From ANTARES toKM3NeT online analysis
platform
DAMIEN DORNIC (CPPM)
MATHIEU LAMOUREUX (CP3)

Chiba - 2023/08/07

Overview

1. Legacy of the ANTARES online analyses
2. The KM3NeT online system
3. First results of the online analyses performed with
KM3NeT

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Multi-messenger follow-ups
Given the current statistics-limited samples of astrophysical neutrinos, oneof the most optimum analysis strategies is to:• Alerts to community upon detection of likely « astrophysical »neutrinos for rapid follow-ups• Real-time searches for neutrino signals in response to transient
events observed in other messengers
These observations can:• Strengthen or re ne detections made in single messenger• Probe source dynamics and populations, even in the absence of
signal• Identify the sources of the observed high-energy astrophysicalneutrinosfi

3ANTARES neutrino telescope‣ 2475m depth in the Mediterranean Sea‣ 40 km o shore Toulon‣ First detection line installed in early 2006
‣ Completed in 2008
‣ Decommissioned in 2022
‣ 3D array of 885 PMTs (10’’)‣ 12 vertical lines‣ Instrumented volume ~0.01 km3

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End of the ANTARES adventure⟹ ANTARES: continuous data-taking between
2007-2022 with very high e ciencies⟹ ANTARES has been switch o in Feb 2022
and full recovery of the materials in June 2022.
⟹ Very competitive physics results. Legacy
analyses still in progress. All the data will
become public soon.
⟹ KM3NeT adventure
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Real-time analysis platforms
ANTARES and IceCube have implemented in 2008-9 a real- me analysis pla orm thattriggers neutrino alerts and that performs me/space correla on analysis for external
triggers.
External
alert
BrokerANTARES Shore Station
Online reconstruction
Neutrino selection
Alert processing

Time/space correlation
Binned analysis

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Real-time analysis platforms
Online follow-up performed quickly after the reception of the external
triggers using simple cut&count analysis method (pure-data driven):- Follow-up of IceCube neutrino alerts
ANTARES has received 115 neutrino triggers from the IceCube alert system and has followed 37 alerts (7HESE, 3 EHE, 10 gold and 17 bronze).

- Follow-up of LIGO/Virgo gravitational wave alerts
ANTARES has followed all the LIGO/Virgo alerts in real time (15 GWs in o2 & 51 in o3)- Follow-up of gamma-ray bursts
ANTARES has followed 317 Swift and 770 Fermi-GBM between 2014 and 2022

- Follow-up of HAWC alerts for transient phenomena
ANTARES has followed 7/22 HAWC transient alerts+ Development of combined HAWC+ANTARES searches within AMON

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Legacy for ANTARES neutrino alerts
ANTARES PSF : ~0.4º (median)

Triggers:

Nb alerts* Doublet of neutrinos: ~0.04 event / yr.
* Single neutrino with direction close to local galaxies: ~1 TeV, ~10 events / yr.
* Single HE neutrinos: ~7 TeV, ~15 event / yr=> Sub-sample HE neutrinos: ~5 TeV, 20 events / yr=> Sub-sample VHE neutrinos: ~30 TeV, ~3-4 events / yr.

Alert message sent via the GCN
using either GCN socket / VO Event⟹ Average delay: ~6-7 s

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Private alert except if a potential
counterpart is founded30

Nb alerts

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10
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1 min

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1h

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delay (s)25

Delays between the time of 1st image and the neutrino
trigger⟹ 218 alerts < 1 day⟹ 55 alerts < 1 min(wait for the alert visibility, stop previous acquisition,
point the telescope, start the acquisition)

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15

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5

0
1

1.5

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ANTARES, Astroparticle Physics, 2012, 35 (8)

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3.5
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4.5
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Delay of the first images (log10[s])8ANTARES follow-up partners
Efficiency of prompt observations vs location on the EarthTAROT
MASTERSVOM telescopes

ANTARES policy: all alerts are private (data exchange upon MoU). Only if a potential counterpart is found, thealert becomes public for further observations

