arXiv subjects

Jean Ballet

Publications and source records attributed to Jean Ballet.

At least 19 recordsLinked to original sources

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

Isolated neutron stars as Science Validation for XMM2ATHENA: Ensuring robust data for future X-ray Astronomy

The discovery of radio-quiet, X-ray thermally emitting isolated neutron stars (XINSs) in the ROSAT All-Sky Survey revealed a previously overlooked component of the neutron star population. Advancements in X-ray instrumentation and the availability of deep, wide-area optical surveys now enable us to explore XINSs at fainter X-ray fluxes and greater distances. In this study, we investigated candidates selected from the 4XMM-DR9 catalogue using XMM-Newton, focusing on long-term flux stability, spectral characterisation, and astrometry. By leveraging resources from the XMM2ATHENA project -- including updated catalogues, multiwavelength characterisation and machine learning classification -- we refined our understanding of this sample of soft X-ray emitters. Our findings enhance the characterisation of XINS candidates, laying the groundwork for more targeted investigations and future catalogue searches.

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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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arXiv2023

A fresh perspective on the 3D dynamics of Tycho's supernova remnant: Ejecta asymmetries in the X-ray band

450 years after the explosion of the Type Ia SN1572, the dynamics of the Tycho supernova remnant can give us keys to understand the explosion mechanism and the interaction of the remnant with the interstellar medium. To probe the asymmetries and the evolution of the SNR, we track the ejecta dynamics using new methods applied to the deep X-ray observations available in the Chandra space telescope archive. For the line of sight velocity measurement Vz, we use the Doppler effect focused on the bright Si line in the 1.6-2.1 keV band. Using the component separation tool General Morphological Component Analysis (GMCA), we successfully disentangle the red and blueshifted Si ejecta emission. This allows us to reconstruct a map of the peak energy of the Si line with a total coverage of the SNR at a 2'' resolution and a proxy of the velocity in the line of sight. For the proper motions in the plane of the sky Vxy, we develop a new method, named Poisson Optical Flow, to measure the displacement of 2D features between the observations of 2003 and 2009. The result is a field of 1700 velocity vectors covering the entire SNR. These exhaustive 3D velocity measurements reveal the complex and patchy dynamics of the SNR. At the large-scale, an asymmetry with the North being dominantly blueshifted and the South redshifted is observed. The proper motion vector field Vxy highlights different dynamics between the East and the West parts of the SNR. The eastern velocity field is more disturbed by external inhomogeneities and the South-East ejecta knot. In particular, a slow-down is observed in the North-East which could be due to the interaction with higher densities as seen in other wavelengths. The vector field is also used to backtrace the center of the explosion which is then compared with potential stellar progenitors distances from the latest Gaia DR3, leaving only stars B and E as possible candidates.

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arXiv2023

The Third Fermi Large Area Telescope Catalog of Gamma-ray Pulsars

We present 294 pulsars found in GeV data from the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope. Another 33 millisecond pulsars (MSPs) discovered in deep radio searches of LAT sources will likely reveal pulsations once phase-connected rotation ephemerides are achieved. A further dozen optical and/or X-ray binary systems co-located with LAT sources also likely harbor gamma-ray MSPs. This catalog thus reports roughly 340 gamma-ray pulsars and candidates, 10% of all known pulsars, compared to $\leq 11$ known before Fermi. Half of the gamma-ray pulsars are young. Of these, the half that are undetected in radio have a broader Galactic latitude distribution than the young radio-loud pulsars. The others are MSPs, with 6 undetected in radio. Overall, >235 are bright enough above 50 MeV to fit the pulse profile, the energy spectrum, or both. For the common two-peaked profiles, the gamma-ray peak closest to the magnetic pole crossing generally has a softer spectrum. The spectral energy distributions tend to narrow as the spindown power $\dot E$ decreases to its observed minimum near $10^{33}$ erg s$^{-1}$, approaching the shape for synchrotron radiation from monoenergetic electrons. We calculate gamma-ray luminosities when distances are available. Our all-sky gamma-ray sensitivity map is useful for population syntheses. The electronic catalog version provides gamma-ray pulsar ephemerides, properties and fit results to guide and be compared with modeling results.

