Discovery of 105 Hz coherent pulsations in the ultracompact binary IGR J16597-3704

• Author(s) / Creator(s)

  • Sanna, Andrea
  • Bahramian, Arash
  • Bozzo, E.
  • Heinke, Craig O.
  • Wijnands, Rudy
  • Degenaar, Nathalie
  • Maccarone, T.
  • Riggio, Alessandro
  • Di Salvo, Tiziana
  • Iaria, Rosario
  • Burgay, M.
  • Possenti, Andrea
  • Ferrigno, C.
  • Papitto, A.
  • Sivakoff, Gregory Robert
  • D'Amico, Nicolo
  • Burderi, Luciano
  • Altamirano, Diego

• We report the discovery of X-ray pulsations at 105.2 Hz (9.5 ms) from the transient X-ray binary IGR J16597–3704 using NuSTAR and Swift. The source was discovered by INTEGRAL in the globular cluster NGC 6256 at a distance of 9.1 kpc. The X-ray pulsations show a clear Doppler modulation that implies an orbital period of ~46 min and a projected semi-major axis of ~5 lt-ms, which makes IGR J16597–3704 an ultracompact X-ray binary system. We estimated a minimum companion mass of 6.5 × 10−10 M⊙, assuming a neutron star mass of 1.4 M⊙, and an inclination angle of <75° (suggested by the absence of eclipses or dips in its light curve). The broad-band energy spectrum of the source is well described by a disk blackbody component (kT ~ 1.4 keV) plus a comptonised power-law with photon index ~2.3 and an electron temperature of ~30 keV. Radio pulsations from the source were unsuccessfully searched for with the Parkes Observatory.

• Date created

  2018-01-01

• Subjects / Keywords

  • Accretion Disks
  • X-Rays: Binaries
  • Accretion
  • Stars: Neutron
  • Binaries: General

• Type of Item

  Article (Published)

• DOI

  https://doi.org/10.7939/r3-400r-hb98

• License

  © ESO 2018