Pulse phase-resolved analysis of SMC X-3 during its 2016--2017 super-Eddington outburst

Abstract

The Be X-ray pulsar SMC X-3 underwent an extra long and ultraluminous giant outburst from 2016 August to 2017 March. The peak X-ray luminosity is up to $\sim 10^{39}$ erg/s, suggesting a mildly super-Eddington accretion onto the strongly magnetized neutron star. It therefore bridges the gap between the Galactic Be/X-ray binaries ($L_{\mathrm{X}}^{\mathrm{peak}}\le 10^{38}$ erg/s) and the ultraluminous X-ray pulsars ($L_{\mathrm{X}}^{\mathrm{peak}}\ge 10^{40}$ erg/s) found in nearby galaxies. A number of observations were carried out to observe the outburst. In this paper, we perform a comprehensive phase-resolved analysis on the high quality data obtained with the Nustar and XMM-Newton, which were observed at a high and intermediate luminosity levels. In order to get a better understanding on the evolution of the whole extreme burst, we take the Swift results at the low luminosity state into account as well. At the early stage of outburst, the source shows a double-peak pulse profile, the second main peak approaches the first one and merges into the single peak at the low luminosity. The second main peak vanishes beyond 20 keV, and its radiation becomes much softer than that of the first main peak. The line widths of fluorescent iron line vary dramatically with phases, indicating a complicated geometry of accretion flows. In contrast to the case at low luminosity, the pulse fraction increases with the photon energy. The significant small pulse fraction detected below 1 keV can be interpreted as the existence of an additional thermal component located at far away from the central neutron star.

arXiv comment6 pages, 2 tables, 2 figures, Published in Astrophysics and Space Science

References in corpus (21)

• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• Observations of Accreting Pulsars
• Be/X-ray binaries
• Ten eclipsing binaries in the Small Magellanic Cloud: fundamental parameters and SMC distance
• Spectral Formation in Accreting X-Ray Pulsars: Bimodal Variation of the Cyclotron Energy with Luminosity
• The Araucaria Project. The distance to the Small Magellanic Cloud from late-type eclipsing binaries
• The critical accretion luminosity for magnetized neutron stars
• A Be-type star with a black hole companion
• Origin of the Soft Excess in X-ray Pulsars
• The Carnegie Hubble Program: The Distance and Structure of the SMC as Revealed by Mid-infrared Observations of Cepheids
• High-Mass X-ray binaries in the Small Magellanic Cloud
• Constraining the Braking Indices of Magnetars
• The Dipole Magnetic Field and Spin-down Evolutions of The High Braking Index Pulsar PSR J1640-4631
• SMC X-3: the closest ultraluminous X-ray source powered by a neutron star with non-dipole magnetic field
• A Long Look at the Be/X-Ray Binaries of the Small Magellanic Cloud
• XMM-Newton observations of the Small Magellanic Cloud: Be/X-ray binary pulsars active between October 2006 and June 2007
• The 2016 super-Eddington outburst of SMC X-3: X-ray and optical properties and system parameters
• A propelling neutron star in the enigmatic Be-star $\gamma$~Cassiopeia
• Swift observations of SMC X-3 during its 2016-2017 super-Eddington outburst
• Cyclotron Resonance Energies and Orbital Elements of Accretion Pulsar 4U 0115+63 During the Giant Outburst in 2008
• Application of the Ghosh & Lamb Relation to the Spin-up/down Behavior in the X-ray Binary Pulsar 4U 1626-67

Cited by in corpus (6)

• Super-Eddington accretion onto the Galactic ultraluminous X-ray pulsar Swift J0243.6+6124
• Comparing the Super-Eddington accretion of SMC X-3 and RX J0209.6-7427 with Swift J0243.6+6124
• X-Ray Views of Galactic Accreting Pulsars in High-Mass X-Ray Binaries
• NuSTAR and XMM-Newton observations of SXP 59 during its 2017 giant outburst
• Timing and spectral studies of Cen X-3 in multiple luminosity states using $\text{AstroSat}$
• Monte-Carlo simulations on possible collimation effects of outflows to fan-beamed emission of ultraluminous accreting X-ray pulsars