  The new transient IGR 16358-4726 was discovered on 2003 March 19 with
INTEGRAL. We detected the source serendipitously during our 2003 March 24
observation of SGR 1627-41 with the Chandra X-ray Observatory at the 1.7 x
10^{-10} ergs s^{-1} cm^{-2} flux level (2-10 keV) with a very high absorption
column (N_H=3.3(1) x 10^{23} cm^{-2}) and a hard power law spectrum of index
0.5(1). We discovered a very strong flux modulation with a period of 5880(50) s
and peak-to-peak pulse fraction of 70(6)% (2-10 keV), clearly visible in the
x-ray data. The nature of IGR 16358-4726 remains unresolved. The only neutron
star systems known with similar spin periods are low luminosity persistent
wind-fed pulsars; if this is a spin period, this transient is a new kind of
object. If this is an orbital period, then the system could be a compact Low
Mass X-ray Binary (LMXB).

Astrophysics