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Kumiko Kotera - Institut d’Astrophysique de Paris EuCAPT - 07/07/2020 ν γ Fe GW p Towards EeV Astronomy catching the sources of ultra-high-energy cosmic rays
Exciting times! Extragalactic First 1020 eV cosmic ray origin confirmed Auger evidences large CR detected scale anisotropy > 8 EeV First 1015 eV PeV neutrino neutrinos astronomy begins! IC170922 in coincidence ν detected with TXS 0506+056 1962 2013 2015 2017 new TDEs, magnetar flares, blazar flares, FRBs, γ gamma-ray bursts, superluminous SNe… First GW astronomy gravitational begin! GW waves detected kilonova associated with GW170817 And we still don't know the origin of UHECRs 2
A UHECR journey Source? - particle injection? - acceleration? shocks? Cosmic backgrounds reconnection?… interactions on CMB, UV/opt/ IR photons cosmogenic neutrino and Outflow gamma-ray production - structure? - B? - size? Intergalactic magnetic fields magnetic deflection Source population temporal & angular spread/shifts emissivity evolution affects the diffuse p Fe astroparticle fluxes γν Backgrounds - - radiative? baryonic? evolution, density? γν - magnetic field: deflections? associated neutrino and gamma-ray production Observables UHECR neutrinos multi-wavelength photons GW - mass - flavors - spectral features - spectrum - spectrum - spectrum - time variabilities - arrival - anisotropy - anisotropy - angular spread directions - time variabilities - source distribution - time 3
Learning from UHECR data Energy spectrum J(E) × E3 [km-2 yr-1 sr-1 eV2] JAuger/JTA 1.4 1038 1.2 1 0.8 1037 0.6 Telescope Array combined (ICRC 2015) 0.4 Auger combined (ICRC 2015) 0.2 36 10 0 18 19 20 10 10 10 1018 1019 1020 E [eV] E [eV] Verzi et al. (2017) – 22 – Arrival directions Fig. 14 Left panel: comparison between the TA and Auger combined spectra presented 90° at the 34rd International Cosmic Ray Conference (ICRC 2015) [28, 29]. The TA spectrum 60° is shown in the energy range where Auger data are available. The ratio of the Auger fluxAuger to Coll. ICRC 2017 the TA flux versus energy 30° is plotted in the right panel. Mass composition 180° 120 ° 60° 0° 300 ° 240 ° ankle presented in Table 4 and 5 can be compared directly. As expected, they are in good agreement. In the region -30° of the cut-o↵, on the other hand, the comparison is more difficult, since the parameters that define the two functional forms have di↵erent meanings. However, an unambiguous comparison -60° can be made using the parameter suggested in [6] that defines the position of the observed -90° cuto↵. This is the energy E1/2 , at which the integral spectrum E>1019 eV drops by a factor of two Auger below & TA that combined which would be expected in the absence of the cuto↵. analysis E1/2 g. 7.— Arrival hasof Auger directions been calculated events Aab by hemisphere) (red points in the South both etTelescope al. (2014) collaborations. and Array ones For TA, E1/2 = 60 ± 7 EeV (statistical 4
Learning from the energy spectrum maximum acceleration energy? KK & Olinto 11 or GZK cut-off? knee ankle 5
Dans notre photons cas, le proton a une énergie colossale, donc des photons peu énergéti supplémentaires. 2.1 Théoriquement, Productionplusieurs réactions entresur par interactions un rayon les Energy losses of UHECRs and the GZK horizon probablement cosmiquede fonds à obtenir Dans notre cas, le proton a une la et photons un photon peuvent conduire réaction. Supposons donc un donc énergie colossale, photon desd’énergie photons ⇥peu et calcu énerg à la production de particules secondaires intéressantes. Par mesure de simplicité, commençons nécessaire pourà nos Ep probablement obtenirinteractions. laphoton réaction. La Supposons conservation de la donc unnorme photon ded’énergie l’énergie-impul ⇥ et ca Théoriquement, plusieurs réactions entre un rayon cosmique par étudier le cas d’un proton. Dans les milieux astrophysique que l’on considère, les processus et un peuvent conduire (en Esupposant p nécessaire une impulsion nulle pour Lales produits de del’interaction, et une coll à d’interaction la productionnotables de particules que lessecondaires protons peuvent intéressantes. subir sont Parpour lamesure nos interactions. de simplicité, photo-production conservation de commençons pions : la norme de l’énergie-im forleproton cosmic rays: dans (enleastrophysique référentiel supposant backgrounds: CMB duIR/optical/UV une laboratoire), impulsion pourpour nulle photons la photo-production de pions : les produits de l’interaction, et une par étudier cas d’un proton. Dans les milieux que l’on considère, les processus p + dans ⌅N + n⇤ , le sont référentiel du laboratoire), pour (2.1) ⇥ de⇥ pions m (m +de 2m p ) cla :photo-production : 4 d’interaction notables que les protons peuvent subir la photo-production Ep pions ⇤ 10 eV 19 1 où N est un nucléon et n le nombre de pions produits, et la production m (m 2⇥ de + paires 2mp ) électrons- c4 10 3 eV ⇥ ⇥ 1 RI 13 July 2011 pion 14:26 photoproduction p + et pour⌅ Nla+production n⇤ , de Epaires p électrons-positrons (2.1) ⇤ :106 xeV 19 10 eV 3 19 positrons, appelée aussi effet Bethe-Heitler : 2⇥ 10 eV où N est un nucléon et n le nombre de pions produits, et pour la et productionla production de paires m mde paires électrons- électrons-positrons : ⇥ ⇥ 1 e p pair photoproduction p+ ⌅ p + e+42+ e . Ep ⇤ 510 ⇥19 10eV 18 eV(2.2) des3 autres astroparticules ⇥ . positrons, appelée aussi effet Bethe-Heitler : ⇥me mp La production 10 eV⇥ 1 lors de Les pions produits se désintégreront enOn voit ainsi neutrinos, qu’à ultra-haute E énergie, ⇤ 5 ⇥ 10 mêmesecondaires, 18 des photonseV de3très faible. énergie pou + photons et électrons/positrons p p+ ⌅p+e +e . ⇥ (2.2) 10 eV et ces derniers pourront enclencher des buer cascades On à la voit production ainsi qu’àdeultra-haute électromagnétiques, particules secondaires. i.e. énergie, créer encore même Cecidesest d’autres intéressant, photons de trèscarfaible les seuls fond énergie Les pions10 5produits photons se désintégreront en neutrinos, supplémentaires. dans buer à photons l’Univers qui et la production ontélectrons/positrons une densité raisonnablement de particules secondaires, secondaires. Ceciélevée pour jouercar est intéressant, unlesrôle seulsici, et cesDans derniersnotrepourront cas, le proton enclencher a une des cascades diffus énergie