We consider the broadband spectral energy distribution of the high energy peaked (HBL) blazar Mkn 501 using $\textit{Swift}$-XRT/UVOT, NuSTAR and $\textit{Fermi}$-LAT observations taken between 2013 and 2022. The spectra were fitted with a one-zone leptonic model using synchrotron and synchrotron self-Compton emission from different particle energy distributions such as a broken power-law, log-parabola, as well as distributions expected when the diffusion or the acceleration time scale are energy dependent. The jet power estimated for a broken power-law distribution was $ \sim 10^{47} (10^{44})$ erg s$^{-1}$ for a minimum electron energy $γ_\text{min} \sim 10 (10^3)$. However, for electron energy distributions with intrinsic curvature (such as the log-parabola form), the jet power is significantly lower at a few times $ 10^{42}$ erg s$^{-1}$ which is a few percent of the Eddington luminosity of a $10^7$ M$_\odot$ black hole, suggesting that the jet may be powered by accretion processes. We discuss the implications of these results.
We present a time-resolved X-ray spectral study of the high energy peaked blazar Mkn 421 using simultaneous broadband observations from the LAXPC and SXT instruments on-board AstroSat. The ~ 400 ksec long observation taken during 3-8 January, 2017 was divided into segments of 10 ksecs. Each segment was fitted using synchrotron emission from particles whose energy distribution was represented by a log-parabola model. We also considered particle energy distribution models where (i) the radiative cooling leads to a maximum energy (ξ max model), (ii) the system has energy dependent diffusion (EDD)…
The X-ray observations of Mkn 421 show significant spectral curvature that can be reproduced by a log-parabola function. The spectra can also be fitted by an analytical model considering synchrotron emission from an electron distribution that is accelerated at a shock front with an energy-dependent diffusion(EDD model). The spectral fit of NuSTAR and Swift-XRT observations using EDD model during different flux states reveal the model parameters are strongly correlated. We perform a detailed investigation of this correlation to decipher the information hidden underneath. The model predicts the …
Blazars host the most powerful persistent relativistic conical jet -- a highly collimated anisotropic flow of material/plasma. Motivated by this, we explore the blazar's broadband spectral energy distribution (SED) in an anisotropic flow of plasma which emits via synchrotron and inverse Compton (IC) mechanism. The flow is conical with two velocity components: a highly relativistic flow component along the jet axis and a random perpendicular component with average random Lorentz factor $\langle γ^{ran} \rangle$ $<<$ than the average component along the jet axis $\langle γ\rangle$. Assuming a br…
Jet Power Estimates of FSRQs PKS 1441+25 and Ton 599 from Broadband SED Modeling
Tezpur University(特佐普尔大学);Inter-University Centre for Astronomy and Astrophysics(大学间天文与天体物理中心);Centre for Space Research, North-West University(西北大学空间研究中心)
We investigated a wealth of X-ray and gamma-ray spectral energy distribution (SED) and multi-band light curve (LC) data of the gamma-ray binary HESS J0632+057 using a phenomenological intrabinary shock (IBS) model. Our baseline model assumes that the IBS is formed by colliding winds from a putative pulsar and its Be companion, and particles accelerated in the IBS emit broadband radiation via synchrotron (SY) and inverse-Compton upscattering (ICS) processes. Adopting the latest orbital solution and system geometry (Tokayer et al. 2021), we reproduced the global X-ray and TeV LC features, two br…
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 corre…
We develop a new physical model for the broadband spectral energy distribution (SED) of X-ray illuminated accretion discs, that takes into account the mutual interaction of the accretion disc and the X-ray corona, including all relativistic effects. We assume a Keplerian, optically thick and geometrically thin accretion disc and an X-ray source in the lamp-post geometry that emits an isotropic power-law spectrum with a high-energy cut-off. We assume that all the energy that would be released by thermal radiation in the standard disc model in its innermost part, is transported to the corona, ef…
The broadband spectral energy distribution of candidate neutrino blazars
CHRIST (Deemed to be University)(克里斯特大学);North-West University(西北大学);Indian Institute of Astrophysics(印度天体物理研究所);Bhabha Atomic Research Centre(巴哈原子研究中心);Homi Bhabha National Institute(霍米·巴巴国立研究所)
Quasi-Simultaneous Broadband Spectral Energy Distributions of a Sample of Fermi Blazars -- I. Correlation Results
