This paper presents a comprehensive analysis of the Galactic supernova remnant (SNR) Kes 17 (G304.6+0.1). The focus is on its radio synchrotron emission, its surroundings, and the factors ...contributing to the observed
γ
rays. The fitting to the first obtained integrated radio continuum spectrum spanning from 88 to 8800 MHz yields an index
α
= −0.488 ± 0.023 (
S
ν
∝
ν
α
), which is indicative of a linear particle acceleration process at the shock front of the remnant. Accounting for the SNR radio shell size, the distribution of atomic hydrogen (
n
H
~ 10 cm
−3
), and assuming that the SNR is in the Sedov-Taylor stage of its evolution, we estimate that the remnant age is roughly 11 kyr. This result falls at the lower end of the wide range (~2–64 kyr) derived from previous analyses of the diffuse X-ray emission interior to the remnant. Furthermore, we used
12
CO and
13
CO (
J
= 1–0) emission line data as a proxy for molecular hydrogen and provide the first evidence that the eastern shell of Kes 17 is engulfing a molecular enhancement in the surrounding gas, with an average mass 4.2 × 10
4
M
⊙
and density
n
~ 300 cm
−3
. Towards the western boundary of Kes 17, no signatures of carbon monoxide emissions are detected above 3
σ
, despite previously reported infrared observations that revealed shocked molecular gas at this location. This suggests the existence of a CO-dark interacting molecular gas, a phenomenon also recorded in other Galactic SNRs (e.g. CTB 37A and RX J1713.7–3946) that reveals itself both in the infrared and
γ
-ray domains. Additionally, by analysing ~14.5 yr of continuously collected data from the Large Area Telescope on board the satellite
Fermi
, we determined that the best-fit power-law photon index for the 0.3–300 GeV
γ
-ray emission from the Kes 17 region is Γ = 2.39 ± 0.04
−0.114
+0.063
(±stat ±syst), in agreement with prior studies. The energy flux is (2.98 ± 0.14) × 10
−11
erg cm
−2
s
−1
, implying a luminosity (2.22 ± 0.45) × 10
35
erg s
−1
at ~8 kpc. Finally, we successfully modelled the multiwavelength spectral energy distribution by incorporating the radio-synchrotron spectrum and the new measurements of GeV
γ
-rays. Our analysis indicates that the observed
γ
-ray flux most likely originates from the interaction of Kes 17 with a western dark CO zone with a proton density
n
p
~ 400 cm
−3
.
The distribution of the very-high-energy diffuse emission in the inner 200 pc measured by H.E.S.S. indicates the existence of a pronounced cosmic-ray (CR) gradient peaking on the Galactic center ...(GC). Previous studies have shown that these data are consistent with a scenario in which the CRs are diffused away from a stationary source at the GC. We previously showed that, taking the 3D gas distribution and a realistic distribution of supernova explosions into account, CRs accelerated in supernova remnants should account for a large fraction of the GC CRs observed by H.E.S.S.; but the model did not fully reproduce the apparent over-density in the inner 30 pc. In this work, we study the time-energy dependent cosmic rays escape from the remnant that is expected to occur when the shock wave decelerates in the surrounding medium. We show that the resulting CR distribution follows the quasi-stationary profile observed by H.E.S.S. more closely. The main signature is that the energy-dependent escape creates a strong dependency of the morphology of the
γ
-ray emission with the energy. The existence of this energy dependency should be observable by the Cherenkov Telescope Array.
Abstract
The High Energy Stereoscopic System (H.E.S.S.) collaboration revealed the presence of a very high energy (VHE) diffuse emission in the inner 100 pc of the Galaxy in close correlation with ...the central molecular zone (CMZ). Recently, they deduced from this emission a cosmic ray (CR) overdensity in the region with a local peak towards the Galactic Centre (GC) and proposed a diffusive scenario with a stationary source at the GC to explain it. However, the high supernovae (SN) rate in the GC must also create a sustained CR injection in the region via the shocks produced at the time of their explosion. Considering a typical diffusion coefficient close to the interstellar medium (ISM) value yields a diffuse escape time much lower than the recurrence time between each SN explosion, showing that a steady-state model will fail to reproduce the data. This work aims to study the impact of the spatial and temporal distribution of SNs in the CMZ on the VHE emission morphology and spectrum: we build a 3D model of VHE CR injection and diffusive propagation with a realistic gas distribution. We show that a peaked γ-ray profile towards the GC can be obtained using realistic SN spatial distribution taking into account the central massive star cluster. We conclude that the contribution of SNs cannot be neglected, in particular at large longitudes; however, an additional CR injection at the GC is required to reproduce the very central excess.
Aims.
We aim to search for a hidden leptonic accelerator, such as a high-
Ė
pulsar, associated with the unidentified TeV object HESS J1702−420A.
Methods.
We carried out a 72 ks X-ray observation with ...the
XMM-Newton
satellite and analyzed the resulting data jointly with the publicly available HESS spectral energy distribution (SED) results to derive constraints on the leptonic contribution to the TeV emission of HESS J1702−420A. A set of scripts dedicated to the multi-wavelength modeling of X-ray and
γ
-ray data, based on
Gammapy
,
Naima
, and
Xspec
, has been developed in the context of this work and made publicly available along with this paper.
Results.
