射电类星体B31637+436A双峰轮廓宽发射线的光变研究

Investigation of Variations in Double-Peaked Broad Emission Lines of Radio Quasar B31637+436A

通过对比间隔17 yr (静止系12.5 yr)的Sloan Digital Sky Survey (SDSS)、Keck LRIS (Low-Resolution Imaging Spectrograph)和Baryon Oscillation Spectroscopic Survey (BOSS)的光学光谱,对宽线双峰射电类星体B3 1637+436A的吸积盘性质做了初步研究.该类星体的SDSS (2001年5月21日)和Keck LRIS (2003年6月28日)的连续谱没有明显差异,而BOSS (2018月6月17日)连续谱在V波段比SDSS暗了约1.2星等.这3条光谱的Hα宽发射线均表现出明显的双峰轮廓.和连续谱一样,宽线双峰的发射线轮廓也被认为是来自于吸积盘.通过上述3条光谱的Hα宽线双峰的盘模型拟合发现:BOSS光谱的Hα宽线双峰可以用单个盘模型很好地拟合,谱线发射区距离中心黑洞约900–3000引力半径.而SDSS和Keck LRIS的Hα双峰轮廓需要用两个盘模型拟合,对应的吸积盘发射区有两个区域,其中一个发射区(“外盘”)与BOSS类似,另一个发射区(“内盘”)位于约400–900引力半径范围内,到中心黑洞的距离显著小于外盘.结合连续谱的光变特征,推测内盘消失是造成SDSS/Keck LRIS光谱和BOSS光谱在连续谱和发射线轮廓上同时发生光变的主要原因.

In this paper, by comparing the optical spectra of Sloan Digital Sky Survey(SDSS), Keck and Baryon Oscillation Spectroscopic Survey(BOSS), a preliminary study has been done on the properties of the accretion disk of the double-peaked broad line radio quasar B3 1637+436A. The continuum of the SDSS spectrum of B3 1637+436A(May 21, 2001) and the Keck spectrum(June 28, 2003) is not significantly different, while the continuum of the BOSS spectrum(June 17, 2018) is about 1.2 magnitudes lower than the SDSS spectrum in the V band. The Hα emission lines of the three spectra have a clear double-peaked broad line profile. Like the continuum, the double-peaked broad line profile is also considered to come from the accretion disk. By fitting the disk model of the double-peaked profile of Hα on the three spectra, we found that the double-peaked Hα profile of the BOSS spectrum can be well fit with a single disk model,and the emission line region lies about 900–3000 gravitational radius away from the central black hole. The double-peaked profiles of SDSS and Keck’s Hα need to be fit with two disk models. The corresponding accretion disk emission area has two regions, one of which(“The outer disk”) is similar to BOSS, and the other emission region(“The inner disk”) is located within the range of about 400–900 gravitational radius,which is much smaller than the outer disk. Combining the characteristics of variations of the continuum spectrum, we believe that the disappearance of the inner disk is the main reason for the variation between the SDSS/Keck spectrum and the BOSS spectrum.