Recently, a new class of quasars, called changing-look quasars (CLQs), has been reported. CLQs exhibit significant changes in optical and mid-infrared luminosity, accompanied by the appearance or disappearance of broad emission lines. We performed spectroscopic observations at the Nishi-Harima Astronomical Observatory in 2018 May to identify objects that show long-term (∼10 yr) continuous optical luminosity variations as candidates for CLQs. We discovered significant fluctuations in the Hβ emission line of 3C 332. This source has previously been reported to have a characteristic double-peaked Hα emission line. To explain the shape of the emission lines, a ring disk model has been proposed, and the possibility of a binary black hole has also been suggested. To further investigate the characteristics of 3C 332, we performed nine spectroscopic observations at Okayama Observatory (Kyoto University) from 2020 February to June. Based on the change in the velocity offset of the emission lines and the negative correlation between the line intensity and the velocity difference between the two peaks, we conclude that the double-peaked origin of this source is consistent with the ring disk model. In addition, the timescale of the changing look (of the optical and mid-infrared luminosities) is consistent with the thermal timescale or the propagation timescale of the heating/cooling front.

中文翻译：

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发现新的外观变化类星体 3C 332 和双峰发射线情景的约束

最近，已经报道了一类新的类星体，称为变化外观类星体（CLQ）。CLQ 表现出光学和中红外光度的显着变化，伴随着宽发射线的出现或消失。我们于 2018 年 5 月在 Nishi-Harima 天文台进行了光谱观测，以确定显示长期（~10 年）连续光度变化的物体作为 CLQ 的候选对象。我们发现 3C 332 的 Hβ 发射线存在显着波动。此前​​曾报道该源具有特征性双峰 Hα 发射线。为了解释发射线的形状，有人提出了一个环盘模型，也有人提出了双黑洞的可能性。为了进一步研究 3C 332 的特性，从 2020 年 2 月到 6 月，我们在冈山天文台（京都大学）进行了 9 次光谱观测。根据发射谱线速度偏移的变化以及谱线强度与两峰速度差的负相关，我们得出该源的双峰起源与环盘模型一致。此外，变化外观的时间尺度（光学和中红外光度）与热时间尺度或加热/冷却前沿的传播时间尺度一致。我们得出结论，该源的双峰起源与环盘模型一致。此外，变化外观的时间尺度（光学和中红外光度）与热时间尺度或加热/冷却前沿的传播时间尺度一致。我们得出结论，该源的双峰起源与环盘模型一致。此外，变化外观的时间尺度（光学和中红外光度）与热时间尺度或加热/冷却前沿的传播时间尺度一致。