Bibcode
Casares, J.; Ribó, M.; Ribas, I.; Paredes, J. M.; Martí, J.; Herrero, A.
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 364, Issue 3, pp. 899-908.
Fecha de publicación:
12
2005
Número de citas
191
Número de citas referidas
154
Descripción
The population of high-energy and very high-energy γ-ray sources,
detected with EGRET and the new generation of ground-based Cherenkov
telescopes, forms a reduced but physically important sample. Most of
these sources are extragalactic (e.g. blazars), while among the galactic
ones there are pulsars and supernova remnants. The microquasar LS 5039,
previously proposed to be associated with an EGRET source by Paredes et
al., has recently been detected at TeV energies, confirming that
microquasars should be regarded as a class of high-energy γ-ray
sources. To model and understand how the energetic photons are produced
and escape from LS 5039, it is crucial to unveil the nature of the
compact object, which remains unknown. Here, we present new
intermediate-dispersion spectroscopy of this source, which, combined
with values reported in the literature, provides an orbital period of
Porb= 3.90603 +/- 0.00017 d, a mass function f(M) = 0.0053
+/- 0.0009Msolar and an eccentricity e= 0.35 +/- 0.04.
Atmosphere model fitting to the spectrum of the optical companion,
together with our new distance estimate of d= 2.5 +/- 0.1 kpc, yields
RO= 9.3+0.7-0.6Rsolar,
log(LO/Lsolar) = 5.26 +/- 0.06 and MO=
22.9+3.4-2.9Msolar. These, combined
with our dynamical solution and the assumption of
pseudo-synchronization, yield an inclination and a compact object mass
MX= 3.7+1.3-1.0Msolar. This
is above neutron star masses for most of the standard equations of state
and, therefore, we propose that the compact object in LS 5039 is a black
hole. We finally discuss the implications of our orbital solution and
new parameters of the binary system on the CNO products, the
accretion/ejection energetic balance, the supernova explosion scenario
and the behaviour of the very high-energy γ-ray emission with the
new orbital period.