(Yamaguchi & Takahara 2012, ApJ, 761, 146 ) 大阪大学 山口正輝 共同研究者： 高原文郎 第 25 回理論懇シンポジウム「計算機宇宙物理学の新展開」 ＠つくば国際会議場 2012/12/23

I. ガンマ線連星について II.LS 5039 とその観測 III.X 線放射モデル IV. 結果 V. まとめと結論

ガンマ線が連星周期に同期して変動している連星 AU スケールから 10TeV 以上のガンマ線が出ている！ こんな天体はガンマ線連星だけ！ 高密度星の近くの物理状態を調べられる ( パルサー風やジェット ) … ただ、放射機構はよくわかっていない ObjectsPeriodScaleConsists of … LS d5x10 12 cmO + ?? (BH or NS) LS I +61° 30326d10 13 cmBe + ?? PSR B yr10 14 cmBe + NS HESS J d10 14 cmBe + ?? 1FGL J d10 13 cmO + ?? O star Compact star

A. A. Abdo, et al., 2009, ApJL, 706, 56 F. Aharonian, et al., 2006, A&A, 460, 743 T. Takahashi, et al., 2009, ApJ, 697, 592 Suzaku Fermi HESS ・ TeV 、 GeV は反相関 ・ TeV 、 X 線は相関 ・光度は GeV で最大 Fermi Suzaku Photon energy (eV) Phase-averaged spectra Orbital phase Light curves MS superiorinferior HESS SUPC INFC SUPC

 X 線から TeV を説明しようと する研究はいくつかある  いずれもスペクトルまた は周期変動に問題あり 最も重要なのは … シンクロトロン冷却に よる TeV の抑制  →X 線をシンクロトロン起 源としているのが問題？ T. Takahashi, et al., 2009, ApJ, 697, 592 B. Cerutti, et al., 2010, A&A, 519, 81 MSY & Takahara, 2010, ApJ, 717, 85 磁場強 TeV 小

A. A. Abdo, et al., 2009, ApJL, 706, 56 T. Takahashi, et al., 2009, ApJ, 697, 592 Suzaku Fermi ・ X-ray と GeV がきれいに反相関している ・スペクトルが滑らかにつながりそう ・逆コンプトン (IC) で冷えた電子があるはず Suzaku Photon energy (eV) Phase-averaged spectra Orbital phase Light curves MS superiorinferior SUPC INFC SUPC Fermi X 線は IC 放射？ ( シンクロトロンでなく )

 注入電子の分布： べき 2.5  → IC 冷却により分布変わる ( で決まる )  電子は高密度星の位置にいる  電子の速度は等方として入れる  電子は O 型星の光子を IC 散乱する  星由来光子の異方性考慮  電子静止系ではトムソン散乱 IC スペクトルを軌道位相ごとに計算 ：フリーパラメータとする 注入率を与える → 冷却電子の数を決める 定常の電子分布

 GeV の変動は Fermi スペクトル と合うように、軌 道傾斜角を調整 （ → i = 15° ）  γ min = 10 3  GeV と X 線は同じように変動  X 線のべきが観測とよく合う ( ∵冷却電子の放射 )

 γ min ∝ F GeV のときに X 線観測を再現できた  本質は注入率の変動で冷却電子の数が変動すること

 LS 5039 において、 の電子に対して IC スペ クトルと光度曲線を計算し、 Suzaku の観測と比べた  スペクトルべき指数が観測と一致  γ min ∝ F GeV なら光度曲線を再現  X 線は IC で冷却した電子からの放射  X 線の変動は注入率の変動による  GeV, TeV は IC 放射で説明できる ( 我々の先行研究 )  → X 線から TeV まですべて IC 放射で説明できる 結果

 星風とパルサー風 or ジェットの ( 磁気 ) 流体シミュレーションが必要！  流体計算を取り入れた放射の計算はいくつか ある (Takata et al. 2012; Zabalza et al. 2012)  これからもっと発展させていくべき！ ガンマ線連星系を用いて 高密度星近傍の物理に迫れる ガンマ線連星を本当に理解するには … star

 γ min を固定した時の変数を添え字 0 で表わす  F X : X 線フラックス、 γ X : X 線を出す電子の γ

Microquasar model (= accretion + jet)  コンパクト星は BH  星風を accretion → jet  jet 内の衝撃波で粒子加速 → 非熱的放射 Pulsar model (= pulsar wind + stellar wind)  コンパクト星は NS  二つの wind の衝突により衝撃波  そこで粒子加速 → 非熱的放射 star

 Compact star (CS) + Massive star (MS, O6.5)  Period : 3.9 days  Separation at periastron… ~2R star at apastron…~4R star (R star ~ cm) Orbit of LS 5039(head on) supc infc observer periastron apastron MS CS

A. A. Abdo, et al., 2009, ApJL, 706, 56 F. Aharonian, et al., 2006, A&A, 460, 743 T. Takahashi, et al., 2009, ApJ, 697, 592 Suzaku Fermi HESS ・ X-ray & GeV anticorrelate Fermi Suzaku Photon energy (eV) Phase-averaged spectra Orbital phase Light curves MS superiorinferior HESS SUPC INFC SUPC

