A TeV spectral break in the total flux of cosmic-ray electrons and positrons (CREs) at which the spectral power index softens from $\sim 3$ to $\sim 4$ has been observed by H.E.S.S. and recently confirmed by DAMPE with a high significance of $6.6~σ$. Such an observation is apparently inconsistent with the data from other experiments such as Fermi-LAT, AMS-02 and CALET. We perform a global analysis to the latest CRE data including Fermi-LAT, AMS-02, CALET, DAMPE and H.E.S.S. with energy scale uncertainties taken into account to improve the consistency between the data sets. The fit result strongly favors the existence of the break at $\sim 1$ TeV with an even higher statistical significance of $13.3~σ$. In view of the tentative CRE break, we revisit a number of models of nearby sources, such as a single generic Pulsar Wind Nebula (PWN), known multiple PWNe from the ATNF catalog, and their combinations with either an additional Dark Matter (DM) component or a Supernova Remnant (SNR). We show that the CRE break at $\sim 1$ TeV, together with the known CR positron excess points towards the possibility that the nearby sources should be highly charge asymmetric. Among the models under consideration, the one with a PWN plus SNR is most favored by the current data. The favoured distance and age of the PWN and SNR sources are both within $0.6$ kpc and around $10^{5}$ yr respectively. Possible candidate sources include PSR J0954-5430, Vela and Monogem ring, etc. We find that for the models under consideration, the additional DM component is either unnecessary, or predicts too much photons in tension with the H.E.S.S. data of $γ$-rays from the direction of the Galactic Center. We also show that the current measurement of the anisotropies in the arrival direction of the CRE can be useful in determining the property of the sources.
High energy cosmic ray electrons and positrons probe the local properties of our Galaxy. In fact, electromagnetic energy losses limit the typical propagation scale of GeV-TeV electrons and positrons to a few kpc. In the diffusion model, nearby and dominant sources may produce an observable dipole anisotropy in the cosmic ray fluxes. We present a detailed study on the role of anisotropies from nearby sources in the interpretation of the observed GeV-TeV cosmic ray electron and positrons fluxes. We compute predictions for the anisotropies from known astrophysical sources as supernova remnants an…
The rise in the cosmic-ray positron fraction measured by the PAMELA satellite is likely due to the presence of astrophysical sources of positrons, e.g. pulsars, on the kpc scale around the Earth. Nevertheless, assessing the properties of these sources from the positron data requires a good knowledge of the secondary positron component generated by the interaction of cosmic rays with the interstellar gas. In this paper, we investigate the impact of the spectral hardening in the cosmic-ray proton and helium fluxes recently reported by the ATIC2 and CREAM balloon experiments, on the predictions o…
The Fermi-LAT detects no significant anisotropy of the cosmic-ray (CR) electrons and positrons ($e^-+e^+$) with seven years of data, which provides the strongest restriction to the $e^-+e^+$ anisotropy up to now. As next generation CR observatory, HERD is expected to have a better capability of anisotropy detection than Fermi-LAT. In this paper, we discuss several models aimed to explain the AMS-02 data by the present and future anisotropy measurements. We find that the upper limits of Fermi-LAT disfavor Vela SNR as the dominant source in sub-TeV, while other cases that remain safe under the c…
The DArk Matter Particle Explorer (DAMPE) is a satellite-borne, high-energy particle and $γ$-ray detector, which is dedicated to indirectly detecting particle dark matter and studying high-energy astrophysics. The first results about precise measurement of the cosmic ray electron plus positron spectrum between 25 GeV and 4.6 TeV were published recently. The DAMPE spectrum reveals an interesting spectral softening around $0.9$ TeV and a tentative peak around $1.4$ TeV. These results have inspired extensive discussion. The detector of DAMPE, the data analysis, and the first results are introduce…
The HAWC Gamma-Ray Observatory has reported the discovery of TeV gamma-ray emission extending several degrees around the positions of Geminga and B0656+14 pulsars. Assuming these gamma rays are produced by inverse Compton scattering off low-energy photons in electron halos around the pulsars, we determine the diffusion of electrons and positrons in the local interstellar medium. We will present the morphological and spectral studies of these two VHE gamma-ray sources and the derived positron spectrum at Earth.
