We present timing and broad-band spectral studies of the high mass X-ray binary pulsar 4U 1909+07 using data from Suzaku observation during 2010 November 2-3 .
The pulse period of the pulsar is estimated to be 604.11 \pm 0.14 s. Pulsations are seen in the X-ray light curve up to \sim 70 keV .
The pulse profile is found to be strongly energy-dependent : a complex , multi-peaked structure at low energy that becomes a simple single peak at higher energy .
We found that the 1-70 keV pulse averaged continuum can be fitted by the sum of a black body and a partial covering Negative and Positive power-law with EXponential cutoff ( NPEX ) model .
A weak iron fluorescence emission line at 6.4 keV was detected in the spectrum .
An absorption like feature at \sim 44 keV was clearly seen in the residue of the spectral fitting , independent of the continuum model adopted .
To check the possible presence of a CRSF in the spectrum , we normalized the pulsar spectrum with the spectrum of the Crab Nebula .
The resulting Crab ratio also showed a clear dip centered at \sim 44 keV .
We performed statistical tests on the residue of the spectral fitting and also on the Crab spectral ratio to determine the significance of the absorption like feature and identified it as a CRSF of the pulsar .
We estimated the corresponding surface magnetic field of the pulsar to be 3.8 \times 10 ^ { 12 } Gauss .