Robotic telescopes: ~68% ef ciency with observations within 24h [early] and ~70% for late follow-up [long]=> Main limitations: weather, alert direction too close to the Sun/Moon/Galactic plane
Swift XRT: ~70% follow-up ef ciency=> Main limitations: alert direction too close to the Sun/Moon/Galactic plane, ToO not accepted

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Lessons from the ANTARES follow-up
Key points to be improved:- Important to have all- avor neutrino reconstruction and classi er- Reduce the systematics on the angular direction of the alerts (goodcontrol of the pointing accuracy)- Private / public neutrino alerts (how to optimize the follow-up)- Uniformise the alert format: only VO event- Increase the scienti c interest of the neutrino alerts (provide more astro
content)- Automatize the astro counterpart search directly at the alert level(crossmatch catalogs, LC…)

- Automatize the real-time correlation analyses as much as possible- Have a real organized team to manage the online analyses, not only afew persons. Reinforce the MWL follow-up expertise in the collaboration.
Provide some centralized tools for the shifters
Based on this return of experience, we have built the KM3NeT online

analysis platform.

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KM3NeTKM3NeT is the neutrino research infrastructure in the deep Mediterranean Sea
Oscillation
Researchwith Cosmics
In the Abyss

ORCA: o shore
Toulon, France

2475m

ORCA

Astroparticle
Researchwith Cosmics
In the Abyss

ARCA: o shore
Capo Passero, Italy

3400m

ARCA

Main characteristics:- Extended energy range: 1 GeV ⇾ 10 PeV (+ 10-40 MeV)
- Full sky coverage with the best sensitivity for thegalactic sources- High duty cycle (> 95%)
- All- avor neutrino detection- Good angular resolutions
230 DUs, 128340 PMTs

115 DUs, 64170 PMTs

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KM3NeT online physics framework
5 main functionalities:- CCSN real-time analysis pipeline- Online analysis pipeline for track & shower triggered events- Correlation analysis pipeline- Alert sending program- Incoming alert brokers (GCN, FINK, TNS…)- Auxiliary tools and reporting tools: DBs, event display, storage, SMS/mail senders…

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KM3NeT real-time analysis framework

13Real-time analysis framework

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Real-time event processing- CCSN real-time analysis- Triggered event processing:- Calibration online (as close as possible as in of ine including dynamical positioning)- Track & shower reconstructions (similar algorithms as of ine)
- Event classi cation (atmospheric muons-neutrinos, track-shower, atmospheric/cosmic
neutrinos
Events from each detectors processed separately
Events are copied to a common event dispatcher and stored in a dedicated DB.

-(Similar in ARCA)

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Real-time analysis processing- CCSN self/quasi-online/triggered analyses- Reconstructed event processing:- GCN broker connection + others brokers in dev (ZTF/VRO broker, TNS, …)- KOAP online analysis pipelines: for ORCA, ARCA, up/down-going, tracks/cascades-

searches
Reporting + communication tools + service applications (DBs, writers)

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Actual KM3NeT detectors
Preliminary- ORCA18 > ~10x ANTARES at LE- ARCA21 > ~3x ANTARES at HE

Continuous data ow since 1-2 years
Important work performed in the Collab to havereliable calibration, right now only available inof ine after several months. Online calibration
without dynamical positioning
This yields to a limited angular accuracy ~1-2 deg
at HE, ~2-5 deg at LE
Cascade channel being in operation

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Standard neutrino alert format• De nition of a standard high-energy neutrino alert format will help us

as a community to have the best follow-up [VO Event format, Kafka ?]• Important to add the provenance information for a better tracking of
the information• Common de nition of the scienti c interest (signalness, FAR, astro
prob…) ⟹ criteria depending on the assumed source model. How to bemodel independent ?
• Easy accessibility of all the alerts [VO table] using common astro
tools & services• Healpix skymap to provide the detail error region of the neutrino• How to provide the neutrino alert catalog (others neutrino catalogs) ?
Need also to provide the IRFs. Gamma-py common format [GADF,
VODF] https://gamma-astro-data-formats.readthedocs.io/en/v0.3/

