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Astron. Astrophys. 357, L33-L36 (2000)

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Letter to the Editor

The birth of massive twins in M 17

R. Chini 1, M. Nielbock 1 and R. Beck 2

1 Astronomisches Institut der Ruhr-Universität Bochum, Universitätsstrasse 150/NA 7, 44780 Bochum, Germany
2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

Received 4 April 2000 / Accepted 8 April 2000


We have imaged the ultra-compact HII region M 17-UC1 at J, K, N, Q and 1.3 cm. A comparison with results from earlier epochs reveals an increase of the emitted flux both in the mid-infrared and radio continuum. Our N and Q images exhibit a second source of comparable strength [FORMULA] southwest of M 17-UC1. While M 17-UC1 is not visible at J, faint at K but very bright at 1.3 cm, the second southern source shows rather opposite characteristics, namely being very bright at infrared wavelengths but invisible in the radio continuum, probably due to self-absorption. The spectral energy distributions indicate that the sources are still surrounded by the remnants of their proto-stellar cocoons. The observed luminosities measured between 1.2 and 20.0 µm of about [FORMULA] for both sources leads to the conclusion that they represent the youngest population of early type stars in M 17. The projected linear distance of 8900 AU between M 17-UC1 and its southern companion qualifies them to be a likely binary star system of O or early B-type stars.

Key words: stars: formation – stars: fundamental parameters – stars: binaries: general – stars: circumstellar matter – infrared: stars – radio continuum: stars

Send offprint requests to: R. Chini

Correspondence to: chini@astro.ruhr-uni-bochum.de

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© European Southern Observatory (ESO) 2000

Online publication: June 5, 2000