Study of the Variable Broadband Emission of Markarian 501 during the Most Extreme Swift X-ray Activity

Aims. 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 with the aim of understanding 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 were 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 was 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 good correlation is seen between X-ray and high energy γ-ray fluxes. The spectral hardening with increase in the flux is seen in X-ray band. The power law index vs. flux plot in γ-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 γ-ray part of the SED in all states. The second zone is mainly required to produce less variable optical-UV and low energy γ-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 γ-rays.

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Multiwavelength Milky Way: An Educational Poster

Symposium - International Astronomical Union ◽

10.1017/s0074180900128682 ◽

1998 ◽

Vol 179 ◽

pp. 237-237 ◽

Cited By ~ 1

Author(s):

D. Leisawitz ◽

S.W. Digel ◽

S. Geitz

Keyword(s):

Milky Way ◽

Gamma Ray ◽

Line Emission ◽

Electromagnetic Spectrum ◽

Data Sets ◽

X Ray ◽

Nasa Goddard Space ◽

Broadband Emission ◽

The Galaxy ◽

Effective Use

The Astrophysics Data Facility at NASA Goddard Space Flight Center supports the processing, management, and dissemination of data obtained by past, current, and future NASA and international astrophysics missions, and promotes the effective use of those data by the astrophysics community, educators, and the public. Our Multiwavelength Milky Way poster was printed for broad distribution. It depicts the Galaxy at radio, infrared, optical, X-ray, and gamma-ray wavelengths. In particular, the poster contains images of the Galactic 21-cm and CO (J = 1 → 0) line emission, and IRAS 12, 60, and 100 μm, COBE/DIRBE 1.25, 2.2, and 3.5 μm, Digitized Sky Survey optical wavelength, ROSAT/PSPC 0.25, 0.75, and 1.5 keV X-ray, and CGRO/EGRET E > 100 MeV gamma ray broadband emission. All of the data sets are publicly available. Captions describe the Milky Way and what can be learned about the Galaxy from measurements made in each segment of the electromagnetic spectrum. The poster is intended to be an educational tool, one that will stimulate heightened awareness by laypersons of NASA's contribution to modern astronomy.Through an interface available on the World Wide Web at http://adf.gsfc.nasa.gov/adf/adf.html one may view the images that appear on the poster, read the poster captions, and locate the archived data and references.

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A year in the life of GW170817: the rise and fall of a structured jet from a binary neutron star merger

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2248 ◽

2019 ◽

Cited By ~ 28

Author(s):

E Troja ◽

H van Eerten ◽

G Ryan ◽

R Ricci ◽

J M Burgess ◽

...

Keyword(s):

Neutron Star ◽

Rapid Decline ◽

Late Time ◽

Time Behavior ◽

X Rays ◽

X Ray ◽

Binary Neutron Star ◽

Long Afterglow ◽

Broadband Emission ◽

Turn Over

Abstract We present the results of our year-long afterglow monitoring of GW170817, the first binary neutron star (NS) merger detected by advanced LIGO and advanced Virgo. New observations with the Australian Telescope Compact Array (ATCA) and the Chandra X-ray Telescope were used to constrain its late-time behavior. The broadband emission, from radio to X-rays, is well-described by a simple power-law spectrum with index β ∼0.585 at all epochs. After an initial shallow rise ∝ t0.9, the afterglow displayed a smooth turn-over, reaching a peak X-ray luminosity of LX≈5 ×1039 erg s−1 at 160 d, and has now entered a phase of rapid decline, approximately ∝ t−2. The latest temporal trend challenges most models of choked jet/cocoon systems, and is instead consistent with the emergence of a relativistic structured jet seen at an angle of ≈22○ from its axis. Within such model, the properties of the explosion (such as its blastwave energy EK ≈ 2 × 1050 erg, jet width θc ≈4○, and ambient density n ≈3 × 10−3 cm−3) fit well within the range of properties of cosmological short GRBs.

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Modeling of the spatially resolved nonthermal emission from the Vela Jr. supernova remnant

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832879 ◽

2018 ◽

Vol 618 ◽

pp. A155 ◽

Cited By ~ 6

Author(s):

Iurii Sushch ◽

Robert Brose ◽

Martin Pohl

Keyword(s):

Magnetic Field ◽

High Resolution ◽

Supernova Remnants ◽

High Energy ◽

Radial Dependence ◽

Electromagnetic Spectrum ◽

X Ray ◽

Spatially Resolved ◽

Magnetic Field Profile ◽

Broadband Emission

Vela Jr. (RX J0852.0−4622) is one of just a few known supernova remnants (SNRs) with a resolved shell across the whole electromagnetic spectrum from radio to very-high-energy (>100 GeV; VHE) gamma-rays. Its proximity and large size allow for detailed spatially resolved observations of the source, making Vela Jr. one of the primary sources used for the study of particle acceleration and emission mechanisms in SNRs. High-resolution X-ray observations reveal a steepening of the spectrum toward the interior of the remnant. In this study we aim for a self-consistent radiation model of Vela Jr. which at the same time would explain the broadband emission from the source and its intensity distribution. We solve the full particle transport equation combined with the high-resolution one-dimensional (1D) hydrodynamic simulations (using Pluto code) and subsequently calculate the radiation from the remnant. The equations are solved in the test particle regime. We test two models for the magnetic field profile downstream of the shock: damped magnetic field, which accounts for the damping of strong magnetic turbulence downstream, and transported magnetic field. Neither of these scenarios can fully explain the observed radial dependence of the X-ray spectrum under spherical symmetry. We show, however, that the softening of the spectrum and the X-ray intensity profile can be explained under the assumption that the emission is enhanced within a cone.

