# Workshop on Gravitational Waves and High Energy Neutrinos

Europe/Paris
AstroParticule et Cosmologie (APC)

#### AstroParticule et Cosmologie (APC)

Paris, FRANCE
,
Description

The first Gravitational Wave + High-Energy Neutrino (GW+HEN) Workshop was organized by the Laboratoire AstroParticule et Cosmologie (APC) (location) in Paris (France) at Université Paris Denis Diderot May 18th - 20th, 2009.

This workshop gathered the scientific communities contributing to the major gravitational-wave (GW) and high-energy neutrino (HEN) experiments (currently operating or planned for the near future) to explore their common scientific potential and to establish the basis for a joint data analysis strategy.

Many of the astrophysical sources and violent phenomena observed in our Universe are potential emitters of gravitational waves and high-energy cosmic radiation, in the form of photons, hadrons, and presumably also neutrinos. Both gravitational waves and high-energy neutrinos are alternative cosmic messengers that may escape very dense media and travel unaffected over cosmological distances, carrying information from the innermost regions of the astrophysical engines (from which photons and charged cosmic rays can barely reach us). For the same reasons, such messengers could also reveal new, hidden sources that were not observed by conventional photon-based astronomy.

Coincident observation of GWs and HENs may thus play a critical role in multi-messenger astronomy. This is particularly true at the present time owing to the advent of a new generation of dedicated detectors: ANTARES, now fully operational in the Mediterranean Sea, and Ice Cube, taking data and proceeding with deployment at the South Pole, as well as the GW interferometers Virgo in Italy and LIGO in the United States, both upgrading and preparing for a common science run in mid-2009.

Given the complexity of the instruments, a successful joint analysis of this data set will be possible only if the expertise and knowledge of the data is shared between the two communities.

This perspective is the motivation for this three-day workshop bringing together physicists from the aforementioned collaborations and theorists developing the models of GW+HEN sources. The idea is to foster scientific exchange, and to develop joint strategies and analysis tools to best utilize the common data.

The workshop features reviews of the current theoretical knowledge about the mechanisms of GW and HEN emission and the potential common sources, as well as a status report of each of the detectors. A large amount of time is dedicated to discussions on the combined GW+HEN searches, their scientific pay-off (constraints of the source models, consequences for fundamental physics) and implementation issues (relevant common data sets, analysis pipelines, possibility/feasibility of online alerts).

The workshop included a session with contributed talks with contributions in the topics connected to the GW+HEN search problem including (but not limited to) the observation and modelling for sources of high-energy radiation such as Gamma-Ray Bursts, Soft Gamma-Ray Repeaters, microquasars or other jet sources.

P. Brady (UWM and the LSC, USA), P. Binetruy (APC, France), F. Fidecaro (U. of Pisa and Virgo, Italy), C. Finley (UWM and Ice Cube, USA), T. Gaisser (U. of Delaware and Ice Cube, USA), N. Gehrels (NASA GSFC, USA), F. Halzen (UWM and Ice Cube, USA), P. Hello (LAL and Virgo, France), J. J. Hernandez (U. of Valencia and ANTARES, Spain), Sz. Márka (Columbia U. and the LSC, USA), P. Mészáros (Penn State U., USA), L. Moscoso (CEA and APC, France), T. Piran (Hebrew U. of Jerusalem, Israel), D. Reitze (U. of Florida and the LSC, USA), B. Schutz (Albert-Einstein-Institut and the LSC, Germany), E. Waxman (Weizmann Institute of Science, Israel).

The Local Organizing Committee:
Bruny Baret, Matteo Barsuglia, Eric Chassande-Mottin, Antoine Kouchner, Szabolcs Márka, Thierry Pradier, Véronique Van Elewyck

