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The active galactic nuclei (AGN) are among the most powerful sources with an inherent, pronounced and random variation of brightness. The randomness of their time series is so subtle as to blur the border between aperiodic fluctuations and…

Astrophysics of Galaxies · Physics 2020-07-02 Andjelka B Kovacevic , Luka C. Popovic , Dragana Ilic

In this paper, we used the database of the university of Michigan Radio Astronomy Observatory (UMRAO) at three (4.8 GHz, 8.0 GHZ, and 14.5 GHz) radio frequency to analyze the radio light curves by the power spectral analysis method in…

Astrophysics · Physics 2009-11-13 J. H. Fan , Y. Liu , Y. H. Yuan

FRB 20121102A was the first fast radio burst to be observed to repeat. Since then, thousands of bursts have been detected by multiple radio telescopes around the world. Previous work has shown an indication of a cyclic activity level with a…

High Energy Astrophysical Phenomena · Physics 2025-01-07 C. A. Braga , M. Cruces , T. Cassanelli , M. C. Espinoza-Dupouy , L. Rodriguez , L. G. Spitler , J. Vera-Casanova , P. Limaye

The ability to automatically and robustly self-verify periodicity present in time-series astronomical data is becoming more important as data sets rapidly increase in size. The age of large astronomical surveys has rendered manual…

Instrumentation and Methods for Astrophysics · Physics 2024-06-14 Niall Miller , Philip Lucas , Yi Sun , Zhen Guo , Calum Morris , William Cooper

From the analysis of more than 92 ks of data obtained with the laxpc instrument on board Astrosat we have detected a clear high-frequency QPO whose frequency varies between 67.4 and 72.3 Hz. In the classification of variability classes of…

High Energy Astrophysical Phenomena · Physics 2019-08-14 Tomaso M. Belloni , Dipankar Bhattacharya , Pietro Caccese , Varun Bhalerao , Santosh Vadawale , J. S. Yadav

FRB 20240114A is extraordinarily active, and therefore presents an opportunity to search for the periodicity predicted by magnetar models of Fast Radio Bursts (FRB). Zhang, et al. (2025) observed 11,553 bursts, including 3196 on MJD 60381…

High Energy Astrophysical Phenomena · Physics 2026-01-09 J. I. Katz

Radio observations being insensitive to the dust-obscuration, have been exploited to unveil the population of Active Galactic Nuclei (AGN) residing in galaxies with large dust content. In this paper, we investigate the radio characteristics…

Astrophysics of Galaxies · Physics 2022-11-22 Abhijit Kayal , Veeresh Singh , C. H. Ishwara Chandra , Yogesh Wadadekar , Sushant Dutta

Fast Radio Burst (FRB) is an extremely energetic cosmic phenomenon of short duration. Discovered only recently and with its origin still unknown, FRBs have already started to play a significant role in studying the distribution and…

Instrumentation and Methods for Astrophysics · Physics 2025-07-31 Xuerong Guo , Han Wang , Yifan Xiao , Huaxi Chen , Yinan Ke , ChenChen Miao , Pei Wang , Di Li , Chenwu Jin , Ling He , Yi Feng , Yongkun Zhang , Jiaying Xu , Guangyong Chen

Periodicity search in gamma-ray data is usually difficult because of the small number of detected photons. A periodicity in the timing signal at other energy bands from the counterpart to the gamma-ray source may help to establish the…

Astrophysics · Physics 2008-05-02 Lupin Chun-Che Lin , Hsiang-Kuang Chang

Gamma-ray Bursts (GRBs) are highly energetic events that can be observed at extremely high redshift. However, inherent bias in GRB data due to selection effects and redshift evolution can significantly skew any subsequent analysis. We…

High Energy Astrophysical Phenomena · Physics 2021-11-23 Maria Dainotti , Delina Levine , Nissim Fraija , Poonam Chandra

