arXiv subjects

Jordan Eagle

Publications and source records attributed to Jordan Eagle.

13 recordsLinked to original sources

arXiv2026

A Multiwavelength Interpretation of HESS J1857+026 Emission Using the Fermi-LAT, VERITAS, and HAWC Observatories

We present a new study on the MeV-TeV gamma-ray origin of HESS J1857+026 using data collected from the Fermi-LAT, VERITAS, and HAWC observatories. A spatial and spectral study of HESS J1857+026 including radiative modeling of the MeV-TeV spectrum determines the likely dominant gamma-ray origin as a pulsar wind nebula (PWN) powered by the energetic pulsar PSR J1856+0245. The MeV-TeV spectrum is further characterized through basic evolutionary radiative modeling assuming a PWN origin to constrain the physical properties of the system such as the magnetic field strength and PWN age. The results of the PWN evolutionary model are consistent with the observational constraints of the system, finding an age of the system between t = [16,21]kyr and a magnetic field strength between B = [0.4,1.6]muG. These estimates support an evolved PWN scenario where the observed gamma-ray emission is generated by the relativistic electrons inverse Compton scattering (ICS) off local photon fields, however the low-energy (E < 10GeV) spectral component could be dominated by hadronic emission originating from a supernova remnant (SNR). For a PWN component above 10GeV, we measure the conditions for particle diffusion, finding that the local diffusion (D(50TeV) ~ $10^{28}cm^{-2}s^{-1}$) is suppressed compared to the interstellar medium (ISM) value, in agreement with similar TeV PWNe. By measuring the radial surface brightness profiles of the gamma-ray source across multiple instruments, we demonstrate that the combined MeV-TeV spatial information is a powerful tool to constrain particle diffusion properties.

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arXiv2026

Fermi-LAT Gamma-ray Emission Discovered from the Composite Supernova Remnant B0453-685 in the Large Magellanic Cloud

A second extragalactic pulsar wind nebula (PWN) is discovered in the MeV-GeV band using the Fermi-LAT. Faint, point-like gamma-ray emission is detected at the location of the composite supernova remnant (SNR) B0453-685 from energies 300MeV-2TeV. The Fermi-LAT data analysis of the new gamma-ray source is presented together with a detailed multi-wavelength investigation to understand the nature of the observed emission. The observational evidence and physical implications from broadband modeling do not support an SNR gamma-ray origin. Semi-analytic radiative evolutionary models are explored to understand the potential for any pulsar or PWN component responsible for the observed gamma-ray emission. The modeling results favor an evolved PWN ($\tau\sim 14,000$ years) that has been impacted by the return of the SNR reverse shock with a possible substantial pulsar component below $5$GeV. The particle acceleration mechanisms and their efficiency within B0453-685 have important implications for the role PWNe play in generating Cosmic Rays (CRs), but constraints on the synchrotron cut-off are required to accurately characterize the underlying particle properties.

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arXiv2026

Pulsar Wind Nebulae (PWNe) -- A Review

Pulsar Wind Nebulae (PWNe) are relativistic, magnetic winds comprised of radiating electrons and positrons, powered by an energetic pulsar. The pulsar continuously injects particles into the PWN that are accelerated at the termination shock. As the relativistic particles enter the PWN, they radiate away the energy received at the shock as they interact with the PWN environment, generating synchrotron emission from interactions with the magnetic field of the PWN and Inverse Compton Scattering (ICS) from interactions with the local photon fields. Synchrotron emission is observed from the majority of known PWNe from radio to X-ray energies, and the ICS is observed in the $\gamma$-ray bands, from MeV to TeV energies. The particle acceleration processes at the termination shock and elsewhere within the PWN remain to be understood. Recent progress in theoretical studies have provided the capability to explain broadband observations of several PWNe including their spectral and spatial features. This work reviews some of the most compelling outcomes of recent literature, outlining the outstanding questions that remain to be answered, and how the future prospects of $\gamma$-ray astronomy will be instrumental in advancing the current understanding of PWNe.