Zhejiang Normal University(浙江师范大学);Purple Mountain Observatory, Chinese Academy of Sciences(中国科学院紫金山天文台);University of Science and Technology of China(中国科学技术大学);Shanghai Normal University(上海师范大学);Yunnan Observatories, Chinese Academy of Sciences(中国科学院云南天文台);Center for Astronomical Mega-Science, Chinese Academy of Sciences(中国科学院国家天文台);College of Physics and Electronic Engineering, Qilu Normal University(齐鲁师范学院物理与电子工程学院)
We present the results of an extensive analysis of the optical, ultraviolet, X-ray and $γ$-ray data collected from the observations of the BL Lac objects prototype BL Lacertae carried out over a period of nearly 13 years, between August 2008 and March 2021. The source is characterized by strongly variable emission at all frequencies, often accompanied by spectral changes. In the $γ$-ray band several prominent flares have been detected, the largest one reaching the flux of $F_{\rm γ}(>196.7\: {\rm MeV})=(4.39\pm1.01)\times10^{-6}\:{\rm photon\:cm^{-2}\:s^{-1}}$. The X-ray spectral variability o…
We study the long-term behavior of the bright gamma-ray blazar PKS 0402-362. We collected approximately 13 years of Fermi-LAT data between Aug 2008 to Jan 2021 and identified three bright $γ$-ray activity epochs. The second was found to be the brightest epoch ever seen in this source. We observed most of the $γ$-ray flare peaks to be asymmetric in profile suggesting a slow cooling time of particles or the varying Doppler factor as the main cause of these flares. The $γ$-ray spectrum is fitted with PL and LP spectral models, and in both cases, the spectral index is very steep. The $γ$-ray spect…
We attempt to present a multiwavelength variability and correlation study as well as detailed multi-waveband spectral characteristics of the May 2021 $γ$-ray flare of the blazar source TXS 1700+685. The multi-wavelength observation from \textit{Fermi}-LAT, \textit{Swift}-XRT/UVOT as well as radio archival data are used for our spectro-temporal investigation. We estimate the variability time-scale of the source from the flux doubling time in different flaring regions detected in \textit{Fermi}-LAT observation and the shortest variability time is used to put a constraint on the minimum Doppler f…
We present the results obtained from our campaign to characterize the intra-night-optical variability properties of blazars detected by the {\it Fermi} Large Area Telescope. This involves R-band monitoring observations of a sample of 18 blazars, that includes five flat-spectrum radio quasars (FSRQs) and thirteen BL Lac objects (BL Lacs) covering the redshift range z = 0.085$-$1.184. Our observations, carried out using the 1.3 m J.C. Bhattacharya Telescope cover a total of 40 nights ($\sim$200 hrs) between the period 2016 December and 2020 March. We characterized variability using the power enh…
We present joint \textit{XMM-Newton} and \textit{NuSTAR} observations of the `bare' narrow line Seyfert 1 Ton S180 ($z=0.062$), carried out in 2016 and providing the first hard X-ray view of this luminous galaxy. We find that the 0.4--30 keV band cannot be self-consistently reproduced by relativistic reflection models, which fail to account simultaneously for the soft and hard X-ray emission. The smooth soft excess prefers extreme blurring parameters, confirmed by the nearly featureless nature of the RGS spectrum, while the moderately broad Fe K line and the modest hard excess above 10 keV app…
Rapid Variability and Broadband Spectral Modeling in the Flaring Activity of BL Lacertae
Yunnan University(云南大学);Chinese Academy of Sciences(中国科学院);Zhejiang Normal University(浙江师范大学);Yunnan Normal University(云南师范大学);Leshan Normal University(乐山师范学院)
The origin and evolution of spectral curvature in blazar spectral energy distribution (SED) is still unclear. Since the observed SED curvature is related to an intrinsic curvature in emitting electron energy distribution (EED), we study this question by employing a log-parabolic EED with a curvature parameter and peak energy to model the quasi-simultaneous broadband SEDs of selected blazars in Fermi-LAT Bright AGN Sample (LBAS) using synchrotron and inverse Compton (IC) processes. We find that log-parabolic IC model can successfully explain the emission in all blazars in our sample. On average…
The regular monitoring of flat-spectrum radio quasars (FSRQs) in $γ$-rays by Fermi-LAT since past 12 years indicated six sources who exhibited extreme $γ$-ray outbursts crossing daily flux of $10^{-5}$ photons/cm$^{2}$/s. We obtained nearly-simultaneous multi-wavelength data of these sources in radio to $γ$-ray waveband from OVRO, Steward Observatory, SMARTS, Swift-UVOT, Swift-XRT, and Fermi-LAT. The time-averaged broadband Spectral Energy Distributions (SEDs) of these sources in quiescent states were studied to get an idea about the underlying baseline radiation processes. We modeled the SEDs…