Chandra and Swift X-ray Observations of the X-ray Pulsar SMC X-2 During the Outburst of 2015

Abstract

We report the Chandra/HRC-S and Swift/XRT observations for the 2015 outburst of the high-mass X-ray binary (HMXB) pulsar in the Small Magellanic Cloud, SMC X-2. While previous studies suggested that either an O star or a Be star in the field is the high-mass companion of SMC X-2, our Chandra/HRC-S image unambiguously confirms the O-type star as the true optical counterpart. Using the Swift/XRT observations, we extracted accurate orbital parameters of the pulsar binary through a time of arrivals (TOAs) analysis. In addition, there were two X-ray dips near the inferior conjunction, which are possibly caused by eclipses or an ionized high-density shadow wind near the companion's surface. Finally, we propose that an outflow driven by the radiation pressure from day ~10 played an important role in the X-ray/optical evolution of the outburst.

8 pages; accepted for publication in ApJ

References in corpus (7)

• Precise Gamma-Ray Timing and Radio Observations of 17 Fermi Gamma-Ray Pulsars
• γ^2 Velorum: Orbital Solution and Fundamental Parameter Determination with SUSI
• Spectral distribution of Be/X-ray binaries in the Small Magellanic Cloud
• Detection of Cyclotron Resonance Scattering Feature in High Mass X-ray Binary Pulsar SMC X-2
• Precise Orbital Parameters and Anomalous Phase Variations of the Accretion-powered Millisecond Pulsar XTE J1807-294
• An Investigation of Be/X-ray Pulsars with OGLE-III Data
• INTEGRAL observation of the accreting pulsar 1E1145.1-6141

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• Possible Periodic Dips in the Pulsating Ultraluminous X-ray Source M51 ULX-7
• Spectro-timing analysis of Be X-ray pulsar SMC X-2 during the 2022 outburst