Transcript TOPICS

Damien Parent – Moriond, February 2009
PSR J0205+6449, PSR J2229+6114,
and their cousins -- young & noisy gamma ray
pulsars
Damien Parent
on behalf of the Fermi LAT Collaboration
[email protected]
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Damien Parent – Moriond, February 2009
The context
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Before the launch of the Fermi Gamma-ray Space Telescope in 2008 June, we built a list
of gamma-ray pulsar candidates based on their spin-down energy Edot.
It seemed gamma-ray emitting electron-positron cascades occur for Edot > 3 x 1034 erg
s-1 (Thompson et al. 1999). We have selected pulsars with Edot > 1 x 1034 erg s-1. These
pulsars are mainly young, energetic and exhibit rotational instabilities (« timing noise
»).
Extract from the list of gamma-ray pulsar candidates (Smith et al. 2008)
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Discovery of pulsations from PSR
J0205+6449 in SNR 3C 58 with Fermi
Damien Parent – Moriond, February 2009
Supernova remnant 3C 58. Optical(green), 1.466 GHz radio (red).
Fesen et al. (2008)
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PSR J0205+6449,
the X-ray discovery in the SNR 3C 58
Damien Parent – Moriond, February 2009
... suspected by Becker et al. in 1982.
X-ray Observations
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This young pulsar was discovered at X-ray wavelengths by the
Chandra X-ray Observatory with a pulsation period of 65.7 ms
(Murray et al. 2002).
RXTE data allowed a measurement of the spin-down rate of Pdot
= 1.93 x 10-13 s s-1.
The pulsed fraction for the folded light curve is ~ 21%.
The pulsar has a spin-down energy Edot = 2.7 x 1037 erg s-1 (the
third most energetic of the known Galactic pulsars).
Edot = 4p² I Pdot/P3 (I: moment of inertia)
Pulsar Phase
3C 58
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X-ray
Possible remnant of historical supernova SN 1181,
in disagreement with the characteristic age t
(=P/2Pdot) of the pulsar (5400 yrs)
Similar to the comparably aged Crab nebula (a flatspectrum radio nebula, non-thermal extended X-ray
emission, point-like emission due to a pulsar) but
differs both in luminosity and in size.
Distance of ~ 3.2 kpc (Roberts et al. 1993)
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Image of 3C 58 at 1.4 GHz. The arrow marks the position of the pulsar.
PSR J0205+6449,
the radio observations
Damien Parent – Moriond, February 2009
Radio observations
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The radio discovery was made possible by the Chandra X-ray
discovery (Camilo et al. 2002)
Observed with a real weak signal of ~0.045 mJy at 1400 MHz
One sharp pulse of width 2 ms
The distance determined from the dispersion measures of
~141 cm-3 pc is 4.5 kpc.
Timing irregularities
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Extremely high level of timing noise
Two glitches have occured since its discovery
Pulse profile of PSR J0205+6449
displayed
as
a
function
of
time(bottom) and summed (top). Data
at a center frequency of 1375 MHz.
« Giant » glitch comparable to the
glitches from the older Vela
pulsar.
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Damien Parent – Moriond, February 2009
PSR J0205+6449,
the g-ray light curve
dfg-radio= 0.07
dfg= 0.49
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The profile is very similar of the
Vela light curve:
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with a radio delay ~ 0.1
cycles
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a separation of the 0.4-0.5
cycles of the g-ray peaks
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FWHM(P1)= 0.12 +/- 0.03 cycles
FWHM(P2)= 0.08 +/- 0.04 cycles
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Background
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An evidence for an excess
between P1 and P2 appears with
a significance of ~ 6s.
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Unpulsed emission defined
between 0.6 - 1.0 in phase
consistent with the background
estimated from regions around
the source.
9.0 x 10-9 cm-2 s-1 95% CL upper
limit on unpulsed emission
(PWN).
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Abdo et al. (2009) in preparation
Damien Parent – Moriond, February 2009
PSR J0205+6449,
the light curves as a function of the energy
P1/P2 = 0.93 +/- 0.07
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P1/P2 ratio decreases with energy
No significant change in gamma
peak position and shape
Similar behavior as for Vela, Crab,
Geminga and B1951+32.
The highest energy photon is in P2
with an energy of 4 GeV.
P1/P2 = 0.81 +/- 0.08
P1/P2 = 0.22 +/- 0.08
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Damien Parent – Moriond, February 2009
PSR J0205+6449,
the spectral energy distribution
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The young pulsars like Crab or
B1509-58 have the maximum
luminosity below 30 MeV.
