X - ray , Radio , and Optical Observations of the Putative Pulsar in the Supernova Remnant CTA 1

A Chandra image of the central X-ray source RX J0007.0+7303 in the supernova remnant CTA 1 reveals a point source, a compact nebula, and a bent jet, all of which are characteristic of energetic, rotation-powered pulsars. Using the MDM 2.4m telescope we obtain upper limits in the optical at the position of the point source, (J2000) 00 h 07 m 01. these correspond to an X-ray-to-optical flux ratio 100. Neither a VLA image at 1425 MHz, nor a deep pulsar search at 820 MHz using the NRAO Green Bank Telescope, reveal a radio pulsar counterpart to an equivalent lu-minosity limit at 1400 MHz of 0.02 mJy kpc 2 , which is equal to the lowest luminosity known for any radio pulsar. The Chandra point source accounts for ≈ 30% of the flux of RX J0007.0+7303, while its compact nebula plus jet comprise ≈ 70%. The X-ray spectrum of the point source is fitted with a power-law plus blackbody model with Γ = 1.6 ± 0.6, kT ∞ = 0.13 ± 0.05 keV, and R ∞ = 0.37 km, values typical of a young pulsar. An upper limit of T ∞ e < 6.6 × 10 5 K to the effective temperature of the entire neutron star surface is derived, which is one of the most constraining data points on cooling models. The 0.5–10 keV luminosity of RX J0007.0+7303 is ≈ 4 × 10 31 (d/1.4 kpc) 2 ergs s −1 , but the larger (∼ 18 ′ diameter) synchrotron nebula in which it is embedded is two orders of magnitude more luminous. These properties allow us to estimate, albeit crudely, that the spin-down luminosity of the underlying pulsar is in the range 10 36 − 10 37 ergs s −1 , and support the identification of the high-energy γ-ray source 3EG J0010+7309 as a pulsar even though its spin parameters have not yet been determined.