We report on optical and near-infrared observations obtained during and after the 2004 December discovery outburst of the X-ray transient and accretion-powered millisecond pulsar IGRÂ J00291+5934 .
Our observations monitored the evolution of the brightness and the spectral properties of IGRÂ J00291+5934 during the outburst decay towards quiescence .
We also present optical , near-infrared and Chandra observations obtained during true quiescence .
Photometry of the field during outburst reveals an optical and near-infrared counterpart that brightened from R \simeq 23 to R \simeq 17 and from K = 19 to K \simeq 16 .
Spectral analysis of the RIJHK broadband photometry shows excess in the near-infrared bands that may be due to synchrotron emission .
The H \alpha emission line profile suggests the orbital inclination is \simeq 22 ^ { \circ } -32 ^ { \circ } .
The preferred range for the reddening towards the source is 0.7 \leq E ( B - V ) \leq 0.9 , which is equivalent to 4.06 \times 10 ^ { 21 } cm ^ { -2 } \leq N { { } _ { H } } \leq 5.22 \times 10 ^ { 21 } cm ^ { -2 } .
The Chandra observations of the pulsar in its quiescent state gave an unabsorbed 0.5-10 keV flux for the best-fitting power-law model to the source spectrum of ( 7.0 \pm 0.9 ) \times 10 ^ { -14 } ergs cm ^ { -2 } s ^ { -1 } ( adopting a hydrogen column of 4.6 \times 10 { { } ^ { 21 } } cm ^ { -2 } ) .
The fit resulted in a power-law photon index of 2.4 ^ { +0.5 } _ { -0.4 } .
The ( R - K ) _ { 0 } color observed during quiescence supports an irradiated donor star and accretion disk .
We estimate a distance of 2 to 4 kpc towards IGRÂ J00291+5934 by using the outburst X-ray light curve and the estimated critical X-ray luminosity necessary to keep the outer parts of the accretion disk ionized .
Using the quiescent X-ray luminosity and the spin period , we constrain the magnetic field of the neutron star to be < 3 \times { 10 ^ { 8 } } Â Gauss .