électromagnétiques, cosmologique colossale, dans donc des l’Univers qui (CMB) photons ont une i.e. peu créer d’énergie encore moyenne énergétiques densité d’autres raisonnablement su⇥ront 2.7 kB Tpour ⇥CMB ⇧ élevée ⇤ 6 ⇥un10rôle CMB jouer 4 e photons supplémentaires. probablement à obtenir la réaction. Supposons infrarouge diffus donc qui uns’étend cosmologique photonsur d’énergie (CMB) 10 1 moyenne ⇥ et3 calculons ⇥IR ⇤d’énergie eV. l’énergie ⇥CMB ⇧ 2.7 kB TCMB ⇤ 6 ⇥ 10 10 4 EDans notre cas, pourlenosproton a une énergie colossale, donc des photons peu⇥IRénergétiques su⇥ront Proton energy loss lengths (Mpc) p nécessaire interactions. La conservation infrarouge dequi la norme s’étend desur l’énergie-impulsion ⇤ 10 3 1 eV. implique probablement (en supposant à obtenir une impulsionla réaction. nulleSupposons donc un photon pour les produits d’énergie ⇥etetune de l’interaction, calculons collision l’énergie frontale nécessaire Epdans pour nos le référentiel duinteractions. laboratoire),La conservation pour de la normededepions la photo-production l’énergie-impulsion : implique 10 3 (en supposant une impulsionmnulle (m pour + 2m les) cproduits 4 de l’interaction, ⇥ 1et une collision frontale source distance scale p ⇥ dans le référentiel du laboratoire), Ep pour la ⇤ 1019 eV photo-production de 3pions : (2.3) 2⇥ < 100s Mpc 10 eV et pour10la Photo-pionde production production m (m électrons-positrons paires + 2mp ) c4 ⇥ 1 19 : 2 ⇥ Ep loss length Energy ⇤ 10 eV ⇥ (2.3) Interaction length 2⇥ me mp 10⇥ 3 eV 1 et pour la productionInteraction E de paires p ⇤ 5 ⇥ électrons-positrons 10 18 eV: 10 3 eV . (2.4) length ⇥(IR) 10 1 On voit ainsi qu’à ultra-hautePair production ménergie, e mp même18des photons ⇥ de⇥ très 1 faible énergie pourront contri- photon energy (2.4) in proton rest frame Ep ⇤ 5 ⇥ 10 eV Figure 2.4 – . buer à la production de particules ⇥ secondaires. Cosmological expansion > 6x1019 eV Ceci 10 est 3 eV intéressant, car Section les seuls efficace fonds totale pour dela photons photo-production de pions du proton. Les di↵ér Ondansvoitl’Univers ainsi 10 0 qu’à ultra-haute qui ont une énergie, densité GZKmême cut-off des raisonnablement photons teraction sont représentés. Les résonances en pointillés produisent dans un premier temps des de très élevée pourfaible jouer énergie un rôlepourront ici, sontcontri- le fond extragalactic sources + + de vie très limitée ( , N ) qui se désintègrent ensuite en pions ; elles ont une section effica buer à la 10 17 production 10 de 18 particules 10 19secondaires. 10 20 Ceci est 10 21intéressant, 10 22 car les seuls fonds de photons diffus cosmologique (CMB) d’énergie moyenne ⇥CMBinteractions Greisen 1966, ⇧ 2.7 kproduisant B TCMB ⇤ 6 ⇥ 10 eV et le fond 4 plusieurs pions (multi-pion) dominent à haute énergie (tirets courts). O dans l’Univers infrarouge quiqui ont une s’étend sur densité ⇥IR ⇤ 10 (eV) Eraisonnablement 3 1Zatsepin eV. & Kuzmin élevée 1966 jouer within le pic depourla section efficace un derôle ici,~200 la production sontdelela Mpcfond particule (1232) ; c’est la résonance . 6 diffus cosmologique (CMB) d’énergie moyenne ⇥ ⇧ 2.7 k T ⇤ 6 ⇥ 10 4 eV et le fond
Learning from large scale anisotropies Galactic or extragalactic? UHECR source(s) in our Galaxy imply high level of dipole amplitude p 720 A. di Matteo and P. Tinyakov 0.2 Fe di Matteo & Tinyakov 2018 esp. for light mass 0.1 Total composition tions using the two @models different GMF 8 EeVwith the δ same injection model, they are not so large as to impede a meaningful 0.05 interpre- tation of the results in spite of the GMF uncertainties. Conversely, the results from e.g., the three injection Calvez models et al. 2010 do differ 0.02 significantly, dipole expected from LSS with heavier compositions resulting Giacinti in larger et al. 2011 dipole and quadrupole 17 18 19 moments for high energy thresholds (due to the shorter 10 propaga- 10 10 Eichler et al. 2016 E (eV) tion horizon) but smaller ones for lower thresholds (due to larger magnetic deflections). FIG. 2: Galactocentric anisotropy for a source distribution that traces the stellar counts in MW, modeled by random Increasing the energy threshold, the expected generationdipole of 103 and bursts separated by time intervals of 105 yr. quadrupole strengths increase, but at the same time The themodelamount parametersof are the same as in Fig. 1. Although the anisotropy in protons is large at high energies, their con- statistics available decreases due to the steeply falling energy tribution to thespec- total flux is small, so the total anisotropy trum, making it non-obvious whether the overall effect is to make the < 10%, Auger consistent withColl. ScienceThe the observations. 2017 latest GRBs detection of the dipole and quadrupole easier with do not introduce Ahlers a (2018) 1805.08220v1 large degree of anisotropy, as it would be in higher the case or lower of UHE protons, but they can create “hot spots” Emin . To answer this question, we have calculatedand theclusters 99.9 per cent of events. C.L. detection thresholds, i.e. the multipole amplitudes such that FigureGlobus also 6. The magnitude & Piran 2018 —> dipole of the dipole from as a function of LSS thresholdEeV larger values would be measured in less than 0.1 per cent ofdirection 5% @[4-8] the energy ran- of is a sphere with radius RG ∼ 100 kpc and that all the Emin for the three injection models and two GMF models we considered. dom realizations in case of√ an isotropic90 UHECR flux. 2MRS dipole Thearedetection sources at the Galactic Center,0.46 so that the problem The points labelled ‘Auger + TA 2015’ and ‘Auger 2017’ show the dipole thresholds scale like ∝ 1/ N with the number of is events spherically N. Since symmetric: Qi (E, !r , t) = δ(!r )Q0 (E0 /E)γ , magnitude reported in Deligny (2015) and Taborda (2017), respectively. ni (E, !r , t) = ni (E, r). This is admittedly a simplified below the observed cutoff (∼40 EeV) the integral model, spectrum at Earth Auger confirms that UHECRs The dotted lines show the 99.9 per cent C.L. detection thresholds using the current and near-future Auger and TA exposures (see the text for details). −2 N (≥ Emin ) is close to a power law ∝ Emin , the detection and below. threshold we will replace it with a more realistic model 2MRS Neglectingisthe energy losses inside the Galaxy, km-2 sr-1 yr-1 roughly proportional to Emin . At higher energies,one theobtains experimental the5solution EeV of Eq. (2) with a boundary con- are of extragalactic origin sensitivity 180 degrades faster as the result of the cutoff. dition 2corresponding Galaxy: EeV to a diminishing flux outside the -180 0.42 In order to compute the detection thresholds, we assumed the ! "γ 5.2 sigma dipole of 6.5% observed at E>8 EeV energy spectrum measured by Auger (Fenu 2017) and (i) the sum ni (E, r) = Q 0 E0 . (9) 4πr Di (E) E of the exposures used in the most recent Auger (Giaccari 2017) and dipole direction, amplitude TA (Nonaka 2017) analyses (lines labelled ‘2017’);This (ii) solution the sumcorresponds of to energy-dependent compo- sition for E > E0 . Indeed, at critical energy E0,i , which the exposures expected if another 3 yr of data are collected for with and light composition at EeV energies 2 3000 km effective area by each observatory, is different as planned each nucleus, direction of the 0.38solution (9) changes -90 from ∝ Efollowing −γ−δ to ∝ E 1 −γ−2+δ because of the change in 2 in tension with source inside Galaxy the fourfold expansion of TA (Sagawa 2015) (lines labelled D i (E). Since UHECR ‘2020’). the change dipole occurs at a rigidity-dependent Figure 3: Map showing the fluxes of particles in Galactic coordinates. critical energy E = eESky 0 i map in Galactic Z , the larger co- behind nuclei lag The sensitivity is less than what it would be if wethe had uniform ex- 0,i lighter nuclei in terms of the critical energy and the 7 ordinates showing the cosmic-ray flux for E 8 EeV smoothed with a 45 top-hat function. The
Galactic to extragalactic transition region Comparison to other experiments TA talk @UHECR2018 > 8 EeV extragalactic origin knee dipole measurement Galactic Auger Coll. 2018 SNR origin Oct 09, UEHCR 2018 20 virtues of this transition region relatively important particle flux (few 100 cm−2 sr−1 s−1 GeV2) —> accumulate reasonable statistics with mid-sized detectors overlaps with energy range experimentally probed by LHC 8
Learning from mass composition? GRANDProto300 Motivation KASCADE, IceCube, TUNKA Pierre Auger, Telescope Array zoom on transition region data (Nµ) • Mass composition () carries imprint of cosmic-ray sources and rst bu propagation exp. error a y ma r all) exp. error m b Ga nnon (ca • Uncertainties in hadronic interaction models dominate , not data experimental uncertainties (Xmax) LHC LHC • Muon measurements have much pO@10 TeV pp@14 TeV larger spread and are not consistent with Xmax: Muon PuzzleIceCube ICRC 2015 Dembinski Talk@ WHISP 2018 from Kampert & Unger (2012) Based on Kampert & Unger, Astropart. Phys. 35 (2012) 660 Combined approach light—>heavy —> needed to intermediate light —> get precise unambiguous ?? data • Cosmic ray community needs to probe air showers, detect inconsistencies, combine data • Collider community needs to provide relevant reference measurements for model tuning not precise enough for constraints on models Indirect search for physics beyond the standard model at 100 TeV scale 9
On peut aussi remarquer que ⇤esc dépend du transport des particules .cceleration, v?Requiring = c ? perpendicular withthat Ecandidateto the. max ⌘accsources ⇥magnetic ZeBR, ⇥ field 1 B,be where to de thecapable ⌘acc typical diffusion isof le added danssize confining of to account the magnétique champ source par- R, Galactique for(voir annexe A.1.3) nencycosmic puts rwhich L = accelerators? 1.08 constraints Mpc on can be 10 Z Selection of UHECR candidate sources 1 the low E size 18 eV and B the magnetic for non-relativistic 1 nG . field ofoutflows. turbulencesources (1.11) allowing magnétique This tocriterion produce Galactique canKolmogorov, est de type be on trouve ates mic-ray uiring into that a acceleration,simple candidate with selection sourcesE max . ⌘ bes’écrit criterium acc capable ZeBR, where for spectre ⌘ candidate acc is added d’injection tosources toujours account raisonnablewith for en ⌅ 2.35 serait alors nécessair ic outflows, onfinement dans unefor sourcewhich de taillewe L compare rL ⇤ of etconfining L the peut Larmor par- radius and typical se retranscrire size in Bmessenger tion and de la to a façon astronomy, efficiency which extension accelerate, suivante the can (c’estfirstR le detection be low (Hillas confine critère of non-relativistic for de for UHECR and high- 1984): incandidate Hillas source: 1984) : r ' des rayons outflows.R, ' i.e., 0E cosmiques This observé. criterion the can Emax be ⇠ size nto which simple questionsgives erelativistic than selection E answers. outflows, max . criterium As for which ⌘ ZeB developed accwe⇥ compare 0 in R 0 Alves ⇥ the Larmor sources where L Batista R On peut with 0 and B enfin and radius comoving are se demander typicaljusqu’à typical size in quelle énergie les restes de superno dpen extension kpc). Figure questions R Emaxremain (Hillas 1011 1984): presents Br' the 15 on the originL of the 0UHECR, eV Z . R, L ' i.e., so-called 0 . whereE E Hillas their 0max aufigure spectre ⇠ sizedes ofdiagram 0 are cosmiques. rayons (1.12) where can-energy Le mécanisme de Fermi ne peut fonction g the Ecomoving frame, ⇤ which ⌅ gives frame, E⇥max as 1 ⌘ illustrated acc ZeB 1 pc R in R and 1.9 B forthe a typical maximum size Figure 11 presents the so-called µG source aring ic fieldatinthethe highest comoving energies in the frame, asHillas cosmic diagram illustratedray spectrum where confinées restent in figure can- dans la zone d’accélération. Ce confinement a lieu grâce 1.9 for a maximum energy dpagation Bin R aleurs eV. a ofphase-space, BUHECR numériques R and moyennesphase-space, pour the e↵ect taking des restes into taking de of magnetic accountsupernovæ.theinto fields, et ilaccount Lagage their & Cesarsky faut donc que uncertainties the uncertainties le rayon de Larmor de la particule soit inférieur à la édronic un calcul plus détaillé interactions anden prenant en discovery compte l’évolution potentials fordiscussion secondarydes rayonsupernovæ, de Larmor etd’une particuleprimed quantities: d’énergie in comoving E et de charge Z dansframe un milieu Ptitsyna also & PtitsynaTroitsky & 2010 for Troitsky an updated 2010 for an on updated the discussion on the x ⌅ 2and⇥ 10 new eV physics. ⇥ Z (B/1 µG). La prise en compte de l’amplification dus’écrit champ 14 nos, moyen B : hysical objects do not even reach the iron e choc par la rétroaction des rayons cosmiques permet d’atteindre au moins confinement line ⇥ ⇥ 1 strophysical hadrons to very-high objects do energies acceleration in not even energetic sources reach still anthe isneutron iron confinement ' = 1.08 Mpcline 1 E ' B ' tpour candidates les protons. for 10 UHECR Dans tous les cas, l’énergie to be: maximale calculée stars, simplement r L Z . utely fundamental 20 as the Galactic and extragalactic transientpopu- 10 eV 18 1 nG he,prochebest Gamma de celle Ray du Bursts candidates genou eV (pour for (GRBs), 14 les protons) UHECRand pouraccretionne sources 20 pas shocks accelerationy voir La une inrelation. condition todebe: the neutron confinement stars, dans une source de particle taille L s’écrit particle sourcerL ⇤ L ic rays detected from 10 eV to more than 10 eV are yet charge energy mag. field las criterion s noyaux the de bore is cosmic (B) 10a necessary étant high-energy naturellement neutrinoscondition, peu abondants detected but not dans above la 10 en terme sufficient. Galaxie, 13 eV. on d’énergie In estime que de la façon suivante (c’est le critère de Hillas 1984) : AGN), sentiellement des leration Gamma models 20 particulese rely Ray secondaires on time Bursts produites par(GRBs), dependent des noyaux de carbone environments andsteady accretion (C) primaires. and shocks in the B ⇥ L ⇥ comoving rate densities, V cosmic ray injection spectrum and de colonne (ou E ⇤ Emax ⌅ 1015 eV ⇥ Z quera donc le taux d’interaction subi par les primaires et donc la densité sources . e the Larmor radius and typical size in where R0 and B 0 are the typical size ted in figure 1.9 for a maximum energy function of R0 and B 0 , adapted from Alves rces can accelerate respectively protons and s is then required to reach more precise proposed in the literature, such as radio- he es Hillas Oncould Lorentz peut factor ainsi criterion contribute retrouver to distance leur the 1. In is a necessary extragalactic the restetframe parcourue gamma-ray leur tempsofcondition, the de back- magnetized confinement. but not sufficient. In 1 µG 1 pc taccelerated of VHE neutrinos. over aSolving this question transverse distancerequires R/ , awhich On achanges careful choisi ici les valeurs numériques moyennes pour des restes de superno Rionacceleration models processes, in a constant relywith dialogue onobservations. time dependent (1983) ont effectuéenvironments anden prenant en compte l’évolu un calcul plus détaillé on. montrent que Emax ⌅ 2 ⇥ 1014 eV ⇥ Z (B/1 µG). La prise en compte de l’a reforthe Lorentz factor the acceleration of hadrons have 1. beenInidentified the rest and frame of the magnetized magnétique dans le choc par la rétroaction des rayons cosmiques perme nergy requirement, known as the Hillas condition (Hillas, ly be accelerated over a transverse distance l’énergie du R/ genou ,pour which R, Dans changes les protons. B tous les cas, l’énergie maxima able to accelerate cosmic rays up to a given energy. By Astrophysics enUHECRs of (1.12) est trop25 proche de celle du genou (pour les protons) pour ne pa ? /ZeB of a particle of charge Z, mass m, Lorentz factor riterion. to the magnetic field B, to the typical size of the source R, Γ, β 4. Par exemple, les noyaux de bore (B) étant naturellement peu abondants dans size and the magnetic field of sources allowing to produce Θ ceux observés sont essentiellement des particules secondaires produites par des noyaux Le rapport B/C indiquera donc le taux d’interaction subi par les primaires et donc h Emax . ⌘acc ZeBR, where ⌘acc is added to accountgrammage) for Hillas diagramupdated for Hillas various Diagram sources classes, as a function be low for non-relativistic outflows. This criterion can be of R 0 traversée. and B 0 On peut ainsi retrouver leur distance parcourue et leur temps d , adapted from Alves (2019). which we Above the solid compare the red and radius Larmor blue lines, and sources typical can size accelerate in respectively protons and 20 max = 10 eV. 0 0 where R0 and B 0 are the typical sizeAstrophysics of UHECRs 25 max . ⌘acc ZeB R frame, as illustrated in figure 1.9 for a maximum energy alysis andHillas (1984), KK modeling of&the Olinto (2011) properties is then required source 0 to reach0 more precise gram forGuépin various sources classes, as a function (PhD 2019), adapted from Alves Batista (2019) of R and B , adapted from Alves 10
mi acceleration The maximum accessible energy further depends on m for 2 instance, A ⇠ g/ 2 and t ⇠ 10 7 s g E B 1 rgy 009). eCandia escape density The condition timescale U t for B == R 2B /8⇡. In the centralsh successful /(2D), & Roulet (2004);2 Marcowith et al. (2006). acceleration where D is region ofaccan AGN for example, 20 G s Condition tesc =for acceleration is at sources esc e escape timescale ocity racteristics tion generally with gion but can be estimated by comparing the accelerati of the sh the due ⌧ 1 transport magnetic to synchrotron R /(2D), and of g ⌘whereinDthe particles field radiation, D/(r c) (corresponding to L interac- & 1. Majoring luminosity to the this budget Eddington timescale with luminosi racteristics and of the transport on the turbulence features. of particles Detailedinstud- the or mescale and eV toonhadronic and the particles from the acceleration region t , the lifetime o leads B interactions, turbulence ipii (1966); Giacalone G = to a B/1G, features. the maximum & Jokipii (1999); latter stud- t Detailed process ⇠ rad Casse 10 5being 1 acceleration s E B 2 energy in esc . This the timescale central has to regio be co cal media. The timescale for energy losses through 20 G ipii (1966); Giacalone 19 & Jokipii 1/2 (1999); 1/2 Casse ia &⇠ eleration ax ion can Roulet10 clusters be loss time due to expansion and to interactions with the (2004); eV timescale expressed Marcowith g in a B which generic G et al. (2006). way reads sh . (Biermann (Lemoine & & Waxman 2009): tacc = A ia & Roulet ally2 due 1to synchrotron (2004); Marcowith et al. radiation, to interac- (2006). Norman et al. 1995a; Lemoine & Waxman 2009). The co 2 1 & steady sources nmethe Tally armor hadronic )E due to generic B (1 + A)case synchrotron timescale interactions, ,and whereofA theradiation, latter acceleration Ato = interac- process 240 1beingU /U for in an B cor- all types condition outflow, of Fermi Lemoine for acceleration acceleration & Waxman (non, mil( nsity edia. of hadronic radiation timescaleleading interactions, theenergyto pion latter production process being U , to eleration ic, edia. 8⇡. In The 1st The the can then be written t . t , t , t . The escape tim and timescale central time2nd for for region and order energy of >1045 losses an erg/s through the Fermi losses AGN dynamical through for accelerations). example, time acc as- t esc dyn ⇠ For age R/ a non loss R,relativistic W BW c of the1st outfl or an be expressed in a generic way (Biermann & wer 1bebound FRII 2 7 must possess 1 2 in order Γ the an + A) on expressed in the 1 a generic luminosity the di↵usion coefficient, depends on the characteristics o 10 way (Biermann &that a source to b 46-48 erg/s E cnfield for B (1instance, 2(corresponding , where A to Athe ⇠ = g/ Eddington 240 U /U sh B and t luminosity), cor- acc ⇠ 10 s g E 20 B G sh , where sh Eoft 1radiation B ⇠2 (1 10 + 5 A) sleading 1 1 , where E20 BGto. pion 2 A This = 240 timescale production U 20 U /U cor- has, to B to be com- 2 Θ 2 45 FRI Ltimescale WR B /2 >radiative 10 Z rad of and radiation g ⌘ D/(r c) 1. Majoring ambient medium, i.e., on the magnetic field and on the tu leading to production U , to with the nich thereads central(Lemoine region of an AGN for example, & Waxman 2009): tas- acc = A tL , ngnetic the AGN flares central region of an AGN for example, as- tdyn ∼ R /βΓc o(corresponding &a1 for maximumallluminosity types L acceleration theFermiEddington of the(non, B luminosity), acceleration source energy ies of this subject can be found in, e.g., Jokipii (1966); G to of is written as a function on in the central region of AGN of ord mildly, depends of the size (corresponding 2 to the Eddington luminosity), Larmor 5 1 acc. mechanism ⇠Fermi101/2 sEHigh BG 1/2 . This 20 luminosity accelerations). GRB timescale For a non has to be andcom- relativistic 1st order time g⇠ion 10 5 s R E B 1 G in B 2 the . Thissh observer . timescale 10 51-52 erg/s has frame, et al. (2002); Yan & Lazarian (2002); Candia & Roulet to be 2 = A t≫ com- L ,1 in environment motion with Lorentz factor W (an /ads 2 (Lemoine & Waxman 2009): 1 tacc transient sources 20 G 7 and sh (Lemoine t acc Low luminosity ⇠ 10 GRB s g E 20 B 1050-51 G erg/ssh , where the shock ads & Waxman 2009): t acc = A tL ~,1 at best parted ase or 1. all types Majoring with of Fermiaacceleration of acceleration magnetic inwith an field mildly,of characteristic (non,outflow, Energy losses during acceleration are generally due to s this timescale the radiative Lemoine loss strength & Waxman B. This (2009) quant compare or all types of Fermi accelerations). For aacceleration non relativistic (non, 1stmildly, order ward ationand energy accelerations).to the 7derive: dynamical in thea central For non the region 1 relativistic classical time of 1st t AGN order dyn tions with the radiative backgrounds, or to hadronic inte nd tacc ⇠ 10 s g E20 BG sh , where the shock 2 ⇠determination of R/ W W c of of order: thethe field strength outflow, to set a rob usi 7 1 2 nd t ⇠ accpulsars 10 s g E 20 BG sh10,thewhereerg/s the outflow shock magnetic luminosity ission he Majoring luminosity(assuming this timescalethat with equipartition a 45-47 source radiative must loss between possess the in total order energy to be density able to of accelerno an outflow, Majoring energy inthis themostly inefficient in diluted astrophysical media. The ti Lemoine timescale central &withWaxman region the of (2009) compare radiative AGN of loss order: this B 2 20 2 2 2 2 2 45 2 2 1 Edme energy= oftdyn the10 magnetars in⇠the R/ eVE magnetic W W cregion central of:the 20 10L field >for 45-47 erg/s ofoutflow, AGN L to of B ⌘LBa ≡robust example), set order: 2πRRΘdepends W B Γ/2βc > notably 10 Z on E20the erg s . kT hardly synchrotron emission and8πpion production can be express ource must possess in order to compare be able to accelerate lower bound of the bolometric luminosity of source sity flow, L leptonic of Lemoine B &the and Waxmansource hadronic (2009)is written accelerated this as a function particles of4 the (e.g., 3 size Beck 2 of the & 1 accelerat Krause2 20 > flow, yn L Lemoine ⇠BR/⌘ W WWRc&of 2 B Strittmatter Waxman 2 (2009) 45 /2 outflow, the > 10 tocompare Z 2 E20 set 2 1987): erg a robust 1 trad = (6⇡mp c / T meLemoine thiss . The )E &B Waxman(1 + 2009 observer zars syn ⇠ R/ for written must Was W possessframe, aexample, cfunction in of toin the outflow, order motion Celotti ofbethe toto setof size able with & athe robust Lorentz(2008) Ghisellini acceleration accelerate factor discuss W (and that velocity their jets W11)aa
tdyn ⇠ R/ al timeCondition forW W c of theat acceleration outflow, sources to set a robust for transients a source must possess in order to be able to accelerate 2 2 45 2 2 1 L > LB ⌘ W R B /2 > 10 Z E20 erg s . The source bolometric luminosity Lemoine & Waxman 2009 ce is written as a function of the size of the acceleration motion with Lorentz many transient factor W sources (and velocity could make W ) it andGuépin & KK 2016 haracteristic strength Proton maximal energy EB. p (° = This 1) quantityProton is not maximalstraight- energy Ep (° = 10) 56 1056 10 15 21 termination 10 10 of 13 the t var L field strength using 10 the21 synchrotron tvar L 10 tot 17 tot > 1 52 10 >1 5 52 0 10 0 4 etween 10 thelosses synchrotron total 1 0 15 energy rdensitye g 54 of non thermal particleserg 10 19 19 10 19 17 10 48 1 0 48 Blazar flares le), depends notably onBHthe 10 hardly10known ratio 10 between Lbol (erg s°1) Lbol (erg s°1) 17 LL 10 17 mergers GRBs Ep (eV) Ep (eV) SLSNe ed 10 44 particles (e.g., Magnetar IBBeck & Krause 2005). 1044 Magnetar15InGF the case of 15 PS16cgx SNe 10 10 TDEs BH mergers 17 10 ellini 10 (2008) discuss10 that 40 Magnetar SB Novae their jets 10 17 10 are 40 not 13 magnetically 10 13 15 10 I (FRI) radio galaxies, 10 36 10 TeV 15 Crab flares blazars, 10 and BL Lac objects 10 36 11 10 11 13 42 44 1 10 luminosity bounds of order 10 10 32 erg 10 s .13 10 32 9 9 10 10 10°4 10°2 100 102 104 106 108 10 °4 10 °2 10 0 10 2 10 4 10 6 10 8 pe of particles from tvar (s) acceleration regions is an intricate tvar (s) sed in detail in the literature "Hillas plot (note forhowever transients" the works 12 m et al. 2001; Rachen 2008; Allard & Protheroe 2009).