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arXiv2026

New Hard X-Ray and Multiwavelength Study of the PeVatron Candidate PWN G0.9+0.1 in the Galactic Center Region

We present a new X-ray study and multiwavelength spectral energy distribution (SED) modeling of the young pulsar wind nebula (PWN) powered by the energetic pulsar PSR J1747-2809, inside the composite supernova remnant (SNR) G0.9+0.1, located in the Galactic Center region. The source is detected by NuSTAR up to 30 keV with evidence for the synchrotron burnoff effect in the changing spatial morphology with increasing energy. The broadband 2-30 keV spectrum of PWN G0.9+0.1 is modeled by a single power law with photon index $\Gamma=2.11\pm0.07$. We combined the new X-ray data with the multiwavelength observations in radio, GeV, and TeV gamma rays and modeled the SED, applying a one-zone and a multi-zone leptonic model. The comparison of the models is successful, as we obtained physically compatible results in the two cases. Through the one-zone model, we constrain the age of the system to $\sim2.2$ kyr, as well as reproduce the observed PWN and SNR radio sizes. In both the one-zone and multi-zone leptonic models, the electron injection spectrum is well-described by a single power law with spectral index $p \sim 2.6$ and a maximum electron energy of $\sim2$ PeV, suggesting the source could be a leptonic PeVatron candidate. We estimate the average magnetic field to be $B_{\rm PWN} \sim 20\ \mu$G. We also report the serendipitous NuSTAR detection of renewed X-ray activity from the very faint X-ray transient XMMU J174716.1-281048 and characterize its spectrum.

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arXiv2025

A Systematic Search for MeV-GeV Pulsar Wind Nebulae without Gamma-ray Detected Pulsars

An increasing number of pulsar wind nebulae (PWNe) are being identified in the TeV band by ground-based Imaging Air Cherenkov Telescopes such that they constitute the dominant source class of Galactic TeV emitters. However, MeV-GeV PWN counterparts are still largely lacking. To date, only a dozen PWNe are identified by the Fermi-Large Area Telescope (LAT) in the MeV-GeV band. Most PWNe are located along the Galactic plane embedded within the prominent, diffuse Galactic gamma-ray emission, which makes these sources difficult to disentangle from the bright diffuse background. We present a systematic search for gamma-ray counterparts to known PWNe in the 300MeV-2TeV energy band using the Fermi-LAT. We target locations of previously identified PWNe that lack detected Fermi-LAT pulsars to minimize associated pulsar contamination. The sample includes 6 previously identified Fermi-LAT PWNe and 8 Fermi-LAT sources associated with PWNe. We report the analysis of 58 regions of interest and classify detected sources as either a likely PWN or a candidate PWN counterpart based on their morphological and spectral characteristics across the broadband spectrum. There are 9 unidentified Fermi-LAT sources that we consider as likely PWN counterparts, which, if confirmed to be PWNe, would greatly increase the PWN population detected by the Fermi-LAT from 12 to 21. The remaining Fermi-LAT detected sources are considered weaker PWN candidates. A second approach in the systematic search for gamma-ray emitting PWNe will involve studying the off-pulse phases of Fermi-LAT pulsars for the presence of an obscured PWN and will be reported in a subsequent paper.

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arXiv2024

Parkes Radio and NuSTAR X-ray Observations of the Composite Supernova Remnant B0453-685 in the Large Magellanic Cloud

Gamma-ray emission is observed coincident in position to the evolved, composite supernova remnant (SNR) B0453-685. Prior multi-wavelength investigations of the region indicate that the pulsar wind nebula (PWN) within the SNR is the most likely origin for the observed gamma-rays, with a possible pulsar contribution that becomes significant at energies below E ~ 5GeV. Constraints on the PWN hard X-ray spectrum are important for the most accurate broadband representation of PWN emission and determining the presence of a gamma-ray pulsar component. The results of Parkes radio and NuSTAR X-ray observations are presented on PWN B0453-685. We perform a search for the central pulsar in the new Parkes radio data, finding an upper limit of 12uJy. A pulsation search in the new NuSTAR observation additionally provides a 3sigma upper-limit on the hard X-ray pulsed fraction of 56%. The PWN is best characterized with a photon index Gamma_X = 1.91 +\- 0.20 in the 3-78keV NuSTAR data and the results are incorporated into existing broadband models. Lastly, we characterize a serendipitous source detected by Chandra and NuSTAR that is considered a new high mass X-ray binary candidate.