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arXiv2023

XMM2ATHENA, the H2020 project to improve XMM-Newton analysis software and prepare for Athena

XMM-Newton, a European Space Agency observatory, has been observing the X-ray, ultra-violet and optical sky for 23 years. During this time, astronomy has evolved from mainly studying single sources to populations and from a single wavelength, to multi-wavelength or messenger data. We are also moving into an era of time domain astronomy. New software and methods are required to accompany evolving astronomy and prepare for the next generation X-ray observatory, Athena. Here we present XMM2ATHENA, a programme funded by the European Union's Horizon 2020 research and innovation programme. XMM2ATHENA builds on foundations laid by the XMM-Newton Survey Science Centre (XMM-SSC), including key members of this consortium and the Athena Science ground segment, along with members of the X-ray community. The project is developing and testing new methods and software to allow the community to follow the X-ray transient sky in quasi-real time, identify multi-wavelength or messenger counterparts of XMM-Newton sources and determine their nature using machine learning. We detail here the first milestone delivery of the project, a new online, sensitivity estimator. We also outline other products, including the forthcoming innovative stacking procedure and detection algorithms to detect the faintest sources. These tools will then be adapted for Athena and the newly detected or identified sources will enhance preparation for observing the Athena X-ray sky.

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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

Evidence for large-scale excesses associated with low HI column densities in the sky $$\\$$I. Dust excess

Where dust and gas are uniformly mixed, atomic hydrogen can be traced through the detection of far-infrared (FIR) or UV emission of dust. We considered, for the origin of discrepancies observed between various direct and indirect tracers of gas outside the Galactic plane, possible corrections to the zero levels of the Planck-HFI detectors. We set the zero levels of the Planck High Frequency Instrument (HFI) skymaps as well as the 100 $\mu$m map from COBE/DIRBE and IRAS from the correlation between FIR emission and atomic hydrogen column density excluding regions of lowest gas column density. A modified blackbody model fit to those new zero-subtracted maps led to significantly different maps of the opacity spectral index $\beta$ and temperature $T$ and an overall increase in the optical depth at 353 GHz $\tau_{353}$ of 7.1$\times$10$^{-7}$ compared to the data release 2 Planck map. When comparing $\tau_{353}$ and the HI column density, we observed a uniform spatial distribution of the opacity outside regions with dark neutral gas and CO except in various large-scale regions of low NHI that represent 25% of the sky. In those regions, we observed an average dust column density 45% higher than predictions based on NHI with a maximum of 250% toward the Lockman Hole region. From the average opacity $\sigma_{e 353}$=(8.9$\pm$0.1)$\times$10$^{-27}$ cm$^2$ we deduced a dust-to-gas mass ratio of 0.53$\times$10$^{-2}$. We did not see evidence of dust associated to a Reynolds layer of ionized hydrogen. We measured a far-ultraviolet isotropic intensity of 137$\pm$15 photons s$^{-1}$cm$^{-2}$sr$^{-1}$$A$$^{-1}$ in agreement with extragalactic flux predictions and a near-ultraviolet isotropic intensity of 378$\pm$45 photons s$^{-1}$cm$^{-2}$sr$^{-1}$$A$$^{-1}$ corresponding to twice the predicted flux.

astro-ph.GA↗

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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arXiv2022

The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope -- Data Release 3

An incremental version of the fourth catalog of active galactic nuclei (AGNs) detected by the Fermi-Large Area Telescope is presented. This version (4LAC-DR3) derives from the third data release of the 4FGL catalog based on 12 years of E>50 MeV gamma-ray data, where the spectral parameters, spectral energy distributions (SEDs), yearly light curves, and associations have been updated for all sources. The new reported AGNs include 587 blazar candidates and four radio galaxies. We describe the properties of the new sample and outline changes affecting the previously published one. We also introduce two new parameters in this release, namely the peak energy of the SED high-energy component and the corresponding flux. These parameters allow an assessment of the Compton dominance, the ratio of the Inverse-Compton to the synchrotron peak luminosities, without relying on X-ray data.

