# Presentation: 250907

## Gamma ray astronomy

- Patrizia Caraveo
- Istituto di Astrofisica Spaziale e Fisica Cosmica- Milano

## The most energetic part of

**Photons with E> 500 keV**

##  rays are absorbed by the atmosphere

****** ****rays are absorbed by the atmosphere**

**Thus, ********- ray********astronomy******** is a space astronomy**

## - ray photons are detected one-by-one

******- ray photons are detected one-by-one**

**Detection techniques borrowed from accelerator physics**

## The past

**1972-3**
**8,000  ******

**COS-B**

**1975-82**
**158,000  ******

**EGRET**

**1990-1998 900,000  ******

**The past**

**Based on a common design and technology**

## Slide 6

## Slide 7

## The past

**8,000  ******
**3 sources**

**COS-B**

**158,000  ******
**25 sources**

**EGRET**

**900,000  ********271 sources**

**More ********s ****mean more sources**

**The past**

## The reference image

**The reference image**

## On top of the galactic emission... sources

**What kind of sources ?**

## The state of the art in -ray astronomy

**The state of the art in ********-ray astronomy**

**271 sources       172 UGO**

## The presence of unidentified sources is normal, when a field is (still) in its infancy

**The presence of unidentified sources is normal, when a field is (still) in its infancy**

**Improving angular resolution if always beneficial**

## The anomaly with -rays is the time needed (so far) to identify sources 

**The anomaly with ********-rays is the time needed (so far) to identify sources **

**and the **_**very **_**limited choice of source type**

**AGN (Blazars)**
**Neutron Stars (Pulsars)**

## If not, multiwavelength strategy

**Big error boxes require additional inputs**

**If not, multiwavelength strategy**

**variability is the only viable tool**

**Long, complex, success is not guaranteed**

**ID rate: 1 per decade**

## A Multi Strategy

**	****	****	****	****	****can yield**
**a good candididate ****which can be confirmed**
** ****a good candidate ****which cannot be confirmed**
**too many candidates**

## Geminga is a success story based on

**Geminga is a success story based on**
**- luck**
**- endurance**

## LSI 61 303 has been associated to 2CG135+01

**LSI 61 303 has been associated to 2CG135+01**

## Slide 18

## MAGIC detection of a microquasar

**MAGIC detection of a microquasar**

## From association to ID

**Correlated variability has not been detected, yet**

-  25 y to go one step forward

**Ars longa, vita brevis**

## A different textbook

**3EG J0616-3310: 146 sources**

**A different textbook**
**example of coverage  failing to yield**** peculiar sources**

**Improving position accuracy would obsiously help**

**To solve the problem of Unid sources, we need a new generation of instruments**

## TODAY

**AGILE**

**GLAST**

## Second generation instruments

**Based on silicon technology**
**	****	****more compact******** big FOV**
**	****	****instrument is always active**
**	**** ****	****negligible dead time**
**	****	****no consumables**

##                                          AGILE 

**                                         ****AGILE **

## AGILE performances are similar to the EGRET ones for <1/10

**of the weight**
**and**
**limited volume**

## from EGRET 
to AGILE

9 years vs. 9 months...
2 tons vs. 100 kg
NASA great Observatory vs.
						ASI small mission   

**to AGILE**
**	****	****	****	****	****	**_[ ](http://it.wikipedia.org/wiki/Immagine:DUMAS_PERE.jpg)_
- _[ ](http://it.wikipedia.org/wiki/Immagine:DUMAS_PERE.jpg)_** **
**9 years**** ****vs.**** 9 months...**
**2 tons**** ****vs.**** 100 kg**
**NASA great Observatory**** ****vs.**
**	****	****	****	****	****	****ASI small mission   **

## The AGILE Payload: the most compact instrument for high-energy astrophysics

**The AGILE Payload: the most compact instrument for high-energy astrophysics**

**It combines for the first time a**** ****gamma-ray imager ****(30 MeV- 30 GeV)**** ****with a**** hard X-ray imager ****(18-60 keV)**** ****with large FOVs ****(1-2.5 sr)**** and optimal angular resolution**** **

## AGILE: inside the cube...

**AGILE: inside the cube...**

**ANTICOINCIDENCE**

**HARD X-RAY IMAGER (SUPER-AGILE)**

**GAMMA-RAY IMAGER **
**SILICON TRACKER**

**(MINI) CALORIMETER**

## AGILE: 1 year in orbit...

**Launch on April 23, 2007 (Sriharikota, India)**
**>6500 orbits**
**Scientific program open to the community: Cycle-1 Guest Observer Program started on Dec. 1, 2007.**

