- Количество слайдов: 16
Injections of e± from Nearby Pulsars and their Ge. V/Te. V Spectral Features (NK, Ioka & Nojiri 2010 a, Ap. J, 710, 958) (Kashiyama, Ioka & NK 2010, ar. Xiv: 1009. 1141) (NK, Ioka, Ohira & Kashiyama 2010 b, ar. Xiv: 1009. 1142) Norita Kawanaka (KEK/IPNS) COSMO/Cos. [email protected] of Tokyo 2010/9/27
Electron/Positron Excess • positron fraction (PAMELA) rising in 10 -100 Ge. V, contrary to the conventional theory PAMELA: e+ • electron+positron spectrum the excess in 100 Ge. V-1 Te. V (Fermi/HESS) or the possible peak at ~500 Ge. V (ATIC/PPB-BETS) (Adriani et al. 2009) • Additional e± sources? • Dark Matter annihilation/decay? • Astrophysical sources? • forthcoming experiments (AMS 02, CALET, CTA etc. ) will explore >~Te. V spectrum more precisely. e-+e+ (Abdo et al. 2009)
Astrophysical Origin • Pulsar 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, Ioka & Nojiri 10; NK, Ioka, Ohira & Kashiyama 10 • Supernova Remnant Pohl & Esposito 98; Kobayashi+ 04; Shaviv+ 09; Hu+ 09; Fujita, Kohri, Yamazaki & Ioka 09; Blasi & Serpico 09; Mertsch&Sarkar 09; Biermann+ 09; Ahlers, Mertsch & Sarkar 09 What kind of electron/positron spectrum can we expect from astrophysical sources? • Microquasar (Galactic BH) Heinz & Sunyaev 02 • Gamma-Ray Burst Ioka 10 • White Dwarfs Kashiyama, Ioka & NK 10 (see the poster D 2)
CR Propagation Equation and Solution • diffusion equation diffusion injection energy loss (synchrotron, inverse Compton scattering) Spectrum from instantaneous injection from a point source (Atoyan+ 1995) : electron energy at t 0 ：diffusion length In the Thomson limit, cutoff energy: ee~1/btage
The case of transient source: e± spectrum The cutoff energy corresponds to the age of the source. d=1 kpc (a) E=0. 9 x 1050 erg age=2 x 105 yr a=2. 5 (b) E=0. 8 x 1050 erg age=5. 6 x 105 yr a=1. 8 Ioka 2010 (c) E=3 x 1050 erg age=3 x 106 yr a=1. 8
Continuous Injection: Broadened Peak t 0~105 yr background t=5. 6 x 105 yr r=1 kpc Ee+ ~Ee-~1050 erg a=1. 7 Emax=5 Te. V Flux without background Burst-like event (e. g. GRB) Epeak~1/bt ~600 Ge. V NK+ 2010 a
e± Injection from Multiple Sources • Total injection energy required to account for the peak of ATIC/PPB-BETS ~ 1050 erg ~ Rotation energy of a pulsar with P 0~10 msec Too efficient? • Local pulsar birth rate ~10 -5 yr-1 kpc-2 (Narayan 1985; Lorimer+1994) Pulsars which have not been observed via EM radiation may contribute significantly. Young pulsars (age<5 x 105 yr) should exist. • The ATIC 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 NK+ 2010 a; Kashiyama, Ioka & NK 2010 Average flux from nearby sources with a birth rate of R: Flux per source Number of sources which contribute to the energy bin of ee Assuming the Poisson statistics of the source distribution,
e+ fraction solid lines： fave(ee) dashed lines： R~0. 7 x 10 -5/yr/kpc 2 Ee+=Ee-~1048 erg a~1. 9 e±spectrum fave(ee) ±Dfave 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 s level. Such a peak is hardly to produce by the sum of multiple pulsars. 3. Large dispersion in the Te. V range due to the small N(ee) possible explanation for the cutoff inferred by H. E. S. S
Spectral Features in >Te. V Band Will be explored by CALET, CTA etc. Large theoretical dispersion We can expect to observe the contributions from a single young and nearby source. Vela pulsar (age~104 year, distance~290 pc), Cygnus loop, or undiscovered compact objects ? 10 Te. V 100 Te. V
A young PSR/PWN is surrounded by a SNR. CR electrons/positrons from a pulsar should go through the SNR shock. Kennel & Coroniti 93 Low energy particles are r trapped around the shock (i. e. have a smaller diffusion length). shock front LE CR HE CR Lesc Escape condition: x
“Escape-Limited” Model In the Sedov phase, higher energy particles escape the SNR shock earlier (Ptuskin & Zirakashivili 03, 05; Caprioli+ 09; Gabici+ 09; Ohira+ 10) “Age-limited” model (Higher energy particles require a longer time for acceleration) Predict (1) the softening of the CR spectrum from the injection and (2) the spectral break in the g-ray spectrum consistent with observations but NO DIRECT EVIDENCE Models of eesc(t) Nesc Observed CR spectrum eesc(t) e
Te. V e± spectrum can prove the CR escape! • Electron spectrum from Vela SNR/PSR (d=290 pc, tage~104 yr, Etot=1048 erg) Without energydependent escape eesc(t) from Ptuskin & Zirakashvili 03 • Only e± with ee>eesc(tage) can run away from the SNR. Low Energy Cutoff • 5 yr obs. by CALET (SWT=220 m 2 sr days) may detect it. Direct Evidence of Escape-Limited Model for CR accelerators (=SNR)!
