------------------------------------------------------------------------ richichi_I.tex A&A, Jul 2008, in press MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_79293_454038.1216622472820" X-Google-Sender-Auth: 9cd85cb7d361a4ca X-MailScanner-Information: Please contact the postmaster@aoc.nrao.edu for more information X-MailScanner-ID: m6L6fDml007651 X-MailScanner: Found to be clean X-MailScanner-SpamCheck: not spam, SpamAssassin (not cached, score=0.001, required 5, autolearn=disabled, HTML_MESSAGE 0.00) X-MailScanner-From: octavi.fors@gmail.com X-Spam-Status: No ------=_Part_79293_454038.1216622472820 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline %astro-ph/0807.2646 \documentclass{aa} \usepackage{graphicx} \usepackage{longtable} \usepackage{txfonts} \begin{document} \title{Milliarcsecond angular resolution of reddened stellar sources in the vicinity of the Galactic Center\thanks{Based on observations made with ESO telescopes at Paranal Observatory} } \author{A. Richichi\inst{1} \and O. Fors\inst{2}\fnmsep\inst{3} \and E. Mason\inst{4} \and J. Stegmaier\inst{1} \and T. Chandrasekhar\inst{5} } \institute{ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei M\"unchen, Germany \email{arichich@eso.org } \and Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Mart\'{\i} i Franqu\'es 1, 08028 Barcelona, Spain \and Observatori Fabra, Cam\'{\i} de l'Observatori s/n, 08035 Barcelona, Spain \and European Southern Observatory, Santiago, Chile \and Physical Research Laboratory, 380009 Ahmedabad, India } \abstract % context heading (optional) % {} leave it empty if necessary % {heading (optional)} {} % aims heading (mandatory) {For the first time, the lunar occultation technique has been employed on a very large telescope in the near-IR with the aim of achieving systematically milliarcsecond resolution on stellar sources. } % methods heading (mandatory) { We have demonstrated the burst mode of the ISAAC instrument, using a fast read-out on a small area of the detector to record many tens of seconds of data at a time on fields of few squared arcseconds. We have used the opportunity to record a large number of LO events during a passage of the Moon close to the Galactic Center in March 2006. We have developed and employed for the first time a data pipeline for the treatment of LO data, including the automated estimation of the main data analysis parameters using a wavelet-based method, and the preliminary fitting and plotting of all light curves. } % results heading (mandatory) { We recorded 51 LO events over about four hours. Of these, 30 resulted of sufficient quality to enable a detailed fitting. We detected two binaries with subarcsecond projected separation and three stars with a marginally resolved angular diameter of about 2 milliarcseconds. Two more stars, which are cross-identified with SiO maser, were found to be resolved and in one case we could recover the brightness profile of the extended emission, which is well consistent with an optically thin shell. The remaining unresolved stars were used to characterize the performance of the method. } % conclusions heading (optional), leave it empty if necessary { The LO technique at a very large telescope is a powerful and efficient method to achieve angular resolution, sensitivity, and dynamic range that are among the best possible today with any technique. The selection of targets is naturally limited and LOs are fixed-time events, however each observation requires only a few minutes including overheads. As such, LOs are ideally suited to fill small gaps of idle time between standard observations. } \keywords{ Techniques: high angular resolution -- Astrometry -- Occultations -- Binaries -- Masers } ------=_Part_79293_454038.1216622472820 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline
%astro-ph/0807.2646

\documentclass{aa} 
\usepackage{graphicx}
\usepackage{longtable}
\usepackage{txfonts}
\begin{document}
\title{Milliarcsecond angular resolution of reddened stellar sources in the vicinity of the
Galactic Center\thanks{Based on observations made with ESO telescopes at Paranal Observatory}
}

\author{A. Richichi\inst{1}
             \and
            O. Fors\inst{2}\fnmsep\inst{3}
             \and
            E. Mason\inst{4}
             \and
            J. Stegmaier\inst{1}
             \and
           T. Chandrasekhar\inst{5}
           }
\institute{
             European Southern Observatory,
Karl-Schwarzschild-Str. 2, 85748 Garching bei M\"unchen, Germany
             \email{arichich@eso.org}
         \and
             Departament d'Astronomia i Meteorologia, Universitat de 
Barcelona, Mart\'{\i} i Franqu\'es 1, 08028 Barcelona, Spain
         \and
             Observatori Fabra, Cam\'{\i} de l'Observatori s/n, 08035
Barcelona, Spain
   \and
             European Southern Observatory, Santiago, Chile
   \and
         Physical Research Laboratory, 380009 Ahmedabad, India
}

\abstract
  % context heading (optional)
  % {} leave it empty if necessary 
  % {heading (optional)}
   {}
  % aims heading (mandatory)
   {For the first time, the lunar occultation technique has been
   employed on a very large telescope in the near-IR with the aim
   of achieving systematically milliarcsecond resolution on stellar
   sources.
   }
  % methods heading (mandatory)
   {
   We have demonstrated the burst mode of the ISAAC instrument,
   using a fast read-out on a small area of the detector to record
   many tens of seconds of data at a time on fields of few squared arcseconds.
   We have used the opportunity to record a large number of LO events
   during a passage of the Moon close to the Galactic Center in March 2006.
   We have developed and employed for the first time a
   data pipeline for the treatment of LO data, including the automated
   estimation of the main data analysis parameters using a wavelet-based method,
   and the preliminary fitting and plotting of all light curves.
   }
  % results heading (mandatory)
   {
   We recorded 51 LO events over about four hours. Of these, 30 resulted
   of sufficient quality to enable a detailed fitting.  We detected two
   binaries with subarcsecond projected separation and three stars with a
   marginally resolved angular diameter of about 2 milliarcseconds. Two more
   stars, which are cross-identified with SiO maser, were found to be
   resolved and in one case we could recover the brightness profile of
   the extended emission, which is well consistent with an optically thin
   shell. The remaining unresolved stars were used to characterize the
   performance of the method.
   }
  % conclusions heading (optional), leave it empty if necessary
   {
   The LO technique at a very large telescope is
   a powerful and efficient method to achieve
   angular resolution, sensitivity, and dynamic range that are among
   the best possible today with any technique. The selection of targets
   is naturally limited and LOs are fixed-time events, however
   each observation requires only a few minutes including overheads.
   As such, LOs are ideally suited to fill small gaps of idle time
   between standard observations.
   }

   \keywords{
Techniques: high angular resolution --
Astrometry --
Occultations --
Binaries --
Masers
}

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