where F100 is the flux normalization at 100 TeV. randomized trials yielding a value of TS greater than discontinuous and not well defined, but the un- The time-dependent analysis uses the same for- or equal to the one obtained for the actual data. certainties for the Gaussian window show that it Neutrino flares and TXS 0506+56 mulation of the likelihood but searches for clustering in time as well as space by introducing Because the detector configuration and event selections changed as shown in Table 1, the time- is consistent with the box-shaped time window fit. Despite the different window shapes, which IC-170922A – a 290 TeV Neutrino an additional time profile. It is performed sep- dependent analysis is performed by operating on lead to different weightings of the events as a arately for two different generic profile shapes: a each data-taking period separately. (A flare that function of time, both windows identify the same Gaussian-shaped time window and a box-shaped spans a boundary between two periods could be R ES E A RC H time interval as significant. For the box-shaped time window. Each analysis varies the central partially detected in either period, but with re- time window, the best-fitting parameters are sim- time of the window, T0, and the duration TW duced significance.) An additional look-elsewhere R E S E A R C H A R T I C L E S U M M A Rilar Y to those of the Gaussian window,observatories ◥ withIceCube trinos, fluence provides 2 around t (from seconds to years) of the potential signal to correction then needs to be applied for a result in at 100 TeV and spectral index giveng-rays, by x-rays, E J100optical, = ra –2 find the four parameters (F100, g, T0, TW) that an individual dataNEUTRINO segment,ASTROPHYSICS given by the ratio of 2:2þ1:0 "0:8 # 10 "4 TeV cm and g = 2.2 waves, ± 0.2. allowing This for the p of even rapidly fading so maximize the likelihood ratio, which is defined the total 9.5-year observation time to the obser- fluence corresponds to an average flux over Multimessenger observations of a –1 as the test statistic TS. (For the Gaussian time vation time of that data segment (30). 158 days of F100 = 1:6"0:6 þ0:7 # 10"15 TeV RESULTS: cm–2 s–1. A high-ener window, TW represents twice the standard de- When we estimate the significance muon of track the time- was detected viation.) The test statistic includes a factor that Neutrinos from the direction of TXS 0506+056 flaring blazar coincident with dependent result by performing the analysis at dist automatically generatin ◥ corrects for the look-elsewhere effect arising high-energy neutrino IceCube-170922A the coordinates of TXS 0506+056 onONrandomized OUR WEBSITE with from all of the possible time windows that could The results of the time-dependent analysis per- datasets, we allow in each trial a new fit for all andRead the full article sear at http://dx.doi. R ES E A RC H | R E S EA Rbe C Hchosen A R T I C LE(30). formed at the coordinates The IceCubeof TXS 0506+056 Collaboration, Fermi-LAT, areMAGIC, theAGILE, parameters: F100, g,H.E.S.S., ASAS-SN, HAWC, T0, TW. Weorg/10.1126/ find that the a b science.aat1378 For each analysis method (time-integrated and shown in Fig. 1 for each ofKanata, INTEGRAL, the sixKiso, data periods. Kapteyn, Liverpool fraction Telescope,of randomized Subaru, trials that result Swift/NuSTAR, in a more leng .................................................. VERITAS, and VLA/17B-403 teams*† –5 2017 time-dependent), lower limit of 183 TeV, depending only weakly on a robust trophysical significance spectrum, together estimate with One ofcannot issimulated the data periods, be excluded. IC86b from Electromagnetic 2012 to 2015, observations significant excess than the real data Telescope is 7 × 10Collaboration for the assumed astrophysical obtained energy spectrum (25). by performing data, was theused to calculate identical the probability analysis on that a contains are avaluable to assessexcess, significant the possible whichassociation of is identified the box-shaped time window and 3 rection × 10–5offor the neutrinothe w The vast majority of neutrinos detected by neutrino at the observed track energy and zenith a single neutrino to an astrophysical INTRODUCTION: source.are tracers of mic rays. The discovery of an extraterrestrial cataloged g-ray source, 0 Neutrinos IceCube arise from cosmic-raytrials with randomized interactions within angledatasets. in IceCube These is ofare produced astrophysical origin. by Thisboth time-window Following the shapes. cosmic-ray alert, Theperformed acceleration: IceCube excess consists a neutral Gaussian electrically time window. diffuse flux of high-energy neutrinos, This fraction, announced direction. once Thecor- source, a Earth’s atmosphere. Although by randomizing atmospheric neu-the probability, event times and recalculating the so-called signalness of the event of 13 ±complete 5 eventsanalysis above ofthe and traveling expectation at nearly relevant datatheprior speedfrom of the tolight, they rected by IceCube forinthe 2013,ratio of the total has characteristic observation prop- 0506+056 attime a measured trinos are dominant at energies below 100 TeV, (14), was reported to be 56.5% (17). Although 31 October canAlthough 2017. escape theno densest environments additional excess and may erties that hint at contributions from extra- in a flaring state at the atmospheric background. befound The tracedfrom backthe significance to their depends sourceofofTXS origin. High- to the IC86b observation time (9.5 years/3 galactic sources, although the individual sources g-ray activity in the GeV years), their spectrum falls steeply with energy, allowing IceCube can robustly identify astrophysical neu- of neutrinos was direction –4 –4 astrophysical neutrinos to be more Table 1. identi- easily IceCubetrinos neutrino at PeVdata energies, samples. for individual neutrinos on the energies of the energy events, neutrinos their are proximity expected 0506+056 near the time of the alert, there are to be to produced results remain as in yet P values unidentified. of 2 × Continuously10 mon-and 10 servations , respec- by imaging at Candidate Neutrino Source: TXS 0506+056 fied at higher energies. The muon-neutrino as- at Six data-taking periods make up the full 9.5-year data sample. Sample numbers several hundred TeV, an atmospheric the origin coordinates indications clustering in time. at in blazars: intense extragalactic radio, optical, of the 3sTXS level 0506+056, of high-energy This is illustrated characterized and neutrino x-ray, and, in some cases, g-ray sources by relativistic jets their in ofFig. 2, itoring the entire sky for astrophysical neu- tively, corresponding to 3.5s and there is no a priori reason to prefer one telescopes, telescopes, notably the 3.7s. Because Gamma Imagin of the rev Fig. 1. Event display for correspond to the number of detector which shows the time-independent weight of plasma pointing close to our line of generic time windows over the other, we takedetected the the g-r sight. Blazars are among the most reached energie neutrino event IceCube- strings that were operational. During the individual events in the likelihood powerful objects in theanalysis Universe and during more significant one and include a trial factor surements of of 170922A. The time at which a DOM observed a signal is first three periods, the detector was still the IC86b data period. are widely speculated to be sources 2 for the final significance, which is then 3.5s. been complete of high-energy cosmic rays. These cos- radio wavelen reflected in the color of the hit, under construction. The last three periods The Gaussian time mic rayswindow is centered generate high-energy neutri- at 13 Outside the 2012–2015 time period, the next tigated models with dark blues for earliest hits December 2014 [modified Julian day (MJD) 57004] nos and g-rays, which are produced most significant excess is found using the Gauss- and g-ray prod IC170922A: correspond to different data-taking and yellow for latest. Times when the cosmic rays accelerated in correlation of with an uncertainty of ±21 days and a duration ian window in 2017 and includes the IceCube- shown are relative to the first conditions and/or event selections with the þ35 the jet interact with nearby gas or flare of TXS 05 DOM hit according to the track full 86-string detector. T W = 110 "24 days. The photons.best-fitting On 22 parameters September 2017, the for 