Observations of cosmic ray electrons have made great strides in the last decade and direct observations of the all-electron flux as well as separate electron and positron spectra are now available up to ~ 1 TeV. In this invited contribution to the 2022 edition of the Rencontres de Moriond on Very High Energy Phenomena in the Universe, we review the data on cosmic ray electron and positron spectra at TeV energies and offer general comments on their interpretation. Subsequently, we focus on the study of the stochastic fluctuations and a secondary model for the positron excess.
We suggest that white dwarf (WD) pulsars can compete with neutron star (NS) pulsars for producing the excesses of cosmic ray electrons/positrons observed by the PAMELA, ATIC/PPB-BETS, Fermi and HESS experiments. A merger of two WDs leads to a rapidly spinning WD with a rotational energy comparable to the NS case. The birth rate is also similar, providing the right energy budget for the cosmic ray electrons/positrons. Applying the NS theory, we suggest that the WD pulsars can in principle produce electrons/positrons up to 10 TeV. In contrast to the NS model, the adiabatic and radiative energy l…
Recent γ-ray observations suggest that the γ-ray millisecond pulsar (MSP) population is separated into two sub-classes with respect to the pair multiplicity. Here, we calculate the cosmic ray electron/positron spectra from MSPs. Based on the assumption of the equipartition in the pulsar wind region the typical energy of electrons/positrons ejected by a MSP with the pair multiplicity of order unity is \sim 50 TeV. In this case, we find that a large peak at 10 - 50 TeV energy range would be observed in the cosmic ray electron/positron spectrum. Even if the fraction of pair starved MSPs is 10%, t…
It has long been suggested that nearby pulsars within $\sim 1 \,{\rm kpc}$ are the leading candidate of the 10-500 GeV cosmic-ray positron excess measured by PAMELA and other experiments. The recent measurement of surface brightness profile of TeV nebulae surrounding Geminga and PSR~B0656+14 by the High-Altitude Water Cherenkov Observatory (HAWC) suggests inefficient diffusion of particles from the sources, giving rise to a debate on the pulsar interpretation of the cosmic-ray positron excess. Here we argue that GeV observations provide more direct constraints on the positron density in the Te…
Recent observations have detected extended TeV gamma-ray emission surrounding young and middle-aged pulsars. The morphology of these "TeV halos" requires cosmic-ray diffusion to be locally suppressed by a factor of ~100-1000 compared to the typical interstellar medium. No model currently explains this suppression. We show that cosmic-ray self-confinement can significantly inhibit diffusion near pulsars. The steep cosmic-ray gradient generates Alfven waves that resonantly scatter the same cosmic-ray population, suppressing diffusion within ~20 pc of pulsars younger than ~100 kyr. In this model,…
Designed as a high-sensitivity gamma-ray observatory, the Fermi Large Area Telescope is also an electron detector with a large acceptance exceeding 2 sq-mt sr at 300 GeV. Building on the gamma-ray analysis, we have developed an efficient electron detection strategy which provides sufficient background rejection for measurement of the steeply-falling electron spectrum up to 1 TeV. Our high precision data show that the electron spectrum falls with energy as E^(-3.0) and does not exhibit prominent spectral features
The DArk Matter Particle Explorer (DAMPE) experiment has recently announced the first results for the measurement of total electron plus positron fluxes between 25 GeV and 4.6 TeV. A spectral break at about 0.9 TeV and a tentative peak excess around 1.4 TeV have been found. However, it is very difficult to reproduce both the peak signal and the smooth background including spectral break simultaneously. We point out that the numbers of events in the two energy ranges (bins) close to the 1.4 TeV excess have $1σ$ deficits. With the basic physics principles such as simplicity and naturalness, we c…
At energies above a few TeV, no measurements of the cosmic-ray electron spectrum exist yet. By considering the similarity of air showers induced by electrons and gamma rays as seen by ground-based arrays, we use published limits on isotropic gamma-ray fluxes to place first constraints on the >10 TeV electron spectrum. We demonstrate that, due the proximity of known sources, the flux of such electrons (and positrons) can be large. We show how these smoothly connect to lower-energy positrons measured by PAMELA and relate to exciting new indications from Fermi.
