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Wyświetlanie 1-10 z 15
Tytuł:
Optical variability of eight FRII-type quasars with 13 yr photometric light curves
Autorzy:
Kuźmicz, Agnieszka
Jamrozy, Marek
Dróżdż, Marek
Siwak, Michał
Reichart, Daniel E.
Kouprianov, Vladimir V.
Zoła, Stanisław
Ogłoza, Waldemar
Goyal, Arti
Caton, Daniel B.
Opis:
We characterize the optical variability properties of eight lobe-dominated radio quasars (QSOs): B2 0709+37, FBQS J095206.3+235245, PG 1004+130, [HB89] 1156+631, [HB89] 1425+267, [HB89] 1503+691, [HB89] 1721+343, and 4C +74.26, systematically monitored for a duration of 13 yr since 2009. The quasars are radio-loud objects with extended radio lobes that indicate their orientation close to the sky plane. Five of the eight QSOs are classified as giant radio quasars. All quasars showed variability during our monitoring, with magnitude variations between 0.3 and 1 mag for the least variable and the most variable QSOs, respectively. We performed both structure function (SF) analysis and power spectral density (PSD) analysis for the variability characterization and search for characteristic timescales and periodicities. As a result of our analysis, we obtained relatively steep SF slopes (α ranging from 0.49 to 0.75) that are consistent with the derived PSD slopes (∼2–3). All the PSDs show a good fit to single power-law forms, indicating a red-noise character of variability between timescales of ∼13 yr and weeks. We did not measure reliable characteristic timescales of variability from the SF analysis, which indicates that the duration of the gathered data is too short to reveal them. The absence of bends in the PSDs (change of slope from ≥1 to ∼0) on longer timescales indicates that optical variations are most likely caused by thermal instabilities in the accretion disk.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
Multiband flux and spectral variability study of the flaring activity in BL Lacertae during its 2020 outburst
Autorzy:
Agarwal, Aditi
Caton, D. B.
Reichart, Daniel E.
Dawidson, James W.
Jana, Swarnendu
Raj, A.
Agrawal, V.
Kouprianov, V.
Zoła, Stanisław
Bisht, M. S.
Opis:
In this work, we present the results of recent quasi-simultaneous multiband optical observations (in BVRI) of the blazar BL Lacertae over diverse time-scales. For this study, the source was observed from 2020 September–October using six different telescopes around the world, collecting $\sim$ 5800 photometric image frames in BVRI. The source displays many episodes of significant intraday variability, and the amplitude increases with the brightness of the target. Moreover, the object also showed significant variability on a short-term basis, with flux variability amplitudes of 85.6 per cent, 78.9 per cent, 93.4 per cent, and 67.6 per cent in B, V, R, and I passbands, respectively. The colour–magnitude analysis of the source displays dominantly bluer-when-brighter behaviour on both intraday and short time-scales, which can be attributed to the energetic processes in the jet. Correlation analysis points towards a strong correlation between optical bands with no firmly detectable time lags. Moreover, we also performed a periodicity search using the Lomb–Scargle and weighted wavelet Z-transform methods and found plausible indications of the presence of quasi-periodicity in the blazar. We also generated spectral energy distributions for nights with quasi-simultaneous observations in all four bands and found the spectral index to range from 2.9–3.2, which can be ascribed to a strong jet contribution. We discuss the results within the framework of prospective source intrinsic and extrinsic scenarios.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
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
Artykuł
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
Tytuł:
Observational implications of OJ 287’s predicted 2022 disk impact in the black hole binary model
Autorzy:
Kouprianov, Vladimir V.
Uemura, Makoto
Tornikoski, Merja
Matsumoto, Katsura
Štrobl, Jan
Dey, Lankeswar
Reichart, Daniel E.
Mugrauer, Markus
Pursimo, Tapio
Knudstrup, Emil
Nilsson, Kari
Gomez, Jose L.
Berdyugin, Andrei V.
Sadun, Alberto
Sillanpää, Aimo
Drozdz, Marek
Jelínek, Martin
Zejmo, Michal
Valtonen, Mauri J.
Gupta, Alok C.
Hudec, Rene
Lähteenmäki, Anne
Zoła, Stanisław
Lehto, Harry J.
