfer rates (>~ 10^14-15 g/s) and moderately strong white dwarf magnetic
moments (>~ 10^30 G cm^3) stabilize CV disks in GCs and thus prevent most of
them from experiencing frequent outbursts. If it is so, rare cataclysms in GCs
would signal important evolutionary differences between field and cluster CVs.

\\ ( http://arXiv.org/abs/astro-ph/0509359 , 71kb)