We investigate broadband emission properties of the pulsar wind nebula (PWN) 3C 58 using a spectral energy distribution (SED) model. We attempt to match simultaneously the broadband SED and spatial variations of X-ray emission in the PWN. We further the model to explain a possible far-IR feature of which a hint is recently suggested in 3C 58: a small bump at $\sim$$10^{11}$ GHz in the PLANCK and Herschel band. While external dust emission may easily explain the observed bump, it may be internal emission of the source implying an additional population of particles. Although significance for the bump is not high, here we explore possible origins of the IR bump using the emission model and find that a population of electrons with GeV energies can explain the bump. If it is produced in the PWN, it may provide new insights into particle acceleration and flows in PWNe.
Angular momentum loss by the plasma wind is considered as a universal feature of isolated neutron stars including magnetars. The wind nebulae powered by magnetars allow us to compare the wind properties and the spin-evolution of magnetars with those of rotation-powered pulsars (RPPs). In this paper, we construct a broadband emission model of magnetar wind nebulae (MWNe). The model is similar to past studies of young pulsar wind nebulae (PWNe) around RPPs, but is modified for the application to MWNe that have far less observational information than the young PWNe. We apply the model to the MWN …
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 $γ$-ray data from Fermi-LAT are used to generate multiwaveband lightcurves as well as to obtain high flux states…
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…
We study the broadband radiation behavior of a kilonova ejecta-pulsar wind nebula (PWN) system. In this model, we jointly fit the observations of AT 2017gfo in UV-optical-IR bands and the late-time X-ray afterglow of GRB 170817A. Our work shows that a PWN powered by the remnant neutron star (NS) post GW170817 event could affect the optical transient AT 2017gfo and re-brighten the late-time X-ray afterglow of GRB 170817A. The PWN radiation will regulate the trend of future X-ray observations from a flattening to a steep decline until some other sources (e.g., a kilonova afterglow) become domina…
We report on broadband X-ray properties of the Rabbit pulsar wind nebula (PWN) associated with the pulsar PSR J1418-6058 using archival Chandra and XMM-Newton data, and a new NuSTAR observation. NuSTAR data above 10 keV allowed us to detect the 110-ms spin period of the pulsar, characterize its hard X-ray pulse profile, and resolve hard X-ray emission from the PWN after removing contamination from the pulsar and other overlapping point sources. The extended PWN was detected up to $\sim$20 keV and is well described by a power-law model with a photon index $Γ\approx$2. The PWN shape does not var…
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 present observations of HESS J1640-465 with the Fermi-LAT. The source is detected with high confidence as an emitter of high-energy gamma-rays. The spectrum lacks any evidence for the characteristic cutoff associated with emission from pulsars, indicating that the emission arises primarily from the pulsar wind nebula. Broadband modeling implies an evolved nebula with a low magnetic field resulting in a high gamma-ray to X-ray flux ratio. The Fermi emission exceeds predictions of the broadband model, and has a steeper spectrum, possibly resulting from a distinct excess of low energy electron…
The broadband spectral energy distribution(SED) of blazars is generally interpreted as radiation arising from synchrotron and inverse Compton mechanisms.Traditionally, the underlying source parameters responsible for these emission processes,like particle energy density, magnetic field, etc., are obtained through simple visual reproduction of the observed fluxes. However, this procedure is incapable of providing the confidence range on the estimated parameters. In this work, we propose an efficient algorithm to perform a statistical fit of the observed broadband spectrum of blazars using diffe…