astro-ph.HE↗

arXiv2022

Incremental Fermi Large Area Telescope Fourth Source Catalog

We present an incremental version (4FGL-DR3, for Data Release 3) of the fourth Fermi-LAT catalog of gamma-ray sources. Based on the first twelve years of science data in the energy range from 50 MeV to 1 TeV, it contains 6658 sources. The analysis improves on that used for the 4FGL catalog over eight years of data: more sources are fit with curved spectra, we introduce a more robust spectral parameterization for pulsars, and we extend the spectral points to 1 TeV. The spectral parameters, spectral energy distributions, and associations are updated for all sources. Light curves are rebuilt for all sources with 1 yr intervals (not 2 month intervals). Among the 5064 original 4FGL sources, 16 were deleted, 112 are formally below the detection threshold over 12 yr (but are kept in the list), while 74 are newly associated, 10 have an improved association, and seven associations were withdrawn. Pulsars are split explicitly between young and millisecond pulsars. Pulsars and binaries newly detected in LAT sources, as well as more than 100 newly classified blazars, are reported. We add three extended sources and 1607 new point sources, mostly just above the detection threshold, among which eight are considered identified, and 699 have a plausible counterpart at other wavelengths. We discuss degree-scale residuals to the global sky model and clusters of soft unassociated point sources close to the Galactic plane, which are possibly related to limitations of the interstellar emission model and missing extended sources.

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arXiv2022

Characterization of the GeV emission from the Kepler supernova remnant

The Kepler supernova remnant (SNR) is the only historic supernova remnant lacking a detection at GeV and TeV energies which probe particle acceleration. A recent analysis of Fermi-LAT data reported a likely GeV gamma-ray candidate in the direction of the SNR. Using approximately the same dataset but with an optimized analysis configuration, we confirm the gamma-ray candidate to a solid $>6\sigma$ detection and report a spectral index of $2.14 \pm 0.12_{\rm stat} \pm 0.15_{\rm syst}$ for an energy flux above 100 MeV of $(3.1 \pm 0.6_{\rm stat} \pm 0.3_{\rm syst}) \times 10^{-12}$ erg~cm$^{-2}$~s$^{-1}$. The gamma-ray excess is not significantly extended and is fully compatible with the radio, infrared or X-ray spatial distribution of the SNR. We successfully characterized this multi-wavelength emission with a model in which accelerated particles interact with the dense circumstellar material in the North-West portion of the SNR and radiate GeV gamma-rays through $\pi^{o}$ decay. The X-ray synchrotron and inverse-Compton (IC) emission mostly stem from the fast shocks in the southern regions with a magnetic field B$\sim$100 $\mu$G or higher. Depending on the exact magnetic field amplitude, the TeV emission could arise from either the South region (IC dominated) or the interaction region ($\pi^{o}$ decay dominated).

astro-ph.HE↗

arXiv2020

High-energy gamma-ray study of the dynamically young SNR G150.3+4.5

The supernova remnant (SNR) G150.3+4.5 was recently discovered in the radio band; it exhibits a shell-like morphology with an angular size of $\sim 3^{\circ}$, suggesting either an old or a nearby SNR. Extended $\gamma$-ray emission spatially coincident with the SNR was reported in the Fermi Galactic Extended Source Catalog, with a power-law spectral index of $\Gamma$ = 1.91 $\pm$ 0.09. Studying particle acceleration in SNRs through their $\gamma$-ray emission is of primary concern to assess the nature of accelerated particles and the maximum energy they can reach. Using more than ten years of Fermi-LAT data, we investigate the morphological and spectral properties of the SNR G150.3+4.5 from 300 MeV to 3 TeV. We use the latest releases of the Fermi-LAT catalog, the instrument response functions and the Galactic and isotropic diffuse emissions. We use ROSAT all-sky survey data to assess any thermal and nonthermal X-ray emission, and we derive minimum and maximum distance to G150.3+4.5. We describe the $\gamma$-ray emission of G150.3+4.5 by an extended component which is found to be spatially coincident with the radio SNR. The spectrum is hard and the detection of photons up to hundreds of GeV points towards an emission from a dynamically young SNR. The lack of X-ray emission gives a tight constraint on the ambient density $n_0 \leq 3.6 \times 10^{-3}$ cm$^{-3}$. Since G150.3+4.5 is not reported as a historical SNR, we impose a lower limit on its age of $t$ = 1 kyr. We estimate its distance to be between 0.7 and 4.5 kpc. We find that G150.3+4.5 is spectrally similar to other dynamically young and shell-type SNRs, such as RX J1713.7$-$3946 or Vela Junior. The broadband nonthermal emission is explained with a leptonic scenario, implying a downstream magnetic field of $B = 5$ $\mu$G and acceleration of particles up to few TeV energies.

