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 WorkshopESAC (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

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5%

48%

19% 29%

CGRO (7)RADIO-DISCOVERED - PTC - PSUE (69)LAT-ASSISTED - PSC (27)LAT-DISCOVERED (42)

See poster by X. Hou & D. A. Smithon the latest PSUE

discoveries

See 2PC:arXiv:1305.4385

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The multi-wavelength nature of pulsars

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Credit: Thompson 2004

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G-ray X-ray G-ray: Geminga

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Halpern & Holt 1992Halpern et al. 1997

Bignami & Caraveo 1992Mattox et al. 1992

EGRET

COS-B

SAS-2

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X-ray Gamma-ray X-ray:The Gamma Cygni pulsar

6 Lin et al., arXiv:1305.0998 (2013)Weisskopf et al. (2011)Abdo et al. Science 325, 840 (2009)

0.7-2.0 keV

0.15-0.7 keV

2.0-12.0 keV

0.1-300 GeV

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Improvement in sensitivityusing X-ray counterparts

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Dormody et al. 2011

M=log(PF*S/N)

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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)

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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 selectionvia artificial neural networks

11Credit: Salvetti et al. (HEAD 2013)

Preliminary

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The Swift follow-upprogram (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

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2FGL J1744.1-7620Fγ/Fx > 5500

2FGL J1036.1-6722Fγ/Fx > 2200

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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

Romani & Shaw, ApJL 743, 26 (2011)

Romani, ApJL 754, 25 (2012)

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2FGL J1311.7-3429

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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!16

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Thank You!

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