The soft quiescent spectrum of the transiently accreting 11 Hz X-ray pulsar in the globular cluster Terzan 5

Abstract

We report on the quiescent X-ray properties of the recently discovered transiently accreting 11 Hz X-ray pulsar in the globular cluster Terzan 5. Using two archival Chandra observations, we demonstrate that the quiescent spectrum of this neutron star low-mass X-ray binary is soft and can be fit to a neutron star atmosphere model with a temperature of kT^inf~73 eV. A powerlaw spectral component is not required by the data and contributes at most ~20% to the total unabsorbed 0.5-10 keV flux of ~9E-14 erg/cm2/s. Such a soft quiescent spectrum is unusual for neutron stars with relatively high inferred magnetic fields and casts a different light on the interpretation of the hard spectral component, which is often attributed to magnetic field effects. For a distance of 5.5 kpc, the estimated quiescent thermal bolometric luminosity is ~6E32 erg/s. If the thermal emission is interpreted as cooling of the neutron star, the observed luminosity requires that the system is quiescent for at least ~100 years. Alternatively, enhanced neutrino emissions can cool the neutron star to the observed quiescent luminosity.

6 pages, 3 figures, accepted for publication in MNRAS Letters

References in corpus (4)

• Models of crustal heating in accreting neutron stars
• Faint X-ray Sources in the Globular Cluster Terzan 5
• Distances of the bulge globular clusters Terzan 5, Liller 1, UKS 1 and Terzan 4 based on HST NICMOS photometry
• The spin and orbit of the newly discovered pulsar IGR J17480-2446

Cited by in corpus (12)

• Cooling of Accretion-Heated Neutron Stars
• Testing the deep-crustal heating model using quiescent neutron-star very-faint X-ray transients and the possibility of partially accreted crusts in accreting neutron stars
• Quiescent thermal emission from neutron stars in LMXBs
• Evidence for crust cooling in the transiently accreting 11-Hz X-ray pulsar in the globular cluster Terzan 5
• Broad-band characteristics of seven new hard X-ray selected cataclysmic variables
• Continued cooling of the accretion-heated neutron star crust in the X-ray transient IGR J17480-2446 located in the globular cluster Terzan 5
• Time-dependent, compositionally driven convection in the oceans of accreting neutron stars
• Investigating Variability of Quiescent Neutron Stars in the Globular Clusters NGC 6440 and Terzan 5
• The accretion-heated crust of the transiently accreting 11 Hz X-ray pulsar in the globular cluster Terzan 5
• Extreme Quiescent Variability of the Transient Neutron Star Low-mass X-ray Binary EXO 1745-248 in Terzan 5
• Superfluid effects on gauging core temperatures of neutron stars in low-mass X-ray binaries
• Layers of electron captures in the crust of accreting neutron stars