Cosmic-Ray Electron Excess from Pulsars is Spiky or Smooth?: Continuous and Multiple Electron/Positron Injections Cosmic-Ray Electron Excess from Pulsars is Spiky or Smooth?: Continuous and Multiple Electron/Positron Injections (arXiv: , submitted to ApJ) Norita Kawanaka (KEK) Kunihito Ioka (KEK) Mihoko M. Nojiri (KEK/IPMU) KEK Theory Center Cosmophysics Group Workshop on High Energy Astrophysics Nov. 12, 2009

Positron Excess: PAMELA Observed cosmic-ray positron flux seems to exceed that expected in the context of secondary positron production. Similar trend had been observed (AMS, HEAT etc.) Some primary sources are needed! (Adriani et al. 2008) ~1-100GeV

Electron+Positron Flux ATIC/PPB-BETS (Chang et al. 2008)  e ~ GeV bump+sharp cutoff H.E.S.S. (H.E.S.S. collaboration 2008) ~1-5TeV spectral drop

Recent Results Abdo et al. (arXiv: ) Aharonian et al. (arXiv: ) Fermi LAT H.E.S.S. (340GeV~) ATIC/PPB-BETS peak has not been confirmed.

What is the Origin of e ± Excess? Dark Matter Particles annihilation/decay  e ± Cutoff ~600GeV in the ATIC/PPB-BETS corresponds to the mass of DM particles annihilation: required ~O( )cm 3 s -1 >> thermal Overproductions of anti-proton should be avoided. Astrophysical Sources Compact objects in our Galaxy (NS, SNR, BH…) Cutoff ~600GeV in the ATIC/PPB-BETS corresponds to the cooling time for e ± Required energy ~ x10 50 erg/SN ~ erg/SN ~ CR nucleon energy

Astrophysical Origin Pulsar Shen 70; Aharonian+ 95; Atoyan et al. 95; Chi+ 96; Zhang & Cheng 01; Grimani 07; Yuksel+ 08; Buesching+ 08; Hooper+ 08; Profumo 08; Malyshev+ 09; Grasso+ 09; NK+ 09 Supernova Remnant Shen & Berkey 68; Pohl & Esposito 98; Kobayashi+ 04; Shaviv+ 09; Hu+ 09; Fujita, Kohri, Yamazaki & Ioka 09; Blasi 09; Blasi & Serpico 09; Mertsch&Sarkar 09; Biermann+ 09; Ahlers, Mertsch & Sarkar 09 Microquasar (Galactic BH) Heinz & Sunyaev 02 Gamma-Ray Burst Ioka 08 Propagation Effect Delahaye+ 08; Cowsik & Burch 09; Stawarz+09; Schlickeiser & Ruppel 09

Effects of continuous e ± injections on the spectrum Effects of multiple sources Constraints in >TeV range by H.E.S.S. Astrophysical Sources? Or Dark Matter? Can We Discriminate them from the Spectrum? Any characteristic features in the e ± spectrum from astrophysical sources? Can we give any constraints on models by the future missions?

e ± propagation in ISM 1. Random walk due to the Galactic magnetic field  diffusion approx. 2. Synchrotron + inverse Compton scattering  energy loss ？ Propagation effects e±e± 

CR Propagation Equation and Solution diffusion equation injection  Spectrum from instantaneous injection from a point source (Atoyan+ 1995) energy loss (synchrotron, inverse Compton scattering) diffusion cutoff energy:  e ~1/bt age ： diffusion length Galactic Magnetic Fields & Radiation Fields B/C ratio

The case of transient source: e + fraction d=1kpc (a) E=0.9x10 50 erg age=2x10 5 yr  =2.5 (b) E=0.8x10 50 erg age=5.6x10 5 yr  =1.8 (c) E=3x10 50 erg age=3x10 6 yr  =1.8 The cutoff energy corresponds to the age of the source. Ioka 2008

The case of transient source: e ± spectrum (a) E=0.9x10 50 erg age=2x10 5 yr  =2.5 (b) E=0.8x10 50 erg age=5.6x10 5 yr  =1.8 (c) E=3x10 50 erg age=3x10 6 yr  =1.8 d=1kpc The cutoff energy corresponds to the age of the source. Ioka 2008

Continuous injection (expected in pulsars, SNRs, etc.) Case 1: pulsar-type decay Case 2: exponential decay The spectral peak around E e ~1/bt will be broadened! cf.)

Continuous Injection (e + +e - ) background Burst-like event (e.g. GRB) Flux without background t=5.6x10 5 yr r=1kpc E e+ ~E e- ~10 50 erg  =1.7 E max =5TeV E peak ~1/bt ~ 600GeV exponential decay,  0 ~10 5 yr NK+ 2009

Constraints on pulsar-type decay time pulsar type:  0 =10 5 yr pulsar type:  0 =10 4 yr * A significant fraction of observed electrons are emitted recently. H.E.S.S.

e ± Injection from Multiple Sources Total injection energy required to account for the peak of ATIC/PPB-BETS ~ erg ~ Rotation energy of a pulsar with P 0 ~10msec Too efficient? Local pulsar birth rate ~10 -5 yr -1 kpc -2 (Narayan 1985; Lorimer+1994) Pulsars which have not observed (e.g. off- beam) should contribute significantly. Young pulsars (age< 5 x 10 5 yr) should exist. The peak might be made by a pulsar with an extraordinary large amount of energy. Then, what is the spectrum like on average?

Average e ± Spectrum and Its Dispersion Average flux from nearby sources with a birth rate of R : Number of sources which contribute to the energy bin of  e NK Assuming the Poisson statistics of the source distribution, Flux per source

e + fraction e ± spectrum solid lines ： f ave (  e ) dashed lines ： f ave (  e ) ±  f ave R~1/(1.5x10 5 )/yr/kpc 2 E e+ =E e- ~10 48 erg  ~1.9 1.Average spectra are consistent with PAMELA, Fermi & H.E.S.S. 2.ATIC/PPB-BETS peak is largely separated from the average flux to the 10  level.  Such a peak is hardly to produce by the sum of multiple pulsars. 3.Large dispersion in the TeV range due to the small N(  e )  possible explanation for the cutoff inferred by H.E.S.S 3.Large dispersion in the TeV range due to the small N(  e )  possible explanation for the cutoff inferred by H.E.S.S.

CALorimetric Electron Telescope (Torii-san’s talk) CALET With the high energy resolution and statistics of the CALET observations, we will be able to discriminate models of injection. (duration, the functional form of Q 0 (t), etc.) A Dedicated Detector for Electron Observation in 1GeV – 20,000 GeV Red points/errorbars: expected from 5yr obs. by CALET Energy resolution: ~2% (>100GeV) e/p selection power: ~10 5

Summary We investigate the spectral features of CR e ± from continuous/multiple sources (e.g. pulsars). Continuous injection from a single source comparison with the ATIC/PPB-BETS data  peak width ： duration of the source  TeV tail ： upper limit for the duration ( B >~10 11 G for a pulsar)  may be measured by CALET Multiple injections: average flux and its dispersion average e ± spectrum should be quite FLAT & SMOOTH.  seen in the Fermi data ATIC/PPB-BETS peak is hardly to produce by multiple pulsars, and requires a single (or a few) energetic source(s). spectral cutoff at ~a few TeV seen in the H.E.S.S. data : due to the small number of young and nearby sources