Transcript Diapositiva 1

AGILE Pulsar Observations
Alberto Pellizzoni
INAF-Osservatorio Astronomico di Cagliari
on behalf of the
AGILE Team & AGILE Pulsar Working Group
7th Agile Meeting & The bright Gamma-Ray Sky, Frascati
AGILE Timing Calibrations
35000 pulsed counts
collected from Vela
PSR.
5000 ToAs from radio
observations by
Hobart radiotelescope
(Tasmania).
PGAMMA-PRADIO<10-12 s
measured timing
resolution=100 ms
AGILE vs. FERMI
Fermi
EGRET
AGILE
Fermi
EGRET
>0.5 GeV Fermi sensitivity
much better than AGILE.
at 100 MeV (and below)
AGILE sensitivity is
competitive.
AGILE
Vela PSR Observed
by Fermi (Abdo et
al., 2009)
32400 pulsed
counts in 75 days
observation time
Vela PSR Observed by
AGILE (Pellizzoni et
al., 2009 + updates)
35000 pulsed counts in
about 100 days
observation time
AGILE counts = Fermi x 10
AGILE counts = Fermi
Fermi counts = AGILE x 10
Multi-l pulsar observations
AGILE Pulsar Working Group:
AGILE Team & ASDC (PSR SW development and Data Analysis):
A.Pellizzoni (chair), M.Pilia, A.Trois,
P.Santolamazza, F.Verrecchia (ASDC), F.Fuschino (MCAL), E.DelMonte
(SuperAGILE), A.Chen, A.Giuliani, P.Caraveo, S.Mereghetti … +
other collaborators from the AGILE Galactic WG.
Radio-astronomers:
A.Possenti, M.Burgay, M.Kramer, P.Weltevrede, S.Johnston, A.Hotan,
J.Palfreyman, I.Cognard, A.Lyne, J.Halpern, A.Corongiu, G.Hobbs,
R.N. Manchester
X-rays: P.Esposito, A.DeLuca.
Radiotelescopes:
European Pulsar Timing Array (Jodrell Bank, Nancay),
Australia Telescope National Facility (Parkes) & Un. Of Tasmania
(Mt.Pleasant)
The European Pulsar Timing Array
UK - JBCA/University of Manchester
DE - MPIfR
NL - UvA/ASTRON
FR - Nancay/CNRS
IT - INAF Cagliari, Sardinia
EPTA partners
Michael Kramer
Chiang Mai- 28 June 2005
SRT
Parkes, Australia
Hobart, Tasmania
GBT, West Virginia
Sardinia Radio Telescope (64 m dish) by INAF & ASI
will start pulsar observations in 2010
Known Gamma-ray Pulsars (E>100 MeV)
J1952+3252
J1057-5226
J1709-4429
Vela
Geminga
Crab
AGILE Pulsars… two years after…
AGILE detected about 20 gamma-ray pulsars
J2229+6114
J2021+3651
J2043+2740
J1524-5625
GEMINGA
B1509-58
J1016-5857 J0737-3039
B1706-44
B1821-24
J1357-6429
VELA
CRAB
AGILE data on 12 Pulsars published so far including
>40% of AGILE Team pulsar targets (AO1 & AO2)
AGILE Pulsars… two years after…
“High-Resolution Timing Observations of Spin-Powered Pulsars
with the AGILE gamma-ray Telescope”
(Pellizzoni et al., ApJ, 691, 1618, 2009)
July 2007 – April 2008 DATA
GEMINGA
B1706-44
VELA
…a 16-pages long paper also describing pulsar timing
calibration and new tools aimed at precise photon phasing
CRAB
Timing noise uncorrected
1 ms
Pellizzoni et al. 2009
Timing noise corrected
Hobbs et al. 2004
Pellizzoni et al. 2009
Crab PSR
Timing noise corrected
Timing noise
uncorrected
(dashed)
No light-curve “smearing” even in very long observations
Timing noise uncorrected
Timing noise corrected
1 ms
High sampling rate of ToAs required…
Vela PSR by EGRET
Fierro et al., 1998
Vela
E>1 GeV
P2 a-b
complex
E>100 MeV
0.9 ms res.
30<E<100 MeV
Radio
Pellizzoni et al. 2009
E > 1 GeV
P2
P2
P1
P1
P3
P3
E < 100 MeV
P3
Crab
0.5<E<30 GeV
AGILE
?
E>100 MeV
0.7 ms bins
SuperAGILE
18-60 keV
Radio
Pellizzoni et al. 2009
(Moffet & Hankins; 1996, 1999)
Crab
P3 is coincident with
the feature HFC2
that appears in the
radio profile above 4
GHz.
3.7s
HFC2 polarization
suggest that this
peak may come from
a lower emission
region, near polar
cap
(Moffet & Hankins;
1996, 1999)
P3: low altitude
cascades?
Pellizzoni et al. 2009
MAGIC (The Magic Collaboration,
2008Sci...322.1221C)
AGILE
P3: low
altitude
cascades?
P1-P2: Highaltitude gap
(MAGIC)?
Crab
P3 from Giant
Pulses?
We can tag GPs
from radio
observations and
fold at highenergy GPs
events only…
Pellizzoni et al. 2009
Geminga
E>1 GeV
complex?
E>100 MeV
2.4 ms
30<E<100 MeV
X-rays
(XMM)
2-10 keV
Pellizzoni et al. 2009
B1706-44
E>30 MeV
2.6 ms
Pellizzoni et al. 2009
Structured energy-dependent peaks (more than two)
are evident in the light curves.
How many particle acceleration sites in the pulsars
magnetospheres? And where?
Multiple gap models may be invoked… find more in
Pellizzoni et al., 2009.
Acceleration gap sizes are related to the width of lightcurve peaks?
The theoretical width of a light-curve peak associated with
an infinitely small gap would be Dt=P/2pG, <1 ms (typically).
Therefore, the width of the apex of the peak can be
related to the core gap size.
Gap location  Magnetic field  Gap size  Peak width
Broad peak: outer region, narrow peak: inner region
Ten(s)
kilometers
1 km or less
Acceleration
gap sizes are
related to the
width of lightcurve peaks?
...pulsar science topics: challenges
High resolution timing of known gamma-ray pulsars
(precise phase-aligned multifrequency light curves).

