Andrea Caliandro

PSR J1833-1034: the youngest gamma-ray pulsar in the Galaxy?

Andrea Caliandro

(INFN - Bari)

on behalf the FERMI-LAT collaboration

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 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 Andrea Caliandro 2

SNR G21.5-0.9 observed by Chandra

(Matheson & Safi-Harb 2005)

SNR PSR

PSR J1833-1034 not pulsing in X-rays

Radio pulsation discovery

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 Age c = 4.8kyr

Andrea Caliandro It is a very faint radio pulsar (flux density ~70  Jy @ 1.4GHz) 4

Giant Metrewave Radio Telescope

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) Andrea Caliandro 5

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

Launched on June 11, 2008

With Delta-II rocket, From Cape Canaveral, Florida 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 cuts

Andrea Caliandro 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/cm 2 s for the pulsed fraction of this source Using this results the S 2 /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

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

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Spectral analysis

• Likelihood spectral analysis

n ij

: number of counts in the pixel ij



ij

: number of counts predicted by the model Galactic model Extragalactic Investigated source 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 c

a

in the ‘investigated source’ model Andrea Caliandro 9

INTEGRAL data

keV–TeV multiwave spectrum

Preliminary

Chandra models FERMI data

•

X-ray Chandra models (Safi-Harb et. al 2001)

⁃

PSR:

 ⁃

PWN:

 ⁃

SNR:



1.4

2.3

2.4

•

INTEGRAL data (DeRosa et al. 2008)

HESS spectral fit

•

HESS model: (Djannati-Atai et al. 2007)

⁃

PWN:



2.08

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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  No X-rays pulsation detection significance) – 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