SN 1987A's circumstellar envelope. II. Kinematics of the three rings and the diffuse nebula

We present several different measurements of the velocities of structures within the circumstellar envelope of SN 1987A, including the inner, equatorial ring (ER), the outer rings (ORs), and the diffuse nebulosity at radii less than or similar to 5 pc, based on CTIO 4 m and Hubble Space Telescope (HST) data. A comparison of STIS and WFPC2 [NII] lambda 6583 loci for the rings show that the ER is expanding in radius at 10.5 +/- 0.3 km s(-1) (with the northern OR expanding along the line of sight at similar to 26 km s(-1), and for the southern OR, similar to 23 km s(-1)). The best fit to CTIO 4 m echelle spectra of the CN rrl lambda 6583 line show the ORs expanding at similar to 23 km s(-1) along the line of sight. Accounting for inclination, the best fit to all data for the expansion in radius of both ORs is 26 km s(-1). The ratio of the ER to the OR velocity is nearly equal to the ratio of the ER to the OR radius, so the rings are roughly homologous, all having been created similar to 20,000 yr before the supernova (SN) explosion. This makes the previously reported, large compositional differences between the ER and ORs difficult to understand. Additionally, a grid of long-slit 4 m echelle spectra centered on the SN shows two velocity components over a region roughly coextensive with the outer circumstellar envelope extending similar to 5 pc (20) from the SN. One component is blueshifted similar to 10 km s(-1) relative to the systemic velocity of the SN, while the other is redshifted by a similar amount. These features may represent a bipolar flow expanding from the SN, in which the ORs are propelled 10-15 km s(-1) faster than that of the surrounding envelope into which they propagate. The kinetic timescale for the entire nebula is greater than or similar to 350,000 yr (and probably more, since material may be accumulating in an outer contact discontinuity). The kinematics of these different structures constrain possible models for the evolution of the progenitor and its formation of a mass-loss nebula.