1. Michael Baker Using Time Dependent Methods for Neutrino Point Source Searches with IceCube Michael Baker Prelim Presentation January 15, 2009 Major Professor: Teresa Montaruli

2. 2 Michael Baker Outline Cosmic Rays Astrophysical Neutrino Production Multiwavelength Resources IceCube Neutrino Observatory IC-22 Point Source Results Time-Dependent Analyses -- Hotspot -- Microquasars -- Multi Wavelength Flare Search Future Prospects

3. 3 Michael Baker Cosmic rays are highly energetic particles, mainly protons, which come from outer space and collide with the atmosphere. The spectrum spans energies up to that of a tennis ball The differential energy flux of cosmic rays exhibits a broken power-law spectrum.

4. 4 Michael Baker Fermi Acceleration - Each time a particle crosses a shock it gains energy - Regardless of which direction the particle encounters the shock - Results in approximately an E^-2 energy spectrum Shocks found in Supernova remnants, also from GRBs and AGN jets Shock UpstreamDownstream What do we think accelerates Cosmic Rays?

5. 5 Michael Baker “Below the knee” Protons will be confined to the galaxy for > 10^6 years The flux of cosmic rays at these energies is about 0.1 of the energy believed to be released by supernovae in the Milky Way, so SNR acceleration is a possible explanation. “The Ankle” Above ~1PeV, first protons and heavier nuclei with increasing energy will not be confined to our galaxy, so we need to find new sources. AGN? GRB?

6. 6 Michael Baker Neutrino Production 1 : 2 : 0 1 : 1 : 1 (after oscillations)‏ High energy particles can interact with nearby matter (or gammas)‏ Neglecting absorption, the flux of gamma rays from πº and neutrinos are proportional.

7. 7 Michael Baker Astronomy with Neutrinos Charged particles are deflected by magnetic fields in space, so they don't point back to their source. High Energy photons can be absorbed on the way from the source. However, neutrinos will give us a line of sight directly back to the source and aren't attenuated. The problem is that they are hard to detect once they get to Earth due to small cross-sections, so we need a big detector.

8. 8 Michael Baker About how big? Here we have plots for the sensitivities for neutrino telescopes of different sizes and at different longitudes.

9. 9 Michael Baker Source Candidates In a nutshell, our candidate sources are anything that could accelerate particles to very high energies... ← Supernova remnants Active Galaxies -> Microquasars ->

10. 10 Michael Baker Microquasars Compact object in a binary system with a star with evidence for a radio jet. The compact object will pull off matter from its companion, forming an accretion disk. Microquasar LS I +61 303 exhibits periodicity in all photon wavebands Is there a periodicity in neutrino emission?

11. 11 Michael Baker H.E.S.S (Imaging Atmospheric Cherenkov Telescope) has seen TeV gamma emission from LS 5039 Gamma emission from πº decay? If inelastic pp collisions make πº we also expect charged pion production in equal proportions Ls I +61 303 has also been observed to be periodic in >400 MeV photons from MAGIC (IACT)‏ From Ls I +61, Can expect 4 signal & 5 background events in 1 yr with full detector. (Torres and Halzen 2008)‏

12. 12 Michael Baker AGN and microquasars have the same underlying principle powering them Difference is a matter of scale of the jet, AGN have higher Lorenz factors.

13. 13 Michael Baker Marscher 2008 Models of AGN acceleration The matter distribution in AGN jets is clumpy and can be followed by radio interferometers

14. 14 Michael Baker The Spectral Energy Distribution (SED) for blazars has two bumps that fits the Synchrotron Self-Compton description with some contribution from the light emitted by the AGN's accretion disk. There are also models that use hadronic processes to explain the second bump. This SED is from Markarian 421 from 2005-6. Multi Wavelength studies are useful to see what changes happen in the peaks and relative heights of the two bumps.

15. 15 Michael Baker Multi-Wavelength Resources

16. 16 Michael Baker WIYN 0.9 meter optical telescope Campaign for monitoring blazars with Whipple/VERITAS collaborators Currently monitoring: Mrk 421, 1ES1959+650, H1426+428 W Comae, 1ES0806+524 In previous years: 1ES2344+514, Mrk 501, 1ES1218+304

17. 17 Michael Baker Whipple telescope: Imaging Atmospheric Cherenkov Telescope Detects air showers from 100 GeV – 10 TeV photons

18. 18 Michael Baker Both the Swift BAT and All Sky Monitor on XTE use a coded mask to get a wide field of view, so they scan the entire sky several times a day.

