The main scientific interest of the Russian Gamma-400 team: Observe gamma-rays above approximately 50 GeV with excellent energy and angular resolution with the goals of: (1) Studying the fine spectral structure of the isotropic high-energy gamma-radiation, (2) Attempting to identify the many still-unidentified Fermi-LAT gamma-ray sources. Gamma-400 will likely be the only space-based gamma-ray observatory operating at the end of the decade. In our proposed Gamma-400-LE version, it will substantially improve upon the capabilities of Fermi LAT and AGILE in both LE and HE energy range. Measuring gamma-rays from approx 20 MeV to approx 1 TeV for at least 7 years, Gamma-400-LE will address the topics of dark matter, cosmic ray origin and propagation, neutron stars, flaring pulsars, black holes, AGNs, GRBs, and actively participate in multiwavelength campaigns

Mitchell, John

Moiseev, Alexander

Thompson, David

NASA Technical Reports Server

Gamma-400 science objectives built on 
the current HE gamma-ray and CR 
results 
Alexander Moiseev (NASA/GSFC and CRESST/ 
University of Maryland, College Park) 
John Mitchell (NASA/GSFC) 
David Thompson (NASA/GSFC) 
https://ntrs.nasa.gov/search.jsp?R=20120011795 2019-08-30T21:08:34+00:00Z
The main scientific interest of the Russian Gamma-400 team: 
Observe gamma-rays above "'50 GeV with excellent energy and angular resolution 
with the goals of: 
• Studying the fine spectral structure of the isotropic high-energy gamma-
radiation, 
• Attempting to identify the many still-unidentified Fermi-LAT gamma-ray 
sources 
However, in order to best exploit its promise as a NEXT GENERA TlON 
GAMMA-RA Y MISSION, it is critical for Gamma-400: 
• To be capable of precise measurements in the very important energy range 
from "'20 MeV to a few hundred MeV, where the LAT energy resolution, 
angular resolution and background rejection are relatively poor 
• For multiwavelength analysis: to have gamma-ray measurements in the tens of 
MeV to tens of GeV energy range, simultaneous with X-ray and ground-based 
TeV gamma observations, as well as with neutrino and gravitational radiation 
detectors such as IceCube, KM3NeT, ALiGO. Currently none are planned after 
Fermi-LA T observations end 
J\lexander M(Jiseev A;:> ril 19, 2012 2 
The anticipated focus of the Gamma-400 program: 
• Pointed observations of the most interesting sources from Fermi, TeVCat and 
other catalogs: 
-. Unidentified sources ('" 1/3 of all currently known GeV gamma-ray sources1 ) 
- Detailed investigation of the Galactic Center 
- Sources at energy more than several tens of GeV with better (than Fermi 
LAT) angular resolution and background rejection 2 
- Variable sources 
• Diffuse gamma-ray emission at energies above'" 10 GeV 
• High-energy emission from transient sources, including gamma-ray bursts 
• Search for features in the spectra of high-energy CR electrons-positrons and 
nuclei 
1 Abdo et aI., arXiv:~108.1435, 2011 
2 Abdo et aI., ApJ 707, 1310, 2009 
Alexander Moiseev April 19, 2012 3 
Scientific Goals of Gamma-400 optimized at Low and High 
Energies (I) 
o Search for Dark Matter signatures 
• One major goal of Fermi is to greatly advance the search for the identity of non-
. baryonic OM 
• Although a clear signature of OM has not yet been detected by LAT (or any other 
instrument), sensitive cross-section limits for WIMPs, the most probable 
candidate for OM, have been established via LAT observations of: 
- the Galactic Center and halo, 
- the extragalactic background radiation (EGB), 
- dwarf spheroidal satellite galaxies and local group galaxies, 
- gamma-ray lines! 
• The Galactic Center is expected to provide the greatest fluxes of gamma-rays 
from DM annihilation, but the bright diffuse and discrete-source gamma-ray 
emission from astrophysical processes give an intense foreground 
./ Gamma-400 with its superior energy resolution will improve the search for 
high-energy gamma-ray lines from DM emission 
