γ Fe ν p Going further with high-energy multi-messenger astronomy Kumiko Kotera - Institut d’Astrophysique de Paris EuCAPT Symposium - 07/05/2021 Multi-messengers! Gravitational waves Cosmic rays p Fe ν Gamma rays ν Neutrinos 2 Multi-messengers! cosmic rays + others —> temporal coincidence impossible (deflections) but studies of di!use fluxes Gravitational waves GW + electromagnetic (+gamma) GW170817 neutrinos + gammas? TXS0506+056 (blazar flare) Cosmic rays p Fe ν Gamma rays ν Neutrinos Neutrinos 3 RESEARCH | RESEARCH ARTICLE as a fitted parameter. The model parameters are the RA coordinates within each data-taking period. contributing events at boundary times). For the 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 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 mulation of the likelihood but searches for Because the detector configuration and event is consistent with the box-shaped time window Neutrino flares andclustering TXS in time as well0506+56 as space by introducing selections changed as shown in Table 1, the time- fit. Despite the different window shapes, which an additional time profile. It is performed sep- dependent analysis is performed by operating on lead to different weightings of the events as a IC-170922A – a 290arately TeV for two different Neutrino 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 boundaryRESEARCH between 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- ◥ trinos, IceCube provides real-time triggers for time of the window, T0,andthedurationTW duced significance.) An additional look-elsewhere ilar to those of the Gaussian window, with fluence RESEARCH ARTICLE SUMMARY observatories2 around the world measuring (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 J100 optical,= radio, and gravitational T T 1:0 4 –2 waves, allowing for the potential identification find the four parameters (F100, g, 0, W)that an individual dataNEUTRINO segment, ASTROPHYSICS given by the ratio of 2:2þ0:8 10À TeV cm and g =2.2±0.2.This maximize the likelihood ratio, which is defined the total 9.5-year observation time to the obser- fluenceÀ  corresponds to an averageof even flux rapidly over fading sources. 0:7 15 –1 –2 –1 as the test statistic TS. (For the Gaussian time vation time of that data segment (30). 158 days of F100 =1:6þ0:6 10À TeVRESU LTS:cm A high-energys . neutrino-induced Multimessenger observations ofÀ a  muon track was detected on 22 September 2017, window, TW represents twice the standard de- When we estimate the significance of the time- Neutrinos from the direction of automatically generating an alert that was viation.) The test statistic includes a factor that flaring blazar coincidentdependent with result by performing the analysis at distributed worldwide ◥ corrects for the look-elsewhere effect arising TXS 0506+056 the coordinates of TXS 0506+056 onON randomized OUR WEBSITE within 1 min of detection and prompted follow-up from all of the possible time windows that could The results of thehigh-energy time-dependent analysis neutrino per- datasets, IceCube-170922A we allow in each trial a newRead the fit full for article all at http://dx.doi. searches by telescopes over RESEARCH ARTICLE RESEARCH | be chosen (30). formed at the coordinatesThe IceCube of Collaboration, TXS 0506+056Fermi-LAT, are MAGIC,theAGILE parameters:, ASAS-SN, HAWC,F100, g H.E.S.S.,, T0, TW. Weorg/10.1126/ find that the a broad range of wave- INTEGRAL, K anata, K iso, K apteyn, Liverpool Telescope, Subaru, Swift/NuSTAR, science.aat1378 lengths. On 28 September For each analysis method (time-integrated and shown in Fig. 1 for each of the six data periods. fraction of randomized trials that result.................................................. in a more 2017, the Fermi Large Area VERITAS, and VLA/17B-403 teams*† –5 Downloaded from lower limit of 183 TeV, dependingtime-dependent), only weakly on a robusttrophysical significance spectrum, together estimate with is simulatedOne ofcannot the data be excluded. periods, Elect IC86bromagnetic from observations 2012 to 2015, significant excess than the real dataTelescope is 7 × 10 Collaborationfor reported that the di- the assumed astrophysicalobtained energy spectrum by performing (25). data, was the used identical to calculate analysis the probability on thatcontains a are avaluable significant to assess excess, the possible which association is identified of the box-shaped time window and 3 rection× 10–5 offor the neutrino the was coincident with a The vast majority of neutrinos detected by neutrino at the observed track energy and zenith