Cosmological Fast Radio Bursts from Binary White Dwarf Mergers

Transcription

1 Cosmological Fast Radio Bursts from Binary White Dwarf Mergers Kunihito Ioka (KEK) Kashiyama, KI & Mészáros 13

2 ~10 yr ago GRB Cosmology Massive star origin High redshift GRBs Like QSO Like SN Star formation Reionization Metal, Dust Dark energy Larson & Bromm 02 GRBs are useful for probing high-z? z~10-30 GRB QSO, galaxy z~8 13/11/14 Fast Radio Burst by K. Ioka (KEK) 2

3 Radio Dispersion High energy photon Low energy photon Ionized region Luminosity t~δt Time Δt = 4.15 s In a plasma, a light signal is delayed ω 2 = k 2 c 2 +ω p 2 ω p = 4πne2 m " ν % $ ' # 1 GHz & = n 1 2 s 1 2 plasma frequency " DM % $ ' # 10 3 pc cm 3 & Distortion in light curve DM Reionization History 13/11/14 Fast Radio Burst by K. Ioka (KEK) 3

4 Dispersion Measure is the column density of free electrons along light path Dispersion Measure Dispersion Measure Reionization redshift Redshift Reionization History Recombined electrons provide no DM KI 03, Inoue 04 13/11/14 Fast Radio Burst by K. Ioka (KEK) 4

5 KI 03 Intergalactic DM ( 1+ ) ( 1 z) ( 1+ z) ( + ) z t dz 0 dz 2 1 z Δ = 2 e 1 = 2 2πmcν cn H 0 0 z e dt z dz Ω m + +Ω ν 2 p 2 ν Λ 12 DM IGP including missing baryon DM Galaxy ~ pc cm -3 13/11/14 Fast Radio Burst by K. Ioka (KEK) 5

6 DM from Afterglow Distortion at t~δt DM Δt ν -2 KI 03 Unfortunately radio afterglows are not so bright 13/11/14 Fast Radio Burst by K. Ioka (KEK) 6

7 Fast Radio Bursts Thornton m Parkes radio telescope (New South Wales) High Time Resolution Universe (HTRU) Survey High latitude survey (-70 deg < b < -30 deg) ν=1.382 GHz, Δν=400 MHz/1024, Δθ~14 arcmin F= Jy ms!!! Most luminous radio transients if cosmological 13/11/14 Fast Radio Burst by K. Ioka (KEK) 7

8 Dispersion Measure Thornton+ 13 Lorimer Burst δt DM ν -2 Galactic latitude DM= cm -3 pc 13/11/14 Fast Radio Burst by K. Ioka (KEK) 8

9 Summary of FRB Obs. l DM= cm -3 pc (z=0.5-1, d L ~2-6Gpc) l S ν ~Jy E iso ~ erg l δt=5.6ms,<4.3,1.4,1.1ms cδt(1+z) -1 < 1500(1+z) -1 km l Rate~(1±0.5) 10 4 /sky/day~10-3 /yr/galaxy Supernova rate 10-2 /yr/galaxy l No repeated bursts so far l No counterparts so far 13/11/14 Fast Radio Burst by K. Ioka (KEK) 9

10 Expected Rate Low frequency component SKA1 could find an extragalactic burst every hour Hassall+ 13 Lorimer+ 13 Trott event/hour 13/11/14 Fast Radio Burst by K. Ioka (KEK) 10

11 Possible Origins l RRAT (Rotating Radio Transient; intermittent pulsar) l Giant pulse from a msec/young pulsar l Evaporation of BH l SN into a nearby star l Magnetar giant flare l Collapse of hypermassive NS l Binary NS mergers l Superconducting cosmic strings l Nearby flaring stars Rees 77; Blandford 77; Kavic+ 08; Keane+ 12 Colgate+ 71,75; Egorov & Postnov 09 Popov & Postnov 07; Thornton+ 13 Falcke & Rezzolla 13; Zhang 13 Hansen & Lyutikov 01; Totani 13 Cai+ 12 Loeb /11/14 Fast Radio Burst by K. Ioka (KEK) 11

12 Binary White Dwarf Mergers? Kashiyama, KI & Meszaros 13 l Massive WD l SN Ia l Short GRB via NS l WD pulsar CR e ± excess Kashiyama+ 11 l GW sources l FRB? 13/11/14 Fast Radio Burst by K. Ioka (KEK) 12

13 Minimum Requirements l Energetics l Timescale l Event rate 13/11/14 Fast Radio Burst by K. Ioka (KEK) 13

14 Energetics Magnetic Energy Bobs,max~109G 2 3 B 4π r EB ~ 2 10 erg B9 r8.7 8π 3 WD-WD merger Differential rotation B Emax 13/11/14 Fast Radio Burst by K. Ioka (KEK) Loren-Aguilar+ 09, Ji+ 13 GM erg r v Ω ~ 1 s r8.7 r 14

15 Timescale WD radius cδt ( 1+ z) ( 1+ z) 1 cm < cm # r cap r% rω $ c & ( ' 1 2 ~ cm r Ω 0 r cap c ~ 2.3 ms r Ω 0 13/11/14 Fast Radio Burst by K. Ioka (KEK) 15

16 Event Rate WD-WD merger rate R WD 2 ~ yr 1 galaxy 1 ~4000 WDs in SDSS Radial velocity Binary fraction & distribution n(a) a α Badenes & Maoz 12 13/11/14 Fast Radio Burst by K. Ioka (KEK) 16

17 Binary White Dwarf Mergers? Kashiyama, KI & Meszaros 13 l Energetics E B ~10 40 erg l Timescale r cap /c~ms l Event rate ~SN Ia l SN Ia as a counterpart? 13/11/14 Fast Radio Burst by K. Ioka (KEK) 17

18 Counterparts l Supernova Ia (Double degenerate model) l X-ray debris disk L X <10 47 erg/s for ~100sec Swift for nearby FRBs 13/11/14 Fast Radio Burst by K. Ioka (KEK) 18 Loren-Aguilar+ 09, recently Beloborodov 13

19 FRB Cosmology KI 03 McQuinn 13 l Reionization l Missing baryon l Dark energy, cosmological parameters DM IGP = 3cH 0 Ω b 8πGm p d L = c ( 1+ z ) H 0 z z 0 # $ Ω m ( 1+ z)dz ( 1+ z) 3 + Ω Λ dz 1 2 % & Fast radio bursts as cosmological tools New frontier? 0 # Ω m ( 1+ z) 3 $ + Ω % 1 2 Λ 13/11/14 Fast Radio & Burst by K. Ioka (KEK) 19

20 Counterparts to GW Gravitational Wave Sources Neutrino?!!! 21 Nov 2013 Gravitational wave???? U. Tokyo Seminar by Kunihito IOKA (KEK) X-ray Gamma-ray IR-Opt 20 Radio

21 Relativistic Shock Breakout RelaHvisHc Kyutoku, KI & Shibata 12 Not resolved yet by numerical simulation 13/11/14 Fast Radio Burst by K. Ioka (KEK) 21

22 Relativistic Shock Acceleration ρ Γ sh ρ α rela After breakout, shocked matter accelerates to α rela Γ Γ 1+ 3 f sh by converting heat into motion Johnson & McKee 71 13/11/14 Fast Radio Burst by K. Ioka (KEK) 22 r

23 Relativistic Outflow E(> ) (erg) n=3, M sh =10-4 M sun n=3, M sh =10-5 M sun n=4, M sh =10-5 M sun n=6, M sh =10-5 M sun n=3, M sh =10-6 M sun v>>v esc ~0.3c!!! escape velocity for M * = 2.8 M sun and R * = 15 km Kyutoku, KI & Shibata 12 13/11/14 Fast Radio Burst by K. Ioka (KEK) 23

24 Early & High-Energy Emission Macronova Radio flare 13/11/14 Fast Radio Burst by K. Ioka (KEK) 24

25 Summary l Fast Radio Burst l Dispersion Measure Cosmological? l Binary White Dwarf Merger Energetics, Timescale, Event Rate SN Ia, X-ray debris disk l FRB Cosmology Thornton+ 13 KI 03 Kashiyama, KI & Mészáros 13 l Ultrarelativistic EM Counterpart to NS 2 Kyutoku, KI & Shibata 13 13/11/14 Fast Radio Burst by K. Ioka (KEK) 25

26 Thank You

27 BH-NS Merger Kyutoku Only Ejecta Full GR Q=5 χ=0.75 H4 EOS x-z plane, only ejecta Kyutoku, KI & Shibata 13 13/11/14 Fast Radio Burst by K. Ioka (KEK) 27

28 Anisotropic Mass Ejection θ ej 1 5 ϕ ej π Kyutoku, KI & Shibata 13 Viewing angle diversity Polarization Proper motion 13/11/14 Fast Radio Burst by K. Ioka (KEK) 28

29 Spin Down Luminosity L spin B2 r 6 Ω 4 ~ erg s 1 B 2 c 3 9 r Ω 4 0 <<10 43 erg/s B reconnection FRB like solar flares, magnetar flares 13/11/14 Fast Radio Burst by K. Ioka (KEK) 29

30 Φ max BΩ2 r 3 Acceleration 2c 2 ~ Volt B 9 Ω 0 2 r e ± production Coherent radio emission 13/11/14 Fast Radio Burst by K. Ioka (KEK) 30

31 Beaming Kashiyama, KI & Meszaros 13 Injection Emission 13/11/14 Fast Radio Burst by K. Ioka (KEK) 31

32 Brightness Temperature F = πr 2 2ν 2 ν d 2 c 2 kt T ~ K L r 2 43 emi,10 Coherent emission P~ E 2 ~ E 1 +E 2 +E 3 + +E N 2 ~N E 1 2 (incoherent) ~N 2 E 1 2 (coherent) 13/11/14 Fast Radio Burst by K. Ioka (KEK) 32

33 Curvature Radiation ν c γ 3 3c 4πr c ~ 0.72 GHz γ 3 r 1 3 c,10 γ 1100ν 1 3 r c,10 13/11/14 Fast Radio Burst by K. Ioka (KEK) 33

34 L ( P N 2 ) N tot c coh pat Luminosity P c ~ 2γ 4 e 2 c ~ erg s 1 γ r c,10 3r c N coh n e V coh n e 4 γ r 2 c 2 emi ~ n e cm 3 γ r c,10 r emi,10 ν c N pat V emi 1 4π fr 2 emi δr emi ~ cm 3 2 fr emi,10 V coh V coh V coh L ~ erg s 1 fn 2 γ 1 r tot e,7 3 c,10 δr emi,7.8 1 r 4 δr emi,10 emi,7.8 13/11/14 Fast Radio Burst by K. Ioka (KEK) 34

35 Electron Density n ~ cm L 1 2 γ 1 2 r e 43 3 c,10 Necessary multiplicity n e 1 2 r 2 δr 1 2 emi,10 emi,7.8 κ GJ = n e = n GJ B emi Ω 2πce ~ n e,7 B emi,5 Plasma frequency limit ν c ν p γ $ 4π n e # e 2 & 2π % m e ' ) ( 1 2, n e # = n e γ Ω 0 1 n e cm 3 γ /11/14 Fast Radio Burst by 3 rk. Ioka (KEK) 35 c,10

36 Induced Compton Melrose 71 Wilson & Rees 78 Lyubarsky 08 Compton scattering is enhanced by photons To evade the induced Compton γ 2000 r 3 14 r 3 14 n 3 14 c,10 emi,10 e,7 13/11/14 Fast Radio Burst by K. Ioka (KEK) 36