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 2.4 m telescope we obtain upper limits in the optical at the position of the point source, (J2000.0) 00^h07^m01s56, +73^deg03^'08.1", determined to an accuracy of 0.1", of B>25.4, V>24.8, R>25.1, and I>23.7 these correspond to an X-ray-to-optical flux ratio >~100. Neither a Very Large Array 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 luminosity limit at 1400 MHz of 0.02 mJy kpc², 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<6.6×10⁵ 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 ~4×10³¹(d/1.4kpc)² ergs s^-1, but the larger (~18' diameter) synchrotron nebula in which it is embedded is 2 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 10³⁶-10³⁷ 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.