Bibcode
La Palombara, N.; Mignani, R. P.; Hatziminaoglou, E.; Schirmer, M.; Bignami, G. F.; Caraveo, P.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 458, Issue 1, October IV 2006, pp.245-257
Fecha de publicación:
10
2006
Revista
Número de citas
14
Número de citas referidas
10
Descripción
The limited angular resolution of γ-ray telescopes prevents a
direct identification of the majority of sources detected so far. This
is particularly true for the low latitude, probably galactic, ones only
10% of which has been identified. Most counterparts of the identified
low-latitude γ-ray sources are Isolated Neutron Stars (INS), both
radio-loud and radio-quiet (Geminga-like) objects, which are
characterised by an extremely high value of the X-ray-to-optical flux
ratio f_X/f_opt. Therefore, the systematic X-ray and optical coverage of
low-latitude unidentified γ-ray sources aiming at high
f_X/fopt sources seems one of the most promising ways to spot
INS candidate counterparts. Since low latitude sources are heavily
affected by the interstellar absorption at both X-ray and optical
wavelengths, we have focussed on two middle-latitude, probably galactic,
GRO/EGRET sources: 3EG J0616-3310 and 3EG J1249-8330. These two sources,
which could belong to a local galactic population, have been selected
owing to their relatively good positional accuracy, spectral shape and
lack of candidate extragalactic radio counterparts. Here we report on
X-ray observations of the two γ-ray error boxes performed with
XMM-Newton and on their optical follow-up carried on with the Wide Field
Imager at the ESO/MPG 2.2 m telescope. Less than half of the ~300
sources detected by the X-ray coverage have no optical counterparts.
Among those, we have selected few interesting sources with
fX/f_opt≥ 100, which we consider promising INS candidates.