./ Improved angular and energy resolution (as proposed by the US side) will 
make Gamma-400 able to better evaluate and remove foreground sources 
near the Galactic Center, hopefully revealing evidence of DM 
lAckermann et aI., PRL 107, 241302, m:tJ1l,nSAdJlfle~ceslt.nih~ri2012 
Scientific Goals of Gamma-400 optimized at Low and High 
. Energies (II) 
o Diffuse Radiation 
• Galactic and isotropic (extragalactic gamma-ray background EGB) diffuse 
radiation have been studied with the LAT from "'200 MeV to'" 100 GeV1,2 
• To define the spectral structure of this emission and search for gamma-ray 
lines (which may reveal DM contributions)1 these measurements need to be 
- extended to LOWER energy with excellent energy resolution 
- studied with improved energy resolution at high energy 
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Extragalactic background spectrum 
as measured by the LAT. Ovals show 
areas of interest for Gamma-400 
2Abdo et aI., PRL 104, 101101, 2010 Alexander Moiseev April :'c9, 2012 s 
Scientific Goals 0/ Gamma-400 optimized at Low and High 
Energies (III) · 
o Gamma Radiation from Supernova Remnants 
• SNRs are generally thought to be the sources of Galactic cosmic rays; both 
electrons and nuclei are likely accelerated to high-energy in SNR 
• Fermi LAT has measured accurate gamma-ray spectra from many SNR, but 
has, so far, failed to definitely determine whether the radiation originates 
from electrons or hadrons 
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spectrum of W44 as measured by 
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lAbdo et aI., Science 327, 1l03A, 2010 Alexander Moiseev April 19, 2012 6 
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Scientific Goals 0/ Gamma-400 optimized at Low and High 
Energies (IV) 
o Discrete Gamma-ray Sources 
• There are 1,873 sources in the Second Fermi Catalog (2FGL), with about 1/3 
unidentifiedl . 
The fine angular resolution of Gamma-400 will allow identification of additional 
classes of sources 
• Fermi LAT has observed "'500 sources with photons above 10 GeV 
-some of the sources emit gamma rays 
ONLY at high energy and are UNSEEN at 
lower energies 
-a recent example is NGC 1275, which is 
bright at energies of few GeV, but above 
50-100 GeV a nearby source, IC 310, starts 
to shine brightly, while NGC 1275 
diminishes2 
Gamma-400 will carry out a sensitive 
search for high energy emitters 
lAbdo et aI., arXiv:1108.l435, 2011 
2Fermi NASA Press-release 2011 Alexander Moiseev April 19, 2012 7 
Scientific Goals of Gamma-400 optimized at Low and High 
Energies (v. a ) 
o Transient phenomena: totally unexpected flare of Crab 
• The Crab Nebula has long been used as a reference source for instrument 
calibration 
• Several very bright flares, discovered by Fermi LAT1 and AGILE and thought to 
occur in the nebula, have changed our understanding 
Other Crab flares, as well as flares of other pulsars, may be detected by 
continuous Gamma-400 observations. The nature of these flares is still unknown. 
10" 
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Spectra of the quiescent and 
flaring Crab; upper points are 
during outburst (Fermi LAT) 10-12 -Fenni 2011 flare ·""Fermi 8 months 
H.E.S.S. VERITAS 
MAGIC MAGIC 
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1~ 1~ 1~ I~ l~ 1 . Alexander Moiseev Abl'-l.~rlf1J.!),1.2~ence 331, 739A, 2011 
Energy [MeV] 
Scientific Goals of Gamma-400 optimized at Low and High 
Energies (V.b) 
o Transient phenomena: flares of AGN 
• These are expected but not predictable for individual sources 
• More than half the Fermi LAT sources are AGN of different types; many of 
them flare, representing some of the most energetic phenomena in Universel 
Multiwavelength study requires regular observations in gamma-rays 
simultaneous with space-based X-ray and ground-based optic~I, radio, and_ T~V 
observations. 
Opportunity for Gamma-400 to take over when Fermi LAT finishes its operation 
