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From: Ian Glass  isg@canopus.saao.ac.za 
To: gcnews@aoc.nrao.edu
Subject: abstract

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%ftp://ftp.saao.ac.za/pub/isg/survey.ps.gz

\begin{document}
\title{Large Amplitude 
variables near the Galactic Centre} 

\author{I.S. Glass$^1$, S. Matsumoto$^2$, B.S. Carter$^3$ 
and K. Sekiguchi$^4$}
\institute{$^1$South African Astronomical Observatory, PO Box 9,
Observatory 7935, South Africa \\$^2$Institute of Astronomy, University of
Tokyo, Mitaka, Tokyo 181, Japan\\ $^3$Carter Observatory, PO Box 2909,
Wellington, New Zealand \\ $^4$Subaru Telescope, NAOJ, 650 North A'ohoku
Place, Hilo, HI 96720, USA}

\maketitle

\begin{abstract}
We report here the results of a four-year {\it K}-band (2.2\,$\mu$m) survey 
for large-amplitude variable stars in a 24 $\times$ 24 arcmin$^2$ area 
centered on the Galactic Centre. A total of 409 likely long-period variables
(LPVs) were detected, for which positions, amplitudes, average magnitudes and 
periods were obtained whenever possible. The surface density of LPVs is 
more than ten times greater than in the Sgr I Baade's window at 
$l$ = 1.37$^{\circ}$, $b$ = --2.63$^{\circ}$.
      
The limits of completeness arising from interstellar and circumstellar 
absorption are discussed. Most of the area suffers interstellar extinction 
of 20 $<$ $A_V$ $<$ 40 mag. The shorter-period LPVs are less luminous
than the longer-period ones and may be slightly under-represented in the
data. Extremely heavy extinction ($A_V$ $>$ 40 mag), which affects the 
probability of detecting variables, occurs in less than 25\% of the area. 

Almost all of the LPVs are Miras or OH/IR stars, with periods ranging from
150 days to about 800 days. $K$-band counterparts have been found for 59\% 
of the 109 known OH sources in the field. The average period of the variables 
found is 427 days, while that of the OH/IR stars is 524 days. For
comparison, the average period in the Sgr I window, which contains no known 
OH/IR stars, is 333 days and only two stars are detected with $P$ $>$ 600
days. The survey field also contains a number of long-period, large-amplitude 
variables which are not OH emitters.

\end{abstract}

\end{document}

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