The Vela\,X pulsar wind nebula (PWN) is characterized by the extended radio nebula (ERN) and the central X-ray "cocoon". We have interpreted the $γ$-ray spectral properties of the cocoon in the sibling paper (Bao et al.\,2019); here, we account for the broadband photon spectrum of the ERN. Since the diffusive escape of the electrons from the TeV emitting region is expected to play an insignificant role in shaping the spectrum of the ERN, we attribute the GeV cutoff of the ERN to the reverse shock-PWN interaction. Due to the disruption of the reverse shock, most of plasma of the PWN is driven i…
In this third paper in a series of three, we present a detailed study of the AGN broadband SED based on a nearby unobscured Type 1 AGN sample. We perform a systematic cross-correlation study of the following key parameters: $Γ_{2-10keV}$, $L_{2-10keV}$, $L_{bol}$, $L_{bol}/L_{Edd}$, $κ_{2-10keV}$, $κ_{5100A}$, FWHM$_{Hβ}$, M$_{BH}$, $α_{ox}$, $α_{X}$ and $α_{UV}$, and identify various strong correlations among these parameters. The principal component analysis (PCA) is performed on the correlation matrix of the above parameters, which shows that the three physical parameters, i.e. black hole m…
Cygnus X-1 is a well observed microquasar. Broadband observations at all wavelengths have been collected over the years. The origin of the MeV tail observed with COMPTEL and INTEGRAL is still under debate and it has mostly been attributed to the corona, although its high degree of polarization suggests it is synchrotron radiation from a jet. The origin of the transient emission above $\sim 100$ GeV is also unclear. We aim to disentangle the origin of the broadband spectral energy distribution (SED) of Cygnus X-1, focusing particularly on the gamma-ray emission, and to gain information on the p…
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…
We present broadband (3 -- 78 keV) NuSTAR X-ray imaging and spectroscopy of the Crab nebula and pulsar. We show that while the phase-averaged and spatially integrated nebula + pulsar spectrum is a power-law in this energy band, spatially resolved spectroscopy of the nebula finds a break at $\sim$9 keV in the spectral photon index of the torus structure with a steepening characterized by $ΔΓ\sim0.25$. We also confirm a previously reported steepening in the pulsed spectrum, and quantify it with a broken power-law with break energy at $\sim$12 keV and $ΔΓ\sim0.27$. We present spectral maps of the…
Blazars radiate from radio through gamma-ray frequencies thereby being ideal targets for multifrequency studies. Such studies allow constraining the properties of the emitting jet. 3C 279 is among the most notable blazars and therefore subject to extensive multifrequency campaigns. We report the results of a campaign ranging from near-IR to gamma-ray energies of an outburst of 3C 279 in June 2015. The overall spectral energy distribution from near-IR to gamma rays can be well represented by either a leptonic or a lepto-hadronic radiation transfer model. Even though the data are equally well re…
We present Spitzer Infrared Spectrograph (IRS) observations of the ultra-luminous X-ray source (ULX) NGC 6946 X-1 and its associated nebula MF 16. This ULX has very similar properties to the famous Holmberg II ULX, the first ULX to show a prominent infrared [O IV] emission line comparable to those found in AGN. This paper attempts to constrain the ULX Spectral Energy Distribution (SED) given the optical/UV photometric fluxes and high-resolution X-ray observations. Specifically, Chandra X-ray data and published Hubble optical/UV data are extrapolated to produce a model for the full optical to X…
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…
HESS J1356-645 is considered to be a pulsar wind nebula (PWN) associated with the pulsar PSR J1357-6429. We reanalyze the GeV gamma-ray emission in the direction of HESS J1356-645 with more than 13 years of Fermi Large Area Telescope (LAT) data. The extended gamma-ray emission above 5 GeV is found to be spatially coincident with HESS J1356-645. The spectrum in the energy range of 1 GeV-1 TeV can be described by a power law with an index of $Γ=1.51\pm0.10$. The broadband spectrum of HESS J1356-645 can be reproduced by a leptonic model with a broken power-law electronic spectrum. In addition, we…
