(Aims.) SNR RX J1713.7-3946 is perhaps one of the best observed shell-type supernova remnants with emissions dominated by energetic particles accelerated near the shock front. The nature of the TeV emission, however, is an issue still open to investigation. (Methods.) We carry out a systematic study of four lepton models for the TeV emission with the Markov chain Monte Carlo method. (Results.) It is shown that current data already give good constraints on the model parameters. Two commonly used parametric models do not appear to fit the observed radio, X-ray, and gamma-ray spectra. Models motivated by diffusive shock acceleration and by stochastic acceleration by compressive waves in the shock downstream give comparably good fits. The former has a sharper spectral cutoff in the hard X-ray band than the latter. Future observations with the HXMT and NuSTAR may distinguish these two models.
Recent discovery of the X-ray neutral iron line (Fe I Kαat 6.40 keV) around several supernova remnants (SNRs) show that MeV cosmic-ray (CR) protons are distributed around the SNRs and are interacting with neutral gas there. We propose that these MeV CRs are the ones that have been accelerated at the SNRs together with GeV-TeV CRs. In our analytical model, the MeV CRs are still confined in the SNR when the SNR collides with molecular clouds. After the collision, the MeV CRs leak into the clouds and produce the neutral iron line emissions. On the other hand, GeV-TeV CRs had already escaped from …
In our model, the acceleration and propagation of particles from the Bohm-like diffusion region inside the SNR to the Galactic diffusion region outside the SNR are described through nonlinear diffusive shock acceleration (NLDSA). The main content of our NLDSA model is to solve the hydrodynamic equations numerically for gas density, gas velocity, gas pressure as well as the equation for the quasi-isotropic particle momentum distribution. The consequent multi-band non-thermal emission is from two different regions, namely the acceleration region and the escaping region. Our model is capable of e…
Shock acceleration by the shells of supernova remnants (SNRs) has been hypothesized to be the mechanism that produces the bulk of Galactic Cosmic Rays, possibly up to PeV energies. Some SNRs have been shown to accelerate cosmic rays to TeV energies and above. But which SNRs are indeed efficient accelerators of protons and nuclei? And what is the maximum energy up to which they can efficiently accelerate particles? Measurements of non-thermal emission, especially in the gamma-ray regime, are essential to answer these questions. The High-Altitude Water Cherenkov (HAWC) observatory, surveying the…
G326.3$-$1.8 (also known as MSH 15$-$56) has been detected in radio as a middle-aged composite supernova remnant (SNR) consisting of an SNR shell and a pulsar wind nebula (PWN), which has been crushed by the SNR's reverse shock. Previous $γ$-ray studies of SNR G326.3$-$1.8 revealed bright and extended emission with uncertain origin. Understanding the nature of the $γ$-ray emission allows probing the population of high-energy particles (leptons or hadrons) but can be challenging for sources of small angular extent. With the recent $\textit{Fermi}$ Large Area Telescope data release Pass 8, we in…
Resolving the origin of the unidentified TeV source HESS J1626-490 as a relic of the ancient cosmic-ray factory SNR G335.2+0.1
Ritsumeikan University（立命馆大学）；Research Organization of Science and Technology, Ritsumeikan University（立命馆大学科学技术研究院）；Kyoto University（京都大学）；Yukawa Institute for Theoretical Physics, Kyoto University（京都大学汤川理论物理研究所）；Tohoku University（东北大学）；Gifu University（岐阜大学）；University of Miyazaki（宫崎大学）；Konan University（神户女学院大学）
The Gamma Ray Origin in RXJ0852.0-4622 Quantifying the Hadronic and Leptonic Components: Further Evidence for the Cosmic Ray Acceleration in Young Shell-type SNRs
The synchrotron radiation from secondary electrons and positrons (SEPs) generated by hadronic interactions in the shock of supernova remnant (SNR) could be a distinct evidence of cosmic ray (CR) production in SNR shocks. Here we provide a method where the observed gamma-ray flux from SNRs, created by pion decays, is directly used to derive the SEP distribution and hence the synchrotron spectrum. We apply the method to three gamma-ray bright SNRs. In the young SNR RX J1713.7-3946, if the observed GeV-TeV gamma-rays are of hadronic origin and the magnetic field in the SNR shock is $B\gtrsim 0.5$…
The Supernova Remnant (SNR) HESS J1731-347 displays strong non-thermal TeV gamma-ray and X-ray emission, thus the object is at present time accelerating particles to very high energies. A distinctive feature of this young SNR is the nearby (~30 pc in projection) extended source HESS J1729-345, which is currently unidentified but is in spatial projection coinciding with known molecular clouds (MC). We model the SNR evolution to explore if the TeV emission from HESS J1729-345 can be explained as emission from runaway hadronic cosmic rays (CRs) that are illuminating these MCs. The observational d…
