Elsevier

Astroparticle Physics

Volume 45, May 2013, Pages 56-70
Astroparticle Physics

The Astrophysical Multimessenger Observatory Network (AMON)

https://doi.org/10.1016/j.astropartphys.2013.03.003Get rights and content

Abstract

We summarize the science opportunity, design elements, current and projected partner observatories, and anticipated science returns of the Astrophysical Multimessenger Observatory Network (AMON). AMON will link multiple current and future high-energy, multimessenger, and follow-up observatories together into a single network, enabling near real-time coincidence searches for multimessenger astrophysical transients and their electromagnetic counterparts. Candidate and high-confidence multimessenger transient events will be identified, characterized, and distributed as AMON alerts within the network and to interested external observers, leading to follow-up observations across the electromagnetic spectrum. In this way, AMON aims to evoke the discovery of multimessenger transients from within observatory subthreshold data streams and facilitate the exploitation of these transients for purposes of astronomy and fundamental physics. As a central hub of global multimessenger science, AMON will also enable cross-collaboration analyses of archival datasets in search of rare or exotic astrophysical phenomena.

Introduction

We stand at the dawn of multimessenger astrophysics – a quest to use the messenger particles of all four of nature’s fundamental forces to explore the most violent phenomena in the universe. Observatories first imagined a generation ago are finally being realized, including the Advanced LIGO [1] and Virgo [2] gravitational-wave detectors, the ANTARES [3] and IceCube [4] high-energy neutrino observatories, and the Pierre Auger Cosmic Ray Observatory [5]. On the ground and in space, they are complemented by high-energy observatories including the Swift [6] and Fermi [7] satellites, the HESS [8], VERITAS [9], and MAGIC [10] TeV gamma-ray telescopes, and the HAWC [11] TeV gamma-ray observatory.

Collectively, these facilities promise the first detections of gravitational waves and high-energy cosmic neutrinos, the resolution of the mystery surrounding the origins of ultrahigh-energy cosmic rays, and a new window into the formation and evolution of black holes. Given their nature as first-generation facilities, however, the sensitivities of the non-electromagnetic observatories are naturally limited, with rates of detection for transient events of publishable significance known or expected to be low, perhaps a handful per year (or, in the case of Advanced LIGO and Virgo at design sensitivity, a few dozen [1]).

During the intervals prior to and between detection of these rare high-significance events, the multimessenger facilities will be buffeted by signals from a far greater number of lower-significance events that will be statistically indistinguishable from background or noise processes. Such “subthreshold” events are, by definition, unrecoverable as astrophysical signals in the data stream of any individual facility. However, if they are accompanied by a subthreshold signal in another multimessenger channel they can be identified, and potentially achieve high significance, via careful coincidence analysis of the data streams from multiple facilities.

In this paper we present the scientific case for the Astrophysical Multimessenger Observatory Network and describe its important elements. AMON will weave together existing and forthcoming high-energy astrophysical observatories into a single virtual system, capable of sifting through the various data streams in near real-time, identifying candidate and high-significance multimessenger transient events, and providing alerts to interested observers.

As we show, AMON will enable a significant enhancement in the effective aggregate sensitivity of the world’s leading multimessenger facilities for a small fraction of the facilities’ total cost, provide the first near real-time alerts for multimessenger transient sources, and simplify the mechanics and politics of cross-collaboration analyses for all partners. As such, we believe AMON represents a natural next step in the extension of the global astronomical community’s vision beyond the electromagnetic (EM) spectrum.

The development of AMON is currently underway. Signatories to the AMON Memorandum of Understanding1 (MOU) include the IceCube and ANTARES neutrino observatories, the VERITAS and HAWC TeV γ-ray observatories, and the Swift orbital telescope. Exploratory discussions with the LIGO (including GEO-600), and Fermi scientific collaborations have led to signed letters of commitment, with negotiations toward MOU signatures from all parties ongoing. Discussions have also been initiated with candidate follow-up facilities including ROTSE-III [12] and the Palomar Transient Factory [13], with the goal of bringing these observatories into the collaboration prior to or shortly after the commencement of real-time AMON alert operations.

AMON is structured as an open and extensible network, with an MOU that allows straightforward incorporation of new triggering and follow-up facilities. Collaborations interested in the scientific goals of AMON, and with useful triggering or follow-up capabilities to contribute, are encouraged to contact the authors for information about joining AMON. First versions of the necessary supporting hardware and software infrastructure for AMON are being installed at Penn State, and initial analyses on archival and simulated real-time data streams will get under way shortly thereafter, as a means of preparing to bring the first set of triggering facilities on-line within the next year.

The paper is structured as follows: In Section 2 we provide an overview of the scientific opportunity for AMON which motivates our efforts. In Section 3 we discuss the elements of AMON, including the technical and operational protocols that we propose to adopt in linking the partner facilities, and the algorithms that we will use to identify coincident signals. Section 4 presents detailed simulations of multimessenger transient sources, and additional theoretical case studies, which illustrate the gains that stand to be realized by AMON. Section 5 presents our summary and conclusions.

Section snippets

The AMON science opportunity

AMON is intended to contribute in several ways to the first decade of multimessenger astronomy. A common focus of these approaches is on multimessenger transient events that are observed as coincident (potentially subthreshold) signals in the data of AMON partner facilities corresponding to two or more distinct types of messenger particle. In this section, we briefly review the strongest candidates for these multimessenger transient sources and the current theoretical expectations for their

AMON dataflow and operations

Multimessenger detection of one of the astrophysical sources described above, or of some entirely distinct cosmic phenomenon, will require coordination and cooperation between observatories of strikingly different design and operation. These observatories produce data whose heterogeneity motivates the unified approach of AMON for detecting coincidences. Individual facilities participating in AMON can be characterized as triggering facilities, follow-up facilities, or both. Triggering facilities

Discovery power of AMON

In this section we attempt to quantify the discovery power of AMON. Any such effort must grapple in some way with the vast array of possible discoveries that AMON might contribute to, both in terms of the various candidate source populations (Section 2) and in terms of the diverse set of possible partner facilities (Section 3), including the combinatorial implications of joining those facilities together into a single network.

We take two distinct approaches here. In the first approach, we focus

Summary and conclusions

The Astrophysical Multimessenger Observatory Network under development at Penn State will link multiple high-energy, multimessenger, and follow-up observatories together into a single comprehensive system. We have explored the scientific opportunity for AMON (Section 2), which is centered on the discovery and exploitation of multimessenger transients. The nature of the brightest such transients, which may manifest as the first detections of gravitational waves, high-energy cosmic neutrinos, or

Acknowledgements

Initial development of AMON has been funded by Penn State’s Office of the Senior Vice President for Research, the Eberly College of Science, and the Penn State Institute for Gravitation and the Cosmos. D. F. Cowen acknowledges the support of the Penn State Institute for CyberScience Faculty Fellows Program; I. Bartos and S. Márka acknowledge support from Columbia University and the National Science Foundation under cooperative agreement PHY-0847182.

The authors acknowledge valuable discussions

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