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arXiv2024

2FHLJ1745.1-3035: A Newly Discovered, Powerful Pulsar Wind Nebula Candidate

We present a multi-epoch, multi-observatory X-ray analysis for 2FHL J1745.1-3035, a newly discovered very high energy Galactic source detected by the Fermi Large Area Telescope (LAT) located in close proximity to the Galactic Center (l=358.5319{\deg}; b=-0.7760{\deg}). The source shows a very hard gamma-ray photon index above 50 GeV, Gamma_gamma=1.2+-0.4, and is found to be a TeV-emitter by the LAT. We conduct a joint XMM-Newton, Chandra and NuSTAR observing campaign, combining archival XMM-Newton observations, to study the X-ray spectral properties of 2FHL J1745.1-3035 over a time-span of over 20 years. The joint X-ray spectrum is best-fitted as a broken power law model with break energy E_b~7 keV: the source is very hard at energies below 10 keV, with photon index Gamma_1~0.6, and significantly softer in the higher energy range measured by NuSTAR with photon index Gamma_2~1.9. We also perform a spatially resolved X-ray analysis with Chandra, finding evidence for marginal extension (up to an angular size r~5 arcsec), a result that supports a compact pulsar wind nebula scenario. Based on the X-ray and gamma-ray properties, 2FHL J1745.1-3035 is a powerful pulsar wind nebula candidate. Given its nature as an extreme TeV emitter, further supported by the detection of a coincident TeV extended source HESS J1745-303, 2FHL J1745.1-3035 is an ideal candidate for a follow-up with the upcoming Cherenkov Telescope Array.

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arXiv2023

Chandra X-ray Observations of PSR J1849-0001, its Pulsar Wind Nebula, and the TeV Source HESS J1849-000

We obtained a 108 ks Chandra X-ray Observatory (CXO) observation of PSR J1849-0001 and its pulsar wind nebula (PWN), coincident with the TeV source HESS J1849-000. By analyzing the new and archival CXO data, we resolved the pulsar from the PWN, explored the PWN morphology on arcsecond and arcminute scales, and measured the spectra of different regions of the PWN. Both the pulsar and the compact inner PWN spectra are hard with power-law photon indices of $1.20 \pm 0.07$ and $1.49 \pm 0.20$, respectively. The jet-dominiated PWN has a relatively low luminosity, lack of gamma-ray pulsations, relatively hard and nonthermal spectrum of the pulsar, and sine-like pulse profile, which indicates a relatively small angle between the pulsar's spin and magnetic dipole axis. In this respect, it shares similar properties with a few other so-called MeV pulsars. Although the joint X-ray and TeV spectral energy distribution can be roughly described by a single-zone model, the obtained magnetic field value is unrealistically low. A more realistic scenario is the presence of a relic PWN, no longer emitting synchrotron X-rays but still radiating in TeV via inverse-Compton upscattering. We calso serendipitously detected surprisingly bright X-ray emission from a very wide binary whose components should not be interacting.

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arXiv2023

The High Energy X-ray Probe (HEX-P): Galactic PeVatrons, star clusters, superbubbles, microquasar jets, and gamma-ray binaries

HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging (<10" FWHM) and broad spectral coverage (0.2-80 keV) with an effective area far superior to current facilities (including XMM-Newton and NuSTAR) to enable revolutionary new insights into a variety of important astrophysical problems. With the recent discoveries of over 40 ultra-high-energy gamma-ray sources (detected above 100 TeV) and neutrino emission in the Galactic Plane, we have entered a new era of multi-messenger astrophysics facing the exciting reality of Galactic PeVatrons. In the next decade, as more Galactic PeVatrons and TeV gamma-ray sources are expected to be discovered, the identification of their acceleration and emission mechanisms will be the most pressing issue in both particle and high-energy astrophysics. In this paper, along with its companion papers (Reynolds et al. 2023, Mori et al. 2023), we will present that HEX-P is uniquely suited to address important problems in various cosmic-ray accelerators, including Galactic PeVatrons, through investigating synchrotron X-ray emission of TeV-PeV electrons produced by both leptonic and hadronic processes.

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arXiv2023

The High Energy X-ray Probe (HEX-P): Supernova remnants, pulsar wind nebulae, and nuclear astrophysics

HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging ($<10"$ full width at half maximum) and broad spectral coverage (0.2--80 keV) with an effective area far superior to current facilities (including XMM-Newton and NuSTAR) to enable revolutionary new insights into a variety of important astrophysical problems. HEX-P is ideally suited to address important problems in the physics and astrophysics of supernova remnants (SNRs) and pulsar-wind nebulae (PWNe). For shell SNRs, HEX-P can greatly improve our understanding via more accurate spectral characterization and localization of non-thermal X-ray emission from both non-thermal-dominated SNRs and those containing both thermal and non-thermal components, and can discover previously unknown non-thermal components in SNRs. Multi-epoch HEX-P observations of several young SNRs (e.g., Cas A and Tycho) are expected to detect year-scale variabilities of X-ray filaments and knots, thus enabling us to determine fundamental parameters related to diffusive shock acceleration, such as local magnetic field strengths and maximum electron energies. For PWNe, HEX-P will provide spatially-resolved, broadband X-ray spectral data separately from their pulsar emission, allowing us to study how particle acceleration, cooling, and propagation operate in different evolution stages of PWNe. HEX-P is also poised to make unique and significant contributions to nuclear astrophysics of Galactic radioactive sources by improving detections of, or limits on, $^{44}$Ti in the youngest SNRs and by potentially discovering rare nuclear lines as evidence of double neutron star mergers. Throughout the paper, we present simulations of each class of objects, demonstrating the power of both the imaging and spectral capabilities of HEX-P to advance our knowledge of SNRs, PWNe, and nuclear astrophysics.