Lx/Lg larger than for older
pulsars.
We analysed the spectrum with a standard analysis tool
for the collaboration « gtlike1 »
The g-ray spectral analysis suggests an index G of 1.97 ±
0.26 with an exponential (b = 1) cut-off Ec = 2.2 ± 1.1 GeV.
N(E)  N 0 E G e(E / Ec )
b
(1) http://fermi.gsfc.nasa.gov/ssc/data/analysis/SAE_overview.html
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Fermi LAT detection of pulsed g-rays
from the Vela-like pulsar J2229+6114
Damien Parent – Moriond, February 2009
... Halpern et al. (2001) report the detection of radio and X-ray
pulsations in the error box of the EGRET source 3EG J2227+6122
0FGL J22290+6114 (see Jean Ballet’s talk)
Radio pulse profile of PSR J2229+6114 at 1412 MHz (Discovery, Halpern
et al. 2001).
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J2229+6114,
the radio observation
Damien Parent – Moriond, February 2009
Radio parameters
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Pulsations at a period of 51.6 ms,
Pdot ~ 7.8 x 10-14 s s-1
Edot = 2.2 x 10+37 erg s-1 (the fourth most
energetic of the known Galactic pulsars)
Characteristic age of ~ 10,500 yrs
Surface magnetic flux density B ~ 2e+12 G
The distance determined from the dispersion
measures of ~200 cm-3 pc is ~ 7 kpc.
Pulse profile
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The radio profile consists of one peak with
FWHM of 0.08 ± 0.02 cycles.
Radio pulse profile of PSR J2229+6114
at 1412 MHz. The phase-averaged flux
density is only ~ 0.25 mJy.
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J2229+6114,
the X-ray observation
Damien Parent – Moriond, February 2009
Association
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Associated with SNR G106.3+2.7 (shell morphology with an
extremely flat radio spectrum)
Distance of ~ 3 kpc estimated from the X-ray absorption
X-ray profile
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The pulsed fraction for the X-ray folded light curve is ~ 75%.
A portion of the Chandra ACIS-I image
showing PSR J2229+6114 and its associated
PWN (greyscale) called the Boomerang
PWN. The NVSS 20 cm map of the partial
shell G106.65+2.96 is overlaid (contours).
X-ray pulse profile of PSR J2229+6114 in the
0.8-10 keV band from the ASCA GIS.
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Damien Parent – Moriond, February 2009
PSR J2229+6114,
the g-ray light curve
dfg-radio= 0.49+/- 0.01
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The g-ray profile consists
of a single, asymmetric
peak.
FWHM(Peak)= 0.17 ± 0.03
cycles
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Damien Parent – Moriond, February 2009
PSR J2229+6114,
the light curves as a function of the energy
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Evolution of the peak as a
function of the energy
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Peak position is not stable
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0.1-0.3 GeV -> 0.5 +/- 0.01
0.3-1.0 GeV -> 0.46 +/- 0.01
1.0-3.0 GeV ->0.45 +/- 0.01
> 3.0 GeV -> 0.42 +/- 0.04
No significant change in gamma
peak shape with energy
The highest energy photon is
observed with an energy of ~
13.5 GeV in the peak.
Abdo et al. (2009) in preparation
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Damien Parent – Moriond, February 2009
Their cousins
PSR J0205+6449, this talk
PSR J2021+3651, Kerr’s talk
Blind search pulsars, Giordano’s talk
PSR J2229+6114, this talk
J1833-1034, Caliandro’s talk
Vela, Razzano’s talk
Crab, Grondin’s talk
MSP pulsars, Guillemot’s talk
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Damien Parent – Moriond, February 2009
Summary
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The Fermi LAT Telescope has discovered two young pulsars in the
Galactic plane, PSR J0205+6449 and PSR J2229+6449 and presents a
new opportunity to study pulsar / PWN associations at high energies.
The gamma-ray light curve for PSR J0205+6449 consists of two peaks
for which the first peak trails the radio pulse by 0.07 and its amplitude
decreases with increasing energy as for the known gamma-ray pulsars
like Vela, Crab and Geminga.
The Vela-like (comparable age) pulsar PSR J2229+6114 consists of one
peak for which the location is variable as a function of the energy.
Our gamma-ray pulsar candidates are becoming gamma-ray pulsar
discoveries. We see what we expected (and more !). Our selection
based on Edot isn’t so bad !
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