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arXiv2019

A novel method for component separation of extended sources in X-ray astronomy

In high-energy astronomy, spectro-imaging instruments such as X-ray detectors allow investigation of the spatial and spectral properties of extended sources including galaxy clusters, galaxies, diffuse interstellar medium, supernova remnants and pulsar wind nebulae. In these sources, each physical component possesses a different spatial and spectral signature, but the components are entangled. Extracting the intrinsic spatial and spectral information of the individual components from this data is a challenging task. Current analysis methods do not fully exploit the 2D-1D (x,y,E) nature of the data, as the spatial and spectral information are considered separately. Here we investigate the application of a Blind Source Separation algorithm that jointly exploits the spectral and spatial signatures of each component in order to disentangle them. We explore the capabilities of a new BSS method (General Morphological Component Analysis; GMCA), initially developed to extract an image of the Cosmic Microwave Background from Planck data, in an X-ray context. The performance of GMCA on X-ray data is tested using Monte-Carlo simulations of supernova remnant toy models, designed to represent typical science cases. We find that GMCA is able to separate highly entangled components in X-ray data even in high contrast scenarios, and can extract with high accuracy the spectrum and map of each physical component. A modification is proposed to improve the spectral fidelity in the case of strongly overlapping spatial components, and we investigate a resampling method to derive realistic uncertainties associated to the results of the algorithm. Applying the modified algorithm to the deep Chandra observations of Cassiopeia A, we are able to produce detailed maps of the synchrotron emission at low energies (0.6-2.2 keV), and of the red/blue shifted distributions of a number of elements including Si and Fe K.

astro-ph.HE↗

arXiv2018

Spatially resolved broad-band synchrotron emission from the non-thermal limbs of SN1006

We present ~400ks NuSTAR observations of the northeast (NE) and southwest (SW) non-thermal limbs of the Galactic SNR SN1006. We discovered three sources with X-ray emission detected at >50keV. Two of them are identified as background AGN. We extract the NuSTAR spectra from a few regions along the non-thermal limbs and jointly analyze them with the XMM-Newton spectra and the radio data. The broad-band radio/X-ray spectra can be well described with a synchrotron emission model from a single population of CR electrons with a power law energy distribution and an exponential cutoff. The power law index of the electron particle distribution function (PDF) is ~1.88-1.95 for both the NE and SW limbs, and we do not find significant evidence for a variation of this index at different energy (curvature). There are significant spatial variations of the synchrotron emission parameters. The highest energy electrons are accelerated in regions with the lowest expansion velocity, which is opposite to what has been found in the Tycho's SNR. In addition to a gradual steepening of synchrotron emission from the center of the non-thermal limbs to larger azimuthal angles, we also find that both the emission spectrum and the PDF are significantly flatter in three regions in the SW limb where the shock encounters higher density ambient medium. The NE limb also shows significantly higher cutoff energy in the PDF than the SW limb. By comparing with the roughly symmetric TeV emission and largely asymmetric GeV emission from the two non-thermal limbs, we conclude that the asymmetry in the ambient medium and magnetic fields may have largely modified the acceleration and emission of CR leptons.

