标题： SN 1986J VLBI：II. 外壳和中心源的演化 显示英文标题

标题： SN 1986J VLBI: II. The Evolution of the Shell and the Central Source

摘要： 我们展示了超新星1986J的新VLBI图像，这些图像是在爆炸后第22到25年之间，在5 GHz、8.4 GHz和22 GHz波段拍摄的。 壳层以t^(0.69+-0.03)的速度膨胀。 我们估计了前身星的质量损失率为(4 ~ 10) * 10^-5 Msol/yr（对于v_w = 10 km/s）。 图像中可以看到两个亮斑。 第一个位于东北方向，现在正在变暗。 第二个非常靠近投影壳的中心，且是SN1986J独有的，相对于壳层仍在增亮，并且现在主导着VLBI图像。 它在22 GHz处勉强可分辨（直径约0.3毫角秒；约10^16厘米，距离10 Mpc）。 SN1986J的综合VLA光谱显示了一个反转点和高频转折点，这两个特征都在频率上向下移动，并归因于中央亮斑。 中央亮斑的光学薄谱指数与壳层无法区分。 中央亮斑的小自行速度1500+-1500 km/s与我们之前将其解释为与预期的黑洞或中子星遗迹相关联是一致的。 现在，另一种情景似乎也是可能的，其中中央亮斑像东北方向的亮斑一样，当冲击波前沿撞击到周围星际介质中的冷凝物时形成。 冷凝物必须如此密集以至于在厘米波长下是不透明的（约比平均相应周围星际介质密度高1000倍），并且恰好位于投影壳的中心附近。 我们提供了一部从t=0到25年之间在5 GHz波段下SN1986J演化的电影。 显示英文摘要

摘要： We present new VLBI images of supernova 1986J, taken at 5, 8.4 and 22 GHz between t=22 to 25 yr after the explosion. The shell expands as t^(0.69+-0.03). We estimate the progenitor's mass-loss rate at (4 ~ 10) * 10^-5 Msol/yr (for v_w = 10 km/s). Two bright spots are seen in the images. The first, in the northeast, is now fading. The second, very near the center of the projected shell and unique to SN1986J, is still brightening relative to the shell, and now dominates the VLBI images. It is marginally resolved at 22 GHz (diameter ~0.3 mas; ~5 * 10^16 cm at 10 Mpc). The integrated VLA spectrum of SN1986J shows an inversion point and a high-frequency turnover, both progressing downward in frequency and due to the central bright spot. The optically-thin spectral index of the central bright spot is indistinguishable from that of the shell. The small proper motion of 1500+-1500 km/s of the central bright spot is consistent with our previous interpretation of it as being associated with the expected black-hole or neutron-star remnant. Now, an alternate scenario seems also plausible, where the central bright spot, like the northeast one, results when the shock front impacts on a condensation within the circumstellar medium (CSM). The condensation would have to be so dense as to be opaque at cm wavelengths (~1000x denser than the average corresponding CSM) and fortuitously close to the center of the projected shell. We include a movie of the evolution of SN1986J at 5 GHz from t=0 to 25 yr.