------------------------------------------------------------------------ young_stars.tex ApJ, 638, 183, 2006 in press Date: Thu, 26 Jan 2006 14:43:33 -0800 X-Mailer: Apple Mail (2.746.2) X-Probable-Spam: no X-Spam-Hits: 0.087 X-Spam-Report: HTML_40_50,HTML_MESSAGE X-Scanned-By: smtp.ucla.edu on 169.232.47.136 X-MailScanner-Information: Please contact postmaster@aoc.nrao.edu for more information X-MailScanner: Found to be clean X-MailScanner-SpamCheck: not spam, SpamAssassin (score=0.001, required 5, autolearn=disabled, HTML_MESSAGE 0.00) X-MailScanner-From: mmuno@ucla.edu --Apple-Mail-6--1053060336 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed %astro-ph/0509617 \documentclass{emulateapj} \newcommand{\etal}{\mbox{et al.}} \newcommand{\ergcms}{erg cm$^{-2}$ s$^{-1}$} \newcommand{\ergs}{erg s$^{-1}$} \newcommand{\phcms}{ph cm$^{-2}$ s$^{-1}$} \newcommand{\degree}{$^\circ$} \newcommand{\msun}{$M_{\odot}$} \newcommand{\pc}{\,{\rm pc}} \newcommand{\yr}{\,{\rm yr}} \newcommand{\gyr}{\,{\rm Gyr}} \newcommand{\emsun}{\,M_\odot} \newcommand{\au}{\,{\rm AU}} \newcommand{\chandra}{{\it Chandra}} \newcommand{\rosat}{{\it ROSAT}} \newcommand{\granat}{{\it GRANAT}} \newcommand{\asca}{{\it ASCA}} \newcommand{\einstein}{{\it Einstein}} \newcommand{\bepposax}{{\it BeppoSAX}} \newcommand{\xmm}{{\it XMM-Newton}} \newcommand{\integral}{{\it INTEGRAL}} \newcommand{\rxte}{{\it RXTE}} \newcommand{\sgrastar}{\mbox{Sgr A$^*$}} \newcommand{\newbe}{\mbox{CXOGC J174516.1-290315}} \newcommand{\alvin}{\mbox{X174516.1}} \shortauthors{Muno \etal} \shorttitle{Isolated Galactic Center Supergiants} %\submitted{} %\received{2002 November 25} \begin{document} \title{Isolated, Massive Supergiants near the Galactic Center} \author{M. P. Muno,\altaffilmark{1,2} G. C. Bower,\altaffilmark{3} F. K. Baganoff,\altaffilmark{7} W. N. Brandt\altaffilmark{8} California, Los Angeles, CA 90095; mmuno@astro.ucla.edu} \altaffiltext{2}{Hubble Fellow} \altaffiltext{3}{Radio Astronomy Lab, University of California, Berkeley, CA 94720} \altaffiltext{4}{Department of Astrophysics, Division of Physical Sciences, American Museum of Natural History, Central Park West at 79$^{th}$ Street, New York, NY 10024} \altaffiltext{5}{Spitzer Fellow} \altaffiltext{6}{Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under Cooperative Agreement NCC 5-538 with the National Aeronautics and Space Administration, Office of Space Science, Planetary Astronomy Program} \altaffiltext{7}{Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139} \altaffiltext{8}{Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802} We have carried out a pilot project to assess the feasibility of using radio, infrared, and X-ray emission to identify young, massive stars located between 1 and 25 pc from the Galactic center. We first compared catalogs compiled from the Very Large Array, the {\it Chandra X-ray Observatory}, and 2MASS. We identified two massive, young stars: the previously-identified star that is associated with the radio HII region H2, and a newly-identified star that we refer to as \newbe. The infrared spectra of both stars exhibit very strong Brackett-$\gamma$ and He I lines, and resemble those of massive supergiants that have evolved off of the main sequence, but not yet reached the Wolf-Rayet phase. We estimate that each star has a bolometric luminosity $\ga$$10^{6}$$L_{\odot}$. These two stars are also associated with bright mid-infrared sources from the {\it Midcourse Space Experiment} survey, although the origin of this emission is uncertain. Likewise, the detection of these two sources in X-rays is surprising, because stars at similar evolutionary states are not uniformly bright X-ray sources. Therefore, we suggest that both stars are in binary systems that contain either OB stars whose winds collide with those of the luminous supergiants, or compact objects that are accreting from the winds of the supergiants. We also identify X-ray emission from a nitrogen-type Wolf-Rayet star and place upper limits on the X-ray luminosities of three more evolved, massive stars that previously have been identified between 1 and 25 pc from Sgr A*. Finally, we briefly discuss the implications that future searches for young stars will have for our understanding of the recent history of star formation near the Galactic center. \end{abstract} \keywords{stars: emission-line --- Galaxy: center --- radio continuum: stars --- infrared: stars --- X-rays: stars} Michael Muno (310) 825 1672 Hubble Fellow University of California, Los Angeles 3904 Physics and Astronomy Bldg. 430 Portola Plaza Box 951547 Los Angeles, CA 90095 --Apple-Mail-6--1053060336 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=US-ASCII %astro-ph/0509617

