IceCube as a Neutrino Follow-up Observatory for Astronomical - PowerPoint PPT Presentation

IceCube as a Neutrino Follow-up Observatory for Astronomical Transients Kevin Meagher Université libre de Bruxelles On Behalf of the IceCube Collaboration July 17, 2017 35 th International Cosmic Ray Conference Busan, Korea

Overview • Goal: Use IceCube neutrinos to perform follow-up observations for any astronomical transient event within hours of observation • This analysis is separate from previously reported efforts where follow-up observations are made based on initial reports from IceCube • Uses IceCube’s online realtime event stream: Reconstructions are available within minutes of detection • Since the analysis received approval 7 follow-up analyses have been performed 2 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

Motivation • IceCube has detected a significant flux of astrophysical neutrinos • Origin remains a mystery: no point sources, no known astrophysical sources: gamma-ray bursts, AGN • Potential for identifying other sources: rapid follow-up observations necessary to identify transients Red band: Up-going muon tracks Black Crosses: High-energy contained events 3 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

IceCube Realtime Data Pipeline • Processed at the South Pole Station by the online filter • Data records (RA, Dec, Time) sent with median delay ~33 seconds over iridium satellite to Northern Hemisphere • Reconstruction Muon Neutrinos to within 1° • Same sample already in use by optical, x-ray, and gamma-ray follow-up programs [see arXiv:1612.06028 ] Counts 4 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

Analysis Method • Use unbinned liklihood analysis to identify candidate events and determine significance of the observation Example energy PDF for dec=+15° • Where S ( x i ) and B ( x i ) are the signal and background PDFs which incorperate distance from the reconstructed neutrino direction to the source direction and the neutrino energy • Same Likelihood method as used by previous IceCube gamma-ray burst searches as well as fast radio burst search [See talk by Donglian Xu] • Analysis is makes no model assumptions about the source and can be used for any class of transient 5 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

Sensitivity • Analysis is optimized for an E -2 neutrino spectrum • Sensitivity is declination dependent: – Cosmic ray backgrounds from the Southern Hemisphere – Earth Absorption in the Northern Hemisphere 6 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

Results

IceCube-160427A / PS16cgx • IceCube-160427A saw a high-energy starting track with an error circle of 0.6° [GCN #19381] • Pan-STARRS observed supernova PS16cgx candidate within the error circle [GCN #19381] • Searched a time window: ±1.2 days around the time of IceCube event • Used the position of supernova • Removed the HESE event from the likelihood analysis • A single low-energy, non-significant was observed in the time window 8 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

Cygnus X-3 Flare • Fermi-LAT detected a 1 day long February flare in coincidence with a Swift-XRT 2017 Flare and radio flare [ATEL #10243] This Flare • Associated with the transition from ultra-soft state to hard state • X-ray spectral transitions with gamma-ray flares may precede plasmoid ejection and high energy particle acceleration See Tavani et al., Nature 462 , 620 (2009) • Results: Three events were near by but were not significant 9 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

GRB 170405A • Fermi-LAT detected a high energy burst with 13 events above 100 MeV [GCN #20987] • Using time window T-200s to T +1000s to encompass all Fermi-LAT detected gamma-rays • Results: No events found 10 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

AGL J0523+0646 • Unidentified source detected by AGILE at energies above >100 MeV [ATEL #10282] • Flux visible for two days • Unknown if galactic or not: b=-16.1° • No known gamma-ray sources within the AGILE error circle 0.6° • Results: no events observed with IceCube 11 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

IceCube-170506A • Track-like, very-high-energy starting event with a high possibility of being of astrophysical origin • Removed the HESE event from the likelihood analysis • No additional events observed within ±0.5 days of the event 12 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

AT2017eaw • Nearby supernova observed by an armature astronomer using a 0.35m telescope • In the nearby galaxy NGC 6946 5.5 Mpc away (z=0.000133) • Results: 4 poorly localized, low- energy events were observed • Significance: 1.278 σ 13 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

Fermi J1544-0649 • New gamma-ray/X-ray transient source detected with Fermi All-sky Variability Analysis (FAVA) • Flared for a period of 2 weeks • Gamma-ray spectrum: Power-law with a spectral index of 1.7 (300 MeV to 300 GeV) • 2 week period overlapped with the transition from the IceCube 2016 event selection to the 2017 event selection • Results: No significant events found 14 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

Results Summary Source Class Duration P-value Flux upper limit (Significance) [TeV cm 2 ] IceCue-160427A/ IceCube HESE/ 1.2 days >0.19 3.70 × 10 -5 PS16cgx Supernova Cygnus X-3 X-ray Binary Flare 1 day >0.15 5.61 × 10 -5 GRB170405A Gamma-ray Burst 1200 seconds --- 5.66 × 10 -4 AGL J0523+0646 Unidentified 2 days --- 4.12 × 10 -5 Gamma-ray IceCube-170506A IceCube HESE 1 day --- 5.48 × 10 -4 AT2017eaw Supernova 3 days 0.10 (1.3 σ ) 8.87 × 10 -5 Fermi J1544-0649 Unidentified 14 days >0.18 6.46 × 10 -5 Gamma-ray 15 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

Summary • The IceCube astrophysical transient analyses allows for fast follow-up observations with neutrinos • 7 follow-up analyses have been performed to-date • No significant neutrino candidates have been observed • New and improved event selection as of May 2017 • If you know of a transient event you would like to be followed-up with IceCube, please contact the Realtime Oversight Committee: roc@icecube.wisc.edu 16 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

Backup

Point Source Sensitivity • asdf 18 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

Effective Area 19 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

Time Dependence 20 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

Extended Sources 21 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration