from 28 February 2017 to 02 March 2017
Padova, Italy

e-ASTROGAM ('enhanced ASTROGAM') is a breakthrough Observatory mission dedicated to the study of the non-thermal Universe in the photon energy range from 0.3 MeV to 3 GeV. The mission, proposed for the ESA M5 call, is based is based on an advanced space-proven detector technology, with unprecedented sensitivity, angular and energy resolution, combined with polarimetric capability. In the largely unexplored MeVGeV domain, e-ASTROGAM will open a new window on the non-thermal Universe, making pioneering observations of the most powerful Galactic and extragalactic sources, elucidating the nature of their relativistic outflows and their effects on Galactic ecosystems. With a line sensitivity in the MeV energy range one to two orders of magnitude better than previous generation instruments, e-ASTROGAM will determine the origin of key isotopes fundamental to the chemical evolution of our Galaxy.
e-ASTROGAM will operate in a maturing gravitational wave and multi-messenger epoch, opening up entirely new and exciting synergies. The mission will provide unique and complementary data of significant interest to a broad astronomical community, in a decade of powerful observatories such as LIGO-VIRGO, SKA, ALMA, E-ELT, LSST, JWST, Athena, CTA and the promise of eLISA.
The core mission science addresses three major topics of modern astrophysics.

  1. Processes at the heart of the extreme Universe: prospects for the Astronomy of the 2030s
    Observations of relativistic jet and outflow sources (both in our Galaxy and in active galactic nuclei, AGNs) in the X-ray and GeV-TeV energy ranges have shown that the MeV-GeV band holds the key to understanding the transition from the low energy continuum to a spectral range shaped by very poorly understood particle acceleration processes. e-ASTROGAM will:(1) Determine the composition (hadronic or leptonic) of the outflows and jets, which strongly influences the environment - breakthrough polarimetric capability and spectroscopy provide the keys to unlocking this long-standing question; (2) Identify the physical acceleration processes in these outflows and jets (e.g. diffusive shocks, magnetic field reconnection, plasma effects), that may lead to dramatically different particle energy distributions; (3) Clarify the role of the magnetic field in powering ultrarelativistic GRB jets, through time-resolved polarimetry and spectroscopy. In addition, measurements in the e-ASTROGAM energy band will have a big impact on multimessenger astronomy in the 2030s. Joint detection of gravitational waves and gamma-ray transients will be ground-breaking.
  2. The origin and impact of high-energy particles on galaxy evolution, from cosmic rays to antimatter
    e-ASTROGAM will resolve the outstanding issue of the origin and propagation of low-energy cosmic rays affecting star formation. It will measure cosmic-ray diffusion in interstellar clouds and their impact on gas dynamics and state; it will provide crucial diagnostics about the wind outflows and their feedback on the Galactic environment (e.g., Fermi bubbles, Cygnus cocoon). e-ASTROGAM will have optimal sensitivity and energy resolution to detect line emissions from 511 keV up to 10 MeV, and a variety of issues will be resolved, in particular: (1) origin of the gamma-ray and positron excesses toward the Galactic inner regions; (2) determination of the astrophysical sources of the local positron population from a very sensitive observation of pulsars and supernova remnants (SNRs). As a consequence e-ASTROGAM will provide a key contribution to the search for dark matter (DM) signals.
  3. Nucleosynthesis and the chemical enrichment of our Galaxy
    The e-ASTROGAM line sensitivity is more than an order of magnitude better than previous instruments. The deep exposure of the Galactic plane region will determine how different isotopes are created in stars and distributed in the interstellar medium; it will also unveil the recent history of supernova explosions in the Milky Way. Furthermore, e-ASTROGAM will detect a significant number of Galactic novae and supernovae in nearby galaxies, thus addressing fundamental issues in the explosion mechanisms of both core-collapse and thermonuclear supernovae. The gamma-ray data will provide a much better understanding of Type Ia supernovae and their evolution with look-back time and metallicity, which is a pre-requisite for their use as standard candles for precision cosmology. In addition to addressing its core scienti c goals, e-ASTROGAM will achieve many serendipitous discoveries (the unknown unknowns) through its combination of wide field of view (FoV) and sensitivity, measuring the spectral energy distributions of nearly a thousand Galactic and extragalactic sources per year, including solar ares and terrestrial gamma-ray flashes, thereby becoming an important contributor to multi-wavelength time-domain astronomy. The mission has outstanding discovery potential as an Observatory facility that is open to a wide astronomical community.
Figure 1

Figure 1 Point source continuum sensitivity of different X- and γ-ray instruments. The curves for INTEGRAL/JEM-X, IBIS (ISGRI and PICsIT), and SPI are for an observing time Tobs = 1 Ms. The COMPTEL and EGRET sensitivities are given for the time accumulated during the duration of the CGRO mission (Tobs ∼ 9 years). The Fermi/LAT sensitivity is for a high Galactic latitude source over 10 years. For MAGIC, VERITAS, and CTA, the sensitivities are given for Tobs = 50 hours. For HAWC obs = 5 yr, for LHAASO obs = 1 yr, and for HiSCORE obs = 1000 h. The e-ASTROGAM sensitivity is for an e ective exposure of 1 year for a source at high Galactic latitude.

e-ASTROGAM is designed to achieve:

  1. Broad energy coverage (0.3 MeV to 3 GeV), with one-two orders of magnitude improvement in continuum sensitivity in the range 0.3 MeV - 100 MeV compared to previous instruments;
  2. Unprecedented performance for gamma-ray lines, with, for example, a sensitivity for the 847 keV line from Type Ia SNe 70 times better than that of INTEGRAL/SPI;
  3. Large FoV (>2.5 sr), ideal to detect transient sources and hundreds of gamma-ray bursts (GRBs);
  4. Pioneering polarimetric capability for both steady and transient sources;
  5. Optimized source identification capability afforded by the best angular resolution achievable by state-of-the-art detectors in this energy range (about 0.15 degrees at 1 GeV);
  6. Sub-millisecond trigger and alert capability for GRBs and other cosmic and terrestrial transients.

e-ASTROGAM will operate as an Observatory with the data policy established by ESA. The satellite is designed to operate in both pointing and survey modes. The observation schedule will be decided based on core science and guest investigator programs.
The core of the e-ASTROGAM team is EU-based; scienti c and technical contributions from extra-EU countries (USA, Russia and Japan in particular) are envisaged.