Summary • Ge. V/Te. V spectral features of CR e± from pulsars. • Continuous injection from a single source comparison with the ATIC/PPB-BETS data peak width：duration of the source may be measured by CALET • Multiple injections: average flux and its dispersion average e± spectrum 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 Te. V seen in the H. E. S. S. data : due to the small number of young and nearby sources • CR escape from the SNR shock, which is the most important process in determining the CR spectrum, has been never probed directly from observations. The electron flux from a young pulsar may have the low energy cutoff in >~Te. V band, which can be the probe of CR escape from SNRs.
CALorimetric Electron Telescope A Dedicated Detector for Electron Observation in 1 Ge. V – 20, 000 Ge. V Energy resolution: ~2% (>100 Ge. V) e/p selection power: ~105 CALET Red points/errorbars: expected from 5 yr obs. by 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. )
International Collaboration Team Waseda University : S. Torii, K. Kasahara, S. Ozawa, Y. Aakaike, H. Murakami , J. Kataoka, N. Hasebe, N. Yamashita JAXA/ISAS: M. Takayanagi, H. Tomida, S. Ueno, J. Nishimura, Y. Saito H. Fuke, K. Ebisawa，M. Hareyama Kanagawa University : T. Tamura, N. Tateyama, K. Hibino, S. Okuno, S. Udo, T. Yuda Aoyama Gakuin University: A. Yoshida, K. Yamaoka, T. Kotani Shibaura Institute of Technology: K. Yoshida , A. Kubota, E. Kamioka Yokohama National University: Y. Katayose, M. Shibata ICRR, University of Tokyo: Y. Shimizu, M. Takita KEK: K. Ioka, N. Kawanaka National Inst. of Radiological Sciences : Y. Uchihori, H. Kitamura S. Kodaira Hirosaki University: S. Kuramata, M. Ichimura T okyo Technology Inst. : T. Terasawa, Y. Tsunesada Kanagawa University of Human Services : Y. Komori Saitama University: K. Mizutani Shinshu University : K. Munekata Nihon University: A. Shiomi NASA/GSFC: J. W. Mitchell, A. J. Ericson, T. Hams, A. A. Moissev, J. F. Krizmanic, M. Sasaki Louisiana State University: M. L. Cherry, T. G. Guzik, J. P. Wefel Washington University in St Louis: W. R. Binns, M. H. Israel, H. S. Krawzczynski University of Denver: J. F. Ormes University of Siena and INFN: P. S. Marrocchesi , M. G. Bagliesi, G. Bigongiari, A. Caldaroe, M. Y. Kim, R. Cesshi, P. Maestro, V. Millucci , R. Zei University of Florence and INFN: O. Adriani, P. Papini, L. Bonechi, E. Vannuccini University of Pisa and INFN: C. Avanzini, T. Lotadze, A. Messineo, F. Morsani Purple Mountain Observatory: J. Chang, W. Gan, J. Yang Institute of High Energy Physics: Y. Ma, H. Wang, G. Chen