Multi-Messenger Astronomy with CTA

Volodymyr Savchenko

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Adrian Biland, Enrico Bozzo, Alessandro Carosi, Gabriel Emery, Carlo Ferrigno, Luca Foffano, Matthieu Heller, Philippe Jetzer, Merlin Kole, Francesco Lucarelli, Michele Maggiore, Teresa Montaruli, Andrii Neronov, Stephane Paltani, Nicolas Produit, Prasenjit Saha, Shubhanshu Tiwari, Andrea Tramacere, Domenico della Volpe, Roland Walter

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November 24

Swiss CTA Day

CTA and Multi-Messenger Perspective in Astrophysics

Origin of much of the neutrino and some key the GW sources is unknown, and Very High Energy observations with CTA will make key contribution to this rapidly establishing domain.

Exploratory domain, promising discoveries!

• Gamma-Ray Bursts (GRB)
• Galaxies, and their Active Galactic Nuclei
• Tidal Disruption Events (TDE)
• Fast Radio Bursts (FRBs)
• New Technology

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High-energy neutrinos

IceCube, since 2013

Gravitational waves:

LIGO, Virgo, since 2016

CTA and Multi-Messenger Perspective in Astrophysics

Gravitational Waves directly reveal energetic, relativistic, compact core: engine driving the transient

Multi-messenger sources share several key properties:

• they are transients
• they involve compact objects and relativistic jets

VHE photons reveal either hadronic processes or/and characterize properties (magnetization, density, etc) of the sites of the most extreme particle acceleration

Neutrino directly reveal or constrain hadronic processes

CTA

IceCube

LIGO, Virgo, KAGRA

Gamma-Ray Bursts: Proven Multi-Messenger Source

GRBs - stellar-scale gravitationally-driven explosions, culmination of evolution of several progenitors systems, driving ultra-relativistic collimated outflow, producing emission from radio to gamma-ray, reaching us across the universe.

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Likely to produce MeV neutrino (detectable by Super-K, Hyper-K, IceCube) as well as possibly TeV neutrino (IceCube) emision

Unusual GRBs produce most GW!

Most interesting synergies do not necessarily from from the brightest events

LIGO/Virgo, Fermi, INTEGRAL 2017; VS+ 2017

GW

GW

VHE

Gamma-Ray Bursts: Very High Energy Source

GRBs produce Very High Energy photons, detectable by CTA, sometimes many hours after the event, but even brighter during the prompt phase.

VHE emission, the most extreme, distinct component of the GRB, provides unique handle on GRB jet composition, density, magnetization; while GW observation sets valuable initial condition of the outflow.

CTA to reveal perhaps 30% of the event energy budget.

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VHE

VHE

VHE

GW

Neutrino?

Gamma-Ray Bursts: Multi-Messenger CTA Perspectives

VHE GRB detection (sometimes hints) was reported in: very bright and very weak, long and possibly short GRBs. Why some GRBs emit VHE while others do not? Which GRBs are GW and Neutrino sources? Is this decided by the viewing angle? Jet structure? Energetics?

CTA will work in synergy with the next generation GRB telescopes, such as POLAR-2, THESEUS, SVOM, GECAM as well as large FoV optical LSST to uncover previously hidden population of GRBs, broad implications for stellar evolution, origin of elements...

AGN, Starburst Galaxies: IceCube and CTA

IceCube is a prolific source of possible sources of cosmic neutrinos associated with supermassive back holes, and much of these are known to be, or very likely to be also VHE sources, detectable by CTA. Additional hints of Neutrino detection were found at the location of M87 and NGC 1068 galaxies. Important (but uncertain) implications for AGN jet properties.

The strongest association between an IceCube Neutrino source and TXS 0506+056.

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IceCube collaboration 2018

Tidal Disruption Events

Tidal Disruption Events (TDEs) occur when stars pass close to supermassive black holes in the galaxy centers.

Bright, extremely variable TDE, observed jet-on, similar to GRBs. These events should be seen by CTA, and:

• Use variability to reveal complex mechanisms driving the jet orientation structure.
• Constrain most extreme particle acceleration in relativistic outflow
• Reveal possible hadronic processes inside the TDE debris.

IceCube-191001A neutrino concided with optical TDE - AT2019dsg.

TDE might account for 1% or 26 % of total HE neutrino flux (Winter, Lunardini 2020).

Next generation wide-field optical survey, LSST will unveil unprecedented number (several 1000) TDE per year: as long as they involve relativistic jet pointing to the observer - they might be detectable by CTA (few tens per year)

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Brown+2015

x 1000

TDE afterglow at different distances

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Chen+2015

Fast Radio Bursts and Magnetars: Promising Target

In the recent years, we learned about a tantalizing new energetic transient source class: sub-millisecond radio bursts - FRB. Like GRBs - capable of reaching us from across the universe, but with much higher rate: ~1 is found in our galaxy this year. Future radio telescopes (such as SKA) will reveal them routinely.

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At least some FRB are magnetars, but the FRB signals are remarkably diverse: in intensity, temporal properties. CTA will see FRB magnetar birthplaces - remnants of prior explosions.

FRB might be also associated with high-energy neutrino (detectable by IceCube e.g. Metzger+2020) and gravitational waves in pulsar glitches (observable by LIGO/Virgo from our galaxy, e.g. Dado+2020).

Galactic magnetars also produce giant flares - some of the most intense bursts observed on Earth - multi-messenger and VHE signatures of these events are yet to be revealed. Are some magnetars responsible for Ultraluminous X-ray Sources (ULX)?

FRB coincident with soft Gamma-ray impulse

Future: LISA, Einstein Telescope, Athena

By ~2035, in the next milestone of observational Astronomy, gravitational wave detectors (Einstein Telescope and LISA) will push the limit of gravitational wave detection up to cosmological distances. By then, CTA will be fully operational.

ET will see every GRB with binary progenitor detected by CTA, precisely localize them, and even provide early pre-merger warning, sufficient to point CTA before the merger occurs.

Maggiore+ 2020

Multi-messenger Interoperability and Automation

Multi-messenger data analysis and follow-up observations require navigating and treating realtime streams of diverse astronomical events - impossible to achieve with human power alone. Brokers - interpreting and redistributing these events will be an important part of this landscape.

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Research, development environment allows experts to develop standardized, test, and integrate the scientific workflows in safe reproducible way.

experts

Find combinations of data, adapters, statistical methods, publishers, planners, schedule follow-up, distribute standard results in Data Papers/Publications with public data, in Findable, Interoperable, Accessible, Reproducible way

Observatories and Brokers

Summary

• Origin of much of the neutrino and some key the GW sources is unknown, and Very High Energy observations with CTA will make key contribution to this rapidly establishing domain.

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• Multi-messenger sources are often transient, and usually sensitivity-limited: CTA is well suited to improve on this, with:
• Unprecedented reaction time < 20s, to catch elusive events
• Larger Field of View, allowing broader synergies
• Higher sensitivity, especially at lower energy, to find previously unseen event classes

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• CTA observation of VHE emission from Multi-Messenger sources will:
• Constrain or reveal hadronic component and the most extreme particle acceleration processes in several source multi-messenger classes, specially combined with IceCube
• Explore previously unknown unusual kinds of of GRBs, AGN, TDE, and FRB: exploratory domain, promising discoveries!

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The End