ABSTRACT Photometric observations for the totally eclipsing binary system TYC 4002-2628-1, were obtained between November 2020 and 2021. To determine stellar atmospheric parameters, a spectral image was taken with 2.16 m telescope at National Astronomical Observatory of China (NAOC). 4002-2628-1 is low-amplitude (about 0.15 mag Vband) short-period (0.3670495 d) contact total secondary eclipse. Intrinsic light curve variations reversal O’Connell effect are detected in curves, which may be due...

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 The variation mechanism of the blazar is still an open question. In this study, we collect long-term multi-wavelength data 3C 454.3 to conduct a comprehensive study. local cross-correlation functions were computed between $$\gamma$$ -ray and R band fluxes, as well B K fluxes. No significant time lags found among these bands, which suggests that optical emissions are co-spatial. color indices behavior showed redder-when-brighter trend in lower state, saturation state higher state....

ABSTRACT Aiming at the roof control challenges of gob‐side entry retaining in fully mechanized top‐coal caving faces, traditional concrete‐filled steel tube (CFST) support technology exhibits limitations such as slow strength development and complex construction equipment. This study, based on 1311 face Shanxi Runhong Coal Mine, proposes a integrating cutting for pressure relief with by grouted tubes. Through physical experiments, numerical simulations, field tests, mechanical properties...

Abstract Multi-band photometric observations and period investigations of the total eclipsing binary WISE J141530.7+592234 (hereinafter J141530), whose mass ratio close to low limit, were carried out for first time. The stellar atmospheric parameters primary component calculated by spectral fitting, yielding following results: T eff = 5890 ± 22 K, [Fe/H] 0.01 0.03 dex, log g 4.53 0.04 cm s −2 . Our show that light curve V -band on May 2 is about 0.1 mag brighter than observed in February...

We have assembled the historical light curves of BL Lac Object 3FGL J0449.4−4350 at optical and γ-ray bands, time spanning about 10 yr, analyzed periodic variability by using four different methods (Lomb–Scargle periodogram, REDFIT38, Jurkevich DACF). detected a marginally possible quasi-periodic oscillation ∼450 days. Assuming it originates from helical motion jet in supermassive binary black hole system undergoing major merger, we estimate primary mass M ∼ 7.7 × 109 M⊙. To explore origin...

ABSTRACT In this paper, the total eclipsing binary WISE J185503.7+592234 (hereinafter J185503), whose mass ratio is around limit, was observed and investigated for first time. The stellar atmospheric parameters of primary (more massive) component were calculated by spectral fitting, following results are obtained: Teff = 5747 ± 25 K, [Fe/H] −0.16 0.04 dex, logg 4.78 0.05 cm s−2. Although J185503 has a very small amplitude (∼ 0.17 mag in V band) short period (0.2800782 d), its light curves...

Black hole mass is one of the fundamental physical parameters active galactic nuclei (AGNs), for which many methods estimation have been proposed. One set assumes that broad-line region (BLR) gravitationally bound by central black potential, so can be estimated from orbital radius and Doppler velocity. Another observed variability timescale determined near innermost stable orbit around Schwarzschild or Kerr hole, characteristic accretion disk. We collect a sample 21 AGNs, minimum timescales...

Nanoparticles are added to clean fracturing fluids formulate nanoparticle-modified fluids, compared with ordinary fluid, it has the advantages of good temperature resistance, low loss filtration, and so forth, application prospects in coal-bed methane. However, current research on is mostly focused study their rheological properties. The mechanism nano-fracking fluid influence methane adsorption-desorption characteristics not clear. Therefore, this chooses Jiulishan anthracite coal...

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...

We analyzed the radio light curves of 3C 454.3 at frequencies 22 and 37 GHz taken from database Metsähovi Radio Observatory, found evidence quasi-periodic activity. The show great activity with very complicated non-sinusoidal variations. Two possible periods, a weak one 1.57±0.12 yr strong 6.15±0.50 were consistently identified by two methods, Jurkevich method power spectrum estimation. period is consistent results previously reported Ciaramella et al. Webb Applying binary black hole model...

Using a large sample of blazars the Fermi observations presented by Abdo et al., we constructed including high energy peaked BL Lac objects (HBLs), low (LBLs) and flat-spectral radio quasars (FSRQs). These unique characteristics make it possible to unambiguously address question how HBLs, LBLs FSRQs are related. In this paper, investigated relationship between X-ray γ-ray spectral indices (αx−αγ), as well broadband (αro−αrx, αro−αox, αro−αxγ αrx−αxγ) for sample. The color-color diagram shows...

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 compiled the radio, optical and X-ray data of blazars from Sloan Digital Sky Survey database, presented distribution luminosities broadband spectral indices. The shows that averaged luminosity flat spectrum radio quasars (FSRQs) is larger than BL Lacertae (BL Lac) objects. On other hand, energy reveals FSRQs low peaked Lac objects have similar properties, but high a distinct property. This may be due to fact different subclasses intrinsic environments are at cooling levels. Even so,...

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...

ABSTRACT The prompt emission of gamma-ray bursts (GRBs) is a long-standing problem. spectral-lag phenomenon can provide us with some clues about the mechanism. By analogy spectral lag blazars at radio frequencies, we propose using photosphere in jet model to interpret GRBs. Assuming canonical and respecting scaling laws both magnetic field number density radiative particles, radius be predicted. Five long known redshifts are studied. emitting regions these located one or several astronomical...

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...