158 research outputs found
Fermi-Large Area Telescope observations of the brightest Gamma-ray flare ever detected from CTA 102
We present a multi-wavelength study of the FSRQ CTA 102 using Fermi-LAT and
simultaneous Swift-XRT/UVOT observations. The Fermi-LAT telescope detected one
of the brightest flares from this object during Sep, 2016 to Mar, 2017. In the
190 days of observation period the source underwent four major flares. A
detailed analysis of the temporal and spectral properties of these flares
indicates the flare at MJD 57751.594 has a -ray flux of
(30.124.48) ph cm s (from 90 minutes
binning) in the energy range of 0.1--300 GeV. This has been found to be the
highest flux ever detected from CTA 102. Time dependent leptonic modelling of
the pre-flare, rising state, flares and decaying state has been done. A single
emission region of size cm has been used in our work to
explain the multi-wavelength spectral energy distributions. During flares the
luminosity in electrons increases nearly seventy times compared to the
pre-flare state.Comment: 19 pages, 7 figures, Accepted for Publication in Ap
Multiwavelength temporal and spectral study of TeV blazar 1ES 1727+502 during 2014 to 2021
One of the most important questions in blazar physics is the origin of
broadband emission and fast-flux variation. In this work, we studied the
broadband temporal and spectral properties of a TeV blazar 1ES 1727+502 and
explore the one-zone synchrotron-self Compton (SSC) model to fit the broadband
spectral energy distribution (SED). We collected the long-term (2014-2021)
multiband data which includes both the low and high flux states of the source.
The entire light curve is divided into three segments of different flux states
and the best-fit parameters obtained by broadband SED modeling corresponding to
three flux states were then compared. The TeV blazar 1ES 1727+502 has been
observed to show the brightest flaring episode in X-ray followed by optical-UV
and gamma-ray. The fractional variability estimated during various segments
behaves differently in multiple wavebands, suggesting a complex nature of
emission in this source. This source has shown a range of variability time from
days scale to month scale during this long period of observations between
2014-2021. A "harder-when-brighter" trend is not prominent in X-ray but seen in
optical-UV and an opposite trend is observed in gamma-ray. The complex nature
of correlation among various bands is observed. The SED modeling suggests that
the one-zone SSC emission model can reproduce the broadband spectrum in the
energy range from optical-UV to very high energy gamma-ray.Comment: 14 pages, 8 figure, 2 table. Accepted for publication in MNRA
Multi-wavelength temporal and spectral analysis of Blazar S5 1803+78
Blazars are a class of AGN, one of their jets is pointed towards the earth.
Here, we report about the multi-wavelength study for blazar S5 1803+78 between
MJD 58727 to MJD 59419. We analysed -ray data collected by Fermi-LAT,
X-ray data collected by Swift-XRT \& NuSTAR, optical photons detected by
Swift-UVOT \& TUBITAK observatory in Turkey. Three flaring states are
identified by analysing the -ray light curve. A day scale variability
is observed throughout the flares with the similar rise and decay times
suggesting a compact emission region located close to the central engine.
Cross-correlation studies are carried out between -ray, radio, and
X-ray bands, and no significant correlation is detected. The -ray and
optical emission are significantly correlated with zero time lag suggesting a
co-spatial origin of them. A significant positive correlation between the R-I
index and the V magnitude is observed. The broadband spectral energy
distributions (SEDs) modeling was performed for all the flaring episodes as
well as for one quiescent state for comparison. SEDs are best fitted with the
synchrotron-self Compton (SSC) model under a one-zone leptonic scenario. The
SED modeling shows that to explain the high flaring state strong Doppler
boosting is required.Comment: 13 pages, 14 figures, 4 tables, Accepted in MNRA
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