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 sgrb2_gcnews.tex submitted to ApJ
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\documentclass[12pt,preprint]{aastex}
%astro-ph/0908.3637

\def\hho  {H$_2$O}
\def\SgrA {Sgr~A*}
\def\SgrB  {Sgr~B2}
\def\SgrBN {Sgr~B2N}
\def\SgrBM {Sgr~B2M}

\def\c    {$\sqrt{}$}
\def\x    {\phantom{$\sqrt{}$}}
\def\p    {\phantom{0}}
\def\err  {\phantom{$\pm$0.0}}
\def\blankline{\vskip 12 pt}

\def\kms  {km~s$^{-1}$}
\def\kmsperkpc  {km~s$^{-1}$~kpc$^{-1}$}
\def\masy {mas~y$^{-1}$}
\def\uasy {$\mu$as~y$^{-1}$}
\def\uas  {$\mu$as}
\def\deg  {\ifmmode {^\circ}\else {$^\circ$}\fi}
\def\porm {\ifmmode {\pm}\else {$\pm$}\fi}
\def\chisqpdf {\ifmmode {\chi^2_{\rm pdf}}\else {$\chi^2_{\rm pdf}$}\fi}
\def\chisq    {\ifmmode {\chi^2}\else {$\chi^2$}\fi}
\def\Msun {M$_\odot$}

\def\etal {et al.~}
\def\eg   {e.g.~}
\def\ie   {i.e.~}

\def\d    {\ifmmode {{\rlap{.}}^\circ}\else {${\rlap{.}}^\circ$}\fi}
\def\s    {\ifmmode {{\rlap{.}}^s}\else {${\rlap{.}}^s$}\fi}
\def\as   {\ifmmode {{\rlap{.}}^{''}}\else {${\rlap{.}}^{''}$}\fi}

\def\pa    {\ifmmode {\psi} \else {$\psi$}\fi}

\def\vlsr  {\ifmmode {v_{\rm LSR}}\else {$v_{\rm LSR}$}\fi}
\def\vlsrr {\ifmmode {v^r_{\rm LSR}}\else {$v^r_{\rm LSR}$}\fi}
\def\vhelio{\ifmmode {v_{Helio}}\else {$v_{Helio}$}\fi}

\def\ura   {\ifmmode {\mu_\alpha}\else {$\mu_\alpha$}\fi}
\def\udec  {\ifmmode {\mu_\delta}\else {$\mu_\delta$}\fi}

\def\uGal  {\ifmmode {\mu_{Gal}}\else {$\mu_{Gal}$}\fi}
\def\ul    {\ifmmode {\mu_l}\else {$\mu_l$}\fi}
\def\ub    {\ifmmode {\mu_b}\else {$\mu_b$}\fi}

\def\uml   {\ifmmode {v_{gr}}\else {$v_{gr}$}\fi}
\def\umb   {\ifmmode {v_b}\else {$v_b$}\fi}
\def\vsrad {\ifmmode {v_{rad}}\else {$v_{rad}$}\fi}

\def\upl   {\ifmmode {v^p_{gr}}\else {$v^p_{gr}$}\fi}
\def\upb   {\ifmmode {v^p_b}\else {$v^p_b$}\fi}
\def\vprad {\ifmmode {v^p_{rad}}\else {$v^p_{rad}$}\fi}

% Standard Solar Motion
\def\Vo    {\ifmmode {V^{Std}_\odot}\else {$V^{Std}_\odot$}\fi}
\def\Uo    {\ifmmode {U^{Std}_\odot}\else {$U^{Std}_\odot$}\fi}
\def\Wo    {\ifmmode {W^{Std}_\odot}\else {$W^{Std}_\odot$}\fi}
% Best (Hipparcos) Solar Motion
\def\VH    {\ifmmode {V^H_\odot}\else {$V^H_\odot$}\fi}
\def\UH    {\ifmmode {U^H_\odot}\else {$U^H_\odot$}\fi}
\def\WH    {\ifmmode {W^H_\odot}\else {$W^H_\odot$}\fi}
% Generic Solar Motion parameter
\def\V     {\ifmmode {V_\odot}\else {$V_\odot$}\fi}
\def\U     {\ifmmode {U_\odot}\else {$U_\odot$}\fi}
\def\W     {\ifmmode {W_\odot}\else {$W_\odot$}\fi}

% Source peculiar motion in own Galactocentric frame
\def\Vs    {\ifmmode {V_s}\else {$V_s$}\fi}
\def\Us    {\ifmmode {U_s}\else {$U_s$}\fi}
\def\Ws    {\ifmmode {W_s}\else {$W_s$}\fi}

% Average source peculiar motions
\def\Vsbar {\ifmmode {\overline{V_s}}\else {$\overline{V_s}$}\fi}
\def\Usbar {\ifmmode {\overline{U_s}}\else {$\overline{U_s}$}\fi}
\def\Wsbar {\ifmmode {\overline{W_s}}\else {$\overline{W_s}$}\fi}

\def\pars  {\ifmmode{\pi_s}\else{$\pi_s$}\fi}

\def\Ts    {\ifmmode{\Theta_s}\else{$\Theta_s$}\fi}
\def\Tdot  {\ifmmode{d\Theta\over dR}\else{$d\Theta\over dR$}\fi}

\def\Rp    {\ifmmode{R_p}\else{$R_p$}\fi}

\def\To    {\ifmmode{\Theta_0}\else{$\Theta_0$}\fi}
\def\Ro    {\ifmmode{R_0}\else{$R_0$}\fi}

\def\Ho    {\ifmmode{H_0}\else{$H_0$}\fi}
\def\kmspermpc  {km s$^{-1}$ Mpc$^{-1}$}

\def\Dx    {\ifmmode{\Delta x}\else{$\Delta x$}\fi}
\def\Dy    {\ifmmode{\Delta y}\else{$\Delta y$}\fi}


%=================================================================
%\slugcomment{2009 Aug 25}
\shorttitle{Parallax of Sgr B2}
\shortauthors{Reid \etal}

\begin{document}

\title{A Trigonometric Parallax of Sgr B2}

\author{M. J. Reid\altaffilmark{1}, K. M. Menten\altaffilmark{2},
         X. W. Zheng\altaffilmark{3}, A. Brunthaler\altaffilmark{2},
         Y. Xu\altaffilmark{4}
    Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA}
    Auf dem H\"ugel 69, 53121 Bonn, Germany}
\altaffiltext{3}{Department of Astronomy, Nanjing University
    Nanjing 210093, China}
\altaffiltext{4}{Purple Mountain Observatory, Chinese Academy of
    Sciences, Nanjing 210008, China}


\begin{abstract}
We have measured the positions of \hho\ masers in \SgrB, a massive star 
forming region in the Galactic center, relative to an extragalactic 
radio source with the Very Long Baseline Array.  The positions measured 
at 12 epochs over a time span of one year yield the trigonometric 
parallax of \SgrB\ and hence a distance to the Galactic center of 
$\Ro=7.9^{+0.8}_{-0.7}$~kpc.  The proper motion of \SgrB\ relative to 
\SgrA\ suggests that \SgrB\ is $\approx0.13$~kpc nearer than the 
Galactic center, assuming  a low-eccentricity Galactic orbit.
\end{abstract}


\end{document}


-------------------------------------------------------------
Mark J. Reid                 Phone: 617-495-7470
Harvard-Smithsonian CfA      Fax  : 617-495-7345
60 Garden Street             Email: reid@cfa.harvard.edu
Cambridge, MA 02138, USA     Web  : www.cfa.harvard.edu/~reid
-------------------------------------------------------------