Participants
• Andika Hamzah
• Anna Franckowiak
• Antoine Kouchner
• Antonio Capone
• Carsten Richardt
• dafne guetta
• Damien Dornic
• David Eichler
• David Reitze
• Derek Fox
• Dmitri Semikoz
• Eli Waxman
• Els de Wolf
• Eric Chassande-Mottin
• Eric Thrane
• Fabien CASSE
• Francesco Salemi
• François Montanet
• Frederic Piron
• Frédérique MARION
• Fulvio Ricci
• Gareth Jones
• Giovanni Amelino-Camelia
• Guido Chincarini
• Guillaume Trap
• Imre Bartos
• Irene Di Palma
• Johannes van den Brand
• Juan Jose Hernandez
• Kazuhiro Hayama
• Kei Kotake
• Kevin Payet
• Kumiko Kotera
• Luciano Moscoso
• Maria Alessandra Papa
• Maria Pareja
• Matias Reynoso
• Matteo Barsuglia
• Michal Was
• Ofelia Pisanti
• paschal coyle
• Patrice Hello
• Patrick Sutton
• Pau Amaro-Seoane
• Peter Mészáros
• Raffaela Margutti
• Rawash Hamza
• Ricard Tomas
• Samaya Nissanke
• SANDRO MEREGHETTI
• Shin'ichiro Ando
• Sipho van der Putten
• Stephanie Escoffier
• Subhendra Mohanty
• Szabolcs Markà
• Thomas Eberl
• Tsvi Piran
• Vincenzo Flaminio
• Véronique Van Elewyck
• Zeljka Bosnjak
Support
• Monday, 18 May
• 08:30 09:00
Welcome and morning coffee 30m
• 09:00 12:30
Detector status

Scribe: Matteo Barsuglia

• 09:00
Status of ANTARES (P. Coyle, CPPM Marseille) 30m
• 09:30
Search for Transient Sources with IceCube 30m
IceCube, currently under construction in the glacial ice at the geographic South Pole, will be the first neutrino telescope comprising a volume of one cubic kilometer. At the moment three quarters of the detector has been completed and is already taking data while the full detector will be finished in the austral summer of 2010/11. The search for neutrinos of astrophysical origin is among the primary goals of the IceCube neutrino telescope. Source candidates include galactic objects like supernova remnants (SNRs) as well as extragalactic objects like Active Galactic Nuclei (AGN) and Gamma-Ray Bursts (GRBs). We present an overview of the project with special emphasis on results of searches for GRBs and other transient sources. Online neutrino candidate selection combined with fast reconstruction algorithms allow IceCube to trigger a network of optical telescopes, which then search for a possible electromagnetic counterpart. The performance and sensitivity of IceCube's optical follow-up program will be presented.
Speaker: Ms Anna Franckowiak (Humboldt University, Berlin)
• 10:00
break 15m
• 10:15
Status of Virgo and LIGO (Frédérique Marion, LAPP Annecy) 30m
• 10:45
Future gravitational wave and neutrino detectors 30m
An overview is given of the next generation gravitational wave detectors and high-energy neutrino observatories. The status of Advanced Virgo and KM3Net is discussed. Ideas about the third generation gravitational wave detector Einstein Telescope are presented.
Speaker: Prof. Johannes van den Brand (Nikhef)
• 11:15
Ultra high energy neutrinos at the Pierre Auger observatory 30m
The Pierre Auger observatory is able to discriminate between showers induced by Ultra High Energy neutrinos and showers from any other primary. This allows to search for such particles in the data from downgoing showers with large zenith angles (theta > 75°). But the observatory is also sensitive to Earth-skimming tau neutrinos that interact in the Earth's crust to produce a tau lepton that may emerge and trigger an extensive air shower used to sign the presence of the initial neutrino. Both channels were studied, and the last one already gave rise to a publication in PRL based on the data from 1 January 2004 to 31 August 2007. In this talk, we will present the different searches for neutrinos in the Auger data and their present status. In addition, the Auger collaboration has also produced important results, concerning the UHE cosmic rays, that may have important implications regarding the sources of neutrinos, and that we will also discuss briefly.
Speaker: Mr Kevin Payet (LPSC)
• 11:45
Discussion 45m
• 12:30 14:00
Lunch 1h 30m
• 14:00 18:30
Science case for GW and HEN searches

