Andrea Caliandro 1
Andrea Caliandro(INFN - Bari)
on behalf the FERMI-LAT collaboration
PSR J1833-1034: the youngest gamma-ray
pulsar in the Galaxy?
Andrea Caliandro 2
ProloguePrologue
• 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
SNR G21.5-0.9 observed by Chandra
PSR J1833-1034
not pulsing in X-rays
Thermal northern knots
Non thermal limb-
brightened
(Matheson & Safi-Harb 2005)
PSR
SNR
PWN
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Radio pulsation discoveryRadio pulsation discovery
Park
es d
iscovery
ob
serv
ati
on
(Cam
ilo e
t al. 2
00
6)
GM
RT d
iscovery
ob
serv
ati
on
(Gupta
et
al. 2
00
5)
Giant Metrewave Radio Telescope
Parkes Radio Telescope
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
Characteristic parameters• P = 61.8ms
• Pdot = 2.02 E-13s/s
• Edot = 3.3 E+37 ergs s-1
• Agec = 4.8kyr
One of the most powerful pulsars, second
only to Crab in our Galaxy pulsars
It is a very faint radio pulsar(flux density ~70Jy @ 1.4GHz)
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Different pulsar age estimationsDifferent 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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With Delta-II rocket,From Cape Canaveral,Florida
Launched on June 11, 2008
LAT turn on: June 24
Launch & Early Operation (L&EO) will end August 11, 2008
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PSR J1833-1034 Light Curve with optimized PSR J1833-1034 Light Curve with optimized cutscuts
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
Ztest = 49.3Z chance prob. = 5.12e-10Htest = 69.1H chance prob. = 4.00e-08
E>1GeV, 0.5°Pre
limin
ary
Prelim
inar
y
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PSR J1833-1034 Light CurvesPSR J1833-1034 Light Curves
The light curves in this slide are obtained collecting photons within 68% of the Point Spread Function
68%PSF
~0.435
The ratio P1/P2 decrease with
increasing energies
Preliminary
Preliminary
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Spectral analysisSpectral analysis
• Likelihood spectral analysis
nij: number of counts in the pixel ij
ij: number of counts predicted by the model
Galactic model Extragalactic Neighboring sources
Investigated source
• 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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keV–TeV multiwave spectrumkeV–TeV multiwave spectrum
SNR
PWN
PSR
Chandra models
INTEGRALdata
FERMIdata
HESS spectral fit
• 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
PreliminaryPreliminary
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SummarySummary
• PSR J1833-1034 is a really interesting pulsar– It is a faint source in radio (flux density ~70Jy @ 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