Looking for spectral cut-off and breaks (e.g. in highly
magnetized pulsars).

Detection of possible secular variations of the gamma-ray
emission from neutron star magnetospheres.

Unpulsed g-ray emission from plerions in supernova
remnants and searching for time variability of pulsar
wind/nebula interactions (e.g. Crab).

Exploiting low energy data (<100 MeV). At E=50-80 MeV
angular resolution is poor but large effective area and
large number of counts

Gamma-ray emission from pulsar glitches?
• About 6% of pulsars are known to show glitches (Dn/n 10-9-10-6)
with a higher incidence of events in younger pulsars.
• Glitches = Starquakes due to exchange of angular momentum
between the superfluid neutron star core and its normal solid crust?
• Starquake waves can “shake” magnetic fields generating strong
electric fields which accelerate particles to relativistic energies,
possibly emitting a burst of high-energy radiation (Ruderman, 1976,
1991; Alpar et al., 1994).
Eglitch  DErot  4p InDn
2
Gamma-ray emission from pulsar glitches?
• Vela has shown 10 major glitches since 1969.
• The chance occurrence of a strong Vela glitch in the wide
AGILE field of view over three years of mission is 20%.
• Expected AGILE gamma-ray counts from a Vela glitch:
glitch
g
C
Dn
h
 10 h
2
4pd Eg
n
EglitchAeff
Weak: Dn/n=10-9 : <100 Counts
11
Strong: Dn/n=10-6 : <105 Counts
where h is the unknown conversion efficiency of the glitch energy
to gamma-ray emission (Pellizzoni et al., 2009)
Gamma-ray emission from pulsar glitches?
• During early AGILE observations, Vela experienced a weak
glitch clearly detected in radio as a discontinuity in the
pulsar’s spin parameters
• Expected AGILE gamma-ray counts from a Vela glitch:
glitch
g
C
Dn
h
 10 h
2
4pd Eg
n
EglitchAeff
Weak: Dn/n=10-9 : <100 Counts
11
Strong: Dn/n=10-6 : <105 Counts
where h is the unknown conversion efficiency of the glitch energy
to gamma-ray emission (Pellizzoni et al., 2009)
Vela glitch=54,312.5+/-3 MJD
Cgglitch=1011 h Dn/n counts
E>50 MeV
Dn/n10-9
h0.1
15 photons in 4 minutes
Small Vela glitch in August 2007: burst emission possibly detected by AGILE
NEW GAMMA-RAY PULSARS!
AGILE Pulsars… two years after…
“Discovery of New Gamma-ray Pulsars with AGILE”
(Pellizzoni et al., ApJ, 695, L115, 2009)
July 2007 – June 2008
J1524-5625
B1509-58
J2229+6114
J2043+2740
B1821-24
J1016-5857
J1357-6429
Many previously unidentified EGRET sources
and new AGILE sources are Pulsars!
New Gamma-Ray Pulsars
J2229+6114, J2021+3651, …: Vela-like
B1509-58: High B pulsar
B1821-24 : ms PSR in Globular Cluster
----------------------------------
J1016-5857: possibly 3EG source
J1357-6429
J2043+2740: oldest gamma-ray pulsar
J1524-5625
Pellizzoni et al., 2009
PSR J2229+6114
