活动星系核的连续谱变异性： BAL类星体系统抑制波动的证据
Continuum Variability in AGN: Evidence for Systematically Suppressed Fluctuations in the BAL Population
AI总结：
该研究对比BAL与非BAL类星体的流量变异性，发现BAL类星体连续谱变异性系统性更低，证实变异性抑制是连续谱固有特征，或与核遮蔽等因素相关。
AI中文摘要：
我们旨在比较宽吸收线类星体（BAL）与非BAL类星体的流量变异性，通过控制黑洞参数来为BAL现象的产生模型提供信息。使用SDSS DR16和ZTF的g、r波段光变曲线，我们选取红移1.57≤z≤2.00、r星等18.5≤rmag≤19.8的类星体。该红移范围确保g波段覆盖C IV发射线（BAL中的 trough），而r波段探测连续谱变异性，同时允许通过Mg II估算黑洞质量（MBH）。我们用超额方差和阻尼随机游走（DRW）参数（σ_DRW、τ_DRW）量化变异性，还按MBH和爱丁顿比率（REdd）分箱比较DRW指标，以分离具有相同物理属性的天体中BAL现象的影响。结果显示，BAL类星体的超额方差和σ_DRW始终更小，证实其长期变异性更低，且两个样本的g波段变异性均高于r波段。这些差异在固定MBH和REdd分箱中依然存在，表明BAL类星体的变异性抑制并非仅由两类样本的这些属性差异导致。研究结果表明，BAL类星体在两个波段的变异性均系统性低于非BAL类星体，证实这种抑制是连续谱的固有特征，而非发射或吸收线污染的影响。若BAL类星体的MBH值系统性高估≥4倍，样本可达成一致，这意味着其REdd显著更高；此外，BAL类星体的低变异性或与其较低的X射线光度相关，或与显著的核遮蔽有关——若BAL类星体吸积盘内部比吸积盘其余部分更遮蔽且变异性更强。
英文摘要：
We aim to compare the flux variability of Broad Absorption Line quasars (BAL) to non-BAL quasars, controlling for black hole parameters to inform models concerning the generation of the BAL phenomenon. Using SDSS DR16 and ZTF $g$- and $r$-band light curves, we select quasars with $1.57 \leq z \leq 2.00$ and $18.5 \leq rmag \leq 19.8$. This redshift range ensures that the $g$-band covers the C IV emission line (and trough in BALs) while the $r$-band probes continuum variability, and allows black hole mass (MBH) estimates via Mg II. We quantify variability using excess variance and damped random walk (DRW) parameters ($σ_{\mathrm{DRW}}$, $τ_{\mathrm{DRW}}$). We also compared the DRW metrics in bins of MBH and Eddington ratio (REdd) to isolate the influence of the BAL phenomenon in objects with the same physical properties. Excess variance and $σ_{\mathrm{DRW}}$ are consistently smaller for BALs, confirming lower long-term variability, while the $g$-band exhibits higher variability than the $r$-band across both populations. These differences persist in fixed bins of MBH and REdd, indicating that the suppressed variability in BALs is not simply driven by differences in these properties between BAL and non-BAL samples. These results show that BAL quasars are systematically less variable than non-BAL quasars in both bands, confirming that this suppression is an intrinsic feature of the continuum rather than an effect of emission or absorption line contamination. The samples could be made to agree if BAL MBH values were systematically overestimated by a factor $\gtrsim 4$, implying a significantly higher REdd. Alternatively, the lower variability in BALs can be related to their lower X-ray luminosities, or to significant nuclear obscuration, if the inner part of the accretion disc were more obscured in BALs and more variable than the rest of the disc.
