Related papers: Pulsar Timing Constraints on the Fermi Massive Bla…
We investigate the previously proposed possibility that multi-epoch broadband polarimetry could act as a complement or limited proxy for VLBI observations of blazars, in that the number of polarised emission components in the jet, and some…
We present an in-depth and systematic variability study of a sample of 20 powerful blazars, including 12 BL Lacs and 8 flat spectrum radio quasars, applying various analysis tools such as flux distribution, symmetry analysis, and time…
We report on the Swift/XRT observation and classification of eleven blazar candidates at $z>4$. These sources were selected as part of a sample of extremely radio-loud quasars, in order to focus on quasars with jets oriented roughly close…
Variability is a typical observation feature of Fermi blazars, sometimes it shows quasi-periodic oscillation (QPO). In this work, we obtained 5-day binned light curves (with a time coverage of $\sim$ 12.9 yr) for S5 1044+71 based on Fermi…
The extreme variability of blazars, in both timescale and amplitude, is generally explained as the effect of a relativistic jet closely aligned to the observer's line-of-sight. Due to causality arguments, variability characteristics…
Supermassive binary black holes at sub-parsec orbital separations have yet to be discovered, with the possible exception of blazar OJ~287. In parallel to the global hunt for nanohertz gravitational waves from supermassive binaries using…
In the past five years, approximately one third of the 65 pulsars discovered by radio observations of Fermi unassociated sources are black widow pulsars (BWPs). BWPs are binary millisecond pulsars with companion masses ranging from 0.01-0.1…
Quasar pairs are either physically distinct binary quasars or the result of gravitational lensing. The majority of known pairs are in fact lenses, with a few confirmed as binaries, leaving a population of objects that have not yet been…
In this work, we analyzed the long term gamma-ray data by a Fermi Large Area Telescope (Fermi-LAT) of blazar S2 0109+22, ranging from 2008 to 2023. The quasi-periodic oscillations (QPOs) of blazars aided in investigating the physical…
We report a nominally high-confidence $\gamma$-ray quasi-periodic modulation in the blazar PKS 0301$-$243. For this target, we analyze its \emph{Fermi}-LAT Pass 8 data covering from 2008 August to 2017 May. Two techniques, i.e., the maximum…
We investigate the use of optical photometric variability to select and identify blazars in large-scale time-domain surveys, in part to aid in the identification of blazar counterparts to the ~30% of gamma-ray sources in the Fermi 2FGL…
Pulsar-black hole (BH) close binary systems, which have not been found yet, are unique laboratories for testing theories of gravity and understanding the formation channels of gravitational-wave sources. We study the self-gravitational…
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…
Most large galaxies host supermassive black holes in their nuclei and are subject to mergers, which can produce a supermassive black hole binary (SMBHB), and hence periodic signatures due to orbital motion. We report unique periodic radio…
While there has been an increase in interest in the possibility of quasi-periodic oscillations (QPOs) in blazars, the search has hitherto been restricted to sources with well-sampled light curves. Objects with light curves that include gaps…
Blazars, a subset of powerful active galactic nuclei, feature relativistic jets that shine in a broadband electromagnetic radiation, e. g. from radio to TeV emission. Here I present the results of the studies that explore gamma-ray and…
After large galaxies merge, their central supermassive black holes are expected to form binary systems whose orbital motion generates a gravitational wave background (GWB) at nanohertz frequencies. Searches for this background utilize…
A systematic search for cyclical sources of gamma-ray emission on the period range from days to years in the Fermi-LAT sky is performed. Looking for cyclical emission, the sky is binned into equal-area pixels and the generalised…
Although neutron star-black hole binaries have been identified through mergers detected in gravitational waves, a pulsar-black hole binary has yet to be detected. While short-period binaries are detectable due to a clear signal in the…
In this study, we analyze the $\sim 16$ yr Fermi-LAT data of 160 blazars consisting of 92 flat-spectrum radio quasars (FSRQs), 64 BL Lacertae type objects (BL Lacs), and 4 blazar candidates of unknown type objects (BCU), and exhibit their…