标题： NGC 6778：加强行星状星云中极端丰度差异因子与中心星双星性质之间的联系 显示英文标题

标题： NGC 6778: Strengthening the link between extreme abundance discrepancy factors and central star binarity in planetary nebulae

摘要： 我们提供了附近、明亮的行星状星云NGC 6778的新光学光谱。 该星云已知在40多年的时间里发射出强烈的复合线，但这是对其丰度的首次详细研究。 从复合线得出的重元素丰度在星云的整体光谱中比碰撞激发线的丰度高约20倍，这是已知最大的丰度差异因子之一。 光谱的空间分析显示，丰度差异因子在中心区域强烈集中，接近中心恒星处达到约40。 NGC 6778的中心恒星已知是一个短周期双星，这进一步加强了高星云丰度差异因子与中心恒星双星性质之间的联系。 显示英文摘要

摘要： We present new optical spectra of the nearby, bright, planetary nebula NGC 6778. The nebula has been known to emit strong recombination lines for more than 40 years but this is the first detailed study of its abundances. Heavy element abundances derived from recombination lines are found to exceed those from collisionally excited lines by a factor of ~20 in an integrated spectrum of the nebula, which is among the largest known abundance discrepancy factors. Spatial analysis of the spectra shows that the abundance discrepancy factor is strongly, centrally peaked, reaching ~40 close to the central star. The central star of NGC 6778 is known to be a short period binary, further strengthening the link between high nebular abundance discrepancy factors and central star binarity.