As the TeV halos around Geminga and PSR B0656+14 have been confirmed by HAWC, slow diffusion of cosmic rays could be general around pulsars, and the cosmic positron spectrum from pulsars could be significantly changed. As a consequence, the most likely pulsar source of the positron excess, Geminga, is no more a viable candidate under the additional constraint from Fermi-LAT. Moreover, the latest measurement by AMS-02 shows a clear cutoff in the positron spectrum, which sets a strict constraint on the age of the pulsar source. Considering these new developments we reanalyze the scenario in this…
Recently, the gamma-ray telescopes AGILE and Fermi observed several middle-aged supernova remnants (SNRs) interacting with molecular clouds. A plausible emission mechanism of the gamma rays is the decay of neutral pions produced by cosmic ray (CR) nuclei (hadronic processes). However, observations do not rule out contributions from bremsstrahlung emission due to CR electrons. TeV gamma-ray telescopes also observed many SNRs and discovered many unidentified sources. It is still unclear whether the TeV gamma-ray emission is produced via leptonic processes or hadronic processes. In this Letter, w…
Recent precision measurements of the flux of cosmic ray positrons by the Alpha Magnetic Spectrometer show that the spectrum has a marked softening feature for energies close to one TeV. A possible interpretation of this result is that the observed feature measures the maximum energy of a new hard source of positrons perhaps associated to dark matter self--annihilation or decay, or to positron accelerators. A gradual hardening of the positron flux centered at $E \simeq 25$~GeV can also be understood as the signature of the transition where the new source overtakes the conventional component due…
We reveal that the energy spectra of electrons-positrons in primary cosmic rays measured at atmosphere top have double structures: an excess component $Φ^s_{e^+}(E)=Φ^s_{e^-}(E)$ around $400 GeV$, which origins from a strong $e^+e^-$-source and the distorted background $Φ^0_{e^-}(E)$. We supposed that the difference between AMS-CALET and Fermi-LAT-DAMPE data origins from the energy loss of the fluxes due to the anomalous bremsstrahlung effect at a special window. The evolution of spectra under anomalous bremsstrahlung effect satisfies an improved electromagnetic cascade equation. The above spe…
Electron and positron fluxes in cosmic rays are currently measured with unprecedented precision by AMS-02 up to TeV energies, and represent unique probes for the local properties of our Galaxy. The interpretation of their spectra is at present still debated, especially for the excess of positrons above 10 GeV. The hypothesis that pulsars can significantly contribute to this excess has been consolidated after the observation of gamma-ray halos at TeV energies of a few degree size around Geminga and Monogem pulsars. However, the spatial and energetic Galactic distribution of pulsars and the deta…
The total cosmic ray electron spectrum (electrons plus positrons) exhibits a break at a particle energy of $\sim 1\rm~TeV$ and extends without any attenuation up to $\rm \sim 20~ TeV $. Synchrotron and inverse Compton energy losses strongly constrain both the age and the distance of the potential sources of TeV and multi-TeV electrons to $\rm\approx 10^5~yr$ and $\rm \approx 100-500~pc$, depending on both the absolute value and energy dependence of the cosmic ray diffusion coefficient. This suggests that only a few, or just one nearby discrete source may explain the observed spectrum of high e…
Gluons dominate the proton behavior at high energy collisions, they can be condensed at ultra high energy. The collisions of the accelerated high energy protons with interplanetary matter in cosmic rays will produce a huge number of secondary particles at the gluon condensate energy region, which break the primary power-law of cosmic rays. The above predictions seem to be consistent with the recent DAMPE data concerning the electron plus positron spectra. We find that the smoothly broken power-law at $\sim 0.9 TeV$ and $3\sim 4 TeV$ in the DAMPE data can be understood as the gluon condensation…
PAMELA's observation that the cosmic ray positron fraction increases rapidly with energy implies the presence of primary sources of energetic electron-positron pairs. Of particular interest is the possibility that dark matter annihilations in the halo of the Milky Way provide this anomalous flux of antimatter. The recent measurement of the cosmic ray electron spectrum by the Fermi Gamma Ray Space Telescope, however, can be used to constrain the nature of any such dark matter particle. In particular, it has been argued that in order to accommodate the observations of Fermi and provide the PAMEL…
Nearby electron/positron accelerators, mostly Pulsar Wind Nebulae (PWNe), have been proposed as potential origins of the positron excess above 10 GeV. The HAWC Observatory reveals two very extended sources spatially coincident with two nearby middle-aged pulsars: Geminga and PSR B0656+14, suggesting ultrarelativistic electrons/positrons accelerated in our backyard. Morphological studies on these two PWNe provide a constraint on the diffusion coefficient at HAWC energies. In this poster, we will present the model development and morphological studies on these PWNe, and the derived diffusion coe…
We show that R-parity violating decay of Wino dark matter of mass \sim 3 TeV can naturally account for the flux and spectral shape of the cosmic-ray electrons and positrons observed by the PAMELA and Fermi satellites. To provide a theoretical basis for the scenario, we also present a model that trilinear R-parity breaking appears with a coefficient suppressed by powers of the gravitino mass, which naturally leads to the Wino lifetime of O(10^26) sec.
