Abstract We present photometric observations of the BL Lacertae object S5 0716+714 with a temporal resolution 120 s in Sloan <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mi>i</mml:mi> </mml:mrow> <mml:mi>′</mml:mi> </mml:msup> </mml:math> and <mml:mi>r</mml:mi> bands. These were conducted using Comet Search Program telescope at Xingming Observatory from 2018 December 22 to 2020 February 15, more than 5600 effective images obtained on...

ABSTRACT We observed the blazar 2200 + 420 in I, R, and V bands using 1.0 m telescope at Weihai Observatory of Shandong University on eight nights October 2022 obtained over 3800 data points. Using F-test ANOVA test, we analysed light curves found intra-day (IDV) variability every night. that all amplitudes (Amp) are 10 per cent, except for 22, with four having above 20 cent maximum amplitude reaching 42 cent. Additionally, discovered a minimal time-scale 24.6 min bluer-when-brighter (BWB)...

Abstract We investigate analytically the apparent shadows cast by Kerr-Newman black hole with surrounding perfect fluid matter in Rastall gravity theory. With help of Hamilton-Jacobi equation and Carter constant separable method, we derive null geodesics space-time calculate numerical results horizon structures. The reveal that three horizons (Cauchy r − , event + cosmological q ) occur space-time, structure could degenerate while parameter k λ arrives critical value. By fixing value state...

Abstract We present the horizon structures and shadows for Kerr-Newman-AdS black hole located in perfect fluid matter field Rastall gravity. By considering Hamilton-Jacobi equation Carter constant separable method, we obtain null geodesic equations of space-time as well unstable circular photon orbits terms impact parameters. The are calculated numerically. results show that there four roots a general case (the Cauchy <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"...

Abstract We perform the quasi-periodic oscillation (QPO) analysis of blazar PKS 1424−418 in γ -ray (0.1–300 GeV) band from 2009 May 12 to 2019 September 17 (MJD 54963−58743). Using spectral domain methods, Bhatta &amp; Dhital reported that this source has 353 days periodic flux oscillations flux. Adopting time we confirm previous detection a possible QPO ∼355 with high significance level. Combining two methods and provides stronger evidence for existence QPO. Especially, after strongest...

Abstract We propose a jet helical motion model to explain the γ -ray quasiperiodic oscillation of PG 1553+113. In this model, we hypothesize that relativistic with constant angular velocity rotates around axis, causing Doppler factor vary over time, leading periodic changes in flux. addition, consider parameters emission field slightly during observation period and can be obtained by directly fitting their multiwavelength spectra. Then, use resulting information reproduce light curve. Our...

ABSTRACT We examine the fundamental plane of 91 blazars which include flat-spectrum radio quasars and BL Lacertae objects with known X-ray luminosity (LR), (LX), black hole mass measurements (M) to reflect relationship between jet accretion for blazars. The are logLR = ${0.273}_{+0.059}^{-0.059}\log L_X$ + ${0.695}_{+0.191}^{-0.191}\log M$ ${25.457}_{+2.728}^{-2.728}$ ${0.190}_{+0.049}^{-0.049}\log ${0.475}_{+0.157}^{-0.157}\log ${28.568}_{+2.245}^{-2.245}$ after considering effect beam...

Abstract The variability data for the BL Lacertae object TXS 1902+556 in optical and γ-ray wavebands were obtained from 0.76 m Katzman Automatic Imaging Telescope Fermi Large Area (Fermi-LAT), covering periods of 14.4 years 14.7 years, respectively. properties systematically analyzed, with particular emphasis on first comprehensive investigation radiation variation waveband. Four well-established techniques employed this purpose: Lomb-Scargle periodogram, REDFIT program, Jurkevich method,...

Following previous work, we further confirm that the cosmic evolution of steep-spectrum radio-loud AGNs (active galactic nuclei) can be reproduced by a simple combination density (DE) and luminosity (LE). This mixture scenario naturally explain luminosity-dependent AGNs. Our models successfully fitted large amount data on radio functions (RLFs) sources multi-frequency source counts. The modeling indicates DE slowly increase as $(1+z)^{0.3 \thicksim 1.3}$ out to $z 0.8$, then rapidly...

Abstract We have systemically studied the properties of 1ES 1959+650, specifically its multiband variability and emission mechanisms. carefully analyze by four different kinds trusted approaches. In contrast with previous research thanks to our more detailed data, we find that an unprecedented significant quasi-periodic component timescale <?CDATA $P={266.2}_{-7.2}^{+7.5}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>P</mml:mi> <mml:mo>=</mml:mo>...

We fit the spectral energy distributions (SEDs) of 46 GeV - TeV BL Lac objects in frame leptonic one-zone synchrotron self-Compton (SSC) model and investigate physical properties these objects. use Markov Chain Monte Carlo (MCMC) method to obtain basic parameters, such as magnetic field (B), break relativistic electron distribution ($\gamma'_{\rm{b}}$) index. Based on modeling results, we support following scenarios GeV-TeV objects: (1) Some sources have large Doppler factors, implying other...

