# Presentation: 655587

## Science Requirements

**Jonathan F. Ormes**
**Project Scientist**
**NASA GSFC**
**jfo@lheapop.gsfc.nasa.gov**

## EGRET All  Sky Map (>100 MeV)

- 9/27-28/2000

## Science Topics

**Active Galactic Nuclei**
**Isotropic Diffuse Background Radiation**
**Cosmic Ray Production:**
- Molecular Clouds
- Supernova Remnants
- Normal Galaxies
**Endpoints of Stellar Evolution**
- Neutron Stars/Pulsars
- Black Holes
**Unidentified Gamma-ray Sources**
**Dark Matter**
**Solar Physics**
**Gamma-Ray Bursts**

- 9/27-28/2000

## GLAST Simulated All Sky Map

**Virgo Region**
**(E > 1 GeV)**

**One-Year All-Sky Map (E > 100 MeV)**

**Map the gamma-ray sky with sensitivity > 30 times that of EGRET without becoming source confusion limited.**

- 9/27-28/2000

## One Year Point Source Catalog

**AGN**

**3EG catalog**

**Galactic halo**

**Galactic plane**

**5 ******** sources from**
**Simulated All Sky Survey**

- 9/27-28/2000

## Active Galactic Nuclei

**EGRET discovered gamma-ray beams from blazars. Blazars are super massive black hole driven Active Galactic Nuclei (AGN) whose beams point towards Earth.**

- 9/27-28/2000

## Active Galactic Nuclei: Time Variability

**Study variability of bright sources down to the sub-day timescales**
**Obtain significant sky coverage to monitor time variability of large numbers of AGN**
**Constrain the AGN logN-logS function to a factor of > 25 fainter than EGRET**
**Assure clean separation of sources**
**	****on the sky (minimize source **
**	****confusion)**

- 9/27-28/2000

## Active Galactic Nuclei: Spectra

**Measure  the spectra above 100 MeV from AGN (based on blazar logN-logS extrapolations)**
**Explore low-energy spectrum where many AGN have peak emission**
**Measure high-energy cutoffs**
**Overlap with ground-based gamma-ray observations**

- 9/27-28/2000

## Active Galactic Nuclei: Requirements

- Energy response: 20 MeV to > 300 GeV
- Spectral resolution of 10% or better (E > 100 MeV)
- Effective area of > 8000 cm2 (~ 5 times EGRET)
- Flux sensitivity < 6 x 10-9 cm-2 s-1 (1 year of scanning data)
- Point source localization of < 2 arcmin
- FOV of > 2sr (~ 4 times EGRET)

**Cygnus Region 15 x 15 deg**

- 9/27-28/2000

## Isotropic Diffuse Background

**Cosmic Diffuse Background**

**Find point source contribution (AGN + ??)**
**Background rate < 10% of the isotropic diffuse component**
**Extend coverage of diffuse spectral measurements**

- 9/27-28/2000

## Isotropic Diffuse Background: Requirements

- Background < 10% of high latitude diffuse flux (Shreekumar et al.) with goal of 1%
- Energy range:
- 	20 MeV - 300 GeV
- Point source flux sensitivity: (1 year survey)
- 	< 6 x 10-9 cm-2 s-1

- 9/27-28/2000

## Cosmic Ray Production

**LMC Detection**

**Identify  and map supernova remnants and other diffuse features**
**Make spatially resolved precise spectral measurements and explore the pion bump**

- 9/27-28/2000

## Cosmic Ray Production: Requirements

**SNR g-Cygni**

- Single photon angular resolution goal of < 0.5 at 1° GeV
- Point source localization of < 2 arcmin
- Spectral resolution of < 30% at low energies

- 9/27-28/2000

## Endpoints of Stellar Evolution

**Facilitate searches for pulsations from millisecond pulsars**
**Characterize pulse profiles of detected pulsars**
- Requires spectral resolution of ~10%, especially above 1 GeV where pulsar spectral breaks occur
- Requires absolute timing to 10 sec

- 9/27-28/2000

## Unidentified Gamma-ray Sources

**172/271 sources in 3rd EGRET catalog are unidentified**
- Reduce source location error boxes to a few arcminutes
- Monitor unidentified sources for time variability with high-duty-cycle
- Facilitate counterpart searches at X-ray and lower energies and in TeV regimes

- 9/27-28/2000

## Unidentified Gamma-ray Sources: Requirements

- Source localization:
-  	< 5 arc minutes for source of strength 10-8 ph cm-2 s-1
- Sensitivity above 1 GeV and large FOV

- 9/27-28/2000

## Dark Matter

**Constrain cold dark matter candidates**
**Identify relatively narrow spectral lines**
- Requires energy range with response to at least 300 GeV
- Requires spectral resolution:
- 	5% at energies above 10 GeV (goal of 3%)

- 9/27-28/2000

## Solar Physics

**Determine the upper limit of accelerated particle energy in a solar flare**
**Study the variability from flare to flare of the time profile of emission**
**Investigate relation between the relative contribution of electron bremsstrahlung and pion gamma-ray emission to solar flare geometry**
- Requires operation through the solar cycle 24 and solar maximum 2010
- Cover energy band > 20 MeV and to > 1 GeV with high sensitivity

- 9/27-28/2000

## Gamma-Ray Bursts at > 20 MeV

**Gamma-Ray Bursts at > 20 MeV**

**EGRET discovered high energy GRB afterglow**
- only one burst
- dead time limited observations

- 9/27-28/2000

## Gamma-Ray Bursts at > 20 MeV

_**Spatial:**_
**Monitor > 2 sr of the sky at all times**
**Localize sources to with > 100 photons to < 10 arcmin**
_**Temporal:**_
**Perform broad band spectral studies and search for spectral structure**
**Find correlation between 10 keV - 20 MeV and > 20 MeV photons**
**Determine characteristics of > 20 MeV afterglow**

- 9/27-28/2000

## GLAST Burst Monitor (10 keV - 20 MeV)

**Cover the classical gamma-ray band where most of the burst photons are emitted**
**Monitor all of the sky that is visible from low-Earth orbit **
**Identify when and where to re-point the spacecraft to optimize observations and notify other observers**

**10 keV**

**10 GeV**

**10 MeV**

- 9/27-28/2000

## Gamma-ray Bursts: Requirements

**Gamma-ray Bursts: Requirements**

_**LAT:**_
- Capture > 25% of GRBs in LAT FOV (2 sr or more)
- Deadtime of < 100 sec per event
- Spectral resolution < 20%, especially at energies above 1 GeV
_**GBM:**_
- Monitor energy range: 10 keV - 20 MeV
- Monitor FOV of 8 sr (shall overlap
- 	that of the LAT)
- Notify observers world-wide:
- Recognize bursts in realtime
- Determine burst positions to few degree
- 	accuracy
- Transmit (within seconds) GRB
- 	coordinates to the ground
- Re-point the main instrument to GRB
- 	positions within 10 minutes

- 9/27-28/2000

## Discovery Potential

**Have observational capability to be**
**SURPRISED!**

- 9/27-28/2000