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Astron. Astrophys. 324, L69-L72


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Letter to the Editor

Observational limits on machos in the Galactic Halo*

C. Renault1, C. Afonso1, É. Aubourg1, P. Bareyre1, F. Bauer1, S. Brehin1, C. Coutures1, C. Gaucherel1, J.F. Glicenstein1, B. Goldman1, M. Gros1, D. Hardin1, J. de Kat1, M. Lachièze-Rey1, B. Laurent1, É. Lesquoy1, C. Magneville1, A. Milsztajn1, L. Moscoso1, N. Palanque-Delabrouille1, F. Queinnec1, J. Rich1, M. Spiro1, L. Vigroux1, S. Zylberajch1, R. Ansari2, F. Cavalier2, F. Couchot2, B. Mansoux2, M. Moniez2, O. Perdereau2, J.-Ph. Beaulieu3, R. Ferlet3, Ph. Grison3, A. Vidal-Madjar3, J. Guibert4, O. Moreau4, É. Maurice5, L. Prévôt5, C. Gry6, S. Char7, J. Fernandez7
The EROS collaboration

1CEA, DSM, DAPNIA, Centre d'Études de Saclay, F-91191 Gif-sur-Yvette, Cedex, France
2Laboratoire de l'Accélérateur Linéaire, IN2P3 CNRS, Université Paris-Sud, F-91405 Orsay, Cedex, France
3Institut d'Astrophysique de Paris, CNRS, 98 bis Boulevard Arago, F-75014 Paris, France
4Centre d'Analyse des Images de l'INSU, Observatoire de Paris, 61 avenue de l'Observatoire, F-75014 Paris, France
5Observatoire de Marseille, 2 place Le Verrier, F-13248 Marseille, Cedex 04, France
6Laboratoire d'Astronomie Spatiale de Marseille, Traverse du Siphon, Les Trois Lucs, F-13120 Marseille, France
7Universidad de la Serena, Faculdad de Ciencias, Departemento de Fisica, Casilla 554, La Serena, Chile

Received 29 November 1996 / Accepted 19 December 1996

Abstract

We present final results from the first phase of the EROS search for gravitational microlensing of stars in the Magellanic Clouds by unseen deflectors (machos: MAssive Compact Halo Objects). The search is sensitive to events with time scales between 15 minutes and 200 days corresponding to deflector masses in the range 10-7 to a few M FORMULA . Two events were observed that are compatible with microlensing by objects of mass FORMULA 0.1 M FORMULA . By comparing the results with the expected number of events for various models of the Galaxy, we conclude that machos in the mass range [ FORMULA ] M FORMULA make up less than 20 % (95 % C.L.) of the Halo dark matter.

Key words: Galaxy: halo, kinematics and dynamics, stellar content - Cosmology: dark matter, gravitational lensing

Send offprint requests to: cecile.renault@cea.fr
*Based on observations made at the European Southern Observatory, La Silla, Chile.


© European Southern Observatory (ESO) 1997

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