arXiv subjects

Su-Jie Lin

Publications and source records attributed to Su-Jie Lin.

24 records · Page 2Linked to original sources

arXiv2016

Perspective on the cosmic-ray electron spectrum above TeV

The AMS-02 has measured the cosmic ray electron (plus positron) spectrum up to ~TeV with an unprecedent precision. The spectrum can be well described by a power law without any obvious features above 10 GeV. The satellite instrument Dark Matter Particle Explorer (DAMPE), which was launched a year ago, will measure the electron spectrum up to 10 TeV with a high energy resolution. The cosmic electrons beyond TeV may be attributed to few local cosmic ray sources, such as supernova remnants. Therefore, spectral features, such as cutoff and bumps, can be expected at high energies. In this work we give a careful study on the perspective of the electron spectrum beyond TeV. We first examine our astrophysical source models on the latest leptonic data of AMS-02 to give a self-consistent picture. Then we focus on the discussion about the candidate sources which could be electron contributors above TeV. Depending on the properties of the local sources (especially on the nature of Vela), DAMPE may detect interesting features in the electron spectrum above TeV in the future.

astro-ph.HE↗

arXiv2016

Excesses of Cosmic Ray Spectra from A Single Nearby Source

Growing evidence reveals universal hardening on various cosmic ray spectra, e.g. proton, positron, as well as antiproton fraction. Such universality may indicate they have a common origin. In this paper, we argue that these widespread excesses can be accounted for by a nearby supernova remnant surrounded by a giant molecular cloud. Secondary cosmic rays ($\rm p$, $\rm e^+$) are produced through the collisions between the primary cosmic ray nuclei from this supernova remnant and the molecular gas. Different from the background, which is produced by the ensemble of large amount of sources in the Milky Way, the local injected spectrum can be harder. The time-dependent transport of particles would make the propagated spectrum even harder. Under this scenario, the anomalies of both primary ($\rm p$, $\rm e^-$) and secondary ($\rm e^+$, $\rm \bar{p}/p$) cosmic rays can be properly interpreted. We further show that the TeV to sub-PeV anisotropy of proton is consistent with the observations if the local source is relatively young and lying at the anti-Galactic center direction.

astro-ph.HE↗

arXiv2016

Constraints on Dark Matter Annihilation/Decay from the Isotropic Gamma-Ray Background

In this work we study the constraints on dark matter (DM) annihilation/decay from the Fermi-LAT Isotropic Gamma-Ray Background (IGRB) observation. We consider the contributions from both extragalactic and galactic DM components. For DM annihilation, the evolutions of extragalactic DM halos are taken into account. We find that the IGRB constraints under some DM subhalo models can be comparable to those derived from the observations of dwarf spheroidal galaxies. We also use the IGRB results to constrain the parameter regions accounting for the latest AMS-02 electron-positron anomaly. We find that the majority of DM annihilation/decay channels are strongly disfavored by the latest Fermi-LAT IGRB observation; only DM annihilation/decay to $μ^+μ^-$ may be valid.

astro-ph.CO↗

arXiv2015

Implications for dark matter annihilation from the AMS-02 $\bar{p}/p$ ratio

The AMS-02 collaboration has just released the cosmic antiproton to proton ratio $\bar{p}/p$ with a high precision up to $\sim 450$ GeV. In this work, we calculate the secondary antiprotons generated by cosmic ray interactions with the interstellar medium taking into account the uncertainties from the cosmic ray propagation. The $\bar{p}/p$ ratio predicted by these processes shows some tension with the AMS-02 data in some regions of propagation parameters, but the excess is not significant. We then try to derive upper bounds on the dark matter annihilation cross section from the $\bar{p}/p$ data or signal regions favored by the data. It is shown that the constraint derived by the AMS-02 data is similar to that from Fermi-LAT observations of dwarf galaxies. The signal region for dark matter is usually required $m_χ\sim O(10)$ TeV and $\left<σv\right>\sim\mathcal{O}(10^{-23})~\cm^3~\sec^{-1}$.

hep-ph↗

arXiv2015

Quantitative study of the AMS-02 electron/positron spectra: implications for the pulsar and dark matter properties

The AMS-02 has just published the unprecedentedly precise measurement of the cosmic electron and positron spectra. In this paper we try to give a quantitative study on the AMS-02 results by a global fitting to the electron and positron spectra, together with the updated positron fraction data. The Markov Chain Monte Carlo algorithm is adopted to do the fitting. The primary electron spectrum and the parameters for pulsars or dark matter which contribute extra positrons are determined simultaneously. We find that there is a hardening of the primary electron spectrum at $\sim 60$ GeV. With such a new feature at the background spectrum both the pulsars and dark matter can explain the AMS-02 results very well. The dark matter scenario shows a drop at positron fraction at $\sim 300$ GeV, however, suffers very strong constraints from Fermi $γ$-ray observations. The fitting results also suggest that the propagation model with convection may be more favored by the lepton data than the reacceleration model.

astro-ph.HE↗

arXiv2014

Implications of the AMS-02 positron fraction in cosmic rays

The AMS-02 collaboration has just released its first result of the cosmic positron fraction $e^+/(e^-+e^+)$ with high precision up to $\sim 350$ GeV. The AMS-02 result shows the same trend with the previous PAMELA result, which requires extra electron/positron sources on top of the conventional cosmic ray background, either from astrophysical sources or from dark matter annihilation/decay. In this paper we try to figure out the nature of the extra sources by fitting to the AMS-02 $e^+/(e^-+e^+)$ data, as well as the electron and proton spectra by PAMELA and the $(e^-+e^+)$ spectrum by Fermi and HESS. We adopt the GALPROP package to calculate the propagation of the Galactic cosmic rays and the Markov Chain Monte Carlo sampler to do the fit. We find that the AMS-02 data have implied essential difference from the PAMELA data. There is {\rm tension} between the AMS-02 $e^+/(e^-+e^+)$ data and the Fermi/HESS $(e^-+e^+)$ spectrum, that the AMS-02 data requires less contribution from the extra sources than Fermi/HESS. Then we redo the fit without including the Fermi/HESS data. In this case both the pulsars and dark matter annihilation/decay can explain the AMS-02 data. The pulsar scenario has a soft inject spectrum with the power-law index $\sim 2$, while the dark matter scenario needs $τ^+τ^-$ final state with mass $\sim 600$ GeV and a boost factor $\sim 200$.

astro-ph.HE↗