lAbdo et aI., ApJ 707, 1310, 2009 Alexander Moiseev April 19, 2012 9 
Scientific Goals of Gamma-400 optimized at Low and High 
Energies (V.e) 
o Transient phenomena: Nova outburst 
• Fermi LAT detected a remarkable, unexpected gamma-ray outburst from 
nova V407 Cygni 1 
Similar unexpected discoveries can be made during continuous observations of 
large fractions of the sky. 
o Transient phenomena: Solar Flares 
• To study gamma-radiation from 
solar flares high sensitivity at low 
energy « 1 GeV) and regular 
monitoring are critical. Very 
promising science objective for 
Gamma-400 with extended 
capability at low energy Image of V407 Cygni as seen by Fermi 
LAT. Left - before flare, right (in whire 
lAbdo et aI., Science 329, 817A, 2010 Alexander Moiseev April 19, 2012 circle) - during a flare 10 
Scientific Goals of Gamma-400 optimized at Low and High 
Energies (V.d) 
o Transient phenomena: Gamma-ray bursts 
• Detailed study of temporal and spectral behavior by Fermi LAT discovered a 
delay of >100 MeV photons compared to the keV-MeV photons, and other 
temporal and spectral features addressing quantum gravity issues1 
• Observation (or absence) of GRB from coalescing binary systems (e.g. neutron 
star mergers), in synergy with the gravitational wave experiment ALiGO will 
provide critical information about such process 
• Each GRB is different, and observation of a larger GRB sample is critical to 
understand their nature and mechanism, and fundamental physical 
phenomena. This is very promising science objective for Gamma-400 and 
KONUS 
lAbdo et aI., Science 323, 1688, 2009 and I!tl!n~litwwin April 19, 2012 11 
Scientific Goals 0/ Gamma-400 optimized at Low and High 
Energies (VI) 
o Intergalactic magnetic fields 
• TeV photons from AGN interact with the Extragalactic Background Light and 
create lower energy gamma radiation via electromagnetic cascades. Electrons 
of these cascades are deflected by intergalactic magnetic fields (strength not 
known yet), so the angular size of given AGN in gamma-rays increases 
compared to the instrument point spread function (PSF). 
• The difference (if observed) can be used to estimate the magnitude of the 
magnetic field. Current Fermi LAT results do not show significant differences! 
The excellent PSF of Gamma-400 at high energy is crucial in this approach to the 
study of intergalactic fields 
lAbdo et aI., in preparation Alexander Moiseev April 19, 2012 " 7 ~-
Scientific Goals 0/ Gamma-400 optimized at Low and High 
Energies (VII) 
o High-energy electrons 
• Fermi LAT has accurately measured the electron+positron spectrum from 7 
GeV to 1 TeV 1. 
• The spectrum is harder than expected from the superposition of distant 
sources, and exhibits some broad spectral features above'" 200 GeV, but 
does not show the feature reported by ATIC and PPB-BETS 
• The measurements are energy-resolution limited due to the relatively thin 
Fermi LA T calorimeter 
Its much deeper calorimeter allows Gamma-400 to study spectral structure of 
the high-energy electron spectrum with much better energy resolution. Spectral 
structure, if found, would indicate presence of nearby « 1 kpc) source(s} of 
electrons, of either astrophysical (e~g. - pulsars) or exotic (DM) nature. 
lAckermann et aI., PRO 82, 092004, 2010 Alexander Moiseev April 19, 2012 13 
SUMMARY 
Gamma-400 will likely be the only space-based gamma-ray observatory 
operating at the end of the decade. In our proposed Gamma-400-LE version, it 
will substantially improve upon the capabilities of Fermi LAT and AGILE in both 
LE and HE energy range 
Measuring gamma-rays from -20 MeV to - 1 TeV for at least 7 years, 
Gamma-400-LE will address the topics of dark matter, cosmic ray origin and 
propagation, neutron stars, flaring pulsars, black holes, AGNs, GRBs, and 
actively participate in multiwavelength campaigns 
Alexander Moiseev April 19, 2012 14 


Gamma-400 Science Objectives Built on the Current HE Gamma-Ray and CR Results

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