  We present the results obtained from the analysis of high mass X-ray binary
pulsar 4U 1909+07 using NuSTAR and Astrosat observations in 2015 and 2017 July,
respectively. X-ray pulsations at $\approx$604 s are clearly detected in our
study. Based on the long term spin-frequency evolution, the source is found to
spun up in the last 17 years. We observed a strongly energy-dependent pulse
profile that evolved from a complex broad structure in soft X-rays into a
profile with a narrow emission peak followed by a plateau in energy ranges
above 20 keV. This behaviour ensured a positive correlation between the energy
and pulse fraction. The pulse profile morphology and its energy-evolution are
almost similar during both the observations, suggesting a persistent emission
geometry of the pulsar over time. The broadband energy spectrum of the pulsar
is approximated by an absorbed high energy exponential cutoff power law model
with iron emission lines. In contrast to the previous report, we found no
statistical evidence for the presence of cyclotron absorption features in the
X-ray spectra. We performed phase-resolved spectroscopy by using data from the
NuSTAR observation. Our results showed a clear signature of absorbing material
at certain pulse-phases of the pulsar. These findings are discussed in terms of
stellar wind distribution and its effect on the beam geometry of this wind-fed
accreting neutron star. We also reviewed the subsonic quasi-spherical accretion
theory and its implication on the magnetic field of 4U 1909+07 depending on the
global spin-up rate.
