在這篇論文中，我們利用泛星巡天計畫的資料追蹤了34個紅移值介於 0.3和1.2之間的偏紅類星體及122個正常類星體的光度及顏色變化。類星體在光學波段的顏色較為偏藍；然而，在過去三十年間，天文學家陸續發現了為數不少的顏色較為偏紅的類星體。這些偏紅類星體的主要成因和確切定義尚未有明確定論。利用類星體的光譜，我們藉由計算靜止參考系上 3000 埃及 4000 埃的光通量密度比值，定義了偏紅類星體及正常類星體。在 34 個偏紅類星體中，我們發現有 16 個類星體被識別為展源；這些被識別為展源的類星體在短波長端往往呈現較大的光度及顏色變化，我們認為這是由於該類星體的宿主星系中，恆星光的汙染所造成的。另一方面，我們也發現有一些被識別為點源的類星體其顏色變化程度之大，足以改變我們利用光譜所定義它們的顏色分類。由於這些類星體的顏色變化時間尺度相當短（泛星計畫的巡天時間僅有四年），所以我們認為造成該顏色變化的物理機制的規模尺度應當非常小，可能僅有數光年的大小。我們發現有些偏紅類星體的光譜可以用正常類星體被塵埃紅化後的光譜加以解釋。然而，也有一些偏紅類星體的光譜是完全無法用塵埃紅化加以解釋的。

We study the brightness and the color variabilities of 34 red and 122 typical quasi-stellar objects (QSOs) at 𝑧 = 0.3 − 1.2 using data from the Pan-STARRS Medium Deep Survey. The red and the typical QSOs are selected based on the ratios of the flux densities at 3000 Å to those at 4000 Å in the rest frame. We find that 16 out of 34 red QSOs are identified as extended sources, which exhibit strong brightness and color variabilities at shorter wavelengths due to the contamination of the emission from their host galaxies. Some point-like QSOs with significant color variabilities are able to change their color classification according to our spectral definition. The time scales of the color variabilities for these point-like QSOs are within four years, suggesting that the size scales of the mechanisms producing the color variabilities are less than a few light-years. The spectra of some extended and point-like red QSOs can be well fitted with the dust-reddened spectra of a typical QSO, while others are difficult to explain with dust reddening.

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