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Study of the variable broadband emission of Markarian 501 during the most extreme Swift X-ray activity

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834603 ◽

2020 ◽

Vol 637 ◽

pp. A86

Author(s):

◽

V. A. Acciari ◽

S. Ansoldi ◽

L. A. Antonelli ◽

A. Babić ◽

...

Keyword(s):

Gamma Rays ◽

Gamma Ray ◽

Crab Nebula ◽

Spectral Feature ◽

High Energy ◽

Spectral Energy ◽

X Ray ◽

Narrow Component ◽

Broadband Emission ◽

Wide Range

Context. Markarian 501 (Mrk 501) is a very high-energy (VHE) gamma-ray blazar located at z = 0.034, which is regularly monitored by a wide range of multi-wavelength instruments, from radio to VHE gamma rays. During a period of almost two weeks in July 2014, the highest X-ray activity of Mrk 501 was observed in ∼14 years of operation of the Neil Gehrels Swift Gamma-ray Burst Observatory. Aims. We characterize the broadband variability of Mrk 501 from radio to VHE gamma rays during the most extreme X-ray activity measured in the last 14 years, and evaluate whether it can be interpreted within theoretical scenarios widely used to explain the broadband emission from blazars. Methods. The emission of Mrk 501 was measured at radio with Metsähovi, at optical–UV with KVA and Swift/UVOT, at X-ray with Swift/XRT and Swift/BAT, at gamma ray with Fermi-LAT, and at VHE gamma rays with the FACT and MAGIC telescopes. The multi-band variability and correlations were quantified, and the broadband spectral energy distributions (SEDs) were compared with predictions from theoretical models. Results. The VHE emission of Mrk 501 was found to be elevated during the X-ray outburst, with a gamma-ray flux above 0.15 TeV varying from ∼0.5 to ∼2 times the Crab nebula flux. The X-ray and VHE emission both varied on timescales of 1 day and were found to be correlated. We measured a general increase in the fractional variability with energy, with the VHE variability being twice as large as the X-ray variability. The temporal evolution of the most prominent and variable segments of the SED, characterized on a day-by-day basis from 2014 July 16 to 2014 July 31, is described with a one-zone synchrotron self-Compton model with variations in the break energy of the electron energy distribution (EED), and with some adjustments in the magnetic field strength and spectral shape of the EED. These results suggest that the main flux variations during this extreme X-ray outburst are produced by the acceleration and the cooling of the high-energy electrons. A narrow feature at ∼3 TeV was observed in the VHE spectrum measured on 2014 July 19 (MJD 56857.98), which is the day with the highest X-ray flux (>0.3 keV) measured during the entire Swift mission. This feature is inconsistent with the classical analytic functions to describe the measured VHE spectra (power law, log-parabola, and log-parabola with exponential cutoff) at more than 3σ. A fit with a log-parabola plus a narrow component is preferred over the fit with a single log-parabola at more than 4σ, and a dedicated Monte Carlo simulation estimated the significance of this extra component to be larger than 3σ. Under the assumption that this VHE spectral feature is real, we show that it can be reproduced with three distinct theoretical scenarios: (a) a pileup in the EED due to stochastic acceleration; (b) a structured jet with two-SSC emitting regions, with one region dominated by an extremely narrow EED; and (c) an emission from an IC pair cascade induced by electrons accelerated in a magnetospheric vacuum gap, in addition to the SSC emission from a more conventional region along the jet of Mrk 501.

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Broadband study of BL Lac during flare of 2020: Spectral evolution and emergence of HBL component

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab2486 ◽

2021 ◽

Author(s):

Raj Prince

Keyword(s):

Time Lag ◽

Light Curves ◽

X Rays ◽

Spectral Evolution ◽

X Ray ◽

Bl Lacertae ◽

Physical Mechanisms ◽

Broadband Emission ◽

Bl Lac ◽

Astrophysical Neutrinos

Abstract 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 to a maximum ever seen from it in optical and X-rays. It is highly variable in X-rays with fractional variability above 100 per cent (1.8397±0.0181) and the fastest variability time of 11.28 hours within a day. The broadband light curves correlation with X-ray suggest a time lag of one day. A broadband SED modeling is pursued to understand the possible physical mechanisms responsible for broadband emission. Modeling requires two emission regions located at two different sites to explain the low and high flux states. A significant spectral change is observed in the optical-UV and X-ray spectrum during the high state, which eventually leads to shifts in the location of the synchrotron peak towards higher energy, suggesting an emergence of a new HBL component.

