THE MASS AND THE RADIUS OF THE NEUTRON STAR IN THE TRANSIENT LOW-MASS X-RAY BINARY SAX J1748.9-2021


Guver T. , Oezel F.

ASTROPHYSICAL JOURNAL LETTERS, vol.765, no.1, 2013 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 765 Issue: 1
  • Publication Date: 2013
  • Doi Number: 10.1088/2041-8205/765/1/l1
  • Title of Journal : ASTROPHYSICAL JOURNAL LETTERS
  • Keywords: stars: neutron, X-rays: binaries, X-rays: individual (SAX J1748-2021), EQUATION-OF-STATE, SPECTROSCOPIC MEASUREMENTS, SYSTEMATIC UNCERTAINTIES, TIMING-EXPLORER, NGC 6440, BURSTS, EXPANSION, NGC-6440, MATTER, BULGE

Abstract

We use time-resolved spectroscopy of thermonuclear X-ray bursts observed from SAX J1748.9-2021 to infer the mass and the radius of the neutron star in the binary. Four X-ray bursts observed from the source with the Rossi X-ray Timing Explorer enable us to measure the angular size and the Eddington limit on the neutron star surface. Combined with a distance measurement to the globular cluster NGC 6440, in which SAX J1748.9-2021 resides, we obtain two solutions for the neutron star radius and mass, R = 8.18 ± 1.62 km and M = 1.78 ± 0.3 M ? or R = 10.93 ± 2.09 km and M = 1.33 ± 0.33 M ?.

We use time-resolved spectroscopy of thermonuclear X-ray bursts observed from SAX J1748.9-2021 to infer the mass and the radius of the neutron star in the binary. Four X-ray bursts observed from the source with the Rossi X-ray Timing Explorer enable us to measure the angular size and the Eddington limit on the neutron star surface. Combined with a distance measurement to the globular cluster NGC 6440, in which SAX J1748.9-2021 resides, we obtain two solutions for the neutron star radius and mass, R = 8.18 +/- 1.62 km and M = 1.78 +/- 0.3 M-circle dot or R = 10.93 +/- 2.09 km and M = 1.33 +/- 0.33 M-circle dot.