170922A event. This time window is centered significant at t reconstruction, and earlier and the fluence J100 = ∫F100(t)dtIceCube cubic-kilometer and the Neutrino spectral at 22 September 2017 with duration TW = 19deviations days, (sigm later times are shown with the Observatory index are given by Eneutrino2 J100 =2:1 detected þ0:9 # a ~290-TeV 10 "4 TeV cm 290 TeV neutrino –2 g = 1.7 ± 0.6, and fluence E 2 J = 0:2 þ0:4 redshift # 10"4 fo of TXS Downloaded from http://science.sciencemag.org/ on July 12, 2018 from "0:7 a direction consistent 100 "0:2 constraints same colors as the first and last times, respectively. The Sample Start End at 100 TeV and gwith = 2.1the ± 0.2,g-ray flaring respectively. blazar TXS The TeV cm–2 at 100 TeV. No other event besides luminosity the for 0506+056. We report the details of them to be sim total time the event took to joint uncertainty on these parametersand the resultsisofshown IceCube-170922A event contributes significantly cross the detector is ~3000 ns. IC40 5 April 2008 20 May 2009 ............................................................................................. in Fig. 3 along with this observation a skymap follow-up multiwavelength showing a the result campaign. to the best fit. As a consequence, IceCube theColl. uncertainty observed in g-r The size of a colored sphere is IC59 20 May 2009 31 May 2010 CONCLUSION proportional to the logarithm ............................................................................................. IC79 31 May 2010 13 May 2011 of the time-dependent analysis RATIONALE: performed Multimessenger astron-at the on the best-fitting window Science (2018) location and g-rays width and the of the amount of light ............................................................................................. location of TXS 0506+056 and in its vicinity omy aims for globally coordinated spans the entire IC86c period, because any win- blazar jets may Signalness: 56.5% observed at the DOM, with IC86a 13 May 2011 16 May 2012 observations of cosmic rays, neutri- to at least seve ............................................................................................. during the IC86bnos, data period. gravitational waves, and electro- dow containing IceCube-170922A yields a similar association of a larger spheres corresponding IC86b 16 May 2012 18 May 2015 ............................................................................................. The box-shaped time magnetic window radiation across isa centered broad value of the test statistic. Following the trial withcor- a blazar d to larger signals. The total IC86c 18 May 2015 31 October 2017 range of wavelengths. The combi- hanced g-ray e charge recorded is ~5800 photoelectrons. Inset is an overhead perspective view of the ............................................................................................. event. 13 The days later best-fitting with track duration direction is shown nation is expected T = as 158 an days arrow, (from rection procedure for different W to yield crucial Multimessenger observations of blazar TXS 0506+056. The observation periods blazars may ind 13±5 above the background consistent with a zenith angle 5:7þ0:50 IceCube, Fermi-LAT, MAGIC, AGILE, ASAS-SN, HAWC, H.E.S.S, Kapteyn, of energizing [ScienceEM flare atmospheric "0:30 degrees below the horizon. INTEGRAL, the most 361 (2018) powerful astro- neutrinos, no.6398, eaat1378] 3.5σ MJD 56937.81 toinformation Page 8 170922A (dashed red and solid gray contours, respectively), MJD 57096.21, inclusive50% on the mechanisms of and 90% as described containmentabove, thethesignificance regions for neutrino IceCube-of this sought excesssource cosmic rays, and Kanata, Kiso, Liverpool, Subaru, Swift, VERITAS, VLA, Science 2018 physical sources. That the produc- overlain on a V-band optical image of the sky. Gamma-ray sources tion of neutrinos is accompanied by in this region previously detected with the Fermi spacecraft are a sizable fracti trino flux obse electromagnetic radiation from the shown as blue circles, with sizes representing their 95% positional source favors the chances of a multi- uncertainty and labeled with the source names. The IceCube The list of author aff wavelength identification. In par- article online. neutrino is coincident with the blazar TXS 0506+056, whose *The full lists of par ticular, a measured association of optical position is shown by the pink square. The yellow circle team and their affili high-energy neutrinos with a flaring shows the 95% positional uncertainty of very-high-energy g-rays supplementary mate source of g-rays would elucidate the detected by the MAGIC telescopes during the follow-up campaign. †Email: analysis@ic Cite this article as mechanisms and conditions for ac- The inset shows a magnified view of the region around TXS 0506+056 Science 361, eaat13 celeration of the highest-energy cos- on an R-band optical image of the sky. science.aat1378 The IceCube Collaboration et al., Science 361, 146 (2018) 13 July 2018 13
correlated and are expressed as a pair, (F100, g), The resultant P value is defined as the fraction of box-shaped time window, the uncertainties are Neutrino flares and TXS 0506+56 where F100 is the flux normalization at 100 TeV. The time-dependent analysis uses the same for- randomized trials yielding a value of TS greater than 10 or equal to the one obtained for the actual data. public alerts discontinuous and not well defined, but the un- and 41 for certainties archival the Gaussian events window show that it The Multi-Messenger Light Curve mulation of the likelihood but searches for clustering in time as well as space by introducing an additional time profile. It is performed sep- Because the detector configuration Post-trials selections changed as shown in Table 1, the time- dependent analysis is performed by operating on p-value and event for association: is consistent with the box-shaped 3.0σ fit. Despite the different window shapes, which lead to different weightings of the events as a time window IceCube Collaboration, arately for two different generic profile shapes: a Fermi-LAT, MAGIC, AGILE, ASAS-SN, HAWC, H.E.S.S., each data-taking period separately. (A flare that INTEGRAL, et al., Science (2018) function of time, both windows identify the same Gaussian-shaped time window and a box-shaped spans a boundaryRbetween ES E A RC H two periods could be time interval as significant. For the box-shaped time window. Each analysis varies the central partially detected in either period, but with re- time window, the best-fitting parameters are sim- time of the window, T0, and the duration TW duced significance.) An additional look-elsewhere ilar ◥to those of the Gaussian window,trinos, withIceCube fluence prov RESEARCH ARTICLE SUMMARY VHE (from gamma-rays seconds to years) of the potential signal to correction then needs to be applied for a result in at 100 TeV and spectral index giveng-rays, –2 observatories by x-rays, 2 E J100optica arou = þ1:0 "4 find the four parameters (F100, g, T0, TW) that an individual dataNEUTRINO segment,ASTROPHYSICS given by the ratio of 2:2"0:8 # 10 TeV cm and g = 2.2 waves, ± 0.2. allowing This for t of even rapidly fadi maximize the likelihood ratio, which is defined the total 9.5-year observation time to the obser- fluence corresponds to an average flux over Multimessenger observations of a –1 as the test statistic TS. (For the Gaussian time vation time of that data segment (30). 