In a recent letter, the AMS collaboration reported the detailed and extensive data concerning the distribution in energy of electron and positron cosmic rays. A central result of the experimental work resides in the energy regime $30\ {\rm GeV}< E < 1\ {\rm TeV}$ wherein the power law exponent of the energy distribution is measured to be $α({\rm experiment})=3.17$. In virtue of the Fermi statistics obeyed by electrons and positrons, a theoretical value was predicted as $α({\rm theory})=3.151374$ in very good agreement with experimental data. The consequences of this agreement between theory an…
Recently, an excess of high energy positrons in our Galaxy has been observed by AMS-02. The spectrum obtained can be best fitted with the annihilation of $\sim$ TeV dark matter particles. However, recent analysis of Dwarf galaxies by Fermi/LAT observations highly constrains the TeV dark matter annihilation cross-section, and rules out the $b\bar{b}$ and all the leptophilic channels except $4-μ$ channel. In this article, I show that the remaining possible $4-μ$ channel is also ruled out by using the observational data from cool-core clusters. Therefore, all the leptophilic channels that can acc…
Recently cosmic ray electrons and positrons, i.e. cosmic ray charged leptons, have been observed. To understand the distances from our solar system to the sources of such lepton cosmic rays, it is important to understand energy losses from cosmic electrodynamic fields. Energy losses for ultra-relativistic electrons and/or positrons due to classical electrodynamic bremsstrahlung are computed. The energy losses considered are (i) due to Thompson scattering from fluctuating electromagnetic fields in the background cosmic thermal black body radiation and (ii) due to the synchrotron radiation losse…
Nearby pulsars have been suggested as sources of $\sim$TeV $e^+/e^-$ Cosmic Ray (CR) excess on Earth. The High-Altitude Water Cherenkov Observatory (HAWC) detected extended TeV emission regions in the direction of two nearby middle-aged pulsars, Geminga and PSR B0656+14. By modeling the TeV emission as inverse Compton emission from electron-positron pairs diffusing in the interstellar medium (ISM), the HAWC collaboration derives a diffusion coefficient much smaller than the standard value in the vicinity of the two pulsars, which make them unlikely the origin of the positron excess. We propose…
The Fermi Gamma-ray Space Telescope (formerly known as Gamma-ray Large Area Space Telescope, GLAST) was successfully launched on June 11 2008. Its main instrument is the Large Area Telescope (LAT), which detects gamma rays from 20 MeV to more than 300 GeV. It is a pair-conversion telescope with 16 identical towers (tracker and calorimeter), covered by an anti-coincidence detector to reject charged particles. The calorimeter is a hodoscopic array of CsI(Tl) crystals, arranged in 8 alternating orthogonal layers, with a total thickness of 8.6 radiation lengths. In this paper we will present the p…
The hypothesis that pulsar wind nebulae (PWNe) can significantly contribute to the excess of the positron ($e^+$) cosmic-ray flux has been consolidated after the observation of a $γ$-ray emission at TeV energies of a few degree size around Geminga and Monogem PWNe, and at GeV energies for Geminga at a much larger extension. The $γ$-ray halos around these PWNe are interpreted as due to electrons ($e^-$) and $e^+$ accelerated and escaped by their PWNe, and inverse Compton scattering low-energy photons of the interstellar radiation fields. The extension of these halos suggests that the diffusion …
We compute cosmic ray (CR) nuclei, proton, antiproton, electron and positron spectra below 1 TeV at Earth by means of a detailed transport description in the galaxy and in the solar system. CR spectra below 10 GeV are strongly modified by charge-sign dependent propagation effects. These depend on the polarity of the solar magnetic field and therefore vary with the solar cycle. The puzzling discrepancy between the low-energy positron fraction measured by PAMELA and AMS-01 is then easily explained by their different data-taking epochs. We reproduce the observed spectra of CR light nuclei within …
We present a precise measurement of the combined electron plus positron flux from 0.5 GeV to 1 TeV, based on the analysis of the data collected by the Alpha Magnetic Spectrometer during the first 30 months of operations aboard the International Space Station. The statistics and the high resolution of AMS-02 detector provide a precise measurement of the flux. The flux is smooth and reveals new and distinct information. Above 30.2 GeV, the combined electron plus positron flux can be described accurately by a single power law.
