  Detecting axionic dark matter (DM) could be possible in an X-ray spectrum
from strongly magnetized neutron stars (NSs). We examine the possibility of
axion-photon conversion in the magnetospheres of strongly magnetized NSs. In
the current work, we investigate how the modified Tolman Oppenheimer Volkoff
(TOV) system of equations (in the presence of a magnetic field) affects the
energy spectrum of axions and axions-converted-photon flux. We have considered
the distance-dependent magnetic field in the modified TOV system of equations.
We employ three different equations of states (EoSs), namely APR, FPS, and SLY,
to solve these equations. We obtain the axions emission rate by including the
Cooper-pair-breaking formation process and Bremsstrahlung process in the core
of NSs using the NSCool code. We primarily focus on Magnificient seven (M7)
star RXJ 1856.5-3754. We further investigate the impact of the magnetic field
on the actual observables, such as axion energy spectrum and
axion-converted-photon flux at an axion mass in meV range by assuming mass
$M_{NS} \sim 1.4M_{\odot}$. We compare our calculated axion-converted-photon
flux from all available archival data sets from PN+MOS+Chandra. We also study
the variation of the energy spectrum at a fixed energy with varying central
magnetic fields. Our predicted axion-converted-photon flux values as a function
of axion energy closely follow the experimentally archival data, which allows
us to put bounds on the axion mass for the three EoS.
