========================================================================

                              G C N E W S
                             * Newsflash *

            - The Newsletter for Galactic Center Research -

gcnews@mpifr-bonn.mpg.de             http://www.mpifr-bonn.mpg.de/gcnews
========================================================================
Vol. 8, No. 18                                              Jul 31, 1998


Recently submitted papers:
--------------------------

Email    : t.geballe@jach.hawaii.edu
Title    : Detection of H_3^+ in the Diffuse Interstellar Medium:    
           The Galactic Center and Cygnus OB2 No. 12
Author(s): T. R. Geballe(1),  B. J. McCall(2), K. H. Hinkle(3,5), T. Oka(4)
Institute: (1) Joint Astronomy Centre, Hilo, HI 96720   (2) Department 
           of Astronomy and Astrophysics, Department of   Chemistry, 
           and the Enrico Fermi Institute, University of Chicago,   
           Chicago, IL 60637   (3) National Optical Astronomy 
           Observatories(1), Tucson,   AZ 85726   (4) Department of 
           Astronomy and Astrophysics, Department of   Chemistry, and 
           the Enrico Fermi Institute, University of Chicago,   
           Chicago, IL 60637   (5) Operated by the Association of 
           Universities for Research   in Astronomy, Inc. under 
           cooperative agreement with the National Science   Foundation
Paper    : accepted by ApJ

Abstract:
Absorption lines of H_3^+ have been detected in the spectra of two
infrared sources in the galactic center and also towards the heavily
reddened star Cygnus OB2 No. 12, whose line of sight is believed to
include only diffuse interstellar gas. The absorptions toward the
galactic center sources (IRS3 and GCS3-2) probably are due to H_3^+
both in diffuse gas and in molecular clouds. The ratios of H_3^+ line
equivalent width to extinction toward these three sources are much
greater than those toward dense clouds where H_3^+ has been detected
previously. Analysis of the spectra coupled with a simple model for
the abundance of H_3^+ in the diffuse interstellar medium implies that
the observed H_3^+ is present at low densities along long
pathlengths. These are the first detections of H_3^+ in the diffuse
interstellar medium.
------------------------------------------------------------------------


(Older versions of the Newsflash can be found at the gcnews web-page)
========================================================================
			       Edited by
Angela Cotera                                Heino Falcke
(cotera@ipac.caltech.edu)                    (hfalcke@mpifr-bonn.mpg.de)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 For Abstract submission please send the (La)Tex file of your paper to
                          gcnews@mpifr-bonn.mpg.de
========================================================================