http://arxiv.org/abs/1905.09496
Deep NuSTAR observation of X-ray pulsar A 0535+262, performed at a very low luminosity of $\sim7\times10^{34}$ erg s$^{-1}$, revealed the presence of two spectral components. We argue that the high-energy component is associated with cyclotron emission from recombination of electrons collisionally excited to the upper Landau levels. The cyclotron line energy of $E_{\rm cyc}=47.7\pm0.8$ keV was measured at the luminosity of almost an order of magnitude lower than what was achieved before. The data firmly exclude a positive correlation of the cyclotron energy with the mass accretion rate in this source.
S. Tsygankov, V. Doroshenko, A. Mushtukov, et. al.
Fri, 24 May 19
53/60
Comments: 5 pages, 3 figures, accepted by MNRAS Letters