Fast-time variations of supernova neutrino fluxes and detection perspectives

Transcription

1 Fast-time variations of supernova neutrino fluxes and detection perspectives Irene Tamborra GRAPPA Institute, University of Amsterdam Xmas Workshop 2013 Bari, December 23, 2013

2 Outline Supernova explosion mechanism Neutrino signatures of the SN hydrodynamical instabilities Detection perspectives adopting first full-scale 3D SN simulations Conclusions This talk is based on: I. Tamborra, F. Hanke, B. Mueller, H.-T. Janka, and G. Raffelt, PRL 111 (2013) I. Tamborra, F. Hanke, B. Mueller, H.-T. Janka, and G. Raffelt, in preparation.

3 Neutrinos in Supernovae Core-collapse supernovae: Terminal phase of massive stars [ M 8M ]. Stars collapse ejecting the outer mantle by means of shock-wave driven explosions. Expected rate: 1-3 SN/century in our galaxy (~ 10 kpc). Implosion (Collapse) Neutrinos carry 99% of the released energy 53 (~ 10 erg). Explosion neutrino cooling by diffusion Neutrino typical energies: ~ 15 MeV. Neutrino emission time: ~ 10 s.

4 Neutrinos and SN Explosion Mechanism Shock wave forms within the iron core. It dissipates energy dissociating iron layer. Stalled shock wave receives energy from neutrinos to start reexpansion against ram pressure of in-falling stellar matter. (Delayed Neutrino-Driven Explosion.) Convective overturn and shock oscillations (standing accretion shock instability, SASI) enhance efficiency of neutrino heating and revive the shock. <8 Shock wave Neutron # star $ ('' * For more details see H.-T. Janka, arxiv: , H.-T. Janka et al., arxiv:

5 Directional Neutrino Signal First full-scale 3D SN simulations with detailed neutrino transport being performed* SASI and convective motions leave an imprint on the neutrino signal. )*+, %" *-./012 ( ' & % $ # (optimistic * observer direction) - - Close to the SASI plane 3 " large amplitude # " # modulations $ % & "#$%& )*+, %" *-./012 ( ' & % $ # Perpendicularly to the SASI plane (pessimistic observer direction) *+), -.( " small amplitude modulations # " # $ % & "#$%& Large amplitude modulations close to the plane where spiral SASI mode develops. Are such modulations detectable? * For details see also: F. Hanke et al., arxiv:

6 Detection Perspectives In IceCube and Hyper-Kamiokande, neutrinos are primarily detected by inverse beta decay ν e + p n + e + IceCube Hyper-Kamiokande 1 km antarctic ice with 5160 PMT R = 1480 ms -1 bkgd Fiducial mass: 740 kton Background free signal + event-by-event energy information * For details see: Abbasi et al., arxiv: (IceCube), K. Abe et al., arxiv: (Hyper-K).

7 SASI Detection Perspectives (27 M ) sun Our 3D 27 M sun SN progenitor shows pronounced SASI. SASI sinusoidal modulation of the neutrino signal will be detectable by IceCube and Hyper-K. Strong signal modulation (optimistic observer direction) Weak signal modulation (pessimistic observer direction) 456)+78-9 : 012) ("" 01)2.3) '"" ) &"" %"" * $"" #"" "" ("" +,)-./) '"" &"" ) %"" * $"" #"" "" '+, -./ Expected rate above IceCube background Hyper-K rate = 1/3 IceCube rate SASI still detectable 3/ :;<6=>3; % 9*&307& "'()* $ & # " & #'()* +,*(-./012 "#./,)01 " "*+,- ( ) ' % ) #*+,- # " # $ % & 234)*5467

8 SASI Detection Perspectives (27 Msun ) Time evolution of the IceCube observer 8 detection rate on a sky-plot oftamborra et directions. al. "#$%&'( "# )*% high detection rate & "$% )*)+ ) )*)+ "#$$%&',-''.-/01.-/ "$ )*% ()* "% low detection rate "% "$ "$% ()(% "# "# ( & "$% ()(% "#$%&'( ()* &)* &)&+ '())*(+,-*(+ "$ "% "% "$ & "$% &)&+ "# &$ &)* ' Figure 7. 4π maps of the relative variation of the luminosity of ν e with respect to the one computed averaging over all directions the 27 M SN progenitor at 10 kpc for t = 217, 225, 230 ms. availableforat: &#" Nγ (Ee ) = 178 Ee /MeV is the energy-dependent number of Cherenkov photons, and σ (Ee, Eν ) = dσ(ee, Eν )/dee is the IBD cross section, differential with regard to the positron energy. &" ))0/1230/1 Animated visualization &# #'( )*+

9 hardly shows any modulation at all. In a given direction we define the relative time-dependent rate and consider SASI Detection Perspectives (27 M ) its root mean square deviation for the first SASI episode ([t 1,t 2 ] = [120, 250] ms), σ ( t2 t 1 dt Despite the spiral mass motions during this SASI episode and the corresponding, considerable time variability of the emission asymmetry, the time integrated analysis still 1 high reveals a dominant sloshing direction, which produces two signal hot spots in two opposite directions, surrounded by directions with much smaller modulations. 0.8 In the bottom probability signal for of Hyperyieldsof roughly the 900 Other progenitors. Figure 3 shows the IceCube rate 0.6 detection for the other progenitors (11.2 and20m ) in optimal signal fluctuation modulation is alm observing directions. For the heavier case, a strong SASI low 1 Hanke2013 movie/index.html. modulations are r trino time sequen thesun IceCube ν e si shot noise realiza near maximum, p [ ] ) 2 1/2 roughly R R. [t 1,t 2 (1) ] = [120, dom 250] fluctuation ms R background is su signal in the abse tuations alone. F the expected gala the signal is still bin-to-bin fluctua distance reduces dark current, the this distance Hyp A serious strat from the noise in l On average, the fraction of sky where good observation chances apply is significant (> 50%).

10 SASI Detection Perspectives (20 M ) sun For the 27 M For the 20 M sun sun SN progenitor, two SASI episodes occur with a convective phase in between. SN progenitor, only one SASI episode occurs. /*+,- #. # $*0-12 ( ' 5 = & 89:5;< $ " # #" $ )*+,-. $" % we study SNe prog cuss how types of The tw nature, o SASI ph overturns signal in ously exp tic SN by The SA with opp sides of t age signa the conve observed metry be

11 overturns only. SASI Detection Perspectives (20 M ) The SASI modulati signal in 3D SN simulations appears s sun ously expected and it will be easily de tic SN by detectors as IceCube or Hy The SASI modulation of the neutri On average, the fraction of sky where good observation chances with apply opposite is significant phases for (> observer 50%). loc The SASI plane of the 20 M sides of the emitting sphere, in such a sun SN progenitor is not the same as the 27 M sun one. age signal looses all the angle depende the convective phase of the 11 and 27 observed a clear asymmetry that sho metry between neutrinos and antine develops in 3D under the form of spi ( high plane randomly chosen according to t As discussed in (Tamborra2013), Ic "#' Kamiokande will offer us complem since IceCube will be more suitabl distances where probability the shot of noise is s "#& Kamiokande detection will be more of the useful at lar basically background signal modulation free and where i flux would be dominated by noise flu "#% Figure π map as in Fig. 10, but for our 20 M progenitor ([150, 330] ms). pears in the power-spectrum at f 80 Hz, corresponding to the typical frequency of the SASI. This frequency is the same describing large-amplitude fluctuations of the low spherical harmonics SASI amplitude vector in Fig. 2 (right panel on the top) of (Hanke et al. 2013). Such frequency is also well understood analytically, since it is "#$ We thank Ewald Müller for usef low Nicole Schwarz for visualizing the ne for the three supernova progenitors i search was partly supported by the De gemeinschaft through the Transregi Research Center SFB/TR 7 Gravi tronomy and the Cluster of Excellenc and Structure of the Universe (htt cluster.de). It was also supported by t under grant PITN-GA

12 SASI detection perspectives (11.2 M ) sun SASI does not occur for any progenitor. Large scale convection is the dominant hydrodynamic instability in the 11.2 M sun progenitor. SASI spiral mode ( "#' "#& "#% "#$ on (see he first 123,-.#4+/0 # ( ' & $ 9:,;6<, 8, $-5 /67 ##-5 /67 " # #" $ $" % )*+,-.+/0 FIG. 3: IceCube rate for optimal observing directions for the 11.2 and 20 M models at 10 kpc, as in the top panel convective of Fig. motions 1.

13 Power spectrum of the event rate Power spectrum of the IceCube event rate in [100,300] ms Power spectrum M sun 20 M sun 27 M sun IceCube Frequency [Hz] A peak appears at the SASI frequency of ~ 80 Hz for the 20 and 27 M sun SN progenitors.

14 Conclusions World-wide first 3D SN simulations with detailed neutrino transport available. Neutrinos carry imprints of the explosion dynamics. The SN neutrino signal can diagnose the nature of the hydrodynamical instability. SASI modulations of the neutrino signal will be clearly detectable in IceCube and Hyper-K. Detection chances depend on progenitor properties, distance and observer location relative to the main sloshing direction.

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