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Aims: Spectral and temporal analysis of the NuSTAR observation GalacticBe-XRB Swift J1845.7-0037. during its recent outburst. Methods: For thespectral analysis we use both phenomenological and physics-based models. Weemploy an often used empirical model to identify the main characteristics ofthe spectral shape in relation to nominal spectral characteristics of X-raypulsars. Additionally, we used the latest version of Bulk \& Thermalcomptonization model (BW), to assess the validity of the spectral componentsrequired by the empirical model and to investigate the origin of the hard X-rayemission. We also analyzed the source light-curve, studying the pulse shape atdifferent energy ranges and tracking the spectral evolution with pulse phase byusing the model independent hardness ratio (HR). Results: We find that whileboth the empirical and physical (BW) spectral models can produce good spectralfits, the BW model returns physically plausible best-fit values for the sourceparameters and does not require any additional spectral components to thenon-thermal, accretion column emission. The BW model also yielded an estimationof the neutron star magnetic field placing it in the 10^12G range. Conclusions:Our results, show that the spectral and temporal characteristics of the sourceemission are consistent with the scattering processes expected for radiationdominated shocks within the accretion column of highly magnetized accretingneutron stars. We further indicate that physically-derived spectral models suchas BW, can be used to tentatively infer fundamental source parameters, in theabsence of more direct observational signatures.

NuSTAR X-ray spectrum of Be-X-ray pulsar Swift J1845.7-0037: Bulk and thermal Comptonization of cyclotron seed photons in the accretion column