We report on the detection and follow-up high cadence monitoring observations of MAXI J1659 - 152 , a bright Galactic X-ray binary transient with a likely black-hole accretor , by Swift over a 27 day period after its initial outburst detection .
MAXI J1659 - 152 was discovered almost simultaneously by Swift and MAXI on 2010 September 25 , and was monitored intensively from the early stages of the outburst through the rise to a brightness of \sim 0.5 Crab by the Swift X-ray , UV/Optical , and the hard X-ray Burst Alert Telescopes .
We present temporal and spectral analysis of the Swift observations .
The broadband light-curves show variability characteristic of black-hole candidate transients .
We present the evolution of thermal and non-thermal components of the 0.5 - 150 keV combined X-ray spectra during the outburst .
MAXI J1659 - 152 displays accretion state changes typically associated with black-hole binaries , transitioning from its initial detection in the Hard State , to the Steep Power-Law State , followed by a slow evolution towards the Thermal State , signified by an increasingly dominant thermal component associated with the accretion disk , although this state change did not complete before Swift observations ended .
We observe an anti-correlation between the increasing temperature and decreasing radius of the inner edge of the accretion disk , suggesting that the inner edge of the accretion disk in-falls towards the black-hole as the disk temperature increases .
We observed significant evolution in the absorption column during the initial rise of the outburst , with the absorption almost doubling , suggestive of the presence of an evolving wind from the accretion disk .
We detect quasi-periodic oscillations that evolve with the outburst , as well as irregular shaped dips that recur with a period of 2.42 \pm 0.09 hours , strongly suggesting an orbital period that would make MAXI J1659 - 152 the shortest period black-hole binary yet known .