Pilia et al., in preparation
PSR J2229+6114
Pilia et al., in preparation
New Gamma-Ray Pulsars
J2229+6114, J2021+3651, …: Vela-like
B1509-58 : High B pulsar
B1821-24 : ms PSR in Globular Cluster
----------------------------------
J1016-5857: possibly 3EG source
J1357-6429
J2043+2740: oldest gamma-ray pulsar
J1524-5625
Pellizzoni et al., 2009
B1509 -58 by COMPTEL
(Kuiper et al., 1999)
COMPTEL
AGILE
P1
P2
AGILE detection both in timing and likelihood analysis >4s
Two gamma-ray peak with different spectra (P1 “soft”, P2 “hard”)
B1509 -58 by COMPTEL
(Kuiper et al., 1999)
P1
P2
B1509-58: multi-gap model… under construction!
B > 10^13 Gauss:
photon splitting (!)
COMPTEL
AGILE
P1 ?
P2 ?
EGRET
(upper limits)
New Gamma-Ray Pulsars
J2229+6114, J2021+3651, …: Vela-like
B1509-58 : High B pulsar
B1821-24: ms PSR in Globular Cluster
----------------------------------
J1016-5857: possibly 3EG source
J1357-6429
J2043+2740: oldest gamma-ray pulsar
J1524-5625
Pellizzoni et al., 2009
EROT= 2.2x1036 erg/s
P = 3 ms
d = 4.9 kpc
A new (variable??) millisecond gamma-ray pulsar in a globular cluster
AGILE Pulsars… two years after…
New gamma-ray pulsars being discovered also by AGILE
Guest Observers
(Halpern et al., ApJ, 688, L33, 2008)
J2229+6114
J1524-5625
B1509-58
J2021+3651
J2043+2740
B1821-24
J1016-5857
J1357-6429
See http://agile.asdc.asi.it for details
about AGILE Guest Observer Programs
Halpern et al., 2008
Radio PSRs candidates as strong gamma-ray emitters (Pellizzoni et al., 2004)
>50 (new) candidates with
expected fluxes > 5x10-8
ph/cm2/s @ E>100 MeV
Lg  k E ROT
Future plans:
-The search for new gamma-ray pulsars
is a non-stop job.
- Full exploitation of <100 MeV band
(exposure competitive with Fermi)
- Phase-resolved spectra of bright
gamma-ray pulsars.
- “Blind-search” of “soft” radio-quiet
pulsars.
- Gamma-rays from pulsars in binary
systems.
Double neutron star
system 0737-3039
Orbital period: 2.4 h
eccentricity=0.09
(Burgay et al., 2003;
Lyne et al., 2004)
Pellizzoni et al., 2008
Double neutron star
system 0737-3039
Orbital period: 2.4 h
eccentricity=0.09
(Burgay et al., 2003)
Double neutron star
system 0737-3039
Orbital period: 2.4 h
eccentricity=0.09
PSR B
System observed
nearly edge-on
PSRs separation 3
light seconds
PSR A
OBSERVER
PSR A: P=22.7 ms
EROT=6x1033 erg/s,
t=210 Myr
B=6.3x109 G
1.337 MSOL
PSR B
PSR B: P=2.7 s
EROT=2x1030 erg/s
t=50 Myr
B=1.2x1012 G
1.25 MSOL
Lyne et al., 2004
E ROT
PSR A
Wind/magnetosp.
pressure of a
companion NS:
Pellizzoni et al.,
2008
REQ < system separ.
REQ < 103 RLCA
REQ < 10 RLCB
PSR B
PSR A
PRELIMINARY
Pellizzoni et al., in prep.
Thank You!
For information and collaborations, please contact us:
Alberto Pellizzoni: [email protected]
Maura Pilia: [email protected]