Pulsars: The radio/gamma-ray Connection Prospects for pulsar studies with AGILE and GLAST Synergy with radio telescopes –Timing and follow-up –Radio vs.  -ray beams –Polarimetry Alice K. Harding NASA Goddard Space Flight Center

Radio versus  -ray beams

Compton Gamma-Ray Observatory (CGRO) 7 (+3) gamma-ray pulsars detected

Unresolved questions How are particles accelerated so efficiently to 10 TeV?How are particles accelerated so efficiently to 10 TeV? Where does this acceleration take place?Where does this acceleration take place? Do all pulsars emit  -rays?Do all pulsars emit  -rays? How are radio and  -ray emission beams related?How are radio and  -ray emission beams related? How many radio-quiet  -ray pulsars (Gemingas) are there?How many radio-quiet  -ray pulsars (Gemingas) are there?

What do we need from radio telescopes? Find more  -ray pulsarsFind more  -ray pulsars Study the brightest ones in more detailStudy the brightest ones in more detail Sensitive surveysSensitive surveys Pulse timingPulse timing Follow-up observationsFollow-up observations Better pulse profilesBetter pulse profiles Full-phase polarimetryFull-phase polarimetry

AGILE (Astro-rivelatore Gamma a Immagini LEggero) Italian collaboration Launched on 23 April 2007!! Operational Pair production telescope (30 MeV – 30 GeV) Somewhat more sensitive than EGRET Should discover > 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 sensitivity Factor > 30 improvement in sensitivity 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 Telescope (GLAST) e+e+ 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 CGRO Princeton Pulsar Catalog c  Only the youngest and/or nearest pulsars were detectable  5 of the 7 radio pulsars with the highest L SD /d 2 detected

More pulsars detectable with AGILE and GLAST ATNF catalog c  ~53 radio pulsars in error circles of EGRET unidentified sources ( 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 AGILE GLAST

Radio pulsar properties Period Surface B L sd Age EGRETsources Total

Young radio pulsars and EGRET sources PSR J in 3EG J P = 104 ms, t = 17 kyr (Roberts et al 2002) PSR J , 3EG J  = P = 68 ms,  = 82 kyr Ė = erg/s (Cordes et al. 2006)

Predicted GLAST pulsar populations Slot gap (Recycled)

Radio timing needs  Collecting enough  -ray photons requires years  Young, energetic pulsars are weak and/or noisy  225 pulsars above L  ~ 3 x 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 faint young pulsars ( Approved timing proposal of 22 pulsars with flux below 1 mJy for GLAST)

Faint young pulsars Young, energetic pulsars with very low fluxes can be timed only with Arecibo Pulsar nameRadio flux (mJy) J J J B

Puzzling gamma-ray vs. radio profiles VelaCrab 430 MHz radio >100 MeV  -ray Core beam? Cone beam? + core beam?

Relative  -ray and radio emission altitude Crab and Vela Slot gap  -rays Crab High-altitude ( R LC ) radio cone Vela Low-altitude (0.08 R LC ) radio cone  =70 o,  =55 o

Line of sight Rotating Vector Model   B   = -3 0  =  = 9 0  = 3 0

 =  = Full-phase polarimetry – only at Arecibo Everett & Weisberg 2001 Only way to determine viewing and inclination angle  =  =

Follow-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?

SummarySummary 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