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arXiv2023

Fermi-LAT Gamma-ray Emission Discovered from the Composite Supernova Remnant B0453-685 in the Large Magellanic Cloud

We report the second extragalactic pulsar wind nebula (PWN) to be detected in the MeV-GeV band by the Fermi-LAT, located within the Large Magellanic Cloud (LMC). The only other known PWN to emit in the Fermi band outside of the Milky Way Galaxy is N 157B which lies to the west of the newly detected gamma-ray emission at an angular distance of 4 degrees. Faint, point-like gamma-ray emission is discovered at the location of the composite supernova remnant (SNR) B0453-685 with a ~ 4 sigma significance from energies 300 MeV - 2 TeV. We present the Fermi-LAT data analysis of the new gamma-ray source, coupled with a detailed multi-wavelength investigation to understand the nature of the observed emission. Combining the observed characteristics of the SNR and the physical implications from broadband modeling, we argue it is unlikely the SNR is responsible for the gamma-ray emission. While the gamma-ray emission is too faint for a pulsation search, we try to distinguish between any pulsar and PWN component of SNR B0453-685 that would be responsible for the observed gamma-ray emission using semi-analytic models. We determine the most likely scenario is that the old PWN (t ~ 14,000 years) within B0453-685 has been impacted by the return of the SNR reverse shock with a possible substantial pulsar component below 5 GeV.

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arXiv2022

MeV-GeV Gamma-ray Emission from SNR G327.1-1.1 Discovered by the Fermi-LAT

We report the discovery of MeV-GeV gamma-ray emission by the Fermi-LAT positionally coincident with the TeV pulsar wind nebula (PWN) HESS~J1554-550 within the host supernova remnant (SNR) G327.1-1.1. The gamma-ray emission is point-like and faint but significant (> 4 sigma) in the 300MeV-2TeV energy range. We report here the Fermi-LAT analysis of the observed gamma-ray emission followed by a detailed multiwavelength investigation to understand the nature of the emission. The central pulsar powering the PWN within G327.1-1.1 has not been detected in any waveband; however, it is likely embedded within the X-ray nebula, which is displaced from the center of the radio nebula. The gamma-ray emission is faint and therefore a pulsation search to determine if the pulsar may be contributing is not feasible. Prior detailed multiwavelength reports revealed an SNR system that is old, tau ~ 18,000yrs, where the interaction of the reverse shock with the PWN is underway or has recently occurred. We find that the gamma-ray emission agrees remarkably well with a detailed broadband model constructed in a prior report based on independent hydrodynamical and semi-analytic simulations of an evolved PWN. We further investigate the physical implications of the model for the PWN evolutionary stage incorporating the new Fermi-LAT data and attempt to model the distinct particle components based on a spatial separation analysis of the displaced PWN counterparts.

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arXiv2018

2FHL J0826.1-4500: Discovery of a possible shock-cloud interaction on the Western edge of the Vela SNR

We report on the investigation of a very high energy (VHE), Galactic gamma-ray source recently discovered at >50GeV using the Large Area Telescope (LAT) on board the Fermi-LAT. This object, 2FHL J0826.1-4500, displays one of the hardest >50GeV spectra (gamma-ray photon index ~1.6) in the 2FHL catalog, and a follow-up observation with XMM-Newton has uncovered diffuse, soft thermal emission at the position of the gamma-ray source. A detailed analysis of the available multi-wavelength data shows that this source is located on the Western edge of the Vela supernova remnant (SNR): the observations and the spectral energy distribution modelling support a scenario where this gamma-ray source is the byproduct of the interaction between the SNR shock and a neutral Hydrogen cloud. If confirmed, this shock-cloud interaction would make 2FHL J0826.1-4500 a promising candidate for efficient particle acceleration.

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