Radio community has made this e ort
for the FRB triggers, as well as SNEWS
for the CCSN triggers
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Neutrino alert types
Selecting only 1-2 neutrinos per month from 5-6000 atmospheric neutrinos is notan easy task and depending on the selection procedure, we can nd a di erent
sample.
Alerts originate from track and cascade events (all- avor)
Very high-energy single events

Alert form:

Selection of single neutrinos, the ones which
reconstructed energy are the highest of the month⟹ Well adapted to large volume telescope

General template (VOEvent) lled
automatically and checked before sending
Alert distributed publicly through a broker

Multiple events– ID– Detector (ARCA/ORCA)– Type of alerts triggers– Number of events in given timeand space widows– Flavor– Energy– IsRealAlert– FAR– Time– RA, Dec, Longitude, Latitude– Error box 50% and 90%– Reconstruction quality– Probability of neutrino– Probability of astrophysicalneutrino– Alert provenance data

In situations where multiple neutrinos are seen from thesame direction within a limited time (a few sec to few
days, months), an alert will be sent [sliding scan
window]

Very low-energy signal
Mainly for MeV neutrino signal from CCSN

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KM3NeT neutrino alert scheme
Selecting only 1-2 neutrinos per month from 5-6000 atmospheric neutrinos is not an easy task
and depending on the selection procedure, we can nd a di erent sample.
With the growing number of MM/MWL alerts in the future, it is important to increase thescienti c content of the alert. We are trying to implement new type of alerts based on their astro
content.
• Reduce the threshold for the selection to a few per day and investigate the potential
neutrino counterpart. If a potential interesting cosmic source is found, release an alert.
• Keep the pure-based neutrino selection with a very high threshold (> gold)

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SNEWS• SNEWS: Supernova Neutrino Early Warning System(started in 1998, fully operational in 2005)• Neutrino detectors send alerts with FAR < 1 / week.
• 10 second coincidence time window.
=> A public alert is produced if coincidence is found. Prompt
and positive alerts. Less than one false alert per century.
=> No SNEWS alert has been ever sent

KM3NeTSNEWS 2.0 (in development)
Modern multi-messenger scenario, low-threshold alerts
are common => Richer multi-messenger program.
3 level of alerts: Signi cance-based alerts, time-series
sharing, real-time analysis capabilities (e.g.
triangulation).

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CCSN KM3NeT pipelines22Online shifter organization
Goal: build an online analysis group that will take care of the real-time follow-up of theKM3NeT internal alerts and EM/MM external triggers.
Duties:• Monitor the health of the online processes (reco, classi ers, SN
processes), the network and the high-level neutrino performances.
• Monitor the outgoing broker• Organize follow-up for our alerts• Monitor the EM/MM trigger receptions and the online analyses• Report the results

Website withall the required
tools

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Challenges for the neutrino follow-up (1)Need to increase the follow-up capabilities, probably not increasing thenumber of instruments but more by increasing the access to existing/planned
facilities.
For this we should increase the scienti c interest of the astro community⟹ This will help us to have more observing proposals to be accepted by the
TACs.
Sending public alerts is clearly the way to go.
Having the best angular accuracy for the neutrino alerts is the best but with agood control of the systematics (absolute pointing).
The GW/GRB communities have made this e ort to have better organized
analysis groups [ENGRAVE, STARGATE…].

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Challenges for the neutrino follow-up (2)• Wide- eld (ideally all sky) EM counterpart discovery obs. [ZTF, MASTER,

GRANDMA… in visible, Fermi-LAT at high energies]. Rapid dissemination of theinformation.

• Complete MWL follow-up from radio to gamma-rays to identify features[VLBI, X-ray satellites, CTA…]• Easy access to large surveys [ATLAS, Rubin, Euclid, Desi, eRosita…]. In quite

a lot of cases, the potential counterpart has already been characterized, without
spending new observing time…

• In relatively large error box, multiple interesting sources [source confusion,
di erent redshift horizons].

• Better knowledge of the origin of the di erent EM/MM components inside
the sources. Going beyond the 3 .

