Autor: Provencal, J. - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Very high optical activity of blazar OJ287
Autorzy:: Stachowski, G.
Drozdz, M.
Kozieł-Wierzbowska, Dorota
Kuźmicz, Agnieszka
Zoła, Stanisław
Ogloza, W.
Provencal, J.
Liakos, A.
Winiarski, Maciej
Opis:: OJ287 is being monitored in the optical waveband with small telescopes at the Astronomical Observatory of the Jagiellonian University (KRK) and the Mt. Suhora Observatory of the Pedagogical University (SUH) in Poland, and at the University of Athens, Greece (ATH). On April 19th, Mt. Cuba Observatory, USA (MTC), performed additional observations of this target. We report an even higher optical state of OJ287 than that published in Atel #4020 and Atel #4021.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Tytuł:: Very high optical activity of blazar OJ287
Autorzy:: Winiarski, M.
Drozdz, M.
Stachowski, G.
Kozieł-Wierzbowska, Dorota
Kuźmicz, Agnieszka
Zoła, Stanisław
Ogloza, W.
Provencal, J.
Liakos, A.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 3.

Tytuł:: Catching profound optical flares in blazars
Autorzy:: Bhatta, Gopal
Sonbas, Eda
Simon, A.
Drozdz, Marek
Provencal, J.
Góra, Dariusz
Zoła, Stanisław
Matsumoto, Katsura
Pajdosz-Śmierciak, Urszula
Haislip, Joshua
Stachowski, Grzegorz
Reichart, Daniel
Kouprianov, Vladimir
Caton, D.
Opis:: Flaring episodes in blazars represent one of the most violent processes observed in extra-galactic objects. Studies of such events shed light on the energetics of the physical processes occurring in the innermost regions of blazars, which cannot otherwise be resolved by any current instruments. In this work, we present some of the largest and most rapid flares captured in the optical band in the blazars 3C 279, OJ 49, S4 0954+658, TXS 1156+295, and PG 1553+113. The source flux was observed to increase by nearly ten times within a time-scale of a few weeks. We applied several methods of time series analysis and symmetry analysis. Moreover, we also performed searches for periodicity in the light curves of 3C 279, OJ 49 and PG 1553+113 using the Lomb–Scargle method and found plausible indications of quasi-periodic oscillations (QPOs). In particular, the 33- and 22-day periods found in 3C 279, i.e. a 3:2 ratio, are intriguing. These violent events might originate from magnetohydrodynamical instabilities near the base of the jets, triggered by processes modulated by the magnetic field of the accretion disc. We present a qualitative treatment as the possible explanation for the observed large amplitude flux changes in both the source-intrinsic and source-extrinsic scenarios.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Tytuł:: Profound optical flares from the relativistic jets of active galactic nuclei
Autorzy:: Haislip, Joshua
Stachowski, Grzegorz
Kouprianov, Vladimir
Zoła, Stanisław
Drozdz, M.
Bhatta, Gopal
Caton, D.
Pajdosz-Śmierciak, Urszula
Provencal, J.
Matsumoto, Katsura
Sonbas, Eda
Reichart, Daniel
Simon, A.
Góra, Dariusz
Opis:: Intense outbursts in blazars are among the most extreme phenomena seen in extragalactic objects. Studying these events can offer important information about the energetic physical processes taking place within the innermost regions of blazars, which are beyond the resolution of current instruments. This work presents some of the largest and most rapid flares detected in the optical band from the sources 3C 279, OJ 49, S4 0954+658, Ton 599, and PG 1553+113, which are mostly TeV blazars. The source flux increased by nearly ten times within a few weeks, indicating the violent nature of these events. Such energetic events might originate from magnetohydrodynamical instabilities near the base of the jets, triggered by processes modulated by the magnetic field of the accretion disc. We explain the emergence of flares owing to the injection of high energy particles by the shock wave passing along the relativistic jets. Alternatively, the flares may have also arisen due to geometrical effects related to the jets. We discuss both source-intrinsic and source-extrinsic scenarios as possible explanations for the observed large amplitude flux changes
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

Inne

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Skocz do pozycji: 5.

Tytuł:: The morphology of the asteroidal dust around white dwarf stars : optical and near-infrared pulsations in G29-38
Autorzy:: Ogloza, W.
Sargent, J.
Cooper, W.
Provencal, J. L.
Sonbas, Eda
Pringle, J. E.
Pakštienė, Erika
Kim, V.
Walter, B.
Zejmo, M.
Moss, A.
von Hippel, Ted
Kleinman, S. J.
Savery, Z.
Swan, A.
Kusakin, A.
Krugov, M.
Fontaine, G.
Kozyreva, V.
Farihi, J.
Zoła, Stanisław
Serebryanskiy, A.
Hermes, J. J.
Opis:: More than 36 yr have passed since the discovery of the infrared excess from circumstellar dust orbiting the white dwarf G29-38, which at 17.5 pc it is the nearest and brightest of its class. The precise morphology of the orbiting dust remains only marginally constrained by existing data, subject to model-dependent inferences, and thus fundamental questions of its dynamical origin and evolution persist. This study presents a means to constrain the geometric distribution of the emitting dust using stellar pulsations measured at optical wavelengths as a variable illumination source of the dust, which reradiates primarily in the infrared. By combining optical photometry from the Whole Earth Telescope with 0.7–2.5 μm spectroscopy obtained with SpeX at NASA's Infrared Telescope Facility, we detect luminosity variations at all observed wavelengths, with variations at most wavelengths corresponding to the behavior of the pulsating stellar photosphere, but toward the longest wavelengths the light curves probe the corresponding time variability of the circumstellar dust. In addition to developing methodology, we find the pulsation amplitudes decrease with increasing wavelength for principal pulsation modes, yet increase beyond ≈2 μm for nonlinear combination frequencies. We interpret these results as combination modes derived from the principal modes of identical ℓ values and discuss the implications for the morphology of the warm dust. We also draw attention to some discrepancies between our findings and theoretical expectations for the results of the nonlinearity imposed by the surface convection zone on mode–mode interactions and on the behavior of the first harmonic of the highest-amplitude pulsation mode.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 6.

Tytuł:: Precursor Flares in OJ 287
Autorzy:: Chandra, S.
Sillanpää, A.
Berdyugin, A.
Reinthal, R.
Takalo, L.
Gopakumar, A.
Coggins-Hill, S. A.
Baliyan, K. S.
Salo, H.
Ganesh, S.
Lindfors, E.
Liakos, A.
Drozdz, M.
Santangelo, M. M. M.
Pihajoki, P.
Kozieł-Wierzbowska, Dorota
Provencal, J.
Valtonen, M.
Winiarski, Maciej
Nilsson, K.
Zoła, Stanisław
Ogłoza, W.
Opis:: We have studied three most recent precursor flares in the light curve of the blazar OJ 287 while invoking the presence of a precessing binary black hole in the system to explain the nature of these flares. Precursor flare timings from the historical light curves are compared with theoretical predictions from our model that incorporate effects of an accretion disk and post-Newtonian description for the binary black hole orbit. We find that the precursor flares coincide with the secondary black hole descending toward the accretion disk of the primary black hole from the observed side, with a mean z-component of approximately z_{c} = 4000 AU. We use this model of precursor flares to predict that precursor flare of similar nature should happen around 2020.96 before the next major outburst in 2022.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego