110 research outputs found
Fermi-LAT Observations of Supernova Remnant Kesteven 79
In this paper we report on the detection of -ray emission coincident
with the Galactic supernova remnant Kesteven 79 (Kes 79). We analysed
approximately 52 months of data obtained with the Large Area Telescope (LAT) on
board the Fermi Gamma-ray Space Telescope. Kes 79 is thought to be interacting
with adjacent molecular clouds based on the presence of strong CO J = 1
0 and HCO J = 1 0 emission and the detection
of 1720 MHz line emission towards the east of the remnant. Acceleration of
cosmic rays is expected to occur at SNR shocks, and SNRs interacting with dense
molecular clouds provide a good testing ground for detecting and analysing the
production of -rays from the decay of into two -ray
photons. This analysis investigates -ray emission coincident with Kes
79, which has a detection significance of . Additionally we
present an investigation of the spatial and spectral characteristics of Kes 79
using multiple archival XMM-Newton observations of this remnant. We determine
the global X-ray properties of Kes 79 and estimate the ambient density across
the remnant. We also performed a similar analysis for Galactic SNR Kesteven 78
(Kes 78), but due to large uncertainties in the -ray background model,
no conclusion can be made about an excess of GeV -ray associated with
the remnant.Comment: Accepted by ApJ; 16 pages, 5 figures, 6 table
Asymmetries of Heavy Elements in the Young Supernova Remnant Cassiopeia A
Supernova remnants (SNRs) offer the means to study supernovae (SNe) long
after the original explosion and can provide a unique insight into the
mechanism that governs these energetic events. In this work, we examine the
morphologies of X-ray emission from different elements found in the youngest
known core-collapse (CC) SNR in the Milky Way, Cassiopeia A. The heaviest
elements exhibit the highest levels of asymmetry, which we relate to the
burning process that created the elements and their proximity to the center of
explosion. Our findings support recent model predictions that the material
closest to the source of explosion will reflect the asymmetries inherent to the
SN mechanism. Additionally, we find that the heaviest elements are moving more
directly opposed to the neutron star (NS) than the lighter elements. This
result is consistent with NS kicks arising from ejecta asymmetries.Comment: 12 pages, 4 figures, 2 tables Updated to include an analysis of
Emission Measure Maps (vs the, still-included, continuum-subtracted flux
maps), used as another proxy for mass maps. The results have not changed; the
emission measure maps also show increasing asymmetry with ejecta mass. (Now
matches the version published in ApJ. Vol 889 Issue 2 (2020) 144
The Age Evolution of the Radio Morphology of Supernova Remnants
Recent hydrodynamical models of supernova remnants (SNRs) demonstrate that
their evolution depends heavily on the inhomogeneities of the surrounding
medium. As SNRs expand, their morphologies are influenced by the non-uniform
and turbulent structure of their environments, as reflected in their radio
continuum emission. In this paper, we measure the asymmetries of 96 SNRs in
radio continuum images from three surveys of the Galactic plane and compare
these results to the SNRs' radii, which we use as a proxy for their age. We
find that larger (older) SNRs are more elliptical/elongated and more mirror
asymmetric than smaller (younger) SNRs, though the latter vary in their degrees
of asymmetry. This result suggests that SNR shells become more asymmetric as
they sweep up the interstellar medium (ISM), as predicted in hydrodynamical
models of SNRs expanding in a multi-phase or turbulent ISM.Comment: 16 pages, 5 figures, accepted by ApJ; sample expanded from 22 to 96
source
Multi-wavelength analysis of the Galactic supernova remnant MSH 11-61A
Due to its centrally bright X-ray morphology and limb brightened radio
profile, MSH 11-61A (G290.1-0.8) is classified as a mixed morphology supernova
remnant (SNR). H\textsc{i} and CO observations determined that the SNR is
interacting with molecular clouds found toward the north and southwest regions
of the remnant. In this paper we report on the detection of -ray
emission coincident with MSH 11-61A, using 70 months of data from the Large
Area Telescope on board the \textit{Fermi Gamma-ray Space Telescope}. To
investigate the origin of this emission, we perform broadband modelling of its
non-thermal emission considering both leptonic and hadronic cases and
concluding that the -ray emission is most likely hadronic in nature.
Additionally we present our analysis of a 111 ks archival \textit{Suzaku}
observation of this remnant. Our investigation shows that the X-ray emission
from MSH 11-61A arises from shock-heated ejecta with the bulk of the X-ray
emission arising from a recombining plasma, while the emission towards the east
arises from an ionising plasma.Comment: 12 Pages, 8 figures. Accepted for publication in the Astrophysical
Journa
Evidence of Particle Acceleration in the Superbubble 30 Doradus C with NuSTAR
We present evidence of diffuse, non-thermal X-ray emission from the
superbubble 30 Doradus C (30 Dor C) using hard X-ray images and spectra from
NuSTAR observations. For this analysis, we utilize data from a 200 ks targeted
observation of 30 Dor C as well as 2.8 Ms of serendipitous off-axis
observations from the monitoring of nearby SN 1987A. The complete shell of 30
Dor C is detected up to 20 keV, and the young supernova remnant MCSNR
J0536-6913 in the southeast of 30 Dor C is not detected above 8 keV.
Additionally, six point sources identified in previous Chandra and XMM-Newton
investigations have hard X-ray emission coincident with their locations. Joint
spectral fits to the NuSTAR and XMM-Newton spectra across the 30 Dor C shell
confirm the non-thermal nature of the diffuse emission. Given the best-fit
rolloff frequencies of the X-ray spectra, we find maximum electron energies of
70-110 TeV (assuming a B-field strength of 4G), suggesting 30 Dor C is
accelerating particles. Particles are either accelerated via diffusive shock
acceleration at locations where the shocks have not stalled behind the
H shell, or cosmic-rays are accelerated through repeated acceleration
of low-energy particles via turbulence and magnetohydrodynamic waves in the
bubble's interior.Comment: 14 pages, 8 figures, ApJ, in pres
High energy particles from young supernovae: gamma-ray and neutrino connections
Up to about one year after explosion, core-collapse supernovae ("young
supernovae," YSNe) are factories of high-energy neutrinos and gamma-rays as the
shock accelerated protons efficiently interact with the protons in the dense
circumstellar medium. We explore the detection prospects of secondary particles
from YSNe of Type IIn, II-P, II-L, and Ibc. Type IIn YSNe are found to produce
the largest flux of neutrinos and gamma-rays, followed by II-P YSNe. Fermi-LAT
and the Cherenkov Telescope Array (IceCube-Gen2) have the potential to detect
Type IIn YSNe up to ~Mpc (~Mpc), with the remaining YSNe Types being
detectable closer to Earth. We also find that YSNe may dominate the diffuse
neutrino background, especially between ~TeV and ~TeV, while they do
not constitute a dominant component to the isotropic gamma-ray background
observed by Fermi-LAT. At the same time, the IceCube high-energy starting
events and Fermi-LAT data already allow us to exclude a large fraction of the
model parameter space of YSNe otherwise inferred from multi-wavelength
electromagnetic observations of these transients.Comment: 36 pages, 12 figure
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