Blazars, a class of highly variable active galactic nuclei, sometimes exhibit Orphan $γ$-ray flares. These flares having high flux only in $γ$-ray energies do not show significant variations in flux at lower energies. We study the temporal and spectral profile of these Orphan $γ$-ray flares in detail from three $γ-ray$ bright blazars, 3C 273, PKS 1510-089 and 3C 279 and also their simultaneous broadband emissions. We find that the variability timescales of the Orphan $γ$-ray flares were $(0.96\pm0.28)$ days, $(3.12\pm2.40)$ hr and $(2.16\pm0.72)$ hr, for 3C 273, PKS 1510-089 and 3C 279, respec…
We develop a simple one-zone model of the steady-state Crab nebula spectrum encompassing both the radio/soft $X$-ray and the GeV/multi-TeV observations. By solving the transport equation for GeV-TeV electrons injected at the wind termination shock as a log-parabola momentum distribution and evolved via energy losses, we determine analytically the resulting differential energy spectrum of photons. We find an impressive agreement with the observed spectrum of synchrotron emission, and the synchrotron self-Compton component reproduces the previously unexplained broad $200$-GeV peak that matches t…
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 observed radial profiles of the X-ray emission from Pulsar Wind Nebulae (PWNe) have been claimed to conflict with the standard one-dimensional (1-D) steady model. However, the 1-D model has not been tested to reproduce both the volume-integrated spectrum and the radial profile of the surface brightness, simultaneously. We revisit the 1-D steady model and apply it to PWNe 3C 58 and G21.5-0.9. We find that the parameters of the pulsar wind, the radius of the termination shock $r_{\rm s}$ and magnetization $σ$, greatly affect both the photon spectrum and radial profile of the emission. We hav…
The spectral energy distribution (SED) of high-frequency peaked BL Lac objects (HBL) is characterized by two peaks: one in the UV-X-ray and one in the GeV-TeV regime. An interesting object for analyzing these broadband characteristics is PKS 2005-489, which in 2004 showed the softest TeV spectrum ever measured. In 2009, a multi-wavelength campaign has been conducted with, for the first time, simultaneous observations by H.E.S.S. (TeV), Fermi/LAT (GeV), RXTE (keV), Swift (keV, UV, optical) and ATOM (optical) to cover the two peaks of the SED. During this campaign PKS 2005-489 underwent a high s…
MSH 11-62 (G291.1-0.9) is a composite supernova remnant for which radio and X-ray observations have identified the remnant shell as well as its central pulsar wind nebula. The observations suggest a relatively young system expanding into a low density region. Here we present a study of MSH 11-62 using observations with the Chandra, XMM-Newton, and Fermi observatories, along with radio observations from the Australia Telescope Compact Array (ATCA). We identify a compact X-ray source that appears to be the putative pulsar that powers the nebula, and show that the X-ray spectrum of the nebula bea…
The broadband emission of Pulsar Wind Nebulae (PWNe) is well described by non-thermal emissions from accelerated electrons and positrons. However, the standard shock acceleration model of PWNe does not account for the hard spectrum in radio wavelengths. The origin of the radio-emitting particles is also important to determine the pair production efficiency in the pulsar magnetosphere. Here, we propose a possible resolution for the particle energy distribution in PWNe; the radio-emitting particles are not accelerated at the pulsar wind termination shock but are stochastically accelerated by tur…
Although it is widely accepted that the electromagnetic spectrum from radio to very-high-energy $γ$-rays of pulsar wind nebulae (PWNe) originates from leptons, there is still an open question that protons (or more generally, ions) may exist in pulsar wind and are further accelerated in PWN. The broadband spectrum of the prototype PWN Crab, extended recently by the detection of the Tibet AS$γ$ and HAWC experiments above 100 TeV, may be helpful in constraining the acceleration efficiency of ions. Here, we model the broadest energy spectrum of Crab and find that the broadband spectrum can be expl…
