Extending the baseline for SMC X-1's spin and orbital behavior with NuSTAR stray light

Abstract

StrayCats, the catalog of NuSTAR stray light observations, contains data from bright X-ray sources that fall within crowded source regions. These observations offer unique additional data with which to monitor sources like X-ray binaries that show variable timing behavior. In this work, we present a timing analysis of stray light data of the high mass X-ray binary SMC X-1, the first scientific analysis of a single source from the StrayCats project. We describe the process of screening stray light data for scientific analysis, verify the orbital ephemeris, and create both time and energy resolved pulse profiles. We find that the orbital ephemeris of SMC X-1 is unchanged and confirm a long-term spin up rate of $\dot{\nu }=(2.52\pm 0.03)\times 10^{-11}$ Hz s${}^{-1}$. We also note that the shape of SMC X-1's pulse profile, while remaining double-peaked, varies significantly with time and only slightly with energy.

10 pages, 8 figures

References in corpus (6)

• The ephemeris, orbital decay, and masses of 10 eclipsing HMXBs
• Determination of the mass of the neutron star in SMC X-1, LMC X-4 and Cen X-3 with VLT/UVES
• Extending the $Z_n^2$ and $H$ statistics to generic pulsed profiles
• Observing the transient pulsations of SMC X-1 with NuSTAR
• StrayCats: A catalog of NuSTAR Stray Light Observations
• Monitoring the Superorbital Period Variation and the Spin Period Evolution of SMC X-1

Cited by in corpus (7)

• Geminga's pulsar halo: an X-ray view
• The Orbit of NGC 5907 ULX-1
• StrayCats II: An Updated Catalog of NuSTAR Stray Light Observations
• Monitoring observations of SMC X-1's excursions (MOOSE)-II: A new excursion accompanies spin-up acceleration
• Constraining the evolution of the unstable accretion disk in SMC X-1 with NICER
• NuSTAR spectral analysis beyond 79 keV with stray light
• Wavelet-based image decomposition method for NuSTAR stray light background studies