## AGILE orbital parameters 

**Semi-major axis: 6922.5 km (****± 0.1 km)**
**Requirement:       6928.0 ****± 10 km**
**Inclination angle: 2.48° (±0.04°)**
**Requirement:        < 3°**
**Eccentricity:        0.002 (±0.0015)**
**Requirement:      < 0.1°**

## Fotoni a terra e in volo - II

**First gamma-ray ****detected by AGILE in orbit with the nominal GRID trigger configuration (May 10, 2007)**

## AGILE’s technical improvements:

BIG FoV: 1/5 of the sky
Good angular resolution
Small dead time
Simultaneous gamma and X observations

Silicon detectors  (Italy is a world leader)

The BIG FoV (similar to that of an human eye) is an important asset 

**BIG FoV: 1/5 of the sky**
**Good angular resolution**
**Small dead time**
**Simultaneous gamma and X observations**
**Silicon detectors  (Italy is a world leader)**
**The BIG FoV (similar to that of an human eye) is an important asset **

## 120° FoV

**120° FoV**

## Gamma-ray exposure 

**EGRET**

**AGILE**

**~ 3****·10****8**** cm2 s sr**
**(~1 yrs)**

**~ 3****·10****9**** cm2 s sr**
**(~1 yrs)**

## AGILE Sensitivity

## Agile one year in orbit

**Agile one year in orbit**

##  AGILE hard X-ray sky

**Galactic compact objects, 2 AGNs, **
**             ****SEVERAL GRBs  **

## Main science topics  

**Active Galactic Nuclei **
**Pulsars**
**Unidentified gamma-ray sources**
**Microquasars, Gal. compact objects**
** ****Gamma-Ray Bursts  (and Terrestrial Flashes)**

## AGNs detected by AGILE

## Gamma-ray brighter blazars detected by AGILE in 9 months 

**Gamma-ray brighter blazars detected by AGILE in 9 months **

## AGILE blazar main detections                           

**3C 454.3          **
**HB 1510-089   **
**TXS 0716+714 **
**3C 279             **
**3C 273             **
**Mrk 421**
**...****.**
**Strong variability**
**Crucial multifrequency observations**

## Slide 43

## 3C 279detected in 3.5 days at 5 sigma (likelihood analysis)

## 1st published AGILE -ray map 

**1****st**** published AGILE ********-ray map **

**6-day obs.**

**December 2007**
**orbits: 3202-3299**

## Slide 47

## 3C454 one month later 

- Almost no evidence for the need of BLR as external photon source

## Slide 49

## Slide 50

## 0716+714 Sept. 07

**Evidence for a secondary component that produce the rapid flare in this BL Lac. **
**The day duration constraints **
**R < (********5x10****16**** cm. **
**The very  intense and hard ********ray spectrum requires **
**>20**
**whereas the relative peaks position needs  *************>5 x 10****3****.**
**With these ingredients the global power transported into the jet exceeds  ****W = 3 x 10****45**** erg cm****-2 ****s****-1****.**

## Slide 52

## The first object detected simultaneously by the AGILE -ray and hard X-ray detectors

**The first object detected simultaneously by the AGILE ********-ray and hard X-ray detectors**

## First simultaneous  X-ray and gamma-ray detection by AGILE of a blazar: 3C 273

## Multifrequency simultaneous observations are crucial for gamma-ray sources !                          

**WEBT- GASP**
**REM**
**SWIFT**
**INTEGRAL**
**MAGIC**
**HESS**
**VERITAS**

## 
Very interesting blazar data: gamma-ray flaring rate in agreement with EGRET     (above F = 100)

**Very interesting blazar data: gamma-ray flaring ****rate**** in agreement with EGRET     (above F = 100)**

**Rapid (1 day) gamma-ray AGN variability ****ubiquitous**

## Slide 57

## AGILE Galactic sources  

**Pulsars**
**Unidentified gamma-ray sources**
**Microquasars, Gal. compact objects **
**The Galactic Center**
**SNR and origin of cosmic rays**

