Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evolution of timing and spectral characteristics of 4U 1901+03 during
  its 2019 outburst using the Swift and NuSTAR observatories   We report the results from a detailed timing and spectral study of transient
X-ray pulsars, 4U 1901+03 during its 2019 outburst. We performed broadband
spectroscopy in the 1-70 keV energy band using four observations made with
Swift and NuSTAR at different intensity levels. Our timing results reveal the
presence of highly variable pulse profiles dependent on both luminosity and
energy. Our spectroscopy results showed the presence of a cyclotron resonance
scattering feature (CRSF) at ~30 keV. This feature at 30 keV is highly
luminosity and pulse-phase dependent. Phase-averaged spectra during the last
two observations, made close to the declining phase of the outburst showed the
presence of this feature at around 30 keV. The existence of CRSF at 30 keV
during these observations is well supported by an abrupt change in the shape of
pulse profiles found close to this energy. We also found that 30 keV feature
was significantly detected in the pulse-phase resolved spectra of observations
made at relatively high luminosities. Moreover, all spectral fit parameters
showed a strong pulse phase dependence. In line with the previous findings, an
absorption feature at around 10 keV is significantly observed in the
phase-averaged X-ray spectra of all observations and also showed a strong pulse
phase dependence.

11
The categories of this paper are: hep-lat
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
24
The categories of this paper are: dg-ga
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int