The supernova remnant (SNR) HESS J1731-347 is a young SNR which displays a non-thermal X-ray and TeV shell structure. A molecular cloud at a distance of 3.2 kpc is spatially coincident with the western part of the SNR, and it is likely hit by the SNR. The X-ray emission from this part of the shell is much lower than from the rest of the SNR. Moreover, a compact GeV emission region coincident with the cloud has been detected with a soft spectrum. These observations seem to imply a shock-cloud collision scenario at this area, where the stalled shock can no longer accelerate super-TeV electrons o…
Context: The supernova remnant (SNR) G35.6-0.4 shows a non-thermal radio shell, however, no γ-ray or X-ray counterparts have been found for it thus far. One TeV source, HESS J1858+020, was found near the SNR and this source is spatially associated with some clouds at 3.6 kpc. Aims: To attain a better understanding of the origin of HESS J1858+020, we further investigate the association between SNR cosmic rays (CRs) and the clouds through the Fermi-LAT analysis and hadronic modeling. Methods: We performed the Fermi-LAT analysis to explore the GeV emission in and around the SNR. We explored the S…
We investigate the interstellar medium (ISM) towards seven TeV gamma-ray sources thought to be pulsar wind nebulae (PWNe) using Mopra molecular line observations at 7mm [CS(1-0), SiO(1-0,v=0)], Nanten CO(1-0) data and the SGPS/GASS HI survey. We have discovered several dense molecular clouds co-located to these TeV gamma-ray sources , which allows us to search for cosmic-rays (CRs) coming from progenitor SNRs or, potentially, from PWNe. We notably found SiO(1-0,v=0) emission towards HESS J1809-193, highlighting possible interaction between the adjacent supernova remnant SNR G011.0-0.0 and the …
The Galactic TeV $γ$-ray source HESS$\,$J1804$-$216 is currently an unidentified source. In an attempt to unveil its origin, we present here the most detailed study of interstellar gas using data from the Mopra Southern Galactic Plane CO Survey, 7 and 12$\,$mm wavelength Mopra surveys and Southern Galactic Plane Survey of HI. Several components of atomic and molecular gas are found to overlap HESS$\,$J1804$-$216 at various velocities along the line of sight. The CS(1-0) emission clumps confirm the presence of dense gas. Both correlation and anti-correlation between the gas and TeV $γ$-ray emis…
The emission mechanism for hard $γ$-ray spectra from supernova remnants (SNRs) is still a matter of debate. Recent multi-wavelength observations of TeV source HESS J1912+101 show that it is associated with an SNR with an age of $\sim 100$ kyrs, making it unlikely produce the TeV $γ$-ray emission via leptonic processes. We analyzed Fermi observations of it and found an extended source with a hard spectrum. HESS J1912+101 may represent a peculiar stage of SNR evolution that dominates the acceleration of TeV cosmic rays. By fitting the multi-wavelength spectra of 13 SNRs with hard GeV $γ$-ray spe…
A detailed study of the interstellar protons toward the TeV $γ$-ray SNR RX J0852.0$-$4622 (G266.2$-$1.2, Vela Jr.); a third case of the $γ$-rays and ISM spatial correspondence
我们提出了一个新的分析的星际质子对TeV $γ$射线SNR RX J0852.0 $-$ 4622（G266.2 $-$ 1.2，Vela Jr.）。我们使用NANTEN 2 $^{12}$ CO（$J$ = 1-0）和ATCA & Parkes HI数据集，以推导出与SNR的TeV $γ$射线壳层相关的分子和原子气体。我们发现，原子气体的速度范围从$V_\mathrm{LSR}$ = $-4$ km s $^{-1}$到50 km s $^{-1}$或60 km s $^{-1}$与整个SNR，而分子气体与SNR的有限部分。大的速度色散的HI归因于膨胀运动的几个HI壳重叠向SNR，但不是由于银河系的旋转。相关HI和分子气体的总质量估计分别为$\sim2.5 \times 10^4 $ $M_{\odot}$和$\sim10^3$ $M_{\odot}$。与H.E.S.S. TeV $γ$ -射线表明星际质子的平均密度约为100 cm $^{-3}$，并与TeV $γ$ -射线显示出良好的空间对应关系。总宇宙射线质子能量估计为强子$γ$ -射线产生的$\sim10^{48}$ erg，由于星际质子对SNR体积的填充因子很小，这可能仍然被低估了几个因子。这一结果提出了第三种情况下，RX J1713.7 $-$ 3946和HESS J1731 $-$ 347，TeV $γ$ -射线和星…
We report the extended GeV $γ$-ray emission that spatially associated with the high Galactic latitude supernova remnant (SNR) candidate - Calvera's SNR with the Pass 8 data recorded by the {\em Fermi} Large Area Telescope. The $γ$-ray spectrum of Calvera's SNR between 100 MeV and 1 TeV shows an evident ($\sim$ 3.4$σ$) spectral curvature at several tens of GeV. The multi-wavelength data can be fitted with either a leptonic model or a hadronic one. However, the leptonic model exhibits the inconsistent between the flat radio spectrum and the hard GeV $γ$-ray spectrum of Calvera's SNR. For the had…
