Spectral and temporal properties of the ultra-luminous X-ray pulsar in M82 from 15 years of Chandra observations and analysis of the pulsed emission using NuSTAR

摘要: The recent discovery by Bachetti et al. (2014) of a pulsar in M82 that can reach luminosities up to 10^40 ergs s^-1, factor ~100 the Eddington luminosity for 1.4 Msol compact object, poses challenge accretion physics. In order better understand nature this source and its duty cycle, light several physical models have been subsequently published, we conduct spectral temporal analysis 0.5-8 keV X-ray emission from 15 years Chandra observations. We fit spectra with power-law model disk black body model, subjected interstellar absorption M82. carefully assess effect pile-up our observations, where 4/19 observations fraction >10%, which account during modeling convolution model. When fitted average photon index when is at high (L_X>10^39 s^-1) Gamma=1.33+/-0.15. For temperature T=3.24+/-0.65 keV, consistent other luminous pulsars. also investigated inclusion soft excess component break, finding are these features common addition, present NuSTAR over 3-50 range isolated pulsed component. find band best high-energy cut-off, Gamma=0.6+/-0.3 E_C=14^{+5}_{-3} keV. While has previously identified as transient, longer-baseline study it remarkably active 15-year period, 9/19 (47%) analyzed, appears be emitting 10^39 greater than 10 times limit.