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We request 190 ks on a uniform sample of 12 optically-selected low-z radio-quiet SDSS quasars. The range of L/LEdd complement the virgul60 well-studied but potentially biased (in terms of L/LEdd) ..reverberation mapped. (RM) quasars. With both SDSS and HST spectroscopy we are able to estimate L/Ledd from 3 optical/UV-based estimators. X-ray data from Chandra enables a 4th L/LEdd estimator (alpha_ox) for the full sample of 25 objects. The 12 proposed targets lack sufficient Chandra counts to investigate the robustness of the hard X-ray spectral index Gamma as an indicator of L/LEdd. Our observations will enable intercomparison of 5 optical/UV and X-ray estimators of L/LEdd for a well-defined sample of quasars. [truncated! Please see actual data for full text]我们申请了190千秒的观测时长，用于研究由12颗经光学选样的低红移射电宁静斯隆数字巡天（Sloan Digital Sky Survey, SDSS）类星体组成的均匀样本。该样本的爱丁顿光度比（L/L_Edd）范围可补充现有研究充分但在L/L_Edd方面存在潜在偏差的反响映射（reverberation mapping, RM）类星体样本。借助斯隆数字巡天与哈勃空间望远镜（Hubble Space Telescope, HST）的光谱数据，我们可通过3种基于光学/紫外波段的估算器得到L/L_Edd值；钱德拉X射线天文台的X射线数据则可针对全部25个目标样本提供第4种L/L_Edd估算方法——α_ox。本次申请观测的12颗目标天体缺乏足够的钱德拉观测计数数据，无法验证硬X射线光谱指数Γ作为L/L_Edd指示参数的鲁棒性。本次观测将实现针对类星体定义明确样本的5种光学/紫外与X射线波段L/L_Edd估算方法的相互比对。【文本已截断！完整内容请查阅原始数据集】