Scribe: Véronique Van Elewyck

• 14:00
APC Colloquium: Science case for GW and HEN searches (E. Waxman, Weizmann Institute of Science, Israel) 1h
• 15:00
Joint emitters of GW and neutrinos 30m
Speaker: Dr Shin'ichiro Ando Ando (Caltech)
• 15:30
Planck-scale effects on propagation of high-energy particles 30m
One of the subjects that has been most studied over the last decade from a quantum-gravity perspective concerns the implications of Planck-scale effects on the propagation of high-energy particles. From the crude models of the end of the 1990s the literature gradually evolved to more detailed and robust pictures, which I briefly describe. I also stress the relevance of these studies for observatories of high-energy neutrinos and photons
Speaker: Prof. Giovanni Amelino-Camelia (University of Rome "La Sapienza")
• 16:00
break 15m
• 16:15
GRB models of GWHEN emission 45m
I will discuss models of GRB in the light of recent Fermi and Swift data, and the implications of these for GRB as potential gravitational wave and ultra-high energy neutrino sources.
Speaker: Prof. Peter Mészáros (Pennsylvania State University)
• 17:00
Prospects for gravitational waves and neutrino emission from Soft Gamma-Ray Repeaters and Anomaolous X-ray Pulsars 30m
I will review the observational properties of Soft Gamma-Ray Repeaters and Anomaolous X-ray Pulsars and discuss them in the context of the magnetar model. I will also discuss the possibility of detecting GW and high energy neutrinos from these sources.
Speaker: Dr SANDRO MEREGHETTI (INAF-IASF MILANO)
• 17:30
Discussion 1h
• 20:00 23:00
Social dinner at le Café Procope 3h
• Tuesday, 19 May
• 08:30 09:00
Morning coffee 30m
• 09:00 12:30
GRBs from the observation prospective and implication for GWHEN searches

Scribe: Antoine Kouchner

• 09:00
Gamma-Ray Burst Follow-Up: Lessons and Prospects 30m
I will discuss the experiences of multiwavelength observers of gamma-ray bursts, both historically and since the afterglow revolutions of 1997 (long bursts) and 2005 (short bursts). Looking ahead to the coming era of gravitational-wave and high-energy neutrino (GWHEN) astronomy, I believe the experiences of gamma-ray burst observers will have direct relevance to the GWHEN community, whether or not gamma-ray bursts themselves are revealed to be GWHEN sources. I will attempt to summarize these lessons, and also discuss the prospects for multiwavelength-photon observational programs that may enable detection and physical characterization of GWHEN sources.
Speaker: Dr Derek Fox (Pennsylvania State University)
• 09:30
Gamma-Ray Burst Observations with Fermi 30m
Since its successful launch on June 11th, 2008, the Fermi Gamma-Ray Space Telescope has detected gamma-ray emission from Gamma-Ray Bursts (GRBs) spanning a very broad spectral range, from below 10 keV with the Gamma-ray Burst Monitor (GBM) up to more than 10 GeV with the Large Area Telescope (LAT). We will present the results of the combined analysis of GRBs that have been detected by both instruments onboard Fermi, including: the long GRB 080825C which had over a dozen LAT events; the long GRB 080916C with about 150 events above 100 MeV, a long-lived high-energy emission up to 23 minutes after the initial trigger, and the most stringent limit to date on the GRB outflow bulk Lorentz factor; and GRB 081024B, the first ever short GRB with high-energy gamma-ray emission above 1 GeV.
Speaker: Mr Frederic Piron (CNRS/IN2P3/LPTA)
• 10:00
Highlights by the Swift Mission in the context of multi-messenger astronomy 30m
Speaker: Prof. Guido Chincarini (INAF - Astronomical Observatory Brera)
• 10:30
break 15m
• 10:45
Gamma-Ray Bursts with the ANTARES neutrino telescope 30m
Gamma-ray bursts (GRBs) are powerful cosmic particle accelerators producing a highly variable flux of high energy gamma-rays. Under the assumption of hadronic acceleration in jets, a copious flux of neutrinos can be expected. Among the possible astrophysical sources, GRBs offer one of the most promising perspectives for the detection of cosmic neutrinos thanks to an almost background free search. The ANTARES neutrino telescope was completed in May 2008. The collaboration has implemented two different methods to search for GRBs: the first one is based on the search for neutrino candidates relying on the time and position information provided by an external trigger and the second one is based on the optical follow-up of "special neutrino events". The use of these two complementary techniques provides enhanced sensitivity to these transient sources.
Speaker: Dr Stephanie Escoffier (CNRS/IN2P3/CPPM)
• 11:15
Gravitational Waves from Short Gamma Ray Bursts 30m
Merging binary systems consisting of two collapsed objects are among the most promising sources of high frequency gravitational wave, GW, signals for ground based interferometers. Double neutron star or black hole/neutron star mergers are also believed to give rise to short hard bursts, SHBs, a subclass of gamma ray bursts. SHBs might thus provide a powerful way to infer the merger rate of two-collapsed object binaries. Under the hypothesis that most SHBs originate from double neutron star or black hole/neutron star mergers, in this talk I outline here a method to estimate the incidence of merging events from dynamically formed binaries in globular clusters and infer the corresponding GW event rate that can be detected with Advanced LIGO/Virgo. In particular a sizeable fraction of detectable GW events is expected to be coincident with SHBs. The beaming and redshift distribution of SHBs are reassessed and their luminosity function constrained by using the results from recent SHBs observations. We confirm that a substantial fraction of SHBs goes off at low redshifts, where the merging of systems formed in globular clusters through dynamical interactions is expected.
Speaker: Dr dafne guetta (Osservatorio Astronomico di Roma)
• 11:45
Discussion 45m
• 12:30 14:00
Lunch 1h 30m
• 14:00 18:30
More on the emission processes of GW and HEN