• Standard way to infer a correlation probability [need to understand thecorrelation of the MWL emissions in the sources]• Multi-messenger search automatization following FAIR principles (tools forjoint neutrino searches, tools to access to archive observing data)

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First results from the online system

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KM3NeT Online Analysis Pipeline• Alerts received by an orchestrator scheduling some analysis.
• At due time (end of search time window), analyses are launched.

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Running analyses● GRB alerts from Fermi, Swift, INTEGRAL → track searches with ARCA/ORCA- 4 time windows: [T0 - 1 day, T0], …, [T0 - 1 day, T0 + 1 day]- soon to be adapted with more physics-driven windows● IceCube high-energy ν and other transient alerts (HAWC, Fermi-LAT, MAXI)- 2 time windows: [T0 - 1 hour, T0 + 1 hour], [T0 - 1 day, T0 + 1 day]● Gravitational waves alerts from LIGO/Virgo/KAGRA- Track searches with ARCA/ORCA: [T0 - 500 s, T0 + 500 s], [T0 - 500 s, T0 +6 hour]- MeV neutrino search with ARCA+ORCA: [T0, T0 + 2 s]
● After summer: add shower and full-sky

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Online follow-ups performed with KM3NeT❖From October 2022 to June 2023:➢ 300 alerts have been followed up…
➢ … ~60% of these are gamma-ray bursts➢ … 50 IceCube high-energy neutrinos➢ … > 100 GW alerts:■ including low-signi cance ones up to mid-June■ now restricted to signi cant ones (15 in total)

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Online PS analysis method principle
ON-OFF analysis using upgoing track events❖ Search time window: centered on T0.
❖ Region of interest: cone centered on source with radius = max[Source
error, 2º (ARCA) / 4º (ORCA)].
❖ Background: estimated with one week of data prior to the search windowand events spanning same local coordinates as the region of interest.
❖ Fixed event selection❖ Count NON and compare to expected background.
❖ Convert to constraints on the neutrino ux.

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Online GW analysis method principle
ON-OFF analysis using upgoing+downgoing track events❖ Search time window: [-500 s, +500 s], [-500 s, +6 h]❖ Region of interest: GW 90% contour extended by 2°/4° for ARCA/ORCA❖ Background: estimated with two weeks of data prior to the searchwindow and events spanning same local coordinates as the region of interest.
❖ Event selection optimized to achieve 2.7 · 10-3 background❖ Count NON and compare to expected background.
❖ Convert to constraints on the neutrino ux.

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First results❖ No signi cant excess observed in any of the searches.
❖ Results are not yet sent through GCN, but will be (with thecorresponding constraints on the neutrino emission) in the next months.

fi32Analysis improvements❖ Selection optimization: optimize the search region and the cutsfor point-source follow-ups❖ Samples: adding downgoing tracks for point-source follow-ups
and cascades for all follow-ups.
❖ Online data: assess quality for each event and apply dynamic
positioning calibration to get more precise reconstruction.
❖ Statistical method: on longer term, switch from ON-OFF
counting method to full likelihood analysis with PSF.

❖ Follow-up results for GRBs / binary mergers / other potential transient
sources will be reported through GCNs.
➢ scheduled for end of 2023
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Of ine analyses for GRB221009A❖ At T0=2022-10-09T13:16:59, an extraordinarily bright gamma-ray burst was
detected by Fermi-GBM, con rmed by Swift, LHAASO, and others…
❖ Neutrino follow-ups have been performed by IceCube and KM3NeT.
⇒ Available in of ine searches: better detector calibration, dynamical positioning +detailed MC production❖Two search time windows:➢[ 0 − 50 s, 0 + 5000 s]: source abovehorizon, only downgoing track selection➢T0 ±1 d, upgoing+downgoing track
selections❖ON/OFF technique, selection optimized toensure 3σ excess if NON>0.
❖No excess observed in either detectors.
❖Upper limits on the corresponding
ux.

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Of ine follow-up for o3 GW events with ORCA
❖ Same strategy as for ANTARES.
❖ Using ORCA4+6 data and 2019–2020 GW data (GWTC-2/2.1, GWTC-3).
❖ Upgoing track events (GeV–TeV) and MeV searches.
❖ ON-OFF search in region = 90% GW contour + 30° extension.

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Of ine follow-up for IC neutrino alerts±1 day time window. ON/OFF analysis technique:● ON region = cone around source position withradius optimized with MDP technique.
● OFF region: declination band around source.
● Independent searches for ARCA and ORCA.

No signi cant excess for any of the searches.
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Summary
IceCube and ANTARES have proven the high interest of the alert sending with
14-15 years of operation.
• Alerts to community upon detection of likely « astrophysical » neutrinos for
rapid follow-ups and fast multi-messenger follow-ups of external events areat the basis of almost all the neutrino discoveries
But, the concurrence of alerts will increase signi cantly in the coming years with thearrival of new instruments (LSST, SKA, CTA, LVKC…) and even new neutrino
telescopes (KM3NeT, GVD…).
From our point of view, we should go to a global e ort of the neutrino
community to have more standard alerts with easy criteria to judge thepertinence of the alerts, more complete astro information already present in
the alert, to interest more the MWL followers.
The new online framework is ready and already running internally.
• Follow-up results will be released publicly through GCN in the next months.

• High-energy neutrino alerts will also be sent in real-time by end of 2024.
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Back-ups

Multi-messenger synergies
Optical telescopes: TAROT,
GRANDMA, MASTER, LCOGT,
ZTF, LSST…
- Easy access follow-up of large
error box
- Characteristation of thepotential counterpart with
spectroscopy (nature,redshift…)

X-ray telescopes: Swift, INTEGRAL,
SVOM, ATHENA…
- Very clean sky- Provide transient triggers (GRB,
AGN, Novae…)- ToO program (not so easy access)γ-ray telescopes: Fermi-LAT- All-sky complete monitoring- Provide transient triggers(GRB, AGN…)

SED TXS 0506+056

VHE γ-ray telescopes:
HAWC, LHAASO…
- All-sky monitoring- Provide triggers

Radio telescopes: Parkes,
MWA, Lofar, Nenufar, ASKAP,
SKA, VLBI…
- Provide triggers (FRB…)- Follow-up

fifi+ link with LIGO/VIRGO+ SK, SNEWSVHE γ-ray telescopes:
HESS, MAGIC, CTA…
- Most natural common
science case
- Follow-up (not easy
access)Gao et al 2018

Neutrino telescopes:
ANTARES, IceCube,KM3NeT, GVD…
- Mutual follow-up- Con rmation ofsources, improvesigni canceExample: association with PKS0735+178
IceCube: 1 bronze alert (~172 TeV) [GCN #31191]
ANTARES: no coincidence [ATel #15106]
GVD-Baikal: 1 cascade event (~43 TeV), ~4h after the
IC neutrino, ~5deg from the blazar direction (2.85 )[ATel #15112]
KM3NeT: 1 track neutrino candidate (~18 TeV) in
ARCA, 1.8 deg from the blazar (p=0.14). No
coincidence in ORCA [ATel #15290]
Baksan: 1 track neutrino (1 GeV), 2.2 deg from theblazar (~3 ) [ATel #15143]

The blazar was found to experience a strong arein gamma rays (ATel #15099, ATel #15129), X-rays(ATel #15102, ATel #15108, ATel #15109, ATel
#15113, ATel #15130), optical (ATel #15098, ATel
#15100, ATel #15132, ATel #15136, ATel #15148)
and radio (ATel #15105) bands.

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Sahakyan et al (arXiv:2204.05060)

Example: association with PKS0735• PKS 0735+178 (IHBL object) is

one of the brightest BL Lac
objects in the sky both in radio
and gamma• Similar spectral energy

distributions, very high radio
and -ray powers, and parsec
scale jet properties as
TXS0506• Redshift unknown z ≥ 0.424
Sahakyan et al (arXiv:2204.05060)𝛾

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Main followers of neutrino alerts
MASTER

Swift

HAWC
TAROT
ZTF
Fermi GBM / LATHESSINTEGRAL

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