Letters of Intent received in 2016

LoI 2018-1964
The Astrophyiscs of Extreme Transients

Topics

- Explosive events from black holes and neutron stars
- Dense matter and high magnetic fields
- Extreme spacetime physics and gravitational waves
- Multi-messenger astrophysics / Astroparticle physics
- Coherent and high-energy emission
- Probing the universe on all scales with transients
- Massive data filtering and rapid alerting

Rationale

The astrophysics of extreme transients is taking great leaps at the
moment due to a few independent factors:

1. The development of massive surveys with high cadence and large sky
coverage in optical, radio, and at high energies has greatly
accelerated the pace of discovery of new types of transient. These
often turn out to be assoociated with extreme astrophysical
circumstances such as accreting black holes and their jets, neutron
stars, etc. This so-called time domain astronomy is the subject of
separate symposia, and so it will be discussed here only
peripherally, but its results make this meeting extra fruitful.

2. The development of multi-messenger astrophysics is making great
leaps, with the recent discovery of the first gravitational-wave
events, and not many years ago the discovery of the first cosmic
rays traceable to individual sources and the first cosmic
high-energy neutrinos. TeV gamma ray astronomy has become a mature
field, with routinely functioning observatories and many known
sources. Gamma-ray pulsars have been found to be a large class of
source with Fermi, rather than the rare exception. The communities
who work in these areas often come from physics, and are not always
well connected with their colleagues who study the extreme sources
that produce these emissions from the astrophysical viewpoint. An
important reason for wanting to hold this symposium at the GA in
Vienna is to promote good contacts between the astronomy community
and the so-called astroparticle physics community.

3. Vast improvements in computational methods have begun to make
serious first-principles study of the MHD equations that lie at the
basis of many extreme astrophysical sources within reach. No longer
are the calculations at the forefront of this work so far removed
from reality that we cannot apply them to real situations at all.
Extreme GPU acceleration and massively parallel codes are making
inroads into probing the problems of jet launching around black
holes, explosive events on magnetars, and the like. The pace of this
will have picked up even much more between now and when the
symposium will be held. We may therefore expect fruitful exchanges
between these theoretical programmes and the waves of new discovery,
and of detailed study of known types of trasient.

For all these reasons, we feel that this symposium will be a very
timely one, that can bring a very diverse and lively community of
researchers to the Vienna GA. We have listed a target date for the
symposium above, in the first week of the GA, because the form
requires it. We actually have no preference for the start date within
the GA timeframe. We do, however, believe that it should be a full 4-
or 5-day symposium, given the broad scope of the meeting and the many
topics it needs to cover.