------------------------------------------------------------------------
From: Martin Groenewegen  groen@ster.kuleuven.be 
To: gcnews@aoc.nrao.edu
Subject: submit dgc.tex A&A accepted

% astro-ph/0801.2652


\documentclass[]{aa}
\usepackage{graphicx, times, amsfonts}


\renewcommand{\topfraction}{0.999}
\renewcommand{\textfraction}{0.001}

\newcommand{\less}{\raisebox{-1.1mm}{$\stackrel{<}{\sim}$}}
\newcommand{\more}{\raisebox{-1.1mm}{$\stackrel{>}{\sim}$}}
\newcommand{\msol}{\mbox{M$_{\odot}$}}
\newcommand{\rsol}{\mbox{R$_{\odot}$}}
\newcommand{\msolyr}{{M$_{\odot}$}\,yr$^{-1}$ }
\newcommand{\lsol}{\mbox{L$_{\odot}$}}
\newcommand{\bdouble}{\baselineskip 1.25\baselineskip}
\newcommand{\rdouble}{\baselineskip 0.85\baselineskip}
\newcommand{\ratio}{$^{12}$C/$^{13}$C }
\newcommand{\kks}{K km s$^{-1}$}
\newcommand{\ks}{km s$^{-1}$}
\newcommand{\kspc}{km s$^{-1}$ pc$^{-1}$}
\newcommand{\HP}{{\sc hipparcos}}
\newcommand{\C}{cepheids}
\newcommand{\M}{{\sc 2mass}}
\newcommand{\OG}{{\sc ogle}}
\newcommand{\DE}{{\sc denis}}
\newcommand{\tc}{Population {\sc ii} Cepheids}

\begin{document}



\title{The distance to the Galactic Centre based on Population {\sc ii}
Cepheids and RR Lyrae stars
}

\author{
M.A.T.~Groenewegen
\inst{1}
\and
A.~Udalski
\inst{2}
\and
G.~Bono
\inst{3,4}
}


\institute{
Instituut voor Sterrenkunde, Celestijnenlaan 200 D,
B--3001 Leuven, Belgium \\ \email{groen@ster.kuleuven.be}
\and
Warsaw University Observatory, Aleje Ujazdowskie 4, PL-00-478, Warsaw,
Poland
\and
INAF Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monte
Porzio Catone, Italy
\and
European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching
bei Munchen, Germany
}

\date{received: 2007,  accepted:  2008}

\offprints{Martin Groenewegen}


\begin{abstract}The distance to the Galactic Centre (GC) is of importance
for the distance scale in the Universe.  The value derived by
Eisenhauer et al. (2005) of 7.62 $\pm$ 0.32 kpc based on the orbit of
one star around the central black hole is shorter than most other
distance estimates based on a variety of different methods.
To establish an independent distance to the GC with high accuracy.
To this end Population-{\sc ii} Cepheids are used that have been
discovered in
the \OG-{\sc ii} and \OG-{\sc iii} surveys.
Thirty-nine Population-{\sc ii} Cepheids have been monitored with the
SOFI infrared camera on 4 nights spanning 14 days, obtaining typically
between 5 and 11 epochs of data. Light curves have been fitted using
the known periods from the OGLE data to determine the mean $K$-band
magnitude with an accuracy of 0.01-0.02 mag. It so happens that 37 RR
Lyrae stars are in the field-of-view of the observations and mean
$K$-band magnitudes are derived for this sample as well.
After correction for reddening, the period-luminosity relation of
Population-{\sc ii} Cepheids in the $K$-band is determined, and the
derived slope of $-2.24 \pm 0.14$ is consistent with the value derived
by Matsunaga et al. (2006). Fixing the slope to their more accurate
value results in a zero point, and implies a distance modulus to the
GC of 14.51 $\pm$ 0.12, with an additional systematic uncertainty of
0.07 mag.  Similarly, from the RR Lyrae $K$-band period-luminosity
relation we derive a value of 14.48 $\pm$ 0.17 (random) $\pm$ 0.07 (syst.).
The two independent determinations are averaged to find
14.50 $\pm$ 0.10 (random) $\pm$ 0.07 (syst.), or 7.94 $\pm$ 0.37 $\pm$
0.26 kpc.

The absolute magnitude scale of the adopted period-luminosity
relations is tied to an LMC distance modulus of 18.50 $\pm$ 0.07.  }

\end{abstract}
\end{document}


-- 
*********************************************************************

Dr. Martin Groenewegen
PACS ICC-team

Instituut voor Sterrenkunde  Tel= +32 16 32 7005
Celestijnenlaan 200 D        Fax= +32 16 32 7999
B-3001 Leuven                Office= 04.40
Belgium

groen@ster.kuleuven.be    http://www.ster.kuleuven.be/~groen

Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm