Pulsars: Pulsars: The radio/gamma-ray The radio/gamma-ray

ConnectionConnection

Pulsars: Pulsars: The radio/gamma-ray The radio/gamma-ray

ConnectionConnection

• Prospects for pulsar studies with AGILE and GLAST

• Synergy with radio telescopes– Timing and follow-up– Radio vs. -ray beams– Polarimetry

Alice K. Harding Alice K. Harding NASA Goddard Space Flight NASA Goddard Space Flight CenterCenter

Radio versus Radio versus -ray beams-ray beamsRadio versus Radio versus -ray beams-ray beams

Compton Gamma-Ray Observatory Compton Gamma-Ray Observatory (CGRO)(CGRO)

Compton Gamma-Ray Observatory Compton Gamma-Ray Observatory (CGRO)(CGRO)

• 7 (+3) gamma-ray pulsars detected

Unresolved questionsUnresolved questionsUnresolved questionsUnresolved questions

• How are particles accelerated so efficiently to 10 How are particles accelerated so efficiently to 10 TeV?TeV?

• Where does this acceleration take place?Where does this acceleration take place?

• Do all pulsars emit Do all pulsars emit -rays?-rays?

• How are radio and How are radio and -ray emission beams related?-ray emission beams related?

• How many radio-quiet How many radio-quiet -ray pulsars (Gemingas) -ray pulsars (Gemingas) are there?are there?

What do we need from radio What do we need from radio telescopes?telescopes?

What do we need from radio What do we need from radio telescopes?telescopes?

• Find more Find more -ray -ray pulsarspulsars

• Study the Study the brightest ones in brightest ones in more detailmore detail

• Sensitive surveysSensitive surveys• Pulse timingPulse timing• Follow-up Follow-up

observationsobservations

• Better pulse profilesBetter pulse profiles• Full-phase Full-phase

polarimetrypolarimetry

AGILE (Astro-rivelatore Gamma a Immagini LEggero)

AGILE (Astro-rivelatore Gamma a Immagini LEggero)

• Italian collaboration

• Launched on 23 April 2007!!

• Operational 2007-2008

• Pair production telescope (30 MeV – 30 GeV)

• Somewhat more sensitive than EGRET

• Should discover > 15-20 new -ray pulsars

• Very large FOV (~20% of sky), factor 4 greater than EGRET

• Broadband (4 decades in energy, 20 MeV – 300 GeV)

• Unprecedented PSF for gamma rays (factor > 3 better than EGRET for E>1 GeV)

• Factor > 30 improvement in Factor > 30 improvement in sensitivitysensitivity

• Much smaller deadtime per event (25 microsec, factor >4,000 better than EGRET)

• No expendables => long mission without degradation

Calorimeter

Tracker

Gamma-Ray Large Area Space Gamma-Ray Large Area Space Telescope (GLAST)Telescope (GLAST)

Gamma-Ray Large Area Space Gamma-Ray Large Area Space Telescope (GLAST)Telescope (GLAST)

e+

e–

ACD [surrounds 4x4 array of TKR towers]

2 instruments:Large Area Telescope (LAT)Gamma-ray Burst Monitor (GBM)

LAT characteristics

Launch in early 2008

Pulsars detected by CGROPulsars detected by CGROPulsars detected by CGROPulsars detected by CGROPrinceton Pulsar Catalog

c. 1995 Only the youngest and/or nearest pulsars were detectable

5 of the 7 radio pulsars with the highest LSD/d2 detected

More pulsars detectable with AGILE and More pulsars detectable with AGILE and GLASTGLAST

More pulsars detectable with AGILE and More pulsars detectable with AGILE and GLASTGLAST

ATNF catalogc. 2007

~53 radio pulsars in error circles of EGRET unidentified sources (18-20 plausible counterparts)

AGILE will discover new -ray pulsars associated with EGRET sources

GLAST will detect sources 25 times fainter or 5 times further away – possibly 50 – 200 new -ray pulsars

Will be able to detect -ray pulsars further than the distance to the Galactic Center