The vicinity of the unidentified EGRET source 3EG J1420-6038 has undergone extensive study in the search for counterparts, revealing the energetic young pulsar PSR J1420-6048 and its surrounding wind nebula as a likely candidate for at least part of the emission from this bright and extended gamma-ray source. We report on new Suzaku observations of PSR J1420-6048, along with analysis of archival XMM Newton data. The low background of Suzaku permits mapping of the extended X-ray nebula, indicating a tail stretching ~8' north of the pulsar. The X-ray data, along with archival radio and VHE data,…
The Large High Altitude Air Shower Observatory has reported the detection of cosmic-ray sources in Milky Way that can accelerate particles up to PeV (= 10$^{15}$ eV) energies. These sources, so called ``PeVatrons'', are mostly unidentified. Several classes of sources, such as supernova remnants, pulsar wind nebula, or young stellar clusters can potentially be the counterparts of these PeVatrons. The aim of this work is to study a pulsar wind nebula interpretation of one of these PeVatrons, LHAASO J2226+6057, which has a relatively well covered multi-frequency spectrum. We have performed a lept…
We present a novel infrared spectral energy distribution (SED) modeling methodology that uses likelihood-based weighting of the model fitting results to construct probabilistic H-R diagrams (pHRD) for X-ray identified, intermediate-mass (2-8 $M_{\odot}$), pre-main sequence young stellar populations. This methodology is designed specifically for application to young stellar populations suffering strong, differential extinction ($ΔA_V > 10$ mag), typical of Galactic massive star-forming regions. We pilot this technique in the Carina Nebula Complex (CNC) by modeling the 1-8 $μ$m SEDs of 2269 like…
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）
High-energy particle transport in pulsar wind nebulae (PWNe) plays an essential role in explaining the characteristics revealed in multiwavelength observations. In this paper, the TeV-gamma-ray-emitting electrons in the Vela X PWN are approximated to be injected impulsively when the cocoon is formed due to the interaction between the SNR reverse shock and the PWN. By solving the diffusion-loss equation analytically, we reproduce the broadband spectral energy distribution and surface brightness profile simultaneously. The diffusion coefficient of TeV electrons and positrons, which is well const…
We review observations of several classes of neutron-star-powered outflows: pulsar-wind nebulae (PWNe) inside shell supernova remnants (SNRs), PWNe interacting directly with interstellar medium (ISM), and magnetar-powered outflows. We describe radio, X-ray, and gamma-ray observations of PWNe, focusing first on integrated spectral-energy distributions (SEDs) and global spectral properties. High-resolution X-ray imaging of PWNe shows a bewildering array of morphologies, with jets, trails, and other structures. Several of the 23 so far identified magnetars show evidence for continuous or sporadic…
During its early evolution, a pulsar wind nebula (PWN) sweeps the inner part of the supernova ejecta and forms a thin massive shell. Later on, when the shell has been reached by the reverse shock of the supernova remnant, the evolution becomes more complex, in most cases reverting the expansion into a compression: this later phase is called "reverberation". Computations done so far to understand this phase have been mostly performed in the thin-shell approximation, where the evolution of the PWN radius is assimilated to that of the swept-up shell under the effect of both the inner pressure fro…
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 a detailed analysis of broadband X-ray observations of the pulsar PSR J1420-6048 and its wind nebula (PWN) in the Kookaburra region with Chandra, XMM-Newton, and NuSTAR. Using the archival XMM-Newton and new NuSTAR data, we detected 68 ms pulsations of the pulsar and characterized its X-ray pulse profile which exhibits a sharp spike and a broad bump separated by ~0.5 in phase. A high-resolution Chandra image revealed a complex morphology of the PWN: a torus-jet structure, a few knots around the torus, one long (~7') and two short tails extending in the northwest direction, and a bri…
