2024A&A...689A.129F

Aims. We aim to unveil the structure of the continuum and broad-emission line (BEL) emitting regions in the gravitationally lensed quasar SDSS J1339+1310 by examining the distinct signatures of microlensing present in this system. Our study involves a comprehensive analysis of ten years (2009-2019) of photometric monitoring data and seven spectroscopic observations acquired between 2007 and 2017.
Methods. This work focuses on the pronounced deformations in the BEL profiles between images A and B, alongside the chromatic changes in their adjacent continua and the striking microlensing variability observed in the r-band light curves. We employed a statistical model to quantify the distribution and impact of microlensing magnifications and utilized a Bayesian approach to estimate the dimensions of various emission regions within the quasar. To establish a baseline relatively free of microlensing effects, we used the cores of the emission lines as a reference.
Results. The analysis of the r-band light curves reveals substantial microlensing variability in the rest-frame UV continuum, suggesting that image B is amplified relative to image A by a factor of up to six. This finding is corroborated by pronounced microlensing-induced distortions in all studied BEL profiles (Lyα, Si IV, C IV, C III], and Mg II), especially a prominent magnification of image B's red wing. These microlensing signals surpass those typically observed in lensed quasars, and the asymmetric line profile deformations imply an anisotropic broad-line region (BLR). We estimated the average dimensions of the BLR to be notably smaller than usual: the region emitting the blue wings measures R_1/2 = 11.5 ± 1.7 light-days, while the red wings originate from a more compact area of R_1/2 = 2.9 ± 0.6 light-days. From the photometric monitoring data, we inferred that the region emitting the r-band is R_1/2 = 2.2 ± 0.3 light-days across. Furthermore, by assessing the gravitational redshift of the UV Fe III blend and combining it with the blend's microlensing-based size estimate, we calculated the central SMBH's mass to be M_BH ∼ 2 × 10⁸ M_⊙.