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Register a new userBroadband study of OQ 334 during its flaring state
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The blazar OQ 334 displayed a {gamma}-ray flare in 2018, after being in the long quiescent {gamma}-ray state since 2008. Subsequent to the flare, the source was in a higher {gamma}-ray flux state and again flared in 2020. We present here the first spectral and timing analysis of the source at its various flaring states. During the higher {gamma}-ray state, we found four major peaks identified as P1, P2, P3, and P4. From timing analysis, we found the rise and decay time of the order of hours with the fastest variability time of 9.01+/-0.78 hr. We found the highest {gamma}-ray photon of 77 GeV during P4, which suggests the location of the {gamma}-ray emitting region at the outer edge of the broad-line region or the inner edge of the torus. The {gamma}-ray spectral analysis of the source indicates that during P4, the {gamma}-ray spectrum clearly deviates from the power-law behavior. From cross-correlation analysis of the {gamma}-ray and radio lightcurves, we found that the two emission regions are separated by about 11 pc. Our broadband spectral energy distribution modeling of the source during quiescent and active phases indicates that more electron and proton power are required to change the source from low flux to high flux state. The Anderson-Darling test and histogram fitting results suggest that the three days binned {gamma}-ray fluxes follow a lognormal distribution.
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Aim : The nearby TeV blazar 1ES 1959+650 (z=0.047) was reported to be in flaring state during June - July 2016 by Fermi-LAT, FACT, MAGIC and VERITAS collaborations. We studied the spectral energy distributions (SEDs) in different states of the flare during MJD 57530 - 57589 using simultaneous multiwaveband data to understand the possible broadband emission scenario during the flare. Methods : The UV/optical and X-ray data from UVOT and XRT respectively on board Swift and high energy $gamma$-ray data from Fermi-LAT are used to generate multiwaveband lightcurves as well as to obtain high flux states and quiescent state SEDs. The correlation and lag between different energy bands is quantified using discrete correlation function. The synchrotron self Compton (SSC) model was used to reproduce the observed SEDs during flaring and quiescent states of the source. Results : A decent correlation is seen between X-ray and high energy $gamma$-ray fluxes. The spectral hardening with increase in the flux is seen in X-ray band. The powerlaw index vs flux plot in $gamma$-ray band indicates the different emission regions for 0.1 - 3 GeV and 3-300 GeV energy photons. Two zone SSC model satisfactorily fits the observed broadband SEDs. The inner zone is mainly responsible for producing synchrotron peak and high energy $gamma$-ray part of the SED in all states. The second zone is mainly required to produce less variable optical/UV and low energy $gamma$-ray emission. Conclusions : Conventional single zone SSC model does not satisfactorily explain broadband emission during observation period considered. There is an indication of two emission zones in the jet which are responsible for producing broadband emission from optical to high energy $gamma$-rays.
A flare from the TeV blazar Mrk 421, occurring in March 2010, was observed for 13 consecutive days from radio to very high energy (VHE, E > 100 GeV) gamma-rays with MAGIC, VERITAS, Whipple, FermiLAT, MAXI, RXTE, Swift, GASP-WEBT, and several optical and radio telescopes. We model the day-scale SEDs with one-zone and two-zone synchrotron self-Compton (SSC) models, investigate the physical parameters, and evaluate whether the observed broadband SED variability can be associated to variations in the relativistic particle population. Flux variability was remarkable in the X-ray and VHE bands while it was minor or not significant in the other bands. The one-zone SSC model can describe reasonably well the SED of each day for the 13 consecutive days. This flaring activity is also very well described by a two-zone SSC model, where one zone is responsible for the quiescent emission while the other smaller zone, which is spatially separated from the first one, contributes to the daily-variable emission occurring in X-rays and VHE gamma-rays. Both the one-zone SSC and the two-zone SSC models can describe the daily SEDs via the variation of only four or five model parameters, under the hypothesis that the variability is associated mostly to the underlying particle population. This shows that the particle acceleration and cooling mechanism producing the radiating particles could be the main one responsible for the broadband SED variations during the flaring episodes in blazars. The two-zone SSC model provides a better agreement to the observed SED at the narrow peaks of the low- and high-energy bumps during the highest activity, although the reported one-zone SSC model could be further improved by the variation of the parameters related to the emitting region itself ($delta$, $B$ and $R$), in addition to the parameters related to the particle population.
We report the energy-resolved broadband timing analysis of the black hole X-ray transient MAXI J1631-479 during its 2019 outburst from February 11 to April 9, using data from the Insight-Hard X-ray Modulation Telescope (Insight-HXMT), which caught the source from its hard intermediate state to the soft state. Thanks to the large effective area of Insight-HXMT at high energies, we are able to present the energy dependence of fast variability up to ~100 keV. Type-C quasi-periodic oscillations (QPOs) with frequency varying between 4.9 Hz and 6.5 Hz are observed in the 1-100 keV energy band. While the QPO fractional rms increases with photon energy from 1 keV to ~10 keV and remains more or less constant from ~10 keV to ~100 keV, the rms of the flat-top noise first increases from 1 keV to ~8 keV then drops to less than 0.1% above ~30 keV. We suggest that the disappearance of the broadband variability above 30 keV could be caused by the non-thermal acceleration in the Comptonizing plasma. At the same time, the QPOs could be produced by the precession of either a small-scale jet or a hot inner flow model.
A multiwavelength temporal and spectral analysis of flares of 3C 279 during November 2017--July 2018 are presented in this work. Three bright gamma-ray flares were observed simultaneously in X-ray and Optical/UV along with a prolonged quiescent state. A harder-when-brighter trend is observed in both gamma-rays and X-rays during the flaring period. The gamma-ray light curve for all the flares are binned in one-day time bins and a day scale variability is observed. Variability time constrains the size and location of the emission region to 2.1$times$10$^{16}$ cm and 4.4$times$10$^{17}$ cm, respectively. The fractional variability reveals that the source is more than 100% variable in gamma-rays and it decreases towards the lower energy. A cross-correlation study of the emission from different wavebands is done using the textit{DCF} method, which shows a strong correlation between them without any time lags. The zero time lag between different wavebands suggest their co-spatial origin. This is the first time 3C 279 has shown a strong correlation between gamma-rays and X-rays emission with zero time lag. A single zone emission model was adopted to model the multiwavelength SEDs by using the publicly available code GAMERA. The study reveals that a higher jet power in electrons is required to explain the gamma-ray flux during the flaring state, as much as, ten times of that required for the quiescent state. However, more jet power in magnetic field has been observed during the quiescent state compared to the flaring state.
The Flat Spectrum Radio Quasar 3C 279 has been very active since a few years with multiple flaring events occurring at high energies. As part of the H.E.S.S. Target of Opportunity program, 3C 279 was observed multiple times in 2017 and 2018 following high states in optical (February and March 2017) or at high energies as seen with Fermi-LAT (June 2017, January, February and June 2018). While in January 2018 H.E.S.S. detected an unexpected very high energy (VHE) flare at the end of the MeV-GeV flaring state, in June 2018 it was possible to follow almost continuously the decaying part of a strong Fermi-LAT flare, observing with the full array for several nights after the peak of the GeV gamma-ray emission. This has lead to the detection of the source with very high significance. We present here the temporal and spectral results of the H.E.S.S. II dataset together with an overview of the strong multi-wavelength activity seen from 3C 279 between 2017 and 2018.
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