## Crab pulsar

-  **E > 500 MeV**

-  **E > 100 MeV**

-  **18 - 60 keV**

-  **radio**

**Pellizzoni et al,**
**submitted to ApJ.**

-  **SUPER-AGILE **

## Vela pulsar

-  **E > 1 GeV**

-  **E > 100 MeV**

-  **30 - 100 MeV**

-  **radio**

**Pellizzoni et al,**
**submitted to ApJ.**

## Geminga pulsar

-  **E > 1 GeV**

-  **E > 100 MeV**

-  **30 - 100 MeV**

-  **X-rays**

**Pellizzoni et al,**
**submitted to ApJ.**

## Future prospects

**Several new gamma-ray PSRs to be discovered/announced soon**
**Complex time structure (and spectra) **
**Wonderful for theorists...**

## The puzzle of 3EG J1835+5918(Bulgarelli et al. 2008)

**RX J1836.2+5925**

## Bulgarelli et al. 2008

**V = 1.5**

## Micro-QSOs(X-ray dominated)

**Cyg X-1**
**Cyg X-3**
**GRS 1915+105**

## Slide 67

## Cyg X-1

**Cyg X-1**

- the longest continuous hard X-ray monitoring of Cyg X-1
- Total Observation Time: ~ 4.5 Ms
- (1196 Orbits)

- 1 Month

## Cyg X-1

- Del Monte et al., in preparation

- SuperAGILE

- GRID

- SuperAGILE light curve
- LE (20-25 keV): Yellow
- HE (25-50 keV):  Cyan

## Slide 70

## GRS 1915+105

**15 April 2008**
**Recent reactivation of the microquasar **
**GRS 1915+105 **

## GRS 1915+105

**(Trushkin S. et al., ATel #1509)**

**gamma-ray U.L.**

**18-60 keV**

**gamma-ray map**

## Slide 73

## Cygnus X-3 

**Cygnus X-3 **

## Cygnus X-3 region 

**AGILE GRID Images **(50 MeV – 20 GeV) around 18 April 2008

**-2 days**

**-4 days**

**-6 days**

**+2 days**

**18 April 2008**

## Future prospects

**Erratic variability of accreting micro-QSOs**
**Need simultaneous and well-sampled X-ray coverage ! **
**Gamma-ray emission rare, if any.**

## A different micro-QSO

**LS I +61 303**

## Slide 80

## LSI +61°303

**LSI +61°303**

## Galactic gamma-ray transients

**Cygnus region**
**Carina region**
**Crux region**
**AGILE observes variability and detects new transients on time scales of 1 day at flux levels of 10****-6**** cm****-2****s****-1 ****, even in crowded, high diffuse emission Galactic plane regions.**
**NO detectable simultaneous hard X-ray emission****  (F < 20-30 mCrab, 18-60 keV, 1-day integration) **

## AGILE ATEL Transients 

## GRBs

**Several interesting GRBs in the central FOV**
**One detection above 100 MeV                     (GRB 080514B)**
**~1 GRB/week detected by the MCAL**
**Terrestrial flashes**

## most relevant AGILE GRBs

**most relevant AGILE GRBs**

- In the period July '07 – June '08: 49 GRBs detected (~1 GRB / week)
- 9 localized by SWIFT
- 8 localized by IPN (many more expected)
- 5 localized by SuperAGILE (other SuperAGILE localizations without MCAL detection)

- The most off-axis:
- 166 deg!

- GRID field of view

- SA field of view

## AGILE first gamma-ray detection of a GRB:           GRB 080514B  (Mereghetti et al., to be submitted)

**GRB 080514B has been localized jointly by SuperAGILE and IPN**** ****(****GCN 7715****)**** ****and shows a significant gamma ray emission (****GCN 7716****). Follow-up by Swift (****GCN 7719 ****and ****7750****)**** ****provided the afterglow in X-rays. Many telescopes participated in the observation of the optical afterglow: Watcher (****GCN 7718****), GRON (****GCN 7722****), KPNO (****GCN 7725****) and NOT (****GCN 7734****). **

- SuperAGILE – Mars Odyssey annulus

- SuperAGILE 1-D

**AGILE first gamma-ray detection of a GRB:****           GRB 080514B  ****(Mereghetti et al., to be submitted)**

## GRB 080514B(Mereghetti et al. 2008)

## Conclusions

**Very exciting time for gamma-ray and VHE astrophysics**
**AGILE, GLAST will provide a wealth of data on a variety of sources**
**Be ready for variability !**
**Multifrequency approach is crucial**