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Astron. Astrophys. 324, L69-L72 (1997)

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Letter to the Editor

Observational limits on machos in the Galactic Halo *

C. Renault 1, C. Afonso 1, É. Aubourg 1, P. Bareyre 1, F. Bauer 1, S. Brehin 1, C. Coutures 1, C. Gaucherel 1, J.F. Glicenstein 1, B. Goldman 1, M. Gros 1, D. Hardin 1, J. de Kat 1, M. Lachièze-Rey 1, B. Laurent 1, É. Lesquoy 1, C. Magneville 1, A. Milsztajn 1, L. Moscoso 1, N. Palanque-Delabrouille 1, F. Queinnec 1, J. Rich 1, M. Spiro 1, L. Vigroux 1, S. Zylberajch 1, R. Ansari 2, F. Cavalier 2, F. Couchot 2, B. Mansoux 2, M. Moniez 2, O. Perdereau 2, J.-Ph. Beaulieu 3, R. Ferlet 3, Ph. Grison 3, A. Vidal-Madjar 3, J. Guibert 4, O. Moreau 4, É. Maurice 5, L. Prévôt 5, C. Gry 6, S. Char 7 and J. Fernandez The EROS collaboration 7

1 CEA, DSM, DAPNIA, Centre d'Études de Saclay, F-91191 Gif-sur-Yvette, Cedex, France
2 Laboratoire de l'Accélérateur Linéaire, IN2P3 CNRS, Université Paris-Sud, F-91405 Orsay, Cedex, France
3 Institut d'Astrophysique de Paris, CNRS, 98 bis Boulevard Arago, F-75014 Paris, France
4 Centre d'Analyse des Images de l'INSU, Observatoire de Paris, 61 avenue de l'Observatoire, F-75014 Paris, France
5 Observatoire de Marseille, 2 place Le Verrier, F-13248 Marseille, Cedex 04, France
6 Laboratoire d'Astronomie Spatiale de Marseille, Traverse du Siphon, Les Trois Lucs, F-13120 Marseille, France
7 Universidad 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 [FORMULA]. Two events were observed that are compatible with microlensing by objects of mass [FORMULA] 0.1 [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] ] [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

* Based on observations made at the European Southern Observatory, La Silla, Chile.

Send offprint requests to: cecile.renault@cea.fr

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© European Southern Observatory (ESO) 1997

Online publication: May 5, 1998

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