• 14:00
The Most Promising High Energy Neutrino Source 30m
Nature can apparently produce high energy (HE) particle budgets of $10^{50}$ erg/s, lasting tens of seconds, during stellar collapse. Such events account for gamma ray bursts (GRB). However, at typical cosmological distances, GRB would be hard to detect in neutrinos. It is suggested here (as in Eichler and Levinson, 1999) that nearby (D < 1 Gpc) GRB, the vast majority of which are unobservable to us, could nevertheless send HE neutrinos in our direction. These would be the brightest HE neutrino bursts. They could coincide with gravitational wave signals but not necessarily with GRB.
Speaker: Prof. David Eichler (Ben Gurion University)
• 14:30
Gravitational Wave Standard Sirens 30m
Inspiralling compact binaries are excellent standard sirens (the gravitational wave counterpart to standard candles), in that their gravitational wave measurements allow for self-calibrated absolute source distances. Therefore, when coupled with independent electromagnetic redshift measures, standard sirens allow us to map out the Universe's expansion history and enable precision estimates of cosmological parameters. We discuss here how well gravitational wave measurements of inspiralling compact binaries, together with simultaneous electromagnetic observations of short hard gamma ray bursts, constrain cosmological parameters (e.g., the Hubble constant) using different network configurations of advanced ground-based gravitational wave detectors. We finally address what constraints on short hard gamma ray burst progenitor models are possible using only a single channel of GW measurements.
Speaker: Dr Samaya Nissanke
• 15:00
Probing the central engine of core-collapse supernovae through gravitational-wave and neutrino emissions 30m
Core-collapse supernovae are dramatic explosions marking the catastrophic end of massive stars. Optical outbursts begin only hours after the actual onset of the catastrophe in the very center of the star. There the central iron core collapses to a neutron star thereby liberating the gravitational binding energy which causes the supernova explosion. The only means to get direct information about the supernova "engine" is from observations of neutrinos emitted by the forming neutron star, and through gravitational waves which are produced when the hydrodynamic flow or the neutrino flux is not perfectly symmetric. After reviewing the basic physics of core collapse supernovae, the results of our recent simulations about such aspherical processes and the resulting neutrino and gravitational-wave signals will be discussed.
Speaker: Dr Kei Kotake (National Astronomical Observatory of Japan)
• 15:30
break 15m
• 15:45
Probing Core-collapse Supernova Physics with Neutrinos 30m
We discuss how one can exploit the enormous neutrino signal expected in a future galactic supernova (SN) to learn about the physics of the SN. We will concentrate on two different aspects: Firstly we analyze the possibility to locate the SN by using the directionality of the elastic scattering off electrons in a water Cherenkov detector. On the other hand we will show how their weak interaction with matter and their flavor mixing make neutrinos ideal messengers to track the SN explosion mechanism.
Speaker: Mr Ricard Tomas (II. Institut für Theoretische Physik (Universität Hamburg))
• 16:15
Astrophysical jets around compact objects : a source for neutrinos and gravitational waves ? 30m
In this talk, I will try to present a short overview of state-of-the-art studies and simulations dealing with the astrophysical jets being observed in the vicinity of compact objects. I will start by presenting magnetohydrodynamical simulations aiming to explain how can astrophysical plasmas are believed to be accelerated by magnetic field interacting with rotating black holes such as active galactic nuclei and microquasars. I will then continue by presenting mechanisms that may be at work within these flows and that may be responsible for the emission of high energy particles such as cosmic rays and neutrinos. Finally I will mention some works trying to estimate the ability of relativistic jets to give birth to detectable gravitational waves.
Speaker: Dr Fabien CASSE (AstroParticule et Cosmologie (APC))
• 16:45
SS433 as a natural laboratory for astrophysical neutrinos 30m
We discuss the production of very high energy neutrinos in the jets of the microquasar SS433. The interactions of shock-accelerated protons and electrons at the base of the precessing jets give rise, also, to a flux of gamma rays. Taking into account the absorption effects, we can estimate a surviving gamma-ray signal to be detected with Fermi LAT and with Cherenkov telescopes. Neutrinos, which escape unaffected from the production site, could also be observable at neutrino telescopes such as IceCube. In the context of the present model, future measurements of gamma rays can be used to establish constraints on the expected neutrino signal. Experimental results will allow us to check the consistency of the model and to gather important information about key paramaters of the system, such as those related to the gamma-ray absorption processes and the power in relativistic protons.
Speaker: Dr Matias Reynoso (CONICET)
• 17:15
Discussion 1h 15m
• 20:30 22:00
Concert at the Sorbonne Grand Amphithéâtre 1h 30m
• Wednesday, 20 May
• 08:30 09:00
Morning coffee 30m
• 09:00 12:30
Overview of data analysis

