Revealing the nature of the highly obscured galactic source IGR J16318$-$4848\altaffilmark{0}
S. Chaty
\altaffilmark{1,2,4} and P. Filliatre\altaffilmark{2,3}
The X-ray source IGR J16318$-$4848 was the first source discovered by INTEGRAL on 2003, January 29. We carried out optical and near-infrared (NIR) observations at the European Southern Observatory (ESO La Silla) in the course of a Target of Opportunity (ToO) programme. We discovered the optical counterpart and confirmed an already proposed NIR candidate. NIR spectroscopy revealed a large amount of emission lines, including forbidden iron lines and P-Cygni profiles. The spectral energy distribution of the source points towards a high luminosity and a high temperature, with an absorption greater than the interstellar absorption, but two orders of magnitude lower than the X-ray absorption. We show that the source is an High Mass X-ray binary (HMXB) at a distance between $\sim 1$ and $\sim 6$ kpc, the mass donor being an early-type star, probably a sgB[e] star, surrounded by a rich and absorbing circumstellar material. This would make the second High Mass X-ray Binary (HMXB) with a sgB[e] star after CI Cam, indicating that a new class of strongly absorbed X-ray binaries is being unveiled by INTEGRAL.
schaty.tex
\documentclass[preprint,proceedings]{rmaa}
% The preprint option sets the first page header to contain the name
% of the conference. It will be ignored when typesetting the final
% volume. 

%%%
%%% Load any optional packages you need here with \usepackage
%%% 

% This allows compact, in-paragraph, and as-paragraph  versions of the
% standard itemize and enumerate environments. 
\usepackage{paralist}

% These are used in one of the graphics examples
\usepackage{psfrag,color}

%%%
%%% Define any personal macros here
%%% 

% These are some I use in typesetting example code
\newcommand{\bs}{\textbackslash}
\providecommand{\cs}[1]{\texttt{\textbackslash #1}}
\newenvironment{Example}
{\begin{list}{}{\setlength{\leftmargin}{5pt}\setlength{\rightmargin}{5pt}}\item[]}
  {\end{list}}

 \def\microns{\mbox{ } \mu \mbox{m}}
\def\deg{^{\circ}}
 
%%%
%%% Article preamble commands (title, authors, abstract, etc.) 
%%% None of these produce any output themselves, they just set things 
%%% up for \maketitle
%%%

% This is only used for making the header for the preprint version
\SetYear{2003}
\SetConfTitle{Compact Binaries in the Galaxy and beyond}

% Please use mixed case here, since this title gets propagated onto
% the web page, ADS entry, etc. 
\title{Revealing the nature of the highly obscured galactic source IGR J16318$-$4848\altaffilmark{0}} 

% For the conference proceedings, the author affiliations should be
% subscripted, using \altaffil and/or \altaffilmark + \altaffiltext
% Note that \altaffilmark goes after a comma and that `and' is spelt
% out.
\author{
  S. Chaty,\altaffilmark{1,2,4} 
  and P. Filliatre\altaffilmark{2,3}
  }

% Note that \altaffil, \altaffilmark go inside the scope of the
% \author{...} command but \altaffiltext is outside it. 
\altaffiltext{1}{Universit\'e Paris 7, 2 place Jussieu,
F-75 005 Paris, France.}
\altaffiltext{2}{Service d'Astrophysique, DSM/DAPNIA/SAp,
CEA/Saclay, F-91 191 Gif-sur-Yvette, Cedex, France.}
\altaffiltext{3}{F\'ed\'eration de Recherche APC, Paris, France.}
\altaffiltext{4}{chaty@cea.fr}
%, filliatr@discovery.saclay.cea.fr
\altaffiltext{0}{Based on observations collected at the European Southern Observatory, Chile (observing proposal ESO N$^o$ 70.D-0340).}
%  }

% Authors for running headers - surnames only, et al. if more than 3. 
\shortauthor{Chaty \& Filliatre}
% Title for running header
%\shorttitle{Revealing the obscured source IGR J16318$-$4848}

% Full postal addresses (in alphabetical surname order!)
% plus email addresses in parentheses. 
\suppressfulladdresses
%\fulladdresses{
%\item \email{chaty@cea.fr}
%}
% Formatted in list environment, so each group is an \item
%\item S. Chaty: Universit\'e Paris 7, 2 place Jussieu, F-75 005 Paris, France
% and Service d'Astrophysique, DSM/DAPNIA/SAp, CEA/Saclay, F-91 191 Gif-sur-Yvette, Cedex, France
%  (\email{chaty@cea.fr}).
%% Note final period.
%}

% List of authors used to construct table of contents
\listofauthors{S. Chaty \& P. Filliatre}
% Each author in Surname, Initials format, used in generating Author
% Index entries.
\indexauthor{Chaty, S.}
\indexauthor{Filliatre, P.}

% English abstract
\abstract{The X-ray source IGR J16318$-$4848 was the first source discovered by INTEGRAL on 2003, January 29. 
We carried out optical and near-infrared (NIR) observations 
at the European Southern Observatory (ESO La Silla) in the course of a Target of Opportunity (ToO) programme. 
We discovered the optical counterpart and confirmed an already proposed NIR
candidate.
NIR spectroscopy revealed a large amount of emission lines, including forbidden iron lines and P-Cygni profiles. The spectral energy distribution of the source points towards a high luminosity and a high temperature,
 with an absorption greater than the interstellar absorption, but two orders of magnitude lower than the X-ray absorption. We show that the source is an High Mass X-ray binary (HMXB) at a distance between $\sim 1$ and $\sim 6$ kpc, 
the mass donor being an early-type star, probably a sgB[e] star, surrounded by a rich and absorbing circumstellar material. This would make the second High Mass X-ray Binary (HMXB) with a sgB[e] star after CI Cam, indicating that a new class of strongly absorbed X-ray binaries is being unveiled by INTEGRAL.
}

% Spanish abstract - leave blank and it will be translated by the
% editors. 
%\resumen{Presentamos los resultados de observaciones a frecuencias
%  m\'ultiples del proplyd LV~2 (M42~167--317) en la nebulosa de Ori\'on,
%  concentrando sobre nuestra analis\'\i{}s del ``microjet'' unidireccional
%  que sale del frente de ionizci\'on del proplyd.}


% Keywords must be from the standard list and in alphabetical order. 
\addkeyword{stars: circumstellar matter}
\addkeyword{stars: emission-line}
\addkeyword{Be---X-rays: binaries}
\addkeyword{IGR J16318-4848}

%%%
%%% Beginning of document proper
%%%
\begin{document}
% Typeset article header
\maketitle


%\hspace*{0.4cm} OBSERVATIONS AND RESULTS
%\label{sec:intro}

IGR J16318$-$4848 has been the first source to be discovered by 
the INTEGRAL imager IBIS/ISGRI on 2003 January 29, 
$0.5\deg$ south from the galactic equator \citep{courvoisier}.
A subsequent observation by XMM-Newton 
on 2003 February 10 localized it with an accuracy of $4\arcsec$,
the high energy spectrum suggesting
a high column density of $N_{\rm H}> 10^{24}\,\rm cm^{-2}$
(\citet{matt}, \citet{walter}).
In the course of a ToO programme at ESO to look for counterparts of
 high energy sources discovered by satellites including INTEGRAL (PI S. Chaty), we carried out on 2003, February, 23-25 photometric and spectroscopic observations in the optical and NIR
of the high-energy source IGR J16318$-$4848, with EMMI and SOFI instruments on ESO/NTT. 
We discovered the optical counterpart and confirmed the NIR one 
(see \citet{walter}) by independent astrometry.
The optical/NIR images and spectra are shown in Figures \ref{fig:f4},
\ref{fig:f6}, \ref{fig:f15}, \ref{fig:f16} and \ref{fig:f17}.
We derived the absorption along the line of sight: Av$\sim 17.4$ magnitudes,
and the temperature of the companion star: $\sim 18000$ K.
The distance of the source is constrained between $\sim 1$ and $\sim 6$ kpc.
The $0.95 - 2.52\,\micron$ NIR spectrum is highly unusual, very rich in emission lines, suggesting 
a highly complex and stratified circumstellar environment, or an enveloppe.
Study of the spectral lines suggest a sgB[e] star so the system
would be a HMXB, probably hosting a neutron star,
like CI Cam.
The reader should consult \citet{filliatre} for more details.
INTEGRAL is on the course of revealing a new population of
obscured high energy sources, which might help us to understand 
the evolution of high-energy binary systems.

\begin{figure}[!t]
  \includegraphics[width=\columnwidth]{f3label.eps}
  \caption{R band image of the field of view of IGR J16318$-$4848.
We reported the XMM uncertainty circle of $4\arcsec$.}
  \label{fig:f4}
\end{figure}

\begin{figure}[!t]
  \includegraphics[width=\columnwidth]{f8label.eps}
  \caption{Ks band image of the same field.}
  \label{fig:f6}
\end{figure}

\begin{figure}[!t]
  \includegraphics[angle=0,width=\columnwidth]{spec_gbf.eps}
  \caption{NIR spectrum (0.95$-$1.65 $\microns$)}
  \label{fig:f15}
\end{figure}

\begin{figure}[!t]
  \includegraphics[angle=0,width=\columnwidth]{spec_grf_p1.eps}
  \caption{NIR spectrum (1.5$-$2.05 $\microns$)}
  \label{fig:f16}
\end{figure}

\begin{figure}[!t]
  \includegraphics[angle=0,width=\columnwidth]{spec_grf_p2.eps}
  \caption{NIR spectrum (2.0$-$2.55 $\microns$)}
  \label{fig:f17}
\end{figure}

\acknowledgements

SC is grateful to Rob Hynes, Joanna Mikolajewska, Ignacio Negueruela 
and Marc Rib\'o for very helpful
discussions on the nature of the source during this IAU colloquium.

\begin{thebibliography}

\bibitem[Courvoisier et al. (2003)]{courvoisier} Courvoisier, T.J.-L., Walter, R., Rodriguez, J. et al. 2003, \iaucirc., 8063

\bibitem[Filliatre \& Chaty (2004)]{filliatre} Filliatre, P., Chaty, S., 2004, ApJ subm.

%\bibitem[Lebrun et al. (2003)]{lebrun} Lebrun, F., Leray, J. P., Lavocat, P. et al. 2003, \aap, 411, L141

\bibitem[Matt \& Guainazzi (2003)]{matt} Matt, G. \& Guainazzi, M. 2003, \mnras, 341, L13

%\bibitem[Str\"{u}der et al. (2001)]{struder} Str\"{u}der, L., Briel, U., Dennerl, K. et al. 2001, \aap, 365, L18

%\bibitem[Turner et al. (2001)]{turner} Turner, M. J. L., Abbey, A., Arnaud, M. et al. 2001, \aap, 365, L27

%\bibitem[Ubertini et al. (2003)]{ubertini} Ubertini, P., Lebrun, F., Di Cocco, G., et al. 2003, \aap, 411, L131

\bibitem[Walter et al. (2003)]{walter} Walter, R., Rodriguez, J., Foschini, L.
et al. 2003, \aap, 411, L427

\end{thebibliography}

\end{document}

astro-ph0404332.extracted_bib
\begin{thebibliography}

\bibitem[Courvoisier et al. (2003)]{courvoisier} Courvoisier, T.J.-L., Walter, R., Rodriguez, J. et al. 2003, \iaucirc., 8063

\bibitem[Filliatre \& Chaty (2004)]{filliatre} Filliatre, P., Chaty, S., 2004, ApJ subm.

%\bibitem[Lebrun et al. (2003)]{lebrun} Lebrun, F., Leray, J. P., Lavocat, P. et al. 2003, \aap, 411, L141

\bibitem[Matt \& Guainazzi (2003)]{matt} Matt, G. \& Guainazzi, M. 2003, \mnras, 341, L13

%\bibitem[Str\"{u}der et al. (2001)]{struder} Str\"{u}der, L., Briel, U., Dennerl, K. et al. 2001, \aap, 365, L18

%\bibitem[Turner et al. (2001)]{turner} Turner, M. J. L., Abbey, A., Arnaud, M. et al. 2001, \aap, 365, L27

%\bibitem[Ubertini et al. (2003)]{ubertini} Ubertini, P., Lebrun, F., Di Cocco, G., et al. 2003, \aap, 411, L131

\bibitem[Walter et al. (2003)]{walter} Walter, R., Rodriguez, J., Foschini, L.
et al. 2003, \aap, 411, L427

\end{thebibliography}