Thermal X-ray emission of the extended lobe near 1E 2259+586 with CTB 109

Abstract

A “jet-like” lobe runs northeastward from the pulsar 1E2259+586 to the shell within the supernova remnant CTB 109, and it was previously suspected to be an “X-ray jet” in a binary system analogous to SS433/W50 (Gregory & Fahlman, 1983). We report X-ray spectra of the lobe relative to elsewhere in the remnant using ASCA and ROSAT, and comparison with other X-ray jets. X-ray emission from the “jet-like” lobe is thermal with dominant lines of Ne IX, Ne X, Mg XI, and Si XIII, and has softer emission than elsewhere in the remnant. The spectral fit for the lobe indicates that the plasma is in ionization non-equilibrium and its best fit is T s ∼10 6.5 K and n o t∼48,000 cm −3yr. This lobe contrasts with the double lobes in W50 where non-thermal X-ray emission is found (Yamauchi et al., 1994). If the lobe in CTB109 is a jet, it would be similar to the Vela jet because it was recently discovered to have thermal X-rays (Markwardt & Ögelman, 1995). The Vela jet is connected with the pulsar, providing the loss mechanism for most of the pulsar's rotational energy, and it has high pressure of the “cocoon” of shocked jet material. On the contrary, the “jet-like” lobe in CTB 109 is not connected with 1E 2259+586 in the ROSAT image (Rho & Petre, 1997) and does not have higher pressure than elsewhere in the remnant. Therefore, this lobe may not be a supersonic beam; it is neither powered by nor related to the central pulsar. We suggest this lobe was produced by Rayleigh-Taylor instability due to a reflected shock arising from the blast wave-molecular cloud interaction.