The local sources, such as Geminga SNR, may play important role for the anomaly of proton, electron and anisotropy in the past works. In fact, there exists twelve SNRs around solar system within $1$ kpc. One question is that can other SNRs also possibly contribute the spectra of nuclei and electron and explain the special structure of anisotropy? In this work, under the spatial-dependent propagation, we systematically study the contribution of all local SNRs within 1 kpc around solar to the spectra of nuclei and electron, as well as the energy dependence of anisotropy. As a result, only Geming…
HESS J1804-216 is one of the brightest yet most mysterious TeV gamma-ray sources discovered to date. Previous arc-minute scale studies of the interstellar medium (ISM) surrounding this TeV gamma-ray source revealed HESS J1804-216 is likely powered by a mature supernova remnant (SNR) or pulsar, hence its origin remains uncertain. In this paper, we focus on the diffusive escape of cosmic-ray protons from potential SNR accelerators. These cosmic rays interact with the ISM to produce TeV gamma-rays. We utilise the isotropic diffusion equation solution for particles escaping from a shell, to model …
Supernova remnants (SNRs) have long been hypothesized as the main source of Galactic Cosmic Rays up to PeV energies. Some of them have indeed been shown to accelerate protons to TeV energies and above. But which of them are indeed efficient accelerators of protons and nuclei? And up to which energies can they accelerate these particles? Measurements of non-thermal emission, especially in the X-ray and gamma-ray regimes, are essential to answer these questions. The High-Altitude Water Cherenkov (HAWC) observatory, surveying the northern TeV gamma-ray sky, is currently the most sensitive wide fi…
We consider acceleration of leptons up to GeV-TeV energies in the bow shock wind nebula of PSR J0437-4715 and their subsequent diffusion through the interstellar magnetic fields. The leptons accelerated at the pulsar wind termination surface are injected into re-acceleration in colliding shock flows. Modelled spectra of synchrotron emission from the accelerated electrons and positrons are consistent with the far-ultraviolet and X-ray observations of the nebula carried out with the Hubble Space Telescope and Chandra X-ray Observatory. These observations are employed to constrain the absolute fl…
The existence of a "knee" at energy ~1 PeV in the cosmic-ray spectrum suggests the presence of Galactic PeV proton accelerators called "PeVatrons". Supernova Remnant (SNR) G106.3+2.7 is a prime candidate for one of these. The recent detection of very high energy (0.1-100 TeV) gamma rays from G106.3+2.7 may be explained either by the decay of neutral pions or inverse Compton scattering by relativistic electrons. We report an analysis of 12 years of Fermi-LAT gamma-ray data which shows that the GeV-TeV gamma-ray spectrum is much harder and requires a different total electron energy than the radi…
We present a detailed morphological study of TeV gamma rays, synchrotron radiation, and interstellar gas in the young Type Ia supernova remnant (SNR) RCW 86. We find that the interstellar atomic gas shows good spatial correlation with the gamma rays, indicating that the TeV gamma rays from RCW 86 are likely to be dominantly of hadronic origin. In contrast, the spatial correlation between the interstellar molecular cloud and the TeV gamma rays is poor in the southeastern shell of the SNR. We argue that this poor correlation can be attributed to the low-energy cosmic rays (~ 1 TeV) not penetrati…
A Comparative Study of TeV Gamma-Ray Sources with Various Objects
Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台）；State Key Laboratory of Radio Astronomy and Technology, Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台射电天文与技术重点实验室）；School of Astronomy & Space Science, Nanjing University（南京大学天文与空间科学学院）
Galactic cosmic rays (CRs) are believed to be accelerated at supernova remnant (SNR) shocks. In the hadronic scenario the TeV gamma-ray emission from SNRs originates from decaying pions that are produced in collisions of the interstellar gas and CRs. Using CR-magnetohydrodynamic simulations, we show that magnetic obliquity-dependent shock acceleration is able to reproduce the observed TeV gamma-ray morphology of SNRs such as Vela Jr. and SN1006 solely by varying the magnetic morphology. This implies that gamma-ray bright regions result from quasi-parallel shocks (i.e., when the shock propagate…
In recent years some efforts have been made to identify active sources capable of accelerating particles up to $10^{15}$ eV, known as PeVatrons. Measurements of TeV ($10^{12}$ eV) gamma-rays from supernova remnants (SNRs) have shown that efficient particle acceleration can occur in SNR diffusive shocks. In this paper, we obtain the contribution to the high energy and very-high-energy gamma-ray (VHE, $E > 100$ GeV) emission due to cosmic-ray acceleration from SNR G57.2+0.8 hosting the Soft Gamma Repeater (SGR) J1935+2154 with the use of the GALPROP code. To do so, we take into account the SNR +…