astro-ph.HE↗

arXiv2018

The first catalog of Fermi-LAT sources below 100 MeV

We present the first Fermi Large Area Telescope (LAT) low energy catalog (1FLE) of sources detected in the energy range 30 - 100 MeV. The COMPTEL telescope detected sources below 30 MeV, while catalogs released by the Fermi-LAT and EGRET collaborations use energies above 100 MeV. We create a list of sources detected in the energy range between 30 and 100 MeV, which closes a gap of point source analysis between the COMPTEL catalog and the Fermi-LAT catalogs. One of the main challenges in the analysis of point sources is the construction of the background diffuse emission model. In our analysis, we use a background-independent method to search for point-like sources based on a wavelet transform implemented in the PGWave code. The 1FLE contains 198 sources detected above 3 $\sigma$ significance with eight years and nine months of the Fermi-LAT data. For 187 sources in the 1FLE catalog we have found an association in the Fermi-LAT 3FGL catalog: 148 are extragalactic, 22 are Galactic, and 17 are unclassified in the 3FGL. The ratio of the number of flat spectrum radio quasars (FSRQ) to BL Lacertae (BL Lacs) in 1FLE is 3 to 1, which can be compared with an approximately 1 to 1 ratio for the 3FGL or a 1 to 6 ratio for 3FHL. The higher ratio of the FSRQs in the 1FLE is expected due to generally softer spectra of FSRQs relative to BL Lacs. Most BL Lacs in 1FLE are of low-synchrotron peaked blazar type (18 out of 31), which have softer spectra and higher redshifts than BL Lacs on average. Correspondingly, we find that the average redshift of the BL Lacs in 1FLE is higher than in 3FGL or 3FHL. There are 11 sources that do not have associations in the 3FGL. Most of the unassociated sources either come from regions of bright diffuse emission or have several known 3FGL sources in the vicinity, which can lead to source confusion. The remaining unassociated sources have significance less than 4 $\sigma$.

astro-ph.HE↗

arXiv2016

Measurement of the X-ray proper motion in the south-east rim of RX J1713.7-3946

We report on the first proper motion measurement in the supernova remnant RX J1713.7-3946 using the XMM-Newton X-ray telescope on a 13 year time interval. This expansion measurement is carried out in the south-east region of the remnant where two sharp filament structures are observed. For the outermost filament, the proper motion is $0.73\pm0.047_{\rm stat} \pm 0.069_{\rm syst}$ arcsec yr$^{-1}$ which is equivalent to a shock speed of 3500 km s$^{-1}$ at a distance of 1 kpc. In contrast with the bright north-west region where the shock is interacting with the border of the cavity, the shock in the south-east region is probably expanding in the original ambient medium carved by the progenitor and can be used to derive the current density at the shock and the age of the remnant. In the case where the shock is evolving in a wind profile ($\rho \propto r^{-s}$, s=2) or in a uniform medium (s=0), we estimate an age of 2300 yrs and 1800 yrs respectively for an ejecta power-law index n=9. The specific case of n=7 and s=0, yields an age of 1550 yrs which would reconcile RX J1713.7-3946 with the historical records of SN 393. In all scenarios, we derive similar upstream densities of the order of 0.01 cm$^{-3}$, compatible with the lack of thermal X-rays from the shocked ambient medium.

astro-ph.HE↗

arXiv2015

The 1st Fermi Lat Supernova Remnant Catalog

To uniformly determine the properties of supernova remnants (SNRs) at high energies, we have developed the first systematic survey at energies from 1 to 100 GeV using data from the Fermi Large Area Telescope. Based on the spatial overlap of sources detected at GeV energies with SNRs known from radio surveys, we classify 30 sources as likely GeV SNRs. We also report 14 marginal associations and 245 flux upper limits. A mock catalog in which the positions of known remnants are scrambled in Galactic longitude, allows us to determine an upper limit of 22% on the number of GeV candidates falsely identified as SNRs. We have also developed a method to estimate spectral and spatial systematic errors arising from the diffuse interstellar emission model, a key component of all Galactic Fermi LAT analyses. By studying remnants uniformly in aggregate, we measure the GeV properties common to these objects and provide a crucial context for the detailed modeling of individual SNRs. Combining our GeV results with multiwavelength (MW) data, including radio, X-ray, and TeV, demonstrates the need for improvements to previously sufficient, simple models describing the GeV and radio emission from these objects. We model the GeV and MW emission from SNRs in aggregate to constrain their maximal contribution to observed Galactic cosmic rays.

astro-ph.HE↗