EDP Sciences
Free access
Issue A&A
Volume 383, Number 1, February III 2002
Page(s) 163 - 170
Section Stellar clusters and associations
DOI http://dx.doi.org/10.1051/0004-6361:20011730



A&A 383, 163-170 (2002)
DOI: 10.1051/0004-6361:20011730

NGC 6994 - clearly not a physical stellar ensemble

M. Odenkirchen1 and C. Soubiran2

1  Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
    e-mail: odenkirchen@mpia-hd.mpg.de
2  Observatoire de Bordeaux, UMR 5804, BP 89, 33270 Floirac, France
    e-mail: soubiran@observ.u-bordeaux.fr

(Received 24 August 2001 / Accepted 28 November 2001 )

Abstract
The sparse stellar ensemble NGC 6994 = M 73 has recently been discussed as a possible remnant of an old open cluster. In order to solve the controversy regarding the nature of this object we have taken high-resolution spectra of the six brightest stars within 6' angular distance of its nominal position. These stars are the only obvious candidate members of an eventual cluster or cluster remnant since fainter stars do not show any significant concentration in the plane of the sky. The radial velocities, atmospheric parameters, and absolute magnitudes derived from the spectra reveal that the six candidates do not share the same kinematics and lie at different distances from the Sun. The proper motions provided by the Tycho-2 catalogue show that there is also a large spread in the tangential motions of these stars, in agreement with the spectroscopic results. This leads to the conclusion that the few bright stars that constitute NGC 6994 are not a physical system (cluster, cluster remnant, or group). They must instead be understood as a projective chance alignment of physically unrelated field stars.


Key words: galaxy: open clusters and associations: individual: NGC 6994 -- galaxy: open clusters and associations: general

Offprint request: M. Odenkirchen, odenkirchen@mpia-hd.mpg.de

SIMBAD Objects



© ESO 2002

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.

Editor-in-Chief: T. Forveille
Letters Editor-in-Chief: J. Alves
Managing Editor: C. Bertout

ISSN: 0004-6361 ; e-ISSN: 1432-0746
Frequency: 12 volumes per year
Published by: EDP Sciences

Mirror sites: CDS | EDP Sciences
  RSS feeds
© The European Southern Observatory (ESO)