We attempt to interpret the cosmic-ray positron excess by injection from the nearby pulsar Geminga, assuming a two-zone diffusion scenario and an injection spectrum with a low energy cutoff. Since the high energy positrons and electrons from Geminga can induce $γ$ rays via inverse Compton scattering, we take into account the extended $γ$-ray observations around Geminga from HAWC for $\sim 10$ TeV and from Fermi-LAT for $\mathcal{O}(10)$ GeV. According to the extended $γ$-ray observation claimed by an analysis of Fermi-LAT data, we find that Geminga could explain the positron excess for a $30\%…
The High-Altitude Water Cherenkov (HAWC) Observatory records the air showers produced by cosmic rays and gamma rays at a rate of about 20 kHz. While the events observed by HAWC are 99.9% hadronic cosmic rays, this background can be strongly suppressed using topological cuts that preferentially select electromagnetic air showers. Using this capability of HAWC, we can create a sample of air showers dominated by gamma rays and cosmic electrons and positrons. HAWC is one of the few operating observatories capable of measuring showers produced by electron and positron primaries above 1 TeV, and can…
A new population of neutron stars has emerged during the last decade: compact binary millisecond pulsars (CBMSPs). Because these pulsars and their companion stars are in tight orbits with typical separations of $10^{11}$ cm, their winds interact strongly forming an intrabinary shock. Electron-positron pairs reaccelerated at the shock can reach energies of about 10 TeV, which makes this new population a potential source of GeV-TeV cosmic ray positrons. We present an analytical model for the fluxes and spectra of positrons from intrabinary shocks of CBMSPs. We find that the minimum energy $E_{\m…
Cosmic electrons with energies in the TeV range lose their energy rapidly through synchrotron radiation and inverse Compton processes, resulting in a relatively short lifetime (~ 10^5 years). They are only visible from comparatively nearby sources (<1 kpc). Unexpected features in their spectrum at a few hundreds GeV, as measured by several experiments (ATIC, Fermi and H.E.S.S. among others), might be caused by local sources such as pulsars or by dark matter annihilation/decay. In order to investigate these possibilities, new measurements in the TeV energy region are needed. Since the completio…
First results of a cosmic-ray electron + positron spectrum, from 10 GeV to 3 TeV, is presented based upon observations with the CALET instrument on the ISS starting in October, 2015. Nearly a half million electron + positron events are included in the analysis. CALET is an all-calorimetric instrument with total vertical thickness of 30 $X_0$ and a fine imaging capability designed to achieve a large proton rejection and excellent energy resolution well into the TeV energy region. The observed energy spectrum over 30 GeV can be fit with a single power law with a spectral index of -3.152 $\pm$ 0.…
A combined interpretation of the CALET $e^+\, +\, e^-$ spectrum up to 3 TeV and the AMS-02 positron spectrum up to 500 GeV was performed and the results are discussed. To parametrize the background electron flux, we assume a smoothly broken power-law spectrum with an exponential cut-off for electrons and fit this parametrization to the measurements, with either a pulsar or 3-body decay of fermionic Dark Matter as the extra electron-positron pair source responsible for the positron excess. We found that depending on the parameters for the background, both Dark Matter decay and the pulsar model …
Until fairly recently, it was widely accepted that local cosmic ray spectra were largely featureless power laws, containing limited information on their acceleration and transport. This viewpoint is currently being revised in the light of evidence for a variety of spectral breaks in the fluxes of cosmic ray nuclei. Here, we focus on cosmic ray electrons and positrons which at the highest energies must be of local origin due to strong radiative losses. We consider a pure diffusion model for their Galactic transport and determine its free parameters by fitting data in a wide energy range: measur…
CALET (Calorimetric Electron Telescope), installed on the ISS in August 2015, directly measures the electron+positron cosmic rays flux up to 20 TeV. With its proton rejection capability of 1:10^5 and an aperture of 1200 cm^2 sr, it will provide good statistics even well above one TeV, while also featuring an energy resolution of 2%, which allows it to detect fine structures in the spectrum. Such structures may originate from Dark Matter annihilation or decay, making indirect Dark Matter search one of CALET's main science objectives among others such as identification of signatures from nearby …