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A Semianalytic Afterglow with Thermal Electrons and Synchrotron Self-Compton Emission

The Astrophysical Journal ◽

10.3847/1538-4357/ac2f43 ◽

2022 ◽

Vol 924 (1) ◽

pp. 40

Author(s):

Donald C. Warren ◽

Maria Dainotti ◽

Maxim V. Barkov ◽

Björn Ahlgren ◽

Hirotaka Ito ◽

...

Keyword(s):

Power Law ◽

Gamma Ray ◽

Early Time ◽

Spectral Structure ◽

Power Law Distribution ◽

X Ray ◽

Broadband Emission ◽

Dependent Form ◽

Order Of Magnitude ◽

Tev Gamma Rays

Abstract We extend previous work on gamma-ray burst afterglows involving hot thermal electrons at the base of a shock-accelerated tail. Using a physically motivated electron distribution based on first-principles simulations, we compute the broadband emission from radio to TeV gamma rays. For the first time, we present the effects of a thermal distribution of electrons on synchrotron self-Compton emission. The presence of thermal electrons causes temporal and spectral structure across the entire observable afterglow, which is substantively different from models that assume a pure power-law distribution for the electrons. We show that early-time TeV emission is enhanced by more than an order of magnitude for our fiducial parameters, with a time-varying spectral index that does not occur for a pure power law of electrons. We further show that the X-ray closure relations take a very different, also time-dependent, form when thermal electrons are present; the shape traced out by the X-ray afterglows is a qualitative match to observations of the traditional decay phase.

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Demonstration of Near Edge X-ray Absorption Fine Structure Spectroscopy of Transition Metals Using Xe/He Double Stream Gas Puff Target Soft X-ray Source

Materials ◽

10.3390/ma14237337 ◽

2021 ◽

Vol 14 (23) ◽

pp. 7337

Author(s):

Tomasz Fok ◽

Przemysław Wachulak ◽

Łukasz Węgrzyński ◽

Andrzej Bartnik ◽

Michał Nowak ◽

...

Keyword(s):

Fine Structure ◽

Transition Metals ◽

Laser Beam ◽

Measurement System ◽

X Ray ◽

Transitional Metals ◽

Broadband Emission ◽

Dual Channel ◽

X Ray Absorption ◽

Absorption Edges

A near 1-keV photons from the Xe/He plasma produced by the interaction of laser beam with a double stream gas puff target were employed for studies of L absorption edges of period 4 transitional metals with atomic number Z from 26 to 30. The dual-channel, compact NEXAFS system was employed for the acquisition of the absorption spectra. L1–3 absorption edges of the samples were identified in transmission mode using broadband emission from the Xe/He plasma to show the applicability of such source and measurement system to the NEXAFS studies of the transition metals, including magnetic materials.

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Multi-Wavelength Properties of the 2021 Periastron Passage of PSR B1259-63

Universe ◽

10.3390/universe7070242 ◽

2021 ◽

Vol 7 (7) ◽

pp. 242

Author(s):

Maria Chernyakova ◽

Denys Malyshev ◽

Brian van van Soelen ◽

Shane O’Sullivan ◽

Charlotte Sobey ◽

...

Keyword(s):

Binary System ◽

Gamma Ray ◽

X Ray ◽

Broadband Emission ◽

Cone Model ◽

First Results ◽

Multi Wavelength ◽

Be Star ◽

Pulsar Wind ◽

The Times

PSR B1259-63 is a gamma-ray binary system hosting a radio pulsar orbiting around a O9.5Ve star, LS 2883, with a period of ∼3.4 years. The interaction of the pulsar wind with the LS 2883 outflow leads to unpulsed broadband emission in the radio, X-ray, GeV, and TeV domains. One of the most unusual features of the system is an outburst of GeV energies around the periastron, during which the energy release substantially exceeds the spin down luminosity under the assumption of the isotropic emission. In this paper, we present the first results of a recent multi-wavelength campaign (radio, optical, and X-ray bands) accompanied by the analysis of publicly available GeV Fermi/LAT data. The campaign covered a period of more than 100 days around the 2021 periastron and revealed substantial differences from previously observed passages. We report a major delay of the GeV flare, weaker X-ray flux during the peaks, which are typically attributed to the times when the pulsar crosses the disk, and the appearance of a third X-ray peak never observed before. We argue that these features are consistent with the emission cone model proposed by us previously, in the case of a sparser and clumpier disk of the Be star.

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(C7H11N2)2MBr4 (M = Cu, Zn): X‐Ray Sensitive 0D Hybrid Metal Halides with Tunable Broadband Emission

European Journal of Inorganic Chemistry ◽

10.1002/ejic.202100954 ◽

2021 ◽

Author(s):

Timothy M McWhorter ◽

Zheng Zhang ◽

Tielyr D Creason ◽

Leonard M Thomas ◽

Mao-Hua Du ◽

...

Keyword(s):

Metal Halides ◽

X Ray ◽

Broadband Emission

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