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Astron. Astrophys. 329, 74-80 (1998)

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X-ray emission from dark clusters of MACHOs

F. De Paolis 1, G. Ingrosso 2, Ph. Jetzer 1 and M. Roncadelli 3

1 Paul Scherrer Institute, Laboratory for Astrophysics, CH-5232 Villigen PSI, and Institute of Theoretical Physics,
University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
2 Dipartimento di Fisica, Università di Lecce, and INFN, Sezione di Lecce, Via Arnesano, CP 193, I-73100 Lecce, Italy
3 INFN, Sezione di Pavia, Via Bassi 6, I-27100 Pavia, Italy

Received 12 May 1997 / Accepted 4 August 1997

Abstract

MACHOs (Massive Astrophysical Compact Halo Objects) - as discovered by microlensing experiments towards the LMC - provide a natural explanation for the galactic halo dark matter. A realistic possibility is that MACHOs are brown dwarfs of mass [FORMULA]. Various arguments suggest that brown dwarfs should have a coronal X-ray emission of [FORMULA] erg s-1. As MACHOs are presumably clumped into dark clusters (DCs), each DC is expected to have a total X-ray luminosity of [FORMULA] erg s-1. We discuss the possibility that dark clusters contribute to the diffuse X-ray background (XRB) or show up as discrete sources in very deep field X-ray satellite observations. Moreover, from the observed diffuse XRB we infer that the amount of virialized diffuse gas present in the galactic halo can at most make up [FORMULA] of the halo dark matter.

Key words: dark matter – the halo of the Galaxy – Brown dwarfs - X-rays: general

Send offprint requests to: Ph. Jetzer

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© European Southern Observatory (ESO) 1998

Online publication: November 24, 1997
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