Using the Chandra X-ray Observatory, we have pinpointed the location of a faint X-ray point source (CXOU J182913.1-125113) and an associated diffuse nebula in the composite supernova remnant (SNR) G18.95-1.1. These objects appear to be the long-sought pulsar and its wind nebula. The X-ray spectrum of the point source is best described by an absorbed power-law model with Γ = 1.6 and an NH of ∼ 1 x 1022 cm-2. This model predicts a relatively low unabsorbed X-ray luminosity of about L X(0.5-8.0 keV) ≃ 4.1 x 1031 D22 erg s-1, where D2 is the distance in units of 2 kpc. The best-fit model of the diffuse nebula is a combination of thermal (kT = 0.48 keV) and non-thermal (1.4 ≤ Γ ≤ 1.9) emission. The unabsorbed X-ray luminosity of LX ≃ 5.4 x 1033 D2 2 erg s-1 in the 0.5-8 keV energy band seems to be largely dominated by the thermal component from the SNR, providing 87% of LX in this band. No radio or X-ray pulsations have been reported for CXOU J182913.1-125113. If we assume an age of ∼5300 yr for G18.95-1.1 and use the X-ray luminosity for the pulsar and the wind nebula together with the relationship between spin-down luminosity (via magnetic dipole radiation) and period, we estimate the pulsar's period to be P ≃ 0.4 s. Compared to other rotation-powered pulsars, a magnetic field of 2.2 x 1013 G is implied by its location in the P-P diagram, a value which is close to that of the quantum critical field.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
- ISM: supernova remnants
- Pulsars: general
- X-rays: individual (G18.95-1.1)