HAWC J1826-128 is one of the brightest Galactic TeV gamma-ray sources detected by the High Altitude Water Cherenkov (HAWC) Observatory, with photon energies extending up to nearly $\sim$100 TeV. This HAWC source spatially coincides with the H.E.S.S. TeV source HESS J1826-130 and the "Eel" pulsar wind nebula (PWN), which is associated with the GeV pulsar PSR J1826-1256. In the X-ray band, Chandra and XMM-Newton revealed that the Eel PWN is composed of both a compact nebula ($\sim$15") and diffuse X-ray emission ($\sim$6'$\times$2') extending away from the pulsar. Our NuSTAR observation detected…
We present a multi-wavelength study of four high redshift blazars, S5 0014+81 ($z=3.37$), CGRaBS J0225+1846 ($z=2.69$), BZQ J1430+4205 ($z=4.72$), and 3FGL J1656.2$-$3303 ($z=2.40$), using the quasi-simultaneous data from {\it Swift}, {\it NuSTAR}, and {\it Fermi}-Large Area Telescope (LAT) and also the archival {\it XMM-Newton} observations. Other than 3FGL J1656.2$-$3303, none of the sources were known as $γ$-ray emitters and our analysis of $\sim$7.5 years of LAT data reveals the first time detection of the statistically significant $γ$-ray emission from CGRaBS J0225+1846. We generate the b…
We have constructed and calibrated a spherically-symmetric, spatially-dependent particle transport and emission code for young pulsar wind nebulae (PWNe). This code predicts the spectral energy distribution (SED) of the radiation spectrum at different positions in a PWN, thus yielding the surface brightness vs. radius and hence the nebular size as function of energy. It also predicts the X-ray spectral index at different radii from the central pulsar, depending on the nebular B-field profile and particle transport properties. We apply the code to PWN G0.9+0.1 and fit these three functions conc…
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 present a 142-ks Chandra observation of the enigmatic combination supernova remnant G310.6-1.6 consisting of a bright pulsar-wind nebula driven by an energetic pulsar, surrounded by a highly circular, very faint shell with a featureless, probably synchrotron, spectrum. Comparison with an observation 6 years earlier shows no measurable expansion of the shell, though some features in the pulsar-wind nebula have moved. We find an expansion age of at least 2500 yr, implying a current shock velocity less than about 1000 km/s. We place severe upper limits on thermal emission from the shell; if th…
We present the first results from a joint XMM-Newton and NuSTAR observation of the gamma-ray emitting millisecond pulsar compact binary PSR J2129-0429. X-ray emission up to about 40 keV is detected and the joint spectrum can be modeled with a power-law plus a neutron star atmosphere model. At a distance of 1.4 kpc, the 0.3-79 keV luminosity is $3.56\times10^{32}$ erg s$^{-1}$. We also detected the 0.64-day binary orbital period with a double-peaked structure across the wavebands. By combining the updated Fermi GeV data, we modeled the broadband spectral energy distribution as well as the X-ray…
Compton-induced HE -- VHE $γ$-rays from pair cascade emissions in the SEDs of radio galaxies: NGC 1275
University of Johannesburg（约翰内斯堡大学）；The George Washington University（乔治华盛顿大学）；National Institute for Theoretical and Computational Sciences（国家理论与计算科学研究所）
BL Lacertae (BL Lac) is categorized as TeV blazar and considered as a possible source of astrophysical neutrinos. In 2020, the brightest X-ray flare ever detected from it. A detailed study can answer many puzzling questions related to multiband emissions and fast-flux variability often seen in this kind of source. We have performed the temporal and spectral analysis of the brightest flare. The variability is characterized by the fractional variability amplitude and the variability time. We found that the source has crossed all its previous limits of flux and reached the maximum ever seen from …
We present broadband spectral energy distributions (SEDs) and light curves of the gamma-ray binary 1FGL J1018.6$-$5856 measured in the X-ray and the gamma-ray bands. We find that the orbital modulation in the low-energy gamma-ray band is similar to that in the X-ray band, suggesting a common spectral component. However, above a GeV the orbital light curve changes significantly. We suggest that the GeV band contains significant flux from a pulsar magnetosphere, while the X-ray to TeV light curves are dominated by synchrotron and Compton emission from an intrabinary shock (IBS). We find that a s…
