Extending the Baseline for SMC X-1's Spin and Orbital Behavior with NuSTAR Stray Light
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 such as 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 ν ̇ = (2.52 ± 0.03) × 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.
© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 November 12; revised 2022 January 6; accepted 2022 January 17; published 2022 February 24. The authors thank the anonymous referee for their time in reading the manuscript and providing helpful comments. M.C.B. would like to thank J. Thorstensen for communication about calculating orbital ephemerides and acknowledges support from NASA funding award No. 80NSSC21K0263. R.K. acknowledges support from the Russian Science Foundation grant 19-12-00369. R.L. acknowledges the support of NASA through the Hubble Fellowship Program grant HST-HF2-51440.001. Software: HEAsoft (v6.29c; HEASARC 2014), NuSTARDAS, Stingray (Huppenkothen et al. 2019), HENDRICS (Bachetti 2018), MaLTPyNT (Bachetti 2015), nustar-gen-utils.
Accepted Version - 2202.11261.pdf
Published - Brumback_2022_ApJ_926_187.pdf