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

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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 35th International Cosmic Ray Conference Busan, Korea

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Overview

  • Goal: Use IceCube neutrinos to perform follow-up
  • bservations 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

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

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Motivation

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

  • 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
  • bservations necessary to identify transients

Red band: Up-going muon tracks Black Crosses: High-energy contained events

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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
  • ver 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]

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

Counts

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Analysis Method

  • Use unbinned liklihood analysis to identify

candidate events and determine significance

  • f the observation
  • Where S(xi) and B(xi) 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

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

Example energy PDF for dec=+15°

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Sensitivity

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

  • 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

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Results

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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

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

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Cygnus X-3 Flare

  • Fermi-LAT detected a 1 day long

flare in coincidence with a Swift-XRT and radio flare [ATEL #10243]

  • 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

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

This Flare February 2017 Flare

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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

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

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AGL J0523+0646

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

  • 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
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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

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

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AT2017eaw

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

  • 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: 1.278σ
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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

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

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Results Summary

Source Class Duration P-value (Significance) Flux upper limit [TeV cm2] IceCue-160427A/ PS16cgx IceCube HESE/ Supernova 1.2 days >0.19 3.70×10-5 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 Gamma-ray 2 days

  • 4.12×10-5

IceCube-170506A IceCube HESE 1 day

  • 5.48×10-4

AT2017eaw Supernova 3 days 0.10 (1.3σ) 8.87×10-5 Fermi J1544-0649 Unidentified Gamma-ray 14 days >0.18 6.46×10-5 Kevin Meagher (Université libre de Bruxelles) for the IceCube Collaboration

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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

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

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Backup

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Point Source Sensitivity

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

  • asdf
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Effective Area

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

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Time Dependence

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

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Extended Sources

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