19. 19 Michael Baker LAT first Skymap Fermi/GLAST Recently launched Fermi LAT has a 1 steradian FOV constantly scanning the sky for photons in the 100 MeV to 300 GeV energy range

20. 20 Michael Baker Multiwavelength measurements of Mrk 421; 2005-6

21. 21 NESTOR Pylos, Greece ANTARES La-Seyne-sur-Mer, France BAIKAL Russia DUMAND Hawaii (cancelled 1995)‏ NEMO Catania, Italy IceCube/AMANDA, South Pole, Antarctica Cerenkov Neutrino Detectors

22. 22 Between 300-600 nm about 3.5 x 10 4 Cherenkov photons/m of a muon track β ∼ 1 and θ c ∼ 41 o Natural radiator is low cost and allows huge instrumented regions but it takes time to know it well! Main systematic error source wavefron t Concept of Neutrino Detector

23. 23 Michael Baker Neutrinos can create a lepton via charged current interactions, or an energetic shower by a neutral current interaction. Neutrino Detection Reno 2004

24. 24 Michael Baker Distorted from plane wave by scattering θ c = 41º  Ĉerenkov Light Moving charged particles disturb local matter Light emitted interferes constructively to form a cone if v > c/n Ice n=1.31

25. 25 Amundsen-Scott South Pole station South Pole Dome Summer camp AMANDA road to work 1500 m 2000 m [not to scale] www.icecube.wisc.edu

26. 26 Michael Baker The goal is to have a cubic km of ice underneath the South Pole instrumented with photo-multipliers. The depth helps reduce downgoing muons and external light. Currently 5x strings in-ice, and the new season of drilling is under way. 1x strings installed this season!

27. 27 Michael Baker IceCube Construction

28. 28 Michael Baker DOM – Digital Optical Module 10-Inch Hamamatsu PMT Main board Digitize waveform: 300 MHz for 400 ns 40 MHz for 6.4 μs Flasher board with 12 LEDs separate high voltage Time resolution: 2ns

29. 29 Michael Baker Example of an IC-22 event

30. 30 Michael Baker We only have good angular resolution with muons, so we find the best-fit track for our reconstruction. We have the time residual function to describe the probability of a photon arriving at a certain time at a certain distance from its production. The likelihood of the track is the product of these probabilities. Iterate over all the hit DOMs and we minimize the negative log likelihood for the track. Use the most probable track, and fit a paraboloid to the shape of the likelihood space to get the angular resolution of the track.

31. 31 Michael Baker Simulated events let us know if our reconstructed angular resolution is a good measure of the uncertainty in the track direction. Here we have the fraction of events reconstructed within a certain angular distance of the true direction. Where it crosses 0.5 is the definition of the detector's angular resolution.

32. 32 Michael Baker See a deficit in CR shower-produced muons from 3 months of IC40 data. Shows our telescope can 'point' ! L. Gladstone

33. 33 Michael Baker The detector's stability is especially important for time dependent searches, so here we have the event rates at Level 3 processing for IC22 data. Here we still have 11 million events, so it is dominated by mis-reconstructed background, which has a strong seasonal variation. We use a random sample of these events to create equivalent samples for time dependent analyses Rate Stability Studies

34. 34 Michael Baker Unbinned Analysis We use a signal Pdf based on the angular resolution of each event and an energy estimator based on the number of DOMs hit (Nchan)‏ based on simulated neutrino events. The background Pdf is based on density of events in a declination band and the Nchan of the final data sample.

35. 35 Michael Baker Confidence level of the test is the fraction of scrambled background trials which yield higher values for the log likelihood. Detection is for 5σ confidence level (p=5.73e-7)‏ The power is the fraction of trials with a particular level of signal which yield higher values of the log likelihood. 3σ3σ

36. 36 Michael Baker IC22 Point Source Results Hottest spot found at r.a. 153, dec. +11 est. nSrcEvents = 7.7 est. gamma = 1.65 est. pre-trial p-value: -log10(p): 6.14 (4.8 sigma)‏ If it's a steady source, we can confirm it in subsequent years of data Concern that it could be due to a one-time occurrence.