The detection of periodic signals in irregularly-sampled time series is a problem commonly encountered in astronomy. Traditional tools used for periodic searches, such as the periodogram, have poorly defined statistical properties under…

Instrumentation and Methods for Astrophysics · Physics 2025-01-13 A. Gúrpide , M. Middleton

We use machine learning techniques to investigate their performance in classifying active galactic nuclei (AGNs), including X-ray selected AGNs (XAGNs), infrared selected AGNs (IRAGNs), and radio selected AGNs (RAGNs). Using known physical…

Astrophysics of Galaxies · Physics 2021-10-26 Yu-Yen Chang , Bau-Ching Hsieh , Wei-Hao Wang , Yen-Ting Lin , Chen-Fatt Lim , Yoshiki Toba , Yuxing Zhong , Siou-Yu Chang

Fast radio bursts (FRBs) are pulsed radio signals with a duration of milliseconds and a large dispersion measure (DM). Recent observations indicate that FRB 180916 and FRB 121102 show periodic activities. Some theoretical models have been…

High Energy Astrophysical Phenomena · Physics 2022-03-11 Y. J. Wei , Z. Y. Zhao , F. Y. Wang

Rising global energy demand from population growth raises concerns about the sustainability of fossil fuels. Consequently, the energy sector has increasingly transitioned to renewable energy sources like solar and wind, which are naturally…

Systems and Control · Electrical Eng. & Systems 2025-09-30 Afsaneh Mollasalehi , Armin Farhadi

A sizeable fraction of gamma-ray burst (GRB) light curves (LCs) features a sequence of peaks, which holds information on the unknown way energy is dissipated into gamma-rays over time. Traditional searches for periodic signals in GRB LCs…

High Energy Astrophysical Phenomena · Physics 2025-05-21 C. Guidorzi , M. Orlandini , R. Maccary , L. Amati , L. Bazzanini , M. Bulla , L. Ferro , F. Frontera , M. Maistrello , W. -J. Tan , A. Tsvetkova , S. L. Xiong , S. N. Zhang

We have obtained discrete Fourier power spectra of a sample of persistent low-mass neutron-star X-ray binaries using long-term light curves from the All Sky Monitor on board the Rossi X-ray Timing Explorer. Our aim is to investigate their…

Astrophysics · Physics 2009-11-07 P. Reig , I. Papadakis , N. D. Kylafis

In this paper, we explore the use of advanced machine learning (ML) techniques to enhance the sensitivity of double Higgs boson searches in the \( HH \to b\bar{b}\gamma\gamma \) decay channel at $\sqrt{s} = $ 13.6 TeV. Two ML models are…

High Energy Physics - Phenomenology · Physics 2026-02-11 Mohamed Belfkir , Mohamed Amin Loualidi , Salah Nasri

Fast radio bursts (FRBs) are astronomical transients with millisecond timescales. Although most of the FRBs are not observed to repeat, a few of them are detected to repeat more than hundreds of times. There exist a large variety of…

High Energy Astrophysical Phenomena · Physics 2023-04-05 Bo Han Chen , Tetsuya Hashimoto , Tomotsugu Goto , Bjorn Jasper R. Raquel , Yuri Uno , Seong Jin Kim , Tiger Y. -Y. Hsiao , Simon C. -C. Ho

The Beijing-Arizona Sky Survey (BASS) Data Release 3 (DR3) catalogue was released in 2019, which contains the data from all BASS and the Mosaic z-band Legacy Survey (MzLS) observations during 2015 January and 2019 March, about 200 million…

Blazars are known to exhibit variability across a broad range of timescales. This behavior can include periodicity in their $\gamma$-ray emission, whose clear detection remains an ongoing challenge, partly due to the inherent stochasticity…

High Energy Astrophysical Phenomena · Physics 2025-07-08 P. Peñil , M. Ajello , S. Buson , A. Domínguez , J. R. Westernacher-Schneider , A. Rico , S. Adhikari , J. Zrake