Scribe: Eric Chassande-Mottin

• 09:00
ANTARES: recent results (J. Hernandez-Rey, IFIC & Valencia U., Spain) 30m
• 09:30
Data Analysis in IceCube and Implications for GW Coincidence Searches 30m
I will review the triggers, event reconstructions, background rejection and analysis techniques in IceCube, and what they mean for HEN+GW coincidence searches. I will also describe near-term developments in IceCube which may significantly extend the reach of these searches.
• 10:00
Review of GW data analysis 30m
I will review the methods used in "externally triggered" searches for gravitational wave transients. These are scenarios in which we search for a gravitational wave associated with an event detected by an external observatory, such as a gamma-ray burst (GRB), an optical supernova, or a pulsar glitch. Particular emphasis will be placed on methods used in GRB-triggered analyses, and prospects for these searches over the next few years.
Speaker: Dr Patrick Sutton (Cardiff University)
• 10:30
break 15m
• 10:45
Searching for Intermediate-Duration Gravitational-Wave Transients 30m
Searches for gravitational waves traditionally fall into one of four categories: sub-second bursts, inspirals, pulsars, and stochastic. Inspiral and pulsar searches tend to look for signals with highly constrained waveforms whereas burst and stochastic searches are typically more flexible. Intermediate-duration transients (lasting from a few seconds to a few weeks) represent a largely unexplored class of objects. A variety of interesting sources may emit gravitational waves on timescales of several seconds to weeks, including microquasars, long GRBs, pulsar glitches, and supernovae; and in many cases the expected waveform is not highly constrained. Many of these sources may produce large fluxes of neutrinos detectable by large neutrino telescopes. By looking for coincident GW-ν signals, we hope to significantly lower the false alarm rate on a search for gravitational-wave transients.
Speaker: Dr Eric Thrane (University of Minnesota)
• 11:15
Joint Search between Gravitational-wave and High-Energy Neutrino Detectors 30m
Cataclysmic cosmic events, e.g. gamma ray bursts (GRBs), can be plausible sources of both gravitational waves (GWs) and high-energy neutrinos (HENs). Identifying correlations between GW and HEN detection channels shall enable new searches, as one has significant additional information about the common source. Beyond the benefit of a potential discovery, coincident detection of GW and HEN arriving from the same astronomical source might allow us to answer important scientific questions, which would be out of reach for a single channel detector. Analysis method options and Monte Carlo simulations will be discussed to demonstrate the expected performance of feasible searches. A survey of cosmic source candidates will be presented to describe the possible science reach of the data analysis initiative
Speaker: Mr Imre Bartos (Columbia University)
• 11:45
Discussion 30m
• 12:30 14:00
Lunch 1h 30m
• 14:00 18:00
Preparation of topical review paper