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Browsing by Subject "galaxies: jets"

Browsing by Subject "galaxies: jets"

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  • BL Lac object OJ 287: exploring a complete spectrum of issues concerning relativistic jets and accretion 
    Kushwaha, Pankaj (Journal Astrophysical Astronomy, 2022-11)
    BL Lacertae (BL Lac) object OJ 287 is one of the most dynamic blazars across the directly accessible observational windows: spectral, timing, polarization and imaging. Apart from behaviors, considered the characteristics ...
  • Extreme photometric and polarimetric variability of blazar S4 0954+65 at its maximum optical and γ -ray brightness levels 
    Raiteri, C. M. , et.al.; Gaur, H.; Gupta, A. C.; Kishore, S.; Wani, K. (Monthly Notices of the Royal Astronomical Society, 2023-12)
    In 2022 the BL Lac object S4 0954+65 underwent a major variability phase, reaching its historical maximum brightness in the optical and γ -ray bands. We present optical photometric and polarimetric data acquired by the ...
  • Flux and spectral variability of Mrk 421 during its moderate activity state using NuSTAR: Possible accretion disc contribution? 
    Mondal, S.; Rani, P.; Stalin, C. S.; Chakrabarti, S. K.; Rakshit, S. (Astronomy & Astrophysics, 2022-06)
    The X-ray emission in BL Lac objects is believed to be dominated by synchrotron emission from their relativistic jets. However, when the jet emission is not strong, one could expect signatures of X-ray emission from inverse ...
  • Intra-night optical variability study of a non-jetted narrow-line Seyfert 1 galaxy: SDSS J163401.94+480940.1 
    Ojha, Vineet (Journal of Astrophysics & Astronomy, 2022-05)
    SDSS J163401.94þ480940.1 is a non-jetted radio-loud narrow-line Seyfert 1 (NLSy1) galaxy. Optical monitoring of this object was carried out in two intra-night sessions each 3 h with 3.6-m DOT. Intra-night optical ...
  • Intranight optical variability of blazars and radio-quiet quasars using the ZTF survey 
    Negi, Vibhore; Krishna, Gopal; Joshi, Ravi; Chand, Hum; Wiita, Paul J.; Navaneeth, P. K.; Singh, Ravi S. (Monthly Notices of the Royal Astronomical Society, 2023-07)
    We explore the potential of the ongoing Zwicky Transient Facility (ZTF) survey for studying intranight optical variability (INOV) of active galactic nuclei (AGNs), in particular for picking rare events of large INOV ...
  • Intranight optical variability of low-mass active galactic nuclei: a pointer to blazar-like activity 
    Krishna, Gopal, et.al.; Chand, Krishan (Monthly Notices of the Royal Astronomical Society Letters, 2023-01)
    This study aims to characterize, for the first time, intranight optical variability (INOV) of low-mass active galactic nuclei (LMAGNs) which host a black hole (BH) of mass MBH ∼ 106M , i.e. even less massive than the ...
  • Intranight optical variability of TeV blazars with parsec-scale jets dominated by slow-moving radio knots 
    Negi, Vibhore; Krishna, Gopal; Chand, Hum; Britzen, Silke (Monthly Notices of the Royal Astronomical Society, 2023-09)
    BL Lac objects detected at TeV energies preferentially belong to the subclass called ‘high-frequency-peaked’ BL Lacs (HBLs). Parsec-scale radio jetsin these TeV-HBLs often show dominant,slow-moving radio knotsthat are at ...
  • LOFAR discovery of rare large FR I jets in the low-luminosity radio galaxy NGC 5322 
    Omar, Amitesh (Monthly Notices of the Royal Astronomical Society Letters, 2022-11)
    The discovery of faint Fanaroff–Riley type I (FR I) radio jets in the elliptical galaxy NGC 5322 is reported here using the 144-MHz image from Data Release 2 of the Low-Frequency Array (LOFAR) Two-metre Sky Survey (LoTSS). ...
  • Multi-wavelength characterization of Fermi blazars of uncertain type 
    Paliya, Vaidehi S. (Journal of Astrphysics and Astronomy, 2022-06)
    One of the major challenges in the research of jetted active galactic nuclei (AGN) is the completeness of the source catalogs released using the c-ray data taken from the Fermi-large area telescope (LAT). There are about ...
  • Multiband cross-correlated radio variability of the blazar 3C 279 
