相关论文: Understanding extreme quasar optical variability w…

Active galactic nuclei (AGNs) are known to exhibit optical/UV variability and most of them can be well modeled by the damped random walks. Physical processes that are not related to the accretion disk, such as tidal disruption events (TDE)…

Quasars have long been known to be variable sources at all wavelengths. Their optical variability is stochastic, can be due to a variety of physical mechanisms, and is well-described statistically in terms of a damped random walk model. The…

The variability of quasars across multiple wavelengths is a useful probe of physical conditions in active galactic nuclei. In particular, variable accretion rates, instabilities, and reverberation effects in the accretion disk of a…

Extreme Scattering Events are radio-wave lensing events caused by AU-sized concentrations of ionised gas. Although they were discovered more than a decade ago we still have no clear picture of the physical nature of the lenses. To…

A key feature of active galactic nuclei (AGN) is their variability across all wavelengths. Typically, AGN vary by a few tenths of a magnitude or more over periods lasting from hours to years. By contrast, extreme variability of AGN -- large…

We present the results of a systematic search for quasars in the Catalina Real-time Transient Survey exhibiting both strong photometric and spectroscopic variability over a decadal baseline. We identify 73 sources with specific patterns of…

Graham et al. found a sample of active galactic nuclei (AGNs) and quasars from the Catalina Real-time Transient Survey (CRTS) that have long-term periodic variations in optical continuum, the nature of the periodicity remains uncertain. We…

Active galactic nuclei (AGN) are some of the brightest and most variable objects in the Universe. Those with relativistic jets observed at small viewing angles are blazars. Due to Doppler boosting, blazars exhibit extreme stochastic…

Active galactic nuclei (AGNs) are known to exhibit stochastic variability across a wide range of timescales and wavelengths. AGN flares are extreme outbursts that deviate from this typical behavior and may trace a range of energetic…

The variability of active galactic nuclei (AGN) has long held the promise of shedding light on their detailed structure, and possibly other astrophysical phenonema. Different emission mechanisms lead to different patterns of variability in…

Mergers of spinning black holes can give recoil velocities from gravitational radiation up to several thousand km/s. A recoiling supermassive black hole in an AGN retains the inner part of its accretion disk. Marginally bound material…

We have studied the flare characteristics of 55 AGN at 8 different frequency bands between 4.8 and 230 GHz. Our extensive database enables us to study the various observational properties of flares in these sources and compare our results…

Since their discovery more than 60 years ago, accreting supermassive black holes in active galactic nuclei (AGN) were recognized as highly variable sources, requiring an extremely compact, dynamic environment. Their variability traces to…

Context. Changing-look active galactic nuclei (CL-AGNs) challenge the unified model of AGNs and offer key insights into the physics of the accretion processes of super-massive black holes. While systematic spectroscopic comparisons have…

We present the first systematic analysis of the X-ray variability of Sgr A* during the Chandra X-ray Observatory's 2012 Sgr A* X-ray Visionary Project (XVP). With 38 High Energy Transmission Grating Spectrometer (HETGS) observations spaced…

This paper presents an investigation into the gravitational microlensing of quasars by stars and stellar remnants in the Milky Way. We present predictions for the all-sky microlensing optical depth, time-scale distributions and event rates…

We present an analysis of nine years of Catalina Surveys optical photometry for 1.4 million spectroscopically confirmed SDSS galaxies. We find 717 outburst events that were not reported by ongoing transient surveys. These events have…

We analyze 1598 serendipitous Chandra X-ray observations of 462 radio-quiet quasars to constrain the frequency of extreme amplitude X-ray variability that is intrinsic to the quasar corona and innermost accretion flow. The quasars in this…

Context. Multiwavelength studies of transients in actively accreting supermassive black holes have revealed that large-amplitude variability is frequently linked to significant changes in the optical spectra -- a phenomenon known as…

Blazars, a unique class of active galactic nuclei, exhibit highly variable emission across the electromagnetic spectrum. This variability frequently manifests as intense flaring events, sparking an ongoing debate in recent literature about…