158 days of F100 = 1:6"0:6 þ0:7 # 10"15 TeV RESULTS: cm–2 A high- s–1. GeV window, gamma-rays TW represents twice the standard de- When we estimate the significance muon of track the time- was dete viation.) The test statistic includes a factor that Neutrinos from the direction of TXS 0506+056 flaring blazar coincident with dependent result by performing the analysis at automatically gene ◥ corrects for the look-elsewhere effect arising high-energy neutrino IceCube-170922A the coordinates of TXS 0506+056 onONrandomized OUR WEBSITE from all of the possible time windows that could The results of the time-dependent analysis per- datasets, we allow in each trial a new Read the fitfullfor article all at http://dx.doi. X-rays R ES E A RC H | R E S EA Rbe C Hchosen A R T I C LE(30). formed at the coordinates The IceCubeof TXS 0506+056 Collaboration, Fermi-LAT,areMAGIC, theAGILE, parameters: F100, g,H.E.S.S., ASAS-SN, HAWC, T0, TW. Weorg/10.1126/ find that the science.aat1378 For each analysis method (time-integrated and shown in Fig. 1 for each of the six data periods. INTEGRAL, Kanata, Kiso, Kapteyn, Liverpool fraction of randomized trials that result Telescope, Subaru, Swift/NuSTAR, in a more .................................................. VERITAS, and VLA/17B-403 teams*† –5 time-dependent), lower limit of 183 TeV, depending only weakly on a robust trophysical significance spectrum, together estimate with One ofcannot issimulated the data periods, be excluded. IC86b from Electromagnetic 2012 to 2015, observations significant excess than the real data Telescope is 7 × 10Collabora for the assumed astrophysical obtained energy spectrum (25). data, was –5 by performing theused to calculate identical the probability analysis on that a contains are avaluable to assessexcess, significant the possiblewhichassociation of is identified the box-shaped time window and 3 rection × 10 offor the neutr the The vast majority of neutrinos detected by neutrino at the observed track energy and zenith a single neutrino to an astrophysical INTRODUCTION: source.are tracers of mic rays. The discovery of an extraterrestrial cataloged g-ray sour Neutrinos trials with randomized datasets. These is ofare produced origin. by Thisboth time-window shapes. Theperformed excess consists a neutral Gaussian time window.neutrinos, This fraction, once Thecor- X-rays IceCube arise from cosmic-ray Earth’s atmosphere. Although by randomizing spectral interactions within atmospheric neu-the probability, index angle in IceCube event times the so-called astrophysical and recalculating signalness of the event Following the of 13 ±complete cosmic-ray 5 eventsanalysis above alert, ofthe and traveling acceleration: IceCube expectation at nearly relevant data electrically theprior speedfrom of the tolight, diffuse flux of high-energy they rected by IceCube forinthe 2013,ratio announced of the total has characteristic direction. observation prop- 0506+056 attime sourc a meas trinos are dominant at energies below 100 TeV, (14), was reported to be 56.5% (17). Although 31 October canAlthough 2017. escape theno densest environments additional excess and may erties that hint at contributions from extra- in a flaring state at atmospheric background. be traced The back significance to their source of depends origin. High- to thesources, galactic IC86balthough observation the time individual (9.5 years/3 sources g-ray activity in the years), their spectrum falls steeply with energy, allowing IceCube can robustly identify astrophysical neu- of neutrinos was found from the direction of TXS –4 –4 astrophysical neutrinos to be more Table 1. identi- easily IceCubetrinos neutrino at PeVdata energies, samples. for individual neutrinos on the0506+056 energiesnear ofenergy the events, the time of thetheir neutrinos are alert, proximity expected theretoare to be produced results remain as in P values Continuously yet unidentified. of 2 × 10mon-andservations10 , respec- by imagin optical Candidate Neutrino Source: TXS 0506+056 fied at higher energies. The muon-neutrino Six data-taking as- periods 9.5-year data sample. Sample numbers at severalmake hundred up TeV,the an fullatmospheric origin the coordinates in time. in blazars: intense extragalactic radio, optical, of3sTXS indications at the clustering level of This characterized 0506+056, is high-energy neutrino illustrated by relativistic and their x-ray, and, in some cases, g-ray sources in jets Fig. of 2, itoring the entire sky for astrophysical neu- tively, corresponding to 3.5s and 3.7s. Because there is no a priori reason to telescopes, notably prefer one Gamma Im of the telescope Fig. 1. Event display for correspond to the number of detector which shows the time-independent weight of plasma pointing close to our line of generic time windows over the other, we takedetecte the the sight. Blazars are among the most reached en neutrino event IceCube- strings that were operational. During the individual events in the likelihood powerful objects in theanalysis Universe and during more significant one and include a trial factor surement of 170922A. The time at which a DOM observed a signal is first three periods, the detector was still the IC86b data period. are widely speculated to be sources 2 for the final significance, which is then 3.5s. been com of high-energy cosmic rays. These cos- radio wav The Gaussian time window is centered at 13 Outside the 2012–2015 time period, the next radio reflected in the color of the hit, under construction. The last three periods with dark blues for earliest hits December 2014 [modified mic rays generate Julian nos and g-rays, high-energy dayare(MJD) which neutri- produced 57004] most significant excess is found using the Gauss- tigated m and g-ray correspond to different data-taking and yellow for latest. Times when the cosmic rays accelerated in correlatio with an uncertainty of interact ±21 days and agas duration ian window in 2017 and includes the IceCube- shown are relative to the first conditions and/or event selections with the the jet with nearby or flare of TX DOM hit according to the track full 86-string detector. TW = 110þ35 "24 days. The photons.best-fitting On 22 September parameters 2017, the for 170922A event. This time window is centered significan reconstruction, and earlier and the fluence J100 = ∫F100(t)dt and the spectral cubic-kilometer IceCube Neutrino at 22 September 2017 with duration TW = 19deviations days, later times are shown with the Observatory 2 detected þ0:9 a ~290-TeV "4 –2 2 þ0:4 redshift o index are given by Eneutrino J100 =2:1 # 10consistent TeV cm g = 1.7 ± 0.6, and fluence E J100 = 0:2"0:2 # 10"4 Downloaded from http://science.sc same colors as the first and from a direction "0:7 constrain last times, respectively. The Sample Start End at 100 TeV and gwith = 2.1the ± 0.2,g-ray flaring respectively. blazar TXS The TeV cm–2 at 100 TeV. No other event besides luminosit the 0506+056. We report the details of them to b total time the event took to joint uncertainty on these parametersand the resultsisofshown IceCube-170922A event contributes significantly cross the detector is ~3000 IceCube, ns. IC40 Fermi-LAT, 5 April 2008 MAGIC, 20 May 2009AGILE, ............................................................................................. ASAS-SN, HAWC, in Fig. 3 along with H.E.S.S, this observation a skymap follow-up multiwavelength showing INTEGRAL,a the result campaign. toKapteyn, the best fit. As a consequence,Page 16 the uncertainty observed proportional to the logarithm Kanata, The size of a colored sphere is IC59 Kiso, 20 MayLiverpool, 2009 31Subaru, May 2010 Swift, VERITAS, VLA, Science 2018 ............................................................................................. of the time-dependent analysis RATIONALE: performed Multimessenger astron- at the on the best-fitting window location and CONCLU width g-rays and of the amount of light IC79 31 May 2010 13 May 2011 ............................................................................................. location of TXS 0506+056 and in its vicinity omy aims for globally coordinated spans the entire IC86c period, because any win- blazar jets observed at the DOM, with IC86a 13 May 2011 16 May 2012 observations of cosmic rays, neutri- to at least ............................................................................................. during the IC86bnos, data period. gravitational waves, and electro- dow containing IceCube-170922A yields a similar association larger spheres corresponding IC86b 16 May 2012 18 May 2015 ............................................................................................. The box-shaped time magnetic window radiation across isa centered broad value of the test statistic. Following the trial withcor- a bla to larger signals. The total z~0.337 charge recorded Paiano IC86c is ~5800 photoelectrons. 18 etMay Inset isal. an2015 2018 overhead 31 October perspective view 2017 13 days of the event. The ............................................................................................. latertrack best-fitting with range duration direction of wavelengths. is shown nation is expected TWas=toan158 The combi- days (from arrow, rection procedure for different observation periods yield crucial Multimessenger observations of blazar TXS 0506+056. The hanced 14 g- blazars ma þ0:50
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