Middle-aged and older pulsars, including millisecond pulsars should be detected in -rays

AGILEAGILE

GLASTGLAST

Radio pulsar propertiesRadio pulsar propertiesRadio pulsar propertiesRadio pulsar properties

Period Surface B

LsdAge

EGRETsources Total

Young radio pulsars and EGRET Young radio pulsars and EGRET sourcessources

Young radio pulsars and EGRET Young radio pulsars and EGRET sourcessources

PSR J2021+3651 in 3EG PSR J2021+3651 in 3EG J2021+3716J2021+3716

P = 104 ms, t = 17 kyrP = 104 ms, t = 17 kyr

(Roberts et al 2002)(Roberts et al 2002)

PSR J1928+1746, 3EG PSR J1928+1746, 3EG J1928+1733 J1928+1733 P = 68 ms, == 82 kyr

Ė = 1.6 1036 erg/s(Cordes et al. 2006)(Cordes et al. 2006)

Predicted GLAST pulsar Predicted GLAST pulsar populationspopulations

Predicted GLAST pulsar Predicted GLAST pulsar populationspopulations

116

30

Slot gap

1680

49

95 (Recycled)

Radio timing needsRadio timing needsRadio timing needsRadio timing needs Collecting enough -ray photons requires years

Young, energetic pulsars are weak and/or noisy

225 pulsars above L ~ 3 x 1034 erg/s

-ray observations would like 1-10 milli-period accuracy on photon arrival times

Large campaigns planned or underway at major radio telescopes (Parkes, Jodrell, Nancay)Need Arecibo to time the Need Arecibo to time the

faint young pulsarsfaint young pulsars ((Approved timing proposal of 22 Approved timing proposal of 22 pulsars with flux below 1 mJy for pulsars with flux below 1 mJy for GLAST)GLAST)

Faint young pulsarsFaint young pulsarsFaint young pulsarsFaint young pulsars

• Young, energetic pulsars with very low fluxes can be timed only with Arecibo

Pulsar name

Radio flux (mJy)

J1930+1852

0.06

J1928+1746

0.25

J2021+3651

0.1

B1853+01 0.19

Puzzling gamma-ray vs. radio profilesPuzzling gamma-ray vs. radio profilesPuzzling gamma-ray vs. radio profilesPuzzling gamma-ray vs. radio profiles

Vela Crab

430 MHz 430 MHz radioradio

>100 >100 MeV MeV --

rayray

Core beam?Core beam?

Cone Cone beam?beam?

Cone beam?Cone beam?

+ core + core beam?beam?

Relative Relative -ray and radio emission altitude-ray and radio emission altitudeRelative Relative -ray and radio emission altitude-ray and radio emission altitude

Crab and Vela

Slot gap -rays

Crab

High-altitude (0.2-0.6 RLC) radio cone

Vela

Low-altitude (0.08 RLC) radio cone

=70o, =55o

Line of sight

Rotating Vector Rotating Vector ModelModel

Rotating Vector Rotating Vector ModelModel

B

= -30

= -0.10

= 90

= 30

= 1170

= -1.50

Full-phase polarimetry – only at Full-phase polarimetry – only at AreciboAreciboFull-phase polarimetry – only at Full-phase polarimetry – only at AreciboAreciboEverett & Weisberg 2001

Only way to determine Only way to determine viewing viewing andand inclination inclination angleangle

= 1620

= 0.960

Follow-up radio observationsFollow-up radio observationsFollow-up radio observationsFollow-up radio observations

Follow-up radio observations of GLAST sources

Radio period

-ray period

Pulsar “suspects”

-ray sources with hard spectra with

cutoffs, low variability, located in pulsar wind nebulae

Unknown millisecond pulsars?

SummarySummarySummarySummary

• Expect 50 – 100 (?) -ray pulsars in next 5 – 10 years

• 100 – 300 (?) more -ray sources that might be pulsars

• Simultaneous radio timing needed to detect -ray pulsars

• Sensitivity needed • To detect unknown faint radio pulsars

counterparts • To study radio vs. -ray beams• To measure polarization at all pulse phases