X-ray observations and the
search for Fermi-LAT
gamma-ray pulsars
Pablo Saz Parkinson (SCIPP/UCSC)
for the Fermi-LAT Collaboration
XMM-Newton Science Workshop
ESAC (Madrid) 22 May 2013
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Acknowledgements
• Andrea Belfiore (SCIPP/UCSC)
• Patrizia Caraveo, Andrea de Luca, Martino
Marelli, David Salvetti (INAF, Milano)
• N. Gehrels, A. Falcone, and the Swift team
• LAT Collaboration
• Pulsar Timing and Search Consortia ...
in particular all our radio colleagues!
• The conference organizers
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The gamma-ray pulsar pie
See 2PC:
arXiv:1305.4385
19%
29%
5%
48%
CGRO (7)
RADIO-DISCOVERED - PTC - PSUE (69)
LAT-ASSISTED - PSC (27)
LAT-DISCOVERED (42)
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See poster by
X. Hou & D. A. Smith
on the latest PSUE
discoveries
The multi-wavelength nature
of pulsars
Credit: Thompson 2004
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G-ray
X-ray
G-ray:
EGRET
Geminga
COS-B
SAS-2
Halpern & Holt 1992
Halpern et al. 1997
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Bignami & Caraveo 1992
Mattox et al. 1992
X-ray Gamma-ray X-ray:
The Gamma Cygni pulsar
0.15-0.7 keV
0.7-2.0 keV
2.0-12.0 keV
0.1-300 GeV
Abdo et al. Science 325, 840 (2009)
Weisskopf et al. (2011)
6 Lin et al., arXiv:1305.0998 (2013)
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Improvement in sensitivity
using X-ray counterparts
M=log(PF*S/N)
Dormody et al. 2011
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Potential gamma-ray pulsars
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What about 0FGL?
(aka The Bright Source List)
• 205 sources at > 10 sigma (in 3 months)
• Only ~5% unassociated sources left
• 53 (25%) 0FGL sources associated with pulsars
• 75% young pulsars ... of which:
• 60% radio-quiet and 40% radio-loud
• 25% MSPs (all radio-loud)
Conclusion: Not many (if any) radio-quiet MSPs out there!
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Best gamma-ray PSR candidates
•
•
•
•
Bright/Significant
Curved Spectrum
Non-variable
Promising X-ray counterparts
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Improving candidate selection
via artificial neural networks
Preliminary
Credit: Salvetti et al.
(HEAD
2013)
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The Swift follow-up
program (PI: Falcone)
• http://www.swift.psu.edu/unassociated/
• Pulsar candidates ~10 ks
• Other unassociated ~4-5 ks
• 1FGL sources ~ 250 obs.
• 2FGL sources ~ 180 obs.
• Total: ~2000 X-ray sources
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XMM Observations of
pulsar-like unassociated sources
2FGL J1036.1-6722
2FGL J1744.1-7620
Fγ/Fx > 2200
Fγ/Fx > 5500
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LAT Searches for MSPs
• More CPU/memory intensive
• More sensitive to position
• Most (>80%) are in binaries
• Full blind search of binary
pulsars is currently unfeasible
• MWL obs. are desirable for
isolated MSP searches and
essential for binary ones
• Fortunately ... MSPs are
extremely stable! (no F1 scan)
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Searches for Black Widows
2FGL J1311.7-3429
Romani & Shaw, ApJL 743, 26 (2011)
Romani, ApJL 754, 25 (2012)
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Summary
• A large fraction of gamma-ray pulsars are radio-quiet,
making X-rays the next best alternative for their study
• X-ray observations of gamma-ray pulsar candidates
improve the sensitivity of LAT blind searches by:
• pinpointing plausible X-ray counterparts
• identifying binary systems
• constraining the (unknown) pulsar parameters
• X-ray follow-up observations with Swift, Chandra, and
XMM have produced many potential counterparts
• Blind searches in gamma rays are ongoing ... stay tuned!
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Thank You!
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