PSR J18331034 - PowerPoint PPT Presentation

Title: PSR J18331034


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PSR J1833-1034 the youngest gamma-ray pulsar in
the Galaxy?
Andrea Caliandro(INFN - Bari)on behalf the
FERMI-LAT collaboration
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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
  J1833-1034 until 2005
• So far no significant X-ray pulsation is detected
• SNR G21.5-0.9 is detected by HESS at TeV energies

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SNR G21.5-0.9 observed by Chandra
Thermal northern knots
Non thermal limb-brightened
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Radio pulsation discovery

• Two independent discovery of PSR J1833-1034
  pulsation were claimed on 2005-06
• Camilo et al. 2006 using Parkes and GBT telescope
• Gupta et al. 2005 using GBMT telescope

Parkes Radio Telescope
GMRT discovery observation (Gupta et al. 2005)

• Characteristic parameters
• P 61.8ms
• Pdot 2.02 E-13s/s
• Edot 3.3 E37 ergs s-1
• Agec 4.8kyr

One of the most powerful pulsars, second only to
Crab in our Galaxy pulsars
Parkes discovery observation (Camilo et al. 2006)
It is a very faint radio pulsar (flux density
70?Jy _at_ 1.4GHz)
Giant Metrewave Radio Telescope
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Different pulsar age estimations

• Characteristic age of 4800yr
• 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)

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
PSR J1833-1034 could be the youngest known pulsar
in our Galaxy
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Launched on June 11, 2008
LAT turn on June 24
With Delta-II rocket, From Cape Canaveral, Florida
Launch Early Operation (LEO) will end August
11, 2008
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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
Preliminary
Egt1GeV, 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

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PSR J1833-1034 Light Curves
??0.435
68PSF
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
Preliminary
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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

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keVTeV multiwave spectrum
Preliminary

• X-ray Chandra models
• (Safi-Harb et. al 2001)?
• PSR ?? 1.4
• PWN ?? 2.3
• SNR ?? 2.4
• INTEGRAL data
• (DeRosa et al. 2008)
• HESS model
• (Djannati-Atai et al. 2007)
• PWN ?? 2.08

FERMI data
INTEGRAL data
PSR
Chandra models
PWN
HESS spectral fit
SNR
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Summary

• PSR J1833-1034 is a really interesting pulsar
• It is a faint source in radio (flux density
  70?Jy _at_ 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