Neutrinos and gravitational waves from cosmologica

arXiv:astro-ph/0306118v15Jun2003NEUTRINOSANDGRAVITATIONALWAVESFROMCOSMOLOGICALGAMMA-RAYBURSTSGiulioAuriemmaUniversit`adegliStudidellaBasilicata,Potenza,ItalyInvitedpaperpresentedatthe“VulcanoWorkshop2002”,Vulcano,Italy,20-25May,2002.AbstractCosmologicalgammarayburstsareverylikelypowerfulsourcesofhighenergyneutrinosandgravitationalwaves.Theaimofthispaperistore-viewandupdatethecurrentpredictionsabouttheintensityofemissioninthistwoformstobeexpectedfromGRB’s.Inparticulararevisedcalcula-tionoftheneutrinoemissionbyphotohadronicinteractionattheinternalshockisobtainedbynumericalintegration,includingboththeresonantandthehadronizationchannels.ThedetectabilityofgravitationalwavesfromindividualburstscouldbedifficultforpresentlyplanneddetectorsiftheGRB’sarebeamed,butitispossible,aswehaveproposedinapapertwoyearsago,thattheincoherentsuperimpositionofsmallamplitudepulsetrainsofGW’simpingingonthedetector,couldbedetectedasanexcessofnoiseinthefullVIRGOdetector,integratingoveratimeoftheorderofoneyear.11IntroductionTheGammaRayBursts(GRB)areintenseflashesofsoftγ-rays,serendipitouslydiscoveredbytheVelatestbantreaty(Klebesadeletal.1973)andimmediatelyconfirmedbytheSovietKonussatellites(Mazetsetal.1974).Thephenomenol-ogyofGRB’shasbeendiscussedinseveralreviews(seee.g.Djorgovskietal.(2001)andreferencestherein).ThemostimportantbreakthroughintheGRB’sobservationshasbeenthediscoveryin1997ofalonglastingX-ray“afterglow”oftheburstGRB970228bytheBeppo-SaxItalian-Dutchsatellite(Costaetal.1997),whichhasallowedtheidentificationofitshostgalaxy(vanParadijsetal.1997,Sahuetal.1997),makingthestudyofGRB’sa“multi-wavelengthsadventure”(Klose2000).Accordingtoawidelyaccepted(andacceptable)interpretation,thepromptγ-raysburstandthedelayedafterglow,arebothpoweredbythedissipationofthekineticenergyofarelativisticallyexpanding“fireball”(orjet),whoseprimalcauseisnotknown.Thismechanism,qualitativelysuggestedbyCavallo&Rees(1978),hasbeenrefinedbyPaczynski(1986)andputinitsfinalformofastandardmodelbyRees&Meszaros(1994)(forarecentreviewseee.g.M´esz´aros(2002)andreferencestherein).Theobviousexpectationisthatsuchapowerfulhighlyrelativisticexplosionshouldbeaccompaniedbyemissionofneutrinosandgravitationalwaves,thusbecomingtheheraldofthenewastronomy.TheaimofthispaperistoreviewandupdatethecurrentpredictionsabouttheintensityofemissioninthistwoformstobeexpectedfromGRB’s.InthefollowingIwillfirstreviewin§2and§3theessentialquantitativeinformationontheenergeticsandthelargescaledistributionofthesources,whichhasbeenobtainedfrompromptandafterglowsobservations.In§4Ipresentanewcalcu-lationofthephotohadronicneutrinoemissivityinthefireball/jetsystemfromwhichpredictionsabouttheobservabilityofthediffuseneutrinobackgroundcanbederived.In§5Ireexaminethepossibilitythatasimilarstochasticback-groundcouldbeobservedasanadditionalnoisecomponentinthelongtermintegrationofthesignalfromgravitationalwavedetectors.2EnergeticsThetotalenergeticsinvolvedintheGRB’sisthemostimportantparameterformysubsequentemissivityestimate.Adirectestimateoftherestframeenergyoutputcanbeobtainedonlyforburstswithknownredshift.Accordingtoacom-pilationbyJ.Greiner,availableat∼jcg/grbrsh.html,thenumberofGRBwithreliableredshiftmeasurementofthehostgalaxyred-shift,isabout20.Theintrinsicisotropicbolometric(from0.1keVto10MeV)energyrelease,estimatedfromthefluenceof17burstinthe30keV-2MeVrange,spansfrom5.6×1051erg(GRB990712)to2×1054erg(GRB990123),withamedianofhEisoγi=1.8×1053ergandadispersionof0.8dex(r.m.s.)(Bloometal.2001).However,itistobeemphasizedthatthisvalueappliesonlytoGRBswithmeasuredredshift.Thereforeobservationalbiasesinburstdetectionandredshiftdetermination,mightobscurethetrueunderlyingaverageenergyoutputofthetypicalGRB.However,keepinginmindthiscaveat,onecanassumethatthe2kineticenergyinputtotheexpandingrelativisticfireballisoftheorderofhEiso0i≈120%ηγM⊙c2whereηγisthefractionofthefireballkineticenergythatisconvertedintoγrays(Guettaetal.2001).Theafterglowlightcurveofmanyburstsshowsanachromaticbreak,cur-rentlyinterpretedastheevidenceforabeamedemission(Sarietal.1999,Rhoads1999).Inthiscasetheemittedγ-rayenergyEjetγisobviouslyreducedbythefactor(Frailetal.2001)Ejetγ=fjetEisoγwherefjet=1−cosθjet.Inarecentpaper(Bloometal.2003)presentacompletesampleof29gamma-raybursts(GRBs)forwhichithasbeenpossibletodeterminetemporalbreaks(orlim-its)fromtheirafterglowlightcurves.Incorporatingrealisticestimatesoftheambientdensityandpropagatingerrorestimatesonthemeasuredquantities,inagreementwiththepreviousanalysisofasmallersample,thederivedjetopeninganglesofthose29burstsresultinanarrowclusteringofgeometricallycorrectedgamma-rayenergiesabouthEjetγi=1.33×1051ergs,withaburst-to-burstvarianceof0.34dex.Threeconsequencescanbedrawn,ifthisistrue:1.ThecentralenginesofGRBsreleaseenergiesoftheorderofE0≈few×10−220%ηγM⊙c2ThisvalueisindeedcomparabletothekineticenergyoutputofordinarySNe,suggestingaconnectionbetweenthetwophenomena,alsosupportedbytheobservationofbumpsintheafterglowslightcurves(Bloom2003);2.ThelargespreadinobservedfluenceandpeakluminosityofGRBsism