2002ApJ...565.1084S

We present [O III] 500.7 nm and Hα+[N II] images and long-slit, high-resolution echelle spectra in the same spectral regions of Sa 2-237, a possible bipolar planetary nebula. The image shows a bipolar nebula of about 34" extent with a narrow waist and strong point symmetry around the central object, indicating its likely binary nature. The long-slit spectra were taken over the long axis of the nebula and show a distinct 8-shaped pattern in the velocity-space plot with a maximum projected outflow velocity of v_exp=106 km.s^–1, both typical of expanding bipolar planetary nebulae. By model fitting the shape and spectrum of the nebula simultaneously, we derive the inclination of the long axis to be 70° and the maximum space velocity of expansion to be ≤308 km.s^–1. Due to asymmetries in the velocity, we adopt a new value for the system's heliocentric radial velocity of -30 km.s^–1. We use the IRAS and 21 cm radio fluxes, the energy distribution, and the projected size of Sa 2-237 to estimate its distance to be 2.1±0.37 kpc. At this distance, Sa 2-237 has a luminosity of 340 L_☉, a size of 0.37 pc, and–assuming a constant expansion velocity–a nebular age of 624 years. The above radial velocity and distance place Sa 2-237 in the disk of the Galaxy at z=255 pc, albeit with somewhat peculiar kinematics.