Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Newly discovered brown dwarfs not seen in microlensing time scale
  frequency distribution?   The 2-Micron All Sky Survey (2MASS) (Skrutskie et al. 1997) and the DEep Near
Infrared Survey of the southern sky (DENIS) (Epchtein et al. 1997) have
revealed a heretofore unknown population of free brown dwarfs that has extended
the local mass function down to as small as 0.01M_sun (Reid et al. 1999). If
this local proportion of brown dwarfs extends throughout the Galaxy---in
particular in the Galactic bulge---one expects an increase in the predicted
fraction of short time scale microlensing events in directions toward the
Galactic bulge. Zhao et al.(1996) have indicated that a mass function with
30-60% of the lens mass in brown dwarfs is not consistent with empirical
microlensing data. Here we show that even the much lower mass fraction (~ 10%)
of brown dwarfs inferred from the new discoveries appears inconsistent with the
data. The added brown dwarfs do indeed increase the expected number of short
time scale events, but they appear to drive the peak in the time scale
frequency distribution to time scales smaller than that observed, and do not
otherwise match the observed distribution. A reasonably good match to the
empirical data (Alcock et al. 1996) is obtained by increasing the fraction of
stars in the range 0.08<m<0.7M_sun considerably above that deduced from several
star counts. However, all inferences from microlensing about the appropriate
stellar mass function must be qualified by the meagerness of the microlensing
data and the uncertainties in the Galactic model.

11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
33
The categories of this paper are: plasm-ph
12
The categories of this paper are: nucl-th
3
The categories of this paper are: physics
8
The categories of this paper are: hep-ex
1
The categories of this paper are: cs
16
The categories of this paper are: stat
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph