Jonhatan Uriel Guerrero González

Over a 17 yr period, we analyze the multiwavelength relationship in the blazar PKS 1510-089, utilizing γ -ray, multifrequency radio (15, 43, and 230 GHz), optical spectra, and photometric data. Spearman rank correlations suggest that γ -ray production is cospatial with the 43 GHz quasi-stationary core (Q0), while the remaining decoupled from the 15 GHz core ( K 0) due to frequency-dependent opacity. A kinematic analysis identified nine superluminal components (Q2 − Q10) and a stationary feature (Q1) at ∼2.0 pc that we interpret as a downstream accelerator. To investigate the long-term evolution of jet opacity and flaring dynamics, we performed a time-resolved cross correlation analysis by dividing the dataset into four temporal epochs characterized by distinct quiescent γ -ray states. These results reveal that the kinematic transitivity of the jet is state dependent: while plasma disturbances propagate through successive τ ∼ 1 surfaces with clear, resolvable delays during quiescent and discrete flaring epochs, massive energy injections act as a low-pass filter, where extreme optical depth and spatial blending temporarily disrupt this kinematic coherence. Finally, the emergence of component Q10 in 2024 as a γ -ray dark event suggests a fundamental restructuring of the radiative environment of the jet following the 2021 high-energy quenching, likely driven by a depletion of external seed photons or enhanced internal γ -ray opacity.

We re-evaluated 610 sources classified as flat-spectrum radio quasars (FSRQs) in the 5th edition of the Roma-BZCAT. Optical spectra from SDSS DR16 confirmed broad emission lines within 0.11 ≤ 𝑧 ≤ 5.28. To assess their blazar-like behaviour, we combined ZTF optical variability with radio morphologies from FIRST, LOFAR, and VLBI, defining Confirmed, Possible, and Non-Confirmed BZQs. The rest-frame 1.4–10 GHz radio spectra were homogenized and fitted using error-weighted power laws. We show that the scheme of Park et al. (2013) often misclassifies nearly flat spectra as inverted and some prominent steep spectra as flat. Using the individual uncertainty 𝜎𝛼,𝑖 , we classify spectra as flat if |𝛼𝑖 | ≤ 2𝜎𝛼,𝑖 , prominently steep if 𝛼𝑖 > 2𝜎𝛼,𝑖 , and inverted if 𝛼𝑖 < −2𝜎𝛼,𝑖 . This criterion, defined source by source and intended as a phenomenological classification for this sample, better reflects the observed spectral shapes and confirms that most BZQs are consistent with being flat within the measurement precision, although a non-negligible fraction departs from a strict flatness. We also classify full spectral morphologies as power-law, peaked, retriggered-peaked, or inverted-peaked, which are associated with distinct jet processes and activity cycles. Approximately 60% of the sources with at least two decades of frequency coverage exhibited retriggered-peaked spectra, suggesting recurrent jet activity. The observed diversity indicates that the label “flat-spectrum radio quasar” does not fully describe this population and that the more general term BZQ may better reflect its phenomenological diversity.

Aims. This study investigates the relationship between the Mg II λ 2798 Å emission line and the 3000 Å continuum luminosity, as well as the Baldwin effect, in a sample of 40’,685 radio-quiet (RQ) quasars and 441 flat spectrum radio quasars (FSRQs). Methods. We performed a comprehensive re-evaluation of the Mg II-3000 Å correlation, explicitly accounting for dispersion introduced by active galactic nucleus (AGN) variability. After excluding > 3000 radio-loud sources, we employed a binning technique to mitigate variability effects, yielding a refined empirical relation. We also further examined the nonthermal dominance (NTD) parameter, to investigate the dominant source of the continuum. Results. Our analysis reveals statistically significant differences in the slopes of the line-continuum luminosity relation between RQ quasars and FSRQs, with a parallel discrepancy in the Baldwin effect. These findings imply either (1) intrinsic differences in the accretion disk spectra of RQ AGNs and FSRQs or (2) jet-induced continuum emission in FSRQs contributing to broad line region (BLR) ionization. We also find that a substantial fraction of both RQ quasars (43.8%) and blazars (55.5%) exhibit NTD < 1. For blazars, this suggests that the accretion disk alone cannot fully explain BLR ionization. On the other hand, we interpret NTD < 1 in radio-quiet quasars as a signature of several physical mechanisms: anomalies in the BLR structure (such as outflow or inflows), time lags between continuum and line variations, and the suppression of the UV continuum by a strong corona that diverts accretion power. Finally, we demonstrate that the Baldwin effect naturally emerges from the line-continuum luminosity relationship, requiring no additional physical mechanism to explain its origin.

Blazars, a highly variable Active Galactic Nuclei (AGNs) subclass, provide a unique opportunity to explore the physical processes within their relativistic jets and emission regions. In this study, we investigate the multiwavelength variability of the blazar TON 599, a Flat Spectrum Radio Quasar (FSRQ), with a particular emphasis on its emission line behavior. We focus on the Mg II $λ$2798 Å emission line, a key tracer of the ionized gas in the broad-line region (BLR), and its role in jet-induced variability. In addition to optical emission lines, we analyze gamma-rays (0.1-300 GeV), X-rays (0.2-10 keV), optical continuum ($λ$3000 Å), optical polarization, and millimeter-wavelength light curves. Three cross-correlation methods are employed to investigate temporal relationships between the emission line and continuum across various wavelengths. Using the Non-Thermal Dominance (NTD) parameter, our analysis confirms that synchrotron emission dominates the continuum during active states, highlighting the jet's primary role in the observed variability. The Mg II emission line exhibits quasi-simultaneous variability with the optical continuum, suggesting photoionization driven by the jet's non-thermal radiation. Additionally, the minimal time lag between gamma-ray and optical/near-ultraviolet emissions supports a synchrotron self-Compton origin for the most variable component of the gamma-ray emission. These findings highlight the importance of emission line variability and multiwavelength observations in constraining the interaction between jets and the BLR in blazars. The results contribute to a deeper understanding of AGN emission mechanisms and the complex interplay between jets and their surrounding environments.