NuSTAR and XMM-Newton observations of 1e1743.1-2843: indications of a neutron star LMXB nature of the compact object

Simone Lotti, Lorenzo Natalucci, Kaya Mori, Frederick K. Baganoff, Steven E. Boggs, Finn Erland Christensen, William W. Craig, Charles J. Hailey, Fiona A. Harrison, Jaesub Hong, Roman A. Krivonos, Farid Rahoui, Daniel Stern, John A. Tomsick, Shuo Zhang, William W. Zhang

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Abstract

We report on the results of NuSTAR and XMM-Newton observations of the persistent X-ray source 1E1743.1-2843, located in the Galactic Center region. The source was observed between 2012 September and October by NuSTAR and XMM-Newton, providing almost simultaneous observations in the hard and soft X-ray bands. The high X-ray luminosity points to the presence of an accreting compact object. We analyze the possibilities of this accreting compact object being either a neutron star (NS) or a black hole, and conclude that the joint XMM-Newton and NuSTAR spectrum from 0.3 to 40 keV fits a blackbody spectrum with kT ~ 1.8 keV emitted from a hot spot or an equatorial strip on an NS surface. This spectrum is thermally Comptonized by electrons with kTe ~ 4.6 keV. Accepting this NS hypothesis, we probe the low-mass X-ray binary (LMXB) or high-mass X-ray binary (HMXB) nature of the source. While the lack of Type-I bursts can be explained in the LMXB scenario, the absence of pulsations in the 2 mHz-49 Hz frequency range, the lack of eclipses and of an IR companion, and the lack of a Ka line from neutral or moderately ionized iron strongly disfavor interpreting this source as a HMXB. We therefore conclude that 1E1743.1-2843 is most likely an NS-LMXB located beyond the Galactic Center. There is weak statistical evidence for a soft X-ray excess which may indicate thermal emission from an accretion disk. However, the disk normalization remains unconstrained due to the high hydrogen column density (NH ~ 1.6 × 1023 cm−2).
Original languageEnglish
Article number57
JournalAstrophysical Journal
Volume822
Issue number1
Number of pages8
ISSN0004-637X
DOIs
Publication statusPublished - 2016

Keywords

  • Accretion, accretion disks
  • Stars: neutron
  • X-rays: binaries
  • X-rays: individual (1E1743.1-2843)

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