  We report on two short XMM-Newton observations performed in August 2006 and
February 2007 during the quiescence state of the enigmatic black hole candidate
system IGR J17091-3624. During both observations the source was clearly
detected. Although the errors on the estimated fluxes are large, the source
appears to be brighter by several tens of percents during the February 2007
observation compared to the August 2006 observation. During both observations
the 2-10 keV luminosity of the source was close to ~10^{33} erg/s for an
assumed distance of 10 kpc. However, we note that the distance to this source
is not well constrained and it has been suggested it might be as far as 35 kpc
which would result in an order of magnitude higher luminosities. If the
empirically found relation between the orbital period and the quiescence
luminosity of black hole transients is also valid for IGR J17091-3624, then we
can estimate an orbital period of >100 hours (>4 days) for a distance of 10 kpc
but it could be as large as tens of days if the source is truly much further
away. Such a large orbital period would be similar to GRS 1915+105 which has an
orbital period of ~34 days. Orbital periods this large could possibly be
connected to the fact that both sources exhibit the same very violent and
extreme rapid X-ray variability which has so far not yet been seen from any
other black hole system. Alternatively the orbital period of IGR J17091-3624
might be more in line with the other systems (<100 hours) but we happened to
have observed the source in an episode of elevated accretion which was
significantly higher than its true quiescent accretion rate. In that case, the
absence or presence of extreme short-term variability properties as is seen for
IGR J17091-3624 and GRS 1915+105 is not related to the orbital periods of these
black hole systems.