\documentclass{emulateapj}

\newcommand{\etal}{\mbox{et = al.}}
\newcommand{\ergcms}{erg cm$^{-2}$ = s$^{-1}$}
\newcommand{\ergs}{erg = s$^{-1}$}
\newcommand{\phcms}{ph cm$^{-2}$ = s$^{-1}$}
\newcommand{\degree}{$^\circ$}
\newcommand{\= msun}{$M_{\odot}$}
\newcommand{\pc}{\,{\rm = pc}}
\newcommand{\yr}{\,{\rm = yr}}
\newcommand{\gyr}{\,{\rm = Gyr}}
\newcommand{\emsun}{\,M_\odot}
\newcommand{\au}{= \,{\rm AU}}

\newcommand{\chandra}{{\it = Chandra}}
\newcommand{\rosat}{{\it = ROSAT}}
\newcommand{\granat}{{\it = GRANAT}}
\newcommand{\asca}{{\it = ASCA}}
\newcommand{\einstein}{{\it = Einstein}}
\newcommand{\bepposax}{{\it = BeppoSAX}}
\newcommand{\xmm}{{\it = XMM-Newton}}
\newcommand{\integral}{{\it = INTEGRAL}}
\newcommand{\rxte}{{\it RXTE}}

\newcommand{\sgrastar}{\mbox{= Sgr A$^*$}}

\newcommand{\newbe}{\mbox{CXO= GC = J174516.1-290315}}
\newcommand{\alvin}{\mbox{X174516.1}}


\shortauthors{Muno = \etal}
\shorttitle{Isolated Galactic Center = Supergiants}

%\submitted{}
%\rec= eived{2002 November 25}
\begin{document}

\title{Isolated, Massive = Supergiants near the Galactic Center}
\author{M. P. = Muno,\altaffilmark{1,2}
G. C. = Bower,\altaffilmark{3}
A. J. =
M. R. Morris,\altaffilmark{1} and
W. N. = class=3D"khtml-block-placeholder">
\altaffiltext{1}{Department = of Physics and Astronomy, University of California,
Los = Angeles, CA 90095; mmuno@astro.ucla.edu}
\= altaffiltext{2}{Hubble Fellow}
\altaffiltext{3}{Radio = Astronomy Lab, University of California, Berkeley,
CA = 94720}
\altaffiltext{4}{Department of Astrophysics, Division = of Physical
Sciences, American Museum of Natural History, = Central Park West at
79$^{th}$ Street, New York, NY = 10024}
\altaffiltext{5}{Spitzer = Fellow}
\altaffiltext{6}{Visiting Astronomer at the =
Infrared Telescope Facility, which is
operated by = the University of Hawaii under Cooperative Agreement
NCC 5-538 = with the National Aeronautics and Space Administration,
Office = of Space Science, Planetary Astronomy Program} =
\altaffiltext{7}{Kavli Institute for Astrophysics and Space = Research,
Massachusetts Institute of Technology, Cambridge, MA = 02139}
\altaffiltext{8}{Department of Astronomy and = Astrophysics,
The Pennsylvania State University, University = Park, PA 16802}

\begin{abstract}
We= have carried out a pilot project to assess the feasibility of = using
radio, infrared, and X-ray emission to identify young, = massive stars
located between 1 and 25 pc from the Galactic = center.
We first compared catalogs compiled from the Very = Large Array, the
{\it Chandra X-ray Observatory}, and 2MASS. = We identified two
massive, young stars: the = previously-identified star that is associated with
the radio = HII region H2, and a newly-identified star that we refer to =
as \newbe. The infrared spectra of both stars = exhibit
very strong Brackett-$\gamma$ and He I lines, and = resemble those of massive
supergiants that have evolved off of = the main sequence, but not yet
reached the Wolf-Rayet phase. = We estimate that each star has a bolometric
luminosity = $\ga$$10^{6}$$L_{\odot}$. These two stars are also associated = with
bright mid-infrared sources from the {\it Midcourse Space = Experiment}
survey, although the origin of this emission is = uncertain. Likewise, the
detection of these two sources in = X-rays is surprising, because stars at
similar = evolutionary
states are not uniformly bright X-ray sources. = Therefore, we suggest that
both stars are in binary systems = that contain either OB stars whose
winds collide with those of = the luminous supergiants, or compact objects
that are = accreting from the winds of the supergiants.
We also identify = X-ray emission from a nitrogen-type Wolf-Rayet star
and place = upper limits on the X-ray luminosities of
three more evolved, = massive stars that previously have been identified
between 1 = and 25 pc from Sgr A*. Finally, we briefly discuss the implications =
that future searches for young stars will have for our = understanding
of the recent history of star formation near = the Galactic center.
\end{abstract}
\keywords{stars: = emission-line --- Galaxy: center --- radio continuum: = stars
--- infrared: stars --- X-rays: = stars}

Michael Muno

(310) 825 1672


Hubble Fellow

University of California, Los Angeles

3904 Physics and Astronomy = Bldg.

430 = Portola Plaza

Box 951547

Los Angeles, CA 90095


 =

= --Apple-Mail-6--1053060336--