Gopakumar, Achamveedu
Imazawa, Ryo
Ciprini, Stefano
Opis:
We present a summary of the results of the OJ 287 observational campaign, which was carried out during the 2021/2022 observational season. This season is special in the binary model because the major axis of the precessing binary happens to lie almost exactly in the plane of the accretion disc of the primary. This leads to pairs of almost identical impacts between the secondary black hole and the accretion disk in 2005 and 2022. In 2005, a special flare called "blue flash" was observed 35 days after the disk impact, which should have also been verifiable in 2022. We did observe a similar flash and were able to obtain more details of its properties. We describe this in the framework of expanding cloud models. In addition, we were able to identify the flare arising exactly at the time of the disc crossing from its photo-polarimetric and gamma-ray properties. This is an important identification, as it directly confirms the orbit model. Moreover, we saw a huge flare that lasted only one day. We may understand this as the lighting up of the jet of the secondary black hole when its Roche lobe is suddenly flooded by the gas from the primary disk. Therefore, this may be the first time we directly observed the secondary black hole in the OJ 287 binary system.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
Refining the OJ 287 2022 impact flare arrival epoch
Autorzy:
Berdyugin, Andrei V.
Nilsson, Kari
Jelínek, Martin
Matsumoto, Katsura
Tornikoski, Merja
Mugrauer, Markus
Uemura, Makoto
Gopakumar, A.
Štrobl, Jan
Ciprini, Stefano
Drozdz, Marek
Zejmo, Michal
Reichart, Daniel E.
Kouprianov, Vladimir V.
Sillanpää, Aimo
Hudec, Rene
Lehto, Harry J.
Pursimo, Tapio
Valtonen, Mauri J.
Gomez, Jose L.
Zoła, Stanisław
Sadun, Alberto
Dey, Lankeswar
Lähteenmäki, Anne
Gupta, Alok C.
Imazawa, Ryo
Knudstrup, Emil
Opis:
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 SMBH in a binary system. The accretion disc is not rigid but rather bends in a calculable way due to the tidal influence of the secondary. Next, we refer to this phenomenon as a variable disc level. We begin by showing that these flares occur at times predicted by a simple analytical formula, based on general relativity inspired modified Kepler equation, which explains impact flares since 1888. The 2022 impact flare, namely flare number 26, is rather peculiar as it breaks the typical pattern of two impact flares per 12-yr cycle. This is the third bremsstrahlung flare of the current cycle that follows the already observed 2015 and 2019 impact flares from OJ 287. It turns out that the arrival epoch of flare number 26 is sensitive to the level of primary SMBH’s accretion disc relative to its mean level in our model. We incorporate these tidally induced changes in the level of the accretion disc to infer that the thermal flare should have occurred during 2022 July–August, when it was not possible to observe it from the Earth. Thereafter, we explore possible observational evidence for certain pre-flare activity by employing spectral and polarimetric data from our campaigns in 2004/05 and 2021/22. We point out theoretical and observational implications of two observed mini-flares during 2022 January–February.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
Identifying the secondary jet in the RadioAstron image of OJ 287
Autorzy:
Berdyugin, Andrei V.
Nilsson, Kari
Jelínek, Martin
Matsumoto, Katsura
Mugrauer, Markus
Uemura, Makoto
Zhang, Zhongli
Ogloza, Waldemar
Kishore, Shubham
Štrobl, Jan
Ciprini, Stefano
Drozdz, Marek
Zejmo, Michal
Reichart, Daniel E.
Kouprianov, Vladimir V.
Hudec, Rene
Pursimo, Tapio
Susobhanan, Abhimanyu
Valtonen, Mauri J.
Sadun, Alberto
Dey, Lankeswar
Gu, Minfeng
Gupta, Alok C.
Wiita, Paul J.
Davidson, James W.
Imazawa, Ryo
Gopakumar, Achamveedu
Nakaoka, Tatsuya
Zoła, Stanisław
Opis:
The 136 yr long optical light curve of OJ 287 is explained by a binary black hole model where the secondary is in a 12 yr orbit around the primary. Impacts of the secondary on the accretion disk of the primary generate a series of optical flares that follow a quasi-Keplerian relativistic mathematical model. The orientation of the binary in space is determined from the behavior of the primary jet. Here, we ask how the jet of the secondary black hole projects onto the sky plane. Assuming that the jet is initially perpendicular to the disk, and that it is ballistic, we follow its evolution after the Lorentz transformation to the observer’s frame. Since the orbital speed of the secondary is of the order of one-tenth of the speed of light, the result is a change in the jet direction by more than a radian during an orbital cycle. We match the theoretical jet line with the recent 12 μas resolution RadioAstron map of OJ 287 and determine the only free parameter of the problem, the apparent speed of the jet relative to speed of light. It turns out that the Doppler factor of the jet, δ ∼ 5, is much lower than in the primary jet. Besides following a unique shape of the jet path, the secondary jet is also distinguished by a different spectral shape than in the primary jet. The present result on the spectral shape agrees with the huge optical flare of 2021 November 12, also arising from the secondary jet.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Wyświetlanie 1-10 z 15

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