    Mohana A, Krishna; Gupta, Alok C.; Marscher, Alan P.; Sotnikova, Yulia V.; Jorstad, S. G.; Wiita, Paul J.; Cui, Lang; Aller, Margo F.; Aller, Hugh D.; Kovalev, Yu. A.; Kovalev, Y. Y.; Liu, Xiang; Mufakharov, T. V.; Popkov, A. V.; Mingaliev, M. G.; Erkenov, A. K.; Nizhelsky, N. A.; Tsybulev, P. G.; Tsybulev, P. G.; Zhao, Wei; Weaver, Z. R.; Morozova, D. A. (Monthly Notices of the Royal Astronomical Society, 2024-01)
    We present the results of our study of cross-correlations between long-term multiband observations of the radio variability of the blazar 3C 279. More than a decade (2008–2022) of radio data were collected at seven different ...
  • The optical behaviour of BL Lacertae at its maximum brightness levels: a blend of geometry and energetics 
    Raiteri, C. M. , et.al.; Dhiman, V.; Gaur, H.; Gupta, A. C.; Kushwaha, P.; Tripathi, T. (Monthly Notices of the Royal Astronomical Society, 2023-06)
    In 2021 BL Lacertae underwent an extraordinary activity phase, which was intensively followed by the Whole Earth Blazar Telescope (WEBT) Collaboration. We present the WEBT optical data in the BVRI bands acquired at 36 ...
  • Optical flux and colour variability of blazars in the ZTF survey 
    Negi, Vibhore,et.al.; Chand, Krishan; Chand, Hum (Monthly Notices of the Royal Astronomical Society, 2022-02)
    We investigate the temporal and colour variability of 897 blazars, comprising 455 BL Lacertae objects (BL Lacs) and 442 Flat Spectrum Radio Quasars (FSRQs), selected from the Roma-BZCAT catalogue, using the multiband light ...
  • Persistence of the blazar state in flat-spectrum radio quasars 
    Chand, Krishan; Krishna, Gopal (Monthly Notices of the Royal Astronomical Society Letters, 2022-10)
    Flat-spectrum radio quasars (FSRQs), whose brightness is dominated by a relativistically beamed core, are frequently found in the ‘blazar state’ commonly inferred from a high optical polarization (> 3 per cent) and/or a ...
  • Probable low-frequency quasi-periodic oscillations in blazars from the ZTF survey 
    Banerjee, Anuvab; Negi, Vibhore; Joshi, Ravi; Kumar, Nagendra; Wiita, Paul J.; Chand, Hum; Rawat, Nikita; Wu, Xue-Bing; Ho, Luis C. (Monthly Notices of the Royal Astronomical Society, 2023-12)
    We investigate the possible presence of quasi-periodic oscillation (QPO) signals in 2103 blazars from the Zwicky Transient Facility (ZTF) time-domain survey. We detect a low-frequency QPO signal in five blazars observed ...
  • Refining the OJ 287 2022 impact flare arrival epoch 
    Valtonen, Mauri J. , et.al.; Gupta, Alok C. (Monthly Notices of the Royal Astronomical Society, 2023-06)
    The bright blazar OJ 287 routinely parades high brightness bremsstrahlung flares, which are explained as being a result of a secondary supermassive black hole (SMBH) impacting the accretion disc of a more massive primary ...
  • Spectral States of OJ 287 blazar from Multiwavelength Observations with AstroSat 
    Singh, K. P.,et.al.; Kushwaha, P. (Monthly Notices of the Royal Astronomical Society, 2022-01)
    We present AstroSat soft X-ray, near-UV (NUV), and far-UV (FUV) observations of a blazar, OJ 287, carried out in 2017, 2018, and 2020. The simultaneous observations with NuSTAR in 2017 provide a broad-band look encompassing ...
  • The transience and persistence of high optical polarisation state in beamed radio quasars 
    Chand, Krishan; Krishna, Gopal; Omar, Amitesh; Chand, Hum; Bisht, P. S. (Publications of the Astronomical Society of Australia, 2023-02)
    We examine the long-term stability (on decade-like timescales) of optical ‘high polarisation’ (HP) state with popt > 3%, which commonly occurs in flat-spectrum (i.e., beamed) radio quasars (FSRQs) and is a prominent marker ...
  • Transient quasi-periodic oscillations at γ -rays in the TeV blazar PKS 1510-089 
    Roy, Abhradeep,et.al.; Gupta, Alok C. (Monthly Notices of the Royal Astronomical Society, 2022-03)
    We present periodicity search analyses on the γ -ray light curve of the TeV blazar PKS 1510-089 observed by the Fermi Large Area Telescope. We report the detection of two transient quasi-periodic oscillations: A 3.6-d QPO ...
  • The twin radio galaxy TRG J104454+354055 
    Krishna, Gopal, et.al.; Omar, Amitesh (Monthly Notices of the Royal Astronomical Society Letters, 2022-07)
    We report observations of a bright dumb-bellsystem of galaxies(z = 0.162) with the upgraded Giant Metrewave Radio Telescope (uGMRT), which show that each member of this gravitationally bound pair of galaxies hosts bipolar ...

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