follow-up of Gravitational Wave event GW150914 detected by the
Advanced LIGO interferometers on Sept. 14th, 2015
September 14th, 2015 at 9:50:45 UTC, a
gravitational wave signal, labelled GW150914, was recorded
by the LIGO Hanford (Washington, USA) and LIGO Livingston
(Lousiana, USA) detectors. The official announcement of this
detection is reported here.
The 90% confidence level localization skymap of the
potential source covers an area of 590 deg2. The
highly significant event (more than 5σ) was likely produced
by the merger of two black holes of roughly 30 Sun masses
each, at a distance of 410 Mpc.
The ANTARES Collaboration congratulates the LIGO Scientific
Collaboration and the Virgo Collaboration for this discovery.
We summarize here the first
high-energy neutrino follow-up of a significant
gravitational wave detection, i.e. the search for a
neutrino emission temporally and directionally coincident
with the gravitational wave signal, using the data
recorded by the ANTARES
merger of neutron stars and black holes are expected to be
significant sources of gravitational waves. Such systems may
produced electromagnetic emission and emit high energy
neutrinos, if the merger happens in a sufficiently
baryon-dense environment, and a black hole+accretion disk
system is formed. These high energy neutrinos are detectable
by neutrino telescopes such as ANTARES and IceCube, with
angular resolutions ≤ 1°. The detection of such neutrinos in
coincidence with a gravitational wave event would aid
electromagnetic follow-up surveys by providing accurate source
directions. Moreover, while high-energy neutrino observations
are probing the physics of relativistic outflows,
gravitational waves are indicative of the dynamics and
formation of the progenitor that drives the outflow.
A high-energy neutrino follow-up search of GW150914 was
carried out using the data recorded by ANTARES and IceCube in
2015. No neutrino was found temporally and
directionally coincident with the gravitational wave event,
whereas 3 (0) neutrinos detected by IceCube (ANTARES) were
found temporally coincident within 500s of the event, both
numbers consistent with background. This non-detection was
used to constrain, for the first time, neutrino emission from
the gravitational wave transient event.
The obtained limit has been expressed in terms of total energy
emitted in neutrinos, and computed both for a E-2
generic spectrum and for a more realistic E-2
spectrum with a cut-off at 100 TeV, with a result, for a
source at a distance Dgw :
allowed range is due to the large directional
uncertainty of the gravitational wave signal. For
comparison, typical isotropic-equivalent energies
emitted during long (short) gamma-ray bursts are of the
order of 1051 erg (1049 erg).
Given the total energy emitted in gravitational waves,
of the order of 5 x 1054erg for this signal,
the upper limit translates into an energy fraction
emitted under the form of neutrinos lower than 0.2% -
20% of the gravitational wave energy for a source at 410
The following figures show the upper limits on the
high-energy neutrino spectral fluence (for muon
neutrinos and anti-neutrinos) E2dN/dE as a
function of source direction, for the two studied
spectra. The region surrounded by a white line shows the
part of the sky in which ANTARES is more sensitive. For
comparison, the 50% and 90% confidence level contours of
the gravitational wave sky map are also shown. ANTARES,
mostly sensitive to 3 TeV-1 PeV neutrinos in the
Southern hemisphere, constrains well the spectrum with a
cut-off (left plot), where IceCube, sensitive to 200
TeV-100 PeV neutrinos in this region of the sky, is more
constraining for the generic spectrum (right plot). This
nicely illustrates the complementarity of the two
Note that multimessenger analyses constraining the common
sources of high energy neutrinos and gravitational waves
have been carried out in the past, in particular using data
taken by ANTARES and Virgo/LIGO in 2007, and were published
06 (2013) 006. They constrained for the first time
using concomitant observations, the population rate density
of joint gravitational wave+high energy neutrino sources.
The results reported here represent, in contrast, the first
concrete limit on
neutrino emission from this kind of gravitational wave
source, and the first neutrino follow-up of a significant
gravitational wave event.
the upcoming observation periods of Advanced LIGO-Virgo, similar
analyses performed with ANTARES and in the near future with
now under construction in the Mediterranean, will be
important to provide constraints on or to detect joint
gravitational wave and neutrino sources.
The ANTARES Collaboration is
thankful the LIGO Scientific Collaboration and Virgo
Collaboration for the rapid sharing of information and the
cooperation which allowed this multimessenger analysis.
publication corresponding to this search will be available
soon on ArXiV. A draft version of the paper is available here.
See the Official
Press Release by the LIGO and Virgo Collaborations.