High-energy neutrinos could be produced in the interaction of charged cosmic rays with matter
or radiation surrounding astrophysical sources. Transient phenomena, such as gamma-ray bursts,
core-collapse supernovae or active galactic nuclei are promising candidates to emit high-energy
neutrinos. To search for coincidences between a transient event and a neutrino emission, a followup
program of neutrino alerts is in operation within the ANTARES Collaboration since 2009.
This program triggers a network of robotic optical telescopes immediately after the detection of
a neutrino event and schedule several observations in the following weeks. The most interesting
neutrino candidates are also followed by the Swift XRT telescope and the Murchison Wide field
Array radio telescope and the H.E.S.S. very high-energy gamma-ray telescope. By combining
the information provided by the ANTARES neutrino telescope with information coming from
other observatories, the probability of detecting a source is enhanced, allowing the possibility
of identifying a neutrino progenitor from a single detected event. No significant counterpart
associated with a neutrino emission has been identified during image analysis.