Related papers: Potential periodic signals in blazars: significanc…
Here we report an optical quasi-periodic oscillation (QPO) with a period of $\sim$134~day detected in g- and r-band light curves of a narrow-line Seyfert 1 galaxy TXS 1206+549 at redshift of 1.34 with the data from the Zwicky Transient…
We report a 325(-7, +8) day quasi-periodic oscillation (QPO) in the X-ray emission of the blazar Mkn 421, based on data obtained with the Rossi X-ray Timing Explorer (RXTE). The QPO is seen prominently in the ASM data (at least 15 cycles),…
We report our search for quasi-periodic signals in long-term optical and $\gamma$-ray data for the blazar PKS~1222+216, where the data are from the Steward Observatory blazar monitoring program and the all-sky survey with the Large Area…
We study the Rossby wave instability model of high-frequency quasi-periodic oscillations (QPO) of microquasars. We show ray-traced light curves of QPO within this model and discuss perspectives of distinguishing alternative QPO models with…
Long-term gamma-ray variability of a non-blazar Active Galactic Nucleus (AGN) PKS 0521-36 is investigated by using Fermi-LAT pass 8 data covering from 2008 August to 2021 March. The results show that the histogram of the gamma-ray fluxes…
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…
PKS 2155-304 is a well studied BL Lac object in the southern sky. The historical optical data during different period have been collected and compiled. Light curves with a time span of 35 years have been constructed. The R-band light curve…
GRB 250702DBE was time-consequently triggered by GBM onboard the Fermi satellite. It is uncertain which celestial catalog is suitable for this special ultra-long event to belong to. In this paper, we comprehensively investigate the…
Analyses of quasi-periodic oscillations (QPOs) are important to understanding the dynamic behaviour in many astrophysical objects during transient events like gamma-ray bursts, solar flares, magnetar flares and fast radio bursts.…
The observation data of blazar 1ES 1426 + 42.8 were obtained using the 1.02 m optical telescope of Yunnan Observatories during $2021$ to $2023$. Intraday variability (IDV) is detected on seven nights. We use the turbulent model to…
I report on the discovery of 34 new quasi-periodic oscillations (QPOs) in the prompt light curves of long gamma-ray bursts (GRBs) from the Swift/BAT catalog: with one or more constant leading periods, as well as several chirping signals.…
We present a detailed study of the 5 Hz quasi-periodic oscillation (QPO) recently discovered in the bright X-ray transient and black-hole candidate GRS 1739-278 (Borozdin & Trudolyubov 2000) during a Rossi X-ray Timing Explorer observation…
We selected a sample of 24 XMM-Newton light curves (LCs) of four high energy peaked blazars, PKS 0548-322, ON 231, 1ES 1426+428 and PKS 2155-304. These data comprise continuous light curves of 7.67h to 18.97h in length. We searched for…
In the manuscript, a 3.8yr optical quasi-periodic oscillations (QPOs) is reported in blue quasar SDSS J132144+033055 (=\obj) at $z=0.269$, based on 16.3yr-long light curve from both CSS and ZTF directly described by a sinusoidal function.…
The search for periodicity in the multi-wavelength high variable emission of blazars is a key feature to understand dynamical processes at work in this class of active galactic nuclei. The blazar PG 1553+113 is an attractive target due to…
Quasi-periodic pulsations (QPPs), which usually appear as temporal pulsations of the total flux, are frequently detected in the light curves of solar/stellar flares. In this study, we present the investigation of non-stationary QPPs with…
A new model for the explanation of the high frequency quasi-periodic oscillations (QPOs) in pulsars, black holes and white dwarfs is presented. Three circular tori are assumed to be present around the star: an inner torus with charge $Q_i$,…
Many astrophysical sources, especially compact accreting sources, show strong, random brightness fluctuations with broad power spectra in addition to periodic or quasi-periodic oscillations (QPOs) that have narrower spectra. The random…
Blazars are the most luminous and variable AGNs, and thus excellent probes of accretion and emission processes close to the central engine. We focus on PKS 1510-089 ($z=0.36$), one of the brightest gamma-ray sources in the Fermi LAT…
We present the results of a time series analysis of the long-term radio lightcurves of four blazars: 3C 279, 3C 345, 3C 446, and BL Lacertae. We exploit the data base of the University of Michigan Radio Astronomy Observatory (UMRAO)…