37. 37 Michael Baker Time Dependent Analysis of the Hotspot Time-Integrated likelihood factors Time-Dependent likelihood factors

38. 38 Michael Baker Hotspot Analysis – Setup and Null Hypothesis Identified the events near the spot as interesting Still blind to timing information, so we can get an independent value Fix the position and energy of the events, and simulate signal by clustering events in time.

39. 39 Michael Baker Hotspot Analysis – Discovery Potentials I performed tests with and without using the energy weights to fit a Gaussian to derive the best-fit mean and sigma that describes a flare Use events which have S/B > 1 at the hotspot location

40. 40 Michael Baker Hotspot Analysis – Results p-value ~ 0.5 p-value ~ 0.3 Neither analysis finds any significant clustering of events in time

41. 41 Michael Baker Microquasar method For the microquasar study, we take the same idea as the hot spot and look for a Gaussian from the events' time modulo the period of the particular object, which is known with good precision from other studies. Here we have a plot of how precisely we can determine the peak emission with different emission widths and signal events

42. 42 Michael Baker Objects we looked at: ObjectPeriod Cygnus X15.600 days Cygnus X30.1997 days GRO J04220.212 days GRS 191530.8 days Ls I +61 30326.496 days SS 43313.08 days XTE J11180.1699 days

43. 43 Michael Baker Discovery Potentials We found that the discovery potential is better than the time-integrated analysis if the sigma of the emission is less than one fifth of the period. For wider emission widths the added degrees of freedom make the time-dependent search less powerful.

44. 44 Michael Baker Microquasar Results The smallest p-value pretrial we got for the microquasar analysis is 0.06 for SS 433, which isn't significant given we looked at 7 objects SS 433 Here are two examples of the 7 microquasars, the events are plotted in phase. Black is the events per bin, blue the space and energy in the bin, and red is the best-fit Gaussian reconstruction. Ls I +61

45. 45 Michael Baker IC-22 Flares Intro In addition to periodic sources, we are also interested in examining outbursts from transient objects, mainly blazars and microquasars. For the IC-22 run, we took notes of Astronomer's Telegram alerts for objects in our source list. We used light curves from other experiments to define a time window for each flare.

46. 46 Michael Baker IC-22 Flares Selection 3C 454.3 July 24-30 2007 (seen with Agile)‏ Nov. 11-21 2007 (Agile and WEBT)‏ 1ES 1959 Nov 25-28 2007 (Integral report)‏ Cygnus X1 August 8 2007 (Konus-Wind, ASM)‏ S5 0716+71 September 7-12 2007 (Agile, Radio)‏ Oct 19-28 2007 (Agile, Radio)‏

47. 47 Michael Baker Flares Method We compared two methods -- Fix a time window, events fall either inside or out -- Use the window to constrain the mean of a Gaussian

48. 48 Michael Baker Flares Method and Status We find there is a range of widths of signal where the box does better, due to its fewer degrees of freedom for the fit. Still waiting for permission to, unblind, no results yet

49. 49 Michael Baker Future Prospects IC 40 flare analysis Prescription for general flare analysis Program to utilize Fermi data & software tools Other PS improvements -- mirror symmetry in some events -- Investigate different methods for calculating angular resolution

50. 50 Michael Baker IC 40 Flares: Mrk 421 from April 30 – May 3 2008 Whipple sees up to ~10 Crab 3C 454.3 has had several flares June 16, July 24, Nov 20 S50716+714 on April 28 in x-ray AO 0235+16 Large radio outburst from Nov 7-11

51. 51 Michael Baker Conclusions IceCube currently has 5x/80 strings in the ice IC-22 analysis show the detector is working as expected and Moon shadow confirms pointing We have new sources of astronomical data There are many new opportunities in neutrino and multi-messenger astronomy

52. 52 Michael Baker

53. 53 Michael Baker With well-sampled photon data in the future, we would like a method to define flares to single out and take a Pdf directly from that photon data. We're testing a Maximum Likelihood Blocks algorithm to see how well it takes discrete measurements to a continuous function.

54. 54 Michael Baker To test the block method we need to simulate a satellite response and use that for the analysis. How much does the telescope sampling affect what we reconstruct?

55. 55 Michael Baker Here are samples of different trials to simulate ASM data and their reconstructions. This will give a better sense of how well blocks are representing the Pdf, to make sure that the areas are largely in the same place.