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Transcript
PSR J1833-1034:
the youngest gamma-ray pulsar
in the Galaxy?
Andrea Caliandro
(INFN - Bari)
on behalf the FERMI-LAT collaboration
Andrea Caliandro
1
Prologue
• PSR J1833-1034 is the central compact object of the
SNR G21.5-0.9
• G21.5-0.9 is one of the brightest SNR in X-rays
– It is recorded in the Green catalog as plerionic SNR
(SNR + PWN)
– This source was chosen as calibration target for
Chandra X-ray observatory
• No radio pulsation was detected from PSR J18331034 until 2005
• So far no significant X-ray pulsation is detected
• SNR G21.5-0.9 is detected by HESS at TeV energies
Andrea Caliandro
2
SNR G21.5-0.9 observed by Chandra
Thermal northern
knots
Non thermal
limb-brightened
(Matheson & Safi-Harb 2005)
PSR J1833-1034
SNR
PSR
not pulsing in X-rays
Radio pulsation discovery
• Camilo et al. 2006 using Parkes
and GBT telescope
• Gupta et al. 2005 using GBMT
telescope
Characteristic parameters
• P = 61.8ms
(Camilo et al. 2006)
Parkes discovery observation
• Pdot = 2.02 E-13s/s
Andrea Caliandro
• Edot = 3.3 E+37 ergs s-1
• Agec = 4.8kyr
(Gupta et al. 2005)
Parkes Radio Telescope
GMRT discovery observation
Two independent discovery
of PSR J1833-1034 pulsation
were claimed on 2005-06
One of the most powerful
pulsars, second only to
Crab in our Galaxy pulsars
It is a very faint radio pulsar
(flux density ~70Jy @ 1.4GHz)
Giant Metrewave Radio Telescope
4
Different pulsar age estimations
• Characteristic age of 4800yr
Copy of the ancient Chinese
record of the BC 48 guest star in
the Astronomical Chapter No.6 of
Quian Han Shu (History of the
Former Han Dynasty), originally
written by Ban Gu AD 100
• Despite the characteristic
age of the pulsar,
measurements of the
expansion rate of the
supernova remnant give an
estimated age of less than
1000yr under the assumption
of undecelerated expansion
(Bietenholtz & Bartel 2008)
• There is good historical
evidence from ancient
Chinese records to believe
that this pulsar is associated
with a guest star supernova
explosion that took place in
BC 48, making the system
just over 2050 years old
(Wang et al. 2006)
Andrea Caliandro
5
Launched on June 11, 2008
LAT turn on: June 24
With Delta-II rocket,
From Cape Canaveral,
Florida
Andrea Caliandro
Launch & Early Operation
(L&EO) will end August 11,
2008
6
PSR J1833-1034 Light Curve with optimized cuts
Ztest = 49.3
Z chance prob. = 5.12e-10
Htest = 69.1
H chance prob. = 4.00e-08
E>1GeV, 0.5°
A very preliminary spectral analysis carry out a
spectral index of ~1.7 and a flux of ~1e-7
ph/cm2s for the pulsed fraction of this source
Using this results the S2/N ratio is evaluated
for a grid of photon selection cuts (Energy
Low Threshold, ROI radius)
The plot shows that the optimal cuts are in a
narrow region around:
• Energy low cut = 1.0 GeV
• Best Radius = 0.5 deg
Andrea Caliandro
7
PSR J1833-1034 Light Curves
~0.435
68%PSF
The light curves in this slide are obtained
collecting photons within 68% of the
Point Spread Function
The ratio P1/P2
decrease with increasing
energies
Andrea Caliandro
8
Spectral analysis
•
Likelihood spectral analysis
nij: number of counts in the pixel ij
ij: number of counts predicted by the model
Investigated source
Galactic model
•
Extragalactic
Neighboring sources
We would like to evaluate the contribute, in terms of differential flux,
of our source in each energy bin
– For each energy bin we apply the likelihood analysis in an energy range as
large as the width of the bin
– In this case the investigated source is modeled with a segment of power-law
with fixed index ( = 2.0) for each energy bin
– Minimized the Likelihood, the differential flux of our source in each bin is
calculated from the term ca in the ‘investigated source’ model
Andrea Caliandro
9
keV–TeV multiwave spectrum
Preliminary
• X-ray Chandra models
FERMI
data
(Safi-Harb et. al 2001)
⁃ PSR:  1.4
⁃ PWN:  2.3
⁃ SNR:  2.4
INTEGRAL
data
• INTEGRAL data
(DeRosa et al. 2008)
• HESS model:
Chandra models
(Djannati-Atai et al. 2007)
HESS
spectral fit
Andrea Caliandro
10
⁃ PWN:  2.08
Summary
• PSR J1833-1034 is a really interesting pulsar
– It is a faint source in radio (flux density ~70Jy @ 1.4GHz)
– The pulsed signal is strong in gamma-ray(~6 significance)
– No X-rays pulsation detection
– It is a young pulsar, maybe the youngest in our Galaxy
– Its gamma-rays light curve show two peaks separated by ~0.435
in phase and also the Interpulse
– The ratio P1/P2 decrease with increasing energies
– From the SED seems that the FERMI-LAT data points are well
connected at low energy with the X-rays PSR spectrum and at
high energy with the PWN HESS spectrum
Andrea Caliandro
11