No object clearly associated with HESS J1702−420A was found in the
XMM-Newton
data. After excluding the unidentified object Suzaku src B as a possible X-ray counterpart and classifying it as a new cataclysmic variable source candidate, we derived strict upper limits on the level of diffuse X-ray emission in the HESS J1702−420A region:
F
(2 − 10 keV)≲5.4 × 10
−5
keV cm
−2
s
−1
at 2
σ
(≈95.5%) confidence level. A tight constraint on the magnetic field was derived, under a one-zone leptonic scenario, by jointly fitting the
XMM-Newton
spectra and the HESS SED:
B
≲ 1.45 μG at 2
σ
level. We additionally report the serendipitous discovery of a new extended X-ray source with a hard spectral index of 1.99 ± 0.45, named XMMU J170147.3−421407 which is likely Galactic. Its classification as a high-speed runaway pulsar wind nebula (PWN), possibly associated with HESS J1702−420A, is not obvious but cannot be ruled out either.
Conclusions.
The hard
γ
-ray object HESS J1702−420A remains unidentified, but the absence of a clear X-ray counterpart strongly challenges simple leptonic scenarios. The only remaining possible leptonic counterpart for HESS J1702−420A appears to be a newly discovered X-ray source with extended morphology and hard spectral index, which may be a PWN powered by a high-speed runaway pulsar.
We experimentally demonstrate 140-THz bandwidth (at −20 dB) supercontinuum generation in a 10 cm-long all-normal dispersion step-index tellurite fiber pumped by a turn-key femtosecond fiber laser ...emitting at 2.11μm at a repetition rate of 19 MHz. The soliton self-frequency shifted thulium-doped fiber mode-locked laser emits initial transform-limited pulses, with 85-fs pulse duration, that are subsequently quasi-linearly chirped (over more than 50 THz) during the above nJ-level nonlinear propagation. Moreover, we numerically demonstrate the possible pulse compression down to 12 fs by means of additional linear propagation in a standard step-index fluoride fiber with anomalous dispersion.
•Octave-spanning coherent supercontinuum generation in step-index tellurite fibers.•Experimental demonstration based on 2 μm fiber laser pumping.•Numerical simulations confirm possible fiber-based few-cycle pulse compression.
In semiarid conditions, feed is often scarce and variable with underfeeding being common; these factors can potentially induce fertility reductions in both sexes. Sexually active bucks are able to ...very efficiently fertilize out-of-season goats, but we do not know whether underfeeding would reduce the ability of bucks to fertilize goats during these periods. Two experiments were conducted to determine (i) testicular size and change of odor intensity of undernourished bucks exposed to long days and (ii) the ability of these bucks to stimulate reproductive activity in seasonally anestrous goats. In experiment 1, bucks (n = 7) were fed 1.5 times the normal maintenance requirements from September to May and formed the well-fed group. Another group of bucks (n = 7) were fed 0.5 times the maintenance requirements and formed the undernourished group. All bucks were subjected to artificially long days from 1 November to 15 January; this period was followed by a natural photoperiod until 30 May. Body weight, scrotal circumference and male odor intensity changes were determined every 2 weeks. In experiment 2, two groups of female goats (n = 26 each) were exposed to well-fed (n = 2) or undernourished bucks (n = 2) on 31 March. Ovulations and pregnancy rates were determined by transrectal ultrasonography. In experiment 1, a treatment by time interaction was detected for BW, scrotal circumference and odor intensity changes (P < 0.001). The BWs of well-fed bucks were greater than those of the undernourished bucks from October to May (P < 0.01), as were the scrotal circumferences from December to March (P < 0.05) and odor intensities from February to May (P < 0.05). In experiment 2, the proportions of females that ovulated at least once (100% v. 96%) or those that were diagnosed as pregnant (85% v. 77%; P > 0.05) did not differ significantly between the goats exposed to well-fed or undernourished bucks. The interval between the introduction of bucks and the onset of estrous behavior was shorter in goats exposed to well-fed bucks compared to the interval for those goats exposed to undernourished bucks (2.5 ± 0.2 v. 9.5 ± 0.6 days; P < 0.05). We conclude that undernourishment reduces the testicular size and odor intensity responses in bucks exposed to long days, but that undernourished bucks are still able to stimulate reproductive activity in seasonally anestrous goats, as is also the case for well-fed bucks.
We report on far-infrared filament-induced supercontinuum obtained with three chalcogenide glasses. The introduction of more polarizable elements (Se instead of S and Te instead of S and Se) into the ...glasses increases their non-linearity and transmission window and also shifts gradually corresponding zero-dispersion wavelength in the infrared region. Overall chalcogenide glasses were pumped with 65-fs pulses at the optimal wavelength with respect to supercontinuum extension. An infrared spanning reaching the 16-µm threshold is obtained.
We experimentally demonstrate 140-THz bandwidth (at −20 dB) supercontinuum generation in a 10 cm-long all-normal dispersion step-index tellurite fiber pumped by a turn-key femtosecond fiber laser ...emitting at at a repetition rate of 19 MHz. The soliton self-frequency shifted thulium-doped fiber mode-locked laser emits initial transform-limited pulses, with 85-fs pulse duration, that are subsequently quasi-linearly chirped (over more than 50 THz) during the above nJ-level nonlinear propagation. Moreover, we numerically demonstrate the possible pulse compression down to 12 fs by means of additional linear propagation in a standard step-index fluoride fiber with anomalous dispersion.
Tailored tellurite-glasses possess excellent thermo-viscous ability and linear/nonlinear optical properties. Here, bringing together the merits of these materials with fiber optic technology, we ...report on the first tellurite-based core-clad dual-electrode composite fiber made by direct, homothetic preform-to-fiber thermal co-drawing. The rheological and optical properties of the selected glasses allow both to regulate the metallic melting flow and to manage the refractive index core/clad waveguide profile. We demonstrate the electrical continuity of the electrodes over meters of fiber. We believe the drawing of architectures merging electrical and optical features in a unique elongated wave-guiding structure will enable to develop new in-fiber functionalities based on hybrid electric/optic nonlinear effects.
PDF