TeV Halos, extended regions of TeV gamma-ray emission around middle-aged pulsars, have recently been established as a new source class in gamma-ray astronomy. These halos have been attributed to relativistic electrons and positrons that have left the acceleration region close to the pulsar and are diffusing in the surrounding medium. Measuring the morphology of TeV Halos enables for the first time a direct measurement of the electron diffusion on scales of tens of parsecs. There are hints that the presence of relativistic particles affects the diffusion rate in the pulsars' surroundings. Under…
We present a measurement of the cosmic-ray electron+positron spectrum between 7 GeV and 2 TeV performed with almost seven years of data collected with the Fermi Large Area Telescope. We find that the spectrum is well fit by a broken power law with a break energy at about 50 GeV. Above 50 GeV, the spectrum is well described by a single power law with a spectral index of $3.07 \pm 0.02 \; (\text{stat+syst}) \pm 0.04 \; (\text{energy measurement})$. An exponential cutoff lower than 1.8 TeV is excluded at 95\% CL.
The origin of the positron excess is one of the most intriguing mysteries in astroparticle physics. The recent discovery of extended $γ$-ray halos around the pulsars Geminga, Monogem and PSR J0621+3755 have brought indirect evidence that pulsar wind nebulae accelerate $e^{\pm}$ up to very-high-energy. While the precision of previous data does not permit precise evaluation of the parameters for the pulsars, we are able to find the more precise shape of the injection spectrum using new data released by HAWC and LHAASO in 2020 and 2021. We find that this is well fitten by a power-law with an expo…
We present a simple calculation of the flux of secondary positrons produced in the ISM that is based only on priors. Our calculated ISM flux agrees very well with that calculated with the elaborate GALPROP code. It confirms that secondary production of positrons in the ISM by the primary cosmic rays cannot explain the observed sub-TeV flux of CR positrons. Moreover, we show that once energy loss of positrons in source and in the ISM are included, secondary production inside the CR sources plus the ISM does explain the measured near-Earth flux of cosmic ray positrons.
Measurements of cosmic ray electron+positron spectrum above 10 TeV with ground-based experiments is challenging because of the difficulty of rejection of hadronic extensive air shower background. We study the efficiency of rejection of the hadronic background with water Cherenkov detector array supplemented by muon detection layer. We show that addition of a continuous muon detection layer to the experimental setup allows to achieve a ~ 1e-5 rejection factor for hadronic background at 10 TeV and enables measurement of electron spectrum in 10-100 TeV energy range. We show that measurements of e…
High-energy particle transport in pulsar wind nebulae (PWNe) plays an essential role in explaining the characteristics revealed in multiwavelength observations. In this paper, the TeV-gamma-ray-emitting electrons in the Vela X PWN are approximated to be injected impulsively when the cocoon is formed due to the interaction between the SNR reverse shock and the PWN. By solving the diffusion-loss equation analytically, we reproduce the broadband spectral energy distribution and surface brightness profile simultaneously. The diffusion coefficient of TeV electrons and positrons, which is well const…
The DArk Matter Particle Explorer (DAMPE), a high energy cosmic ray and $γ$-ray detector in space, has recently reported the new measurement of the total electron plus positron flux between 25 GeV and 4.6 TeV. A spectral softening at $\sim0.9$ TeV and a tentative peak at $\sim1.4$ TeV have been reported. We study the physical implications of the DAMPE data in this work. The presence of the spectral break significantly tightens the constraints on the model parameters to explain the electron/positron excesses. The spectral softening can either be explained by the maximum acceleration limits of e…
Several groups have reported a possible excess of primary electrons at high energies with the joint fit of the positron fraction and total electron/positron spectra. With the latest release of high-precision electron/positron spectra measured by AMS-02, we further confirm this excess by fitting $ΔΦ$ $\rm(i.e., Φ_{e^-}-Φ_{e^+})$ data in this work. Then we investigate the contribution of a single nearby supernova remnant to the primary electron excess and find that Monogem can reasonably account for this excess. Moreover, we predict that the electron spectrum may harden again at a few TeVs due t…