We present a model-dependent method to estimate the redshifts of three TeV BL Lac objects (BL Lacs) through fltting their (quasi-) simultaneous multi-waveband spectral energy distributions (SEDs) by one-zone leptonic synchrotron self-Compton (SSC) model. Considering impact electron (EEDs) on results, we use types EEDs, such as power-law EED with exponential cut-ofi (PLC), log-parabola (PLLP) and broken (BPL) flt SEDs. also parameter fi describe uncertainties extragalactic background light...

Abstract We studied the optical band periodic variability of 1823+568 using Jurkevich method, Lomb–Scargle periodogram and REDFIT38 software, found evidence quasi-periodic oscillation. An unprecedented with period <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>P</mml:mi> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>283</mml:mn> </mml:mrow> <mml:mo>−</mml:mo> <mml:mn>13</mml:mn> <mml:mo>+</mml:mo> <mml:mn>17</mml:mn> </mml:msubsup> </mml:math> days...

We examine the fundamental plane of 91 Blazars which include FSRQs and BL Lacs with known X-ray luminosity ($L_{R}$), radio ($L_X$), black hole mass measurements ($M$) to reflect relationship between jet accretion for blazars. The are log$L_{R}$=${0.273}_{+0.059}^{-0.059}$log$L_X$+${0.695}_{+0.191}^{-0.191}$log$M$+${25.457}_{+2.728}^{-2.728}$ log$L_{R}$=${0.190}_{+0.049}^{-0.049}$log$L_X$+${0.475}_{+0.157}^{-0.157}$log$M$+${28.568}_{+2.245}^{-2.245}$ after considering effect beam factor. Our...

Abstract The shapes and rotation states (periods pole orientations) of main-belt asteroids are important for understanding their formation evolution. In order to obtain sufficient photometric data covering different apparitions asteroid (81) Terpsichore, ground-based observations in 2020 2021 were carried out. By combining published newly obtained data, we calculated the shape spin parameters Terpsichore using convex inversion method. With this method, have derived a best fitted orientation—...

Abstract We present periodicity search analyses on the long-term γ -ray light curve of BL Lacertae object 4FGL J2139.4−4235 observed by Fermi Large Area Telescope, over a period more than 15 yr, from 2008 August 4 to 2023 December 10. To determine quasiperiodic oscillation (QPO) behavior in 0.3–300 GeV energy range, we used four methods, namely Lomb–Scargle periodogram, weighted wavelet z-transform, phase dispersion minimization, and autoregressive integrated moving average model. A Monte...

The extragalactic background light (EBL) in the IR to UV bands partly absorbs very high energy (VHE, $E \geq$ 100GeV) $\gamma-$ray photons travelling over cosmological distances via pair production. In this paper, get stronger constraints on EBL, we use deliberate selection of EBL model and data five BL Lacs with better statistics harder spectra limit density radiation mechanism Lacs. We constrain upper by fitting spectral distributions (SEDs) TeV find that our results are compatible...

A simple hydration model is used here by taking the composition of cement and initial water: ratio (w/c) into account explicitly. Its conceptual basis a combination Avrami equation Bentz’s based on spatial considerations. In this model, determines reaction, describes following stage. The favors engineers for it relies one experimental parameter has reliable approximation in practice.

Although elastic properties of hydrating cement paste are crucial in concrete engineering practice, there only a few widely available models for engineers to predict the behavior paste. Therefore, this paper, we derive an analytical model efficiently (e.g., Young’s modulus) Notably, proposed provides prediction hydration, percolation, and homogenization paste, enabling study early age elasticity evolution A hydration considering mineral composition initial w/c ratio was used, while...

Very high energy (VHE; $E \geq$ 100GeV) $γ-$ray from cosmological distances are attenuated by the extragalactic background light (EBL) in IR to UV band. By contrasting measured versus intrinsic emission, EBL photon density can be derived. However, neither spectra nor is separately known~-~except their combined effect. Here we first present a flexible model-dependent optical depth method study fitting emission of TeV BL Lacs objects via one-zone leptonic synchrotron self-Compton model (SSC)....

Abstract We present a one-zone homogeneous lepton-hadronic model and obtain steady-state spectra by solving the time-dependent equations to study plausible origin of hard TeV in PKS 2155–304. In this model, we assume steady electron proton injection rate source solve non-linear kinematic that self-consistently consist proton-photon interaction, synchrotron radiation electron/positron pairs proton, inverse Compton scattering, self-absorption. employ reproduce multi-wavelength spectrum...

The extragalactic background light (EBL) in the IR to UV bands partly absorbs very high energy (VHE, $E \geq$ 100GeV) $γ-$ray photons travelling over cosmological distances via pair production. In this paper, get stronger constraints on EBL, we use deliberate selection of EBL model and data five BL Lacs with better statistics harder spectra limit density radiation mechanism Lacs. We constrain upper by fitting spectral distributions (SEDs) TeV find that our results are compatible published...