Relativistic X-ray reflection and highly ionized absorption in the spectrum of NS LMXB 1A 1744−361

Abstract

ABSTRACT We present the results from the spectral and timing analysis of the accreting neutron star (NS) 1A 1744−361 from the Nuclear Spectroscopic Telescope ARray observation performed in its 2022 outbursts. The unabsorbed bolometric X-ray luminosity during this observation in the energy band 0.1–100 keV is 3.9 × 1037 erg s−1, assuming a distance of 9 kpc. During this observation, the source was in the banana branch of the atoll track. The source spectrum exhibits relativistic disc reflection and clear absorption features when an absorbed blackbody and cut-off power-law model describes the continuum emission. The 3–50 keV source spectrum is well fitted using a model combination consisting of an absorbed single-temperature blackbody and a reflection model along with the addition of a warm absorber component. The inner-disc radius, Rin, obtained from the reflection fit is ∼(1.61–2.86)RISCO = (8.4–14.9)Rg (17.6–31.2 km for a 1.4 M⊙ NS). This measurement allowed us to further constrain the magnetic field strength to B ≲ 0.94 × 109 G. The strong absorption features ∼6.91 keV and ∼7.99 keV imply the presence of highly ionized absorbing material with a column density NH of ∼3 × 1022 cm−2, emanating from the accretion disc in the form of disc wind with an outflow velocity of vout ≃ 0.021c ≃ 6300 km s−1.