 Constant and isotropic injection of electrons at CS (power-law distribution)  Cooling only by IC process → cascade  Electrons emit photons at the injection or creation sites  The uniform magnetic field ×: annihilation position We calculate spectra and light curves by ① the cascade process with Monte Carlo method (GeV to TeV) ② the synchrotron emission using the e ± distribution for B = 0.1 G (X-ray) → ： IC photon path MS × × × × CS → ： MS photon path observer (parameters ： the inclination angle & the power-law index of injected electrons)

Electron energy distribution in steady state (index: 2.5) Anisotropic IC spectra without γγ absorption Head-on Rear-end apastron periastron ・ KN effect flattens the electron distribution ・ The electron number is larger at apastron due to suppression of IC cooling ・ Anisotropic IC emission of head- on collision is more intense since collision rate is higher ・ Anisotropy is suppressed by KN effect at higher energy

 Qualitative fit to observations  No fit to X-ray observations when B = 0.1G  When 3G, the best fit Inclination angle: 30° Power-law index: 2.5 INFC SUPC IC cascade synchrotron ____ Photon energy (eV) 0.1G 3G Under this, synchrotron cooling is dominant ・ variation in GeV band ・ ratio of TeV to GeV flux is fitted

TeV: roughly reproduced GeV: well reproduced X-ray: a phase difference X GeV Orbital phase (numerical results are normalized with maxima of observation) TeV Inclination angle: 30° power-law index: 2.5

 TeV: absorption is dominant At supc, flux is smaller than infc by the large density of stellar radiation field  GeV: IC anisotropy is dominant At supc, flux is larger than supc by head-on collision of IC scattering  X-ray: e± number variation by IC cooling At periastron, the e± number in steady state is smaller than apastron by IC cooling in the large density of stellar radiation field, so emissivity by synchrotron is smaller, therefore flux is smaller MS Binary axis TeV MS CS(inferior)CS(superior) GeV MS X-ray CS(superior)CS(inferior) CS(apastron) CS(pariastron)

 If electrons scatter off stellar photons, the break is not reproduced  Assume that the break is due to γγ absorption  Typical energy of absorbed photons: tens of GeV  We assume that electrons scatter off 100 eV photons 0.1G 3G Yamaguchi & Takahara, 2010, ApJ, 717, 85 If 10 times of this Therefore,

 e± are accelerated up to 1TeV and radiate in the area (1) where B=3G  e± are accelerated from 1 to 30TeV and radiate in the area (2) where B=0.1G  We inject e± with energy, e± with  are injected in area(1) and IC photons cascade in 100eV radiation field e± with  are injected in area(2) and IC photons cascade in stellar radiation field we count the escaped photons CS B=3G B=0.1G Calculation method O star

 30TeV photons are emitted and X-ray flux match obs Problem  10GeV spectra do not match obs  As well, 10TeV (SUPC) Inclination angle: 30° INFC SUPC ーーーー

 No influence on Suzaku data  Optical depth τ > 1  e± are accelerated up to 1TeV and emit near 100 eV source where B=3G  e± are accelerated from 1 to 50TeV and emit far from 100 eV source where B=0.1G we calculate cascade with 100eV photons near the source, and with stellar photons far from it O star CS Requirement for 100eV source B=3G B=0.1G Electron injection

 GeV break is reproduced  But…  X-ray spectra terribly underestimate  No orbital variation in GeV & X-ray band

Underestimation at X-ray  Energy density of 100 eV photons is larger than that of stellar photons. → IC cooling time shorter → the number of e± smaller No variation in GeV & X-ray band  e± scatter off photons near CS → direction to CS independent of phase → No modulation in GeV band  The number of electrons does not change by the orbital motion → No modulation in X-ray band Superior conjunction Inferior conjunction CS O star CS O star

Underestimation at TeV  TeV flux is underestimated  GeV flux is overestimated  We assume that 100eV photons are isotropic  The flux by IC scattering is large compared with anisotropic photon field Anisotropic photon field O star Isotropic photon field Photons through head- on collision are seen from any direction HEe± source

 Flux in the 2-area model is larger than the other →the anisotropy of target photons is important  Independent of photon density and target photon 2-area model 2-area model & 1-area model INFC SUPC INFC SUPC Actually, flux of IC in the 100eV field exceed that in the stellar field

 For LS 5039, the break in calculated GeV spectrum is different from that in observed one.  So we introduce 100eV photon source → spectral break is reproduced but…  X-ray flux is underestimated (by large photon density)  X-ray & GeV have no variation (by isotropy of 100eV)  it is difficult to explain the high energy emission by the model with 100 eV photons  With 100eV source, we introduce orbital variation of injection (as in Owocki et al. 2010, proceeding)  Without 100eV source, we regard GeV cutoff as high energy cutoff of injected e±