Geminga pulsar is surrounded by a multi-TeV $γ$-ray halo radiated by the high energy electrons and positrons accelerated by the central pulsar wind nebula (PWN). The angular profile of the $γ$-ray emission reported by HAWC indicates an anomalously slow diffusion for the cosmic-ray electrons and positrons in the halo region around Geminga. In the paper we study the possible mechanism for the origin of the slow diffusion. At first, we consider the self-generated Alfvén waves due to the streaming instability of the electrons and positrons released by Geminga. However, even considering a very opti…
Focusing on the electron and positron spectrum measured with CALET, which shows characteristic structures, we calculate flux contributions of cosmic rays escaped from supernova remnants, which were randomly born. We adopt a Monte Carlo method to take into account the stochastic property of births of nearby sources. We find that without a complicated energy dependence of the diffusion coefficient, simple power-law diffusion coefficients can produce spectra similar to the CALET spectrum even with a dispersion in the injection index. The positron component measured with AMS-02 is consistent with …
The AMS experiment onboard the International Space Station has recently provided cosmic ray electron and positron data with unprecedented precision in the range from 0.5 to 350 GeV. The observed rise in the positron fraction at energies above 10 GeV remains unexplained, with proposed solutions ranging from local pulsars to TeV-scale dark matter. Here, we make use of this high quality data to place stringent limits on dark matter with masses below ~300 GeV, annihilating or decaying to leptonic final states, essentially independent of the origin of this rise. We significantly improve on existing…
Context: An electron-positron beam escaping from the magnetospheric vacuum gap of an accreting black hole interacts with recombination-line photons from surrounding gas clouds. Inverse-Compton scattering and subsequent pair production initiate unsaturated electromagnetic cascades exhibiting a characteristic spectral energy distribution. Aims: By modelling the interactions of beam electrons (positrons) with hydrogen and helium recombination-line photons, we seek to describe the spectral signature of beam-driven cascades in the broad emission-line region of blazar jets. Methods: Employing couple…
The antimatter components measured in the Cosmic Ray (CR) flux are thought as secondary particles induced by the propagation of galactic CRs within the galaxy. Recent results from the PAMELA experiment show an unexpected increase of the positron electron ratio above 10 GeV. There could be different interpretations to explain that result, the most discussed ones being the signature of nearby compact astrophysical source(s) or of dark matter annihilation/decay. Probing the positron-fraction rise above 100 GeV would help to disentangle among different scenarios. Imaging Atmospheric Cherenkov Tele…
The Dark Matter Particle Explorer (DAMPE) satellite detector announced its first result for measuring the cosmic-ray electron/positron (CRE) energy spectrum up to 4.6TeV, including a tentative peak-like event excess at (1.3-1.5)TeV. In this work, we uncover a significant hidden excess in the DAMPE CRE spectrum over the energy range (0.6-1.1)TeV, which has a non-peak-like structure. We propose a new mechanism to explain this excess by a set of 1.5TeV $μ^\pm$ events with subsequent decays into $e^\pm$ plus neutrinos. For explaining this new excess together with the peak excess around 1.4TeV, we …
In supersymmetric unified theories the dark matter particle can decay, just like the proton, through grand unified interactions with a lifetime of order of 10^{26} sec. Its decay products can be detected by several experiments -- including Fermi, HESS, PAMELA, ATIC, and IceCube -- opening our first direct window to physics at the TeV scale and simultaneously at the unification scale 10^{16} GeV. We consider possibilities for explaining the electron/positron spectra observed by HESS, PAMELA, and ATIC, and the resulting predictions for the gamma-ray, electron/positron, and neutrino spectra as wi…
Observations by the Fermi Large Area Telescope of gamma-ray millisecond pulsar light curves imply copious pair production in their magnetospheres, and not exclusively in those of younger pulsars. Such pair cascades may be a primary source of Galactic electrons and positrons, contributing to the observed enhancement in positron flux above ~10 GeV. Fermi has also uncovered many new millisecond pulsars, impacting Galactic stellar population models. We investigate the contribution of Galactic millisecond pulsars to the flux of terrestrial cosmic-ray electrons and positrons. Our population synthesi…