a single neutrinoINTRO to an DU astrophysical CTIO N: Neutrinos source. are tracers of mic rays. The discovery of an extraterrestrial cataloged g-ray source, 0.1° from the neutrino IceCube arise from cosmic-raytrials interactions with randomized within angle datasets. in IceCube These is of are astrophysical produced origin.by This both time-windowFollowing thecosmic-ray alert, shapes. IceCube acceleration: The performed excess electrically consists a neutral Gaussiandiffuse flux of high-energy time window. neutrinos, Thisannounced fraction,direction. once The cor- source, a blazar known as TXS Downloaded from Earth’s atmosphere. Althoughby randomizingatmospheric neu- theprobability, event times the so-called and recalculating signalness of the eventof 13 ±complete 5 events analysis aboveand traveling of the relevant expectation at nearly data the prior speed from ofto light, the they rectedby IceCube for in the 2013, ratio has characteristic of the total prop- observation0506+056 at time a measured redshift of 0.34, was trinos are dominant at energies below 100 TeV, (14), was reported to be 56.5% (17). Although 31 October 2017.can Although escape the no densest additional environments excess and may erties that hint at contributions from extra- in a flaring state at the time with enhanced atmospheric background.be tracedThe back to significance their source of depends origin. High- togalactic the sources, IC86b although observation the individual time sources (9.5 years/3g-ray activity years), in the GeV range. Follow-up ob- 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 moreTable easily 1. identi-IceCubetrinos neutrino at PeV data energies, samples. for individual neutrinoson the0506+056 energies near ofenergy the the time events, neutrinos of the theirare alert, expected proximitythere to are be produced to resultsremain as inyet unidentified.P values Continuously of 2 × 10 mon-andservations 10 ,respec- by imaging atmospheric Cherenkov in blazars: intense extragalactic radio, optical, itoring the entire sky for astrophysical neu- telescopes, notably theMajorAtmospheric fied at higher energies. The muon-neutrino as- at several hundred TeV, an atmospheric originthe coordinatesindications at the of 3s TXSlevel of 0506+056, high-energy neutrino and their tively, corresponding to 3.5s and 3.7s.Because http://science.sciencemag.org/ Six data-taking periods make up the full x-ray, and, in some cases, g-ray sources Gamma Imaging Cherenkov (MAGIC) Candidate9.5-year data sample. Sample Neutrino numbers Source:clustering in time.characterized This TXS is illustrated by relativistic 0506+056 jets in of Fig. 2, there is no a priori reason to prefer onetelescopes, of the revealed periods where http://science.sciencemag.org/ plasma pointing close to our line of the detected g-ray flux from the blazar Fig. 1. Event display for which shows the time-independent weight of generic time windows over the other, we take the correspond to the number of detector sight. Blazars are among the most reached energies up to 400 GeV. Mea- neutrino event IceCube- strings that were operational. During the individual events inpowerful the likelihood objects in the analysis Universe and during more significant one and include a trial factorsurements of of the source have also 170922A. The time at which a the IC86b data period.are widely speculated to be sources 2forthefinalsignificance,whichisthen3.5beens completed. at x-ray, optical, and DOM observed a signal is first three periods, the detector was still of high-energy cosmic rays. These cos- radio wavelengths. We have inves- reflected in the color of the hit,under construction. The last three periods The Gaussian timemic rays window generate high-energy is centered neutri- at 13 Outside the 2012–2015 time period, thetigated next models associating neutrino with dark blues for earliest hitscorrespond to different data-taking December 2014 [modifiednos and g-rays, Julian which day are (MJD) produced 57004] most significant excess is found using the Gauss-and g-ray production and find that and yellow for latest. Times with an uncertaintywhen of the ±21 cosmic days rays andaccelerated a duration in ian window in 2017 and includes the IceCube-correlation of the neutrino with the conditions and/or event selections with the the jet interact with nearby gas or shown are relative to the first 35 flare of TXS 0506+056 is statistically T =110 days. The best-fitting parameters for 170922A event. This time window is centered DOM hit according to the trackfull 86-string detector. W þ24 photons.