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Swift observations of Radio-quiet Fermi pulsars

Swift observations of Radio-quiet Fermi pulsars. Martino Marelli. Swift and the Surprising Sky 24th-25th November 2011. In collaboration with Patrizia Caraveo and Andrea de Luca. Fermi discovers PSRs. The Fermi/LAT. - 20MeV-300GeV (100MeV-10GeV) - Very Large FOV (more than 2sr)

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Swift observations of Radio-quiet Fermi pulsars

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  1. Swift observations of Radio-quiet Fermi pulsars Martino Marelli Swift and the Surprising Sky 24th-25th November 2011 In collaboration with Patrizia Caraveo and Andrea de Luca

  2. Fermi discovers PSRs The Fermi/LAT - 20MeV-300GeV (100MeV-10GeV) - Very Large FOV (more than 2sr) and all-sky monitoring - Very high point source sensitivity (more than 1800 sources in 2 years) - Very low deadtime (~65μs) End of LEO: August 11, 2008

  3. Fermi/LAT pulsar sample 66 radio-loud39 classical27 millisecond 101 (public) pulsar How can the X-ray band help the gamma-ray one?Why should we search for X-ray counterparts of pulsars? 34 discovered in BS (+Geminga), 32 “gamma-ray only” pulsars

  4. The position is fundamental for BS! • Gamma-ray data are sparse. Thousands of rotations may occur between detected gamma rays. Months (years) of analysis are necessary!• The motions of the spacecraft and the Earth are significant compared to the time between pulses (msec to sec).• Solution: do the timing analysis in an intertial reference system, not moving with respect to the pulsar.

  5. Dormody et al., in preparation

  6. With only 5 months of data and a bright pulsar.

  7. The SWIFT fundamental contribution Compared with Chandra and XMM-Newton, high PSF (~15”), low spectral and timing resolutions BUT- rapidly re-pointed- useful for short observations- part of the SWIFT collaboration Counterparts of 4 RQ pulsars found (on 19 observed) few days after the Fermi discovery.For them, the gamma-ray light curve and positioning have been improved (see e.g. J1958+2841)

  8. SWIFT first results J1813-1256 • P = 48.1ms τ = 43 ky • Erot = 6.26*1036 erg/s X-ray spectrum: nH=3.9-2.6+4.4*1022cm-2 p.i.=1.7-1.1+1.5 F0.3-10=8.3-6.3+1.8*10-13erg/cm2s Published on: Abdo et al., 2009, Science, 325, 840

  9. SWIFT first results Published on: Abdo et al., 2009, Science, 325, 840 J1958+2841 • P = 290ms τ = 21 ky Erot = 3.58*1035 erg/s

  10. Are Swift observations useful also with no detection? YES! To obtain an upper limit X-ray flux, necessary for asking deeper observations(e.g. J0357) To study all nearby bright sources, necessary e.g. for Suzaku analysis(e.g. J1413) Papers in preparation: 2nd Fermi pulsar catalog Marelli et al. 2012 So that, Swift can also be useful in combination with other X-ray telescopes Low Nh, powerlaw spectrum => pulsar counterpart High Nh, powerlaw spectrum => pulsar counterpart?

  11. Gamma-rays X-rays When possible, taken from the 1st pulsar catalogue (Abdo et al. ApJ 2011, 193, 22): exponential cutoff and off-pulse tractation.Otherwise, pulsars' preliminary spectral analyses by the collaboration.If both the results were unavailable, I used the 2FGL catalogue's parameters. Assess the X-ray behaviour of Fermi psrs - All the public Swift, Chandra and XMM-Newton data - Processed by using the standard analysis tools. Proton flares subtraction in XMM-Newton data where necessary- Only the appropriate event patterns and energies between 0.3 and 10 keV- Extraction regions in order to maximize the signal-to-noise ratio; a radial brillance profile has been producted where necessary- Spectra added by using ftools- XSPEC to simultaneously fit Chandra/ACIS, XMM-Newton (PN, MOS1,2) and Swift/XRT spectra (where available) by taking into account the different PSFs and cross-calibration studies.- Standard model: absorbed powerlaw. When statistically needed, I added (or used) a blackbody spectrum. Type 0 : no X-ray counterpart detectionType 1 : counterpart detection but spectral shape unknownType 2 : PWN tractation, clear spectral results Marelli et al. 2011, ApJ, 733, 82

  12. The X-ray luminosities LogLx=0.7+0.9logErot χ2red=13 L=f*4πd2F, f dip α,ζ Pulsar geometrical factors? Distance Estimate? • Marelli et al. 2011, ApJ, 733, 82

  13. The γ-ray luminosities LogLγ=2.6+1.5logErot , Erot<4*1035erg/s LogLγ=4.8+0.1logErot , Erot>4*1035erg/s χ2red=7 • Marelli et al. 2011, ApJ, 733, 82

  14. γ-to-X fx=fγ Fγ/Fx=Lγ/Lx*fx/fγ • Marelli et al. 2011, ApJ, 733, 82

  15. γ-to-X Low scatter X-ray underluminous (fx>fγ) Low scatter Radio-Quiet Millisecond • Marelli et al. 2011, ApJ, 733, 82 Radio-Loud High scatter

  16. Assess the X-ray behaviour We can conclude that:- Lx dip Erot with high scatter (distance or geometry?)- Lγ dip Erot with little lower scatter (distance or geometry?)- X and γ-ray emissions are greatly dependent to geometry; moreover, they show no simple correlation good for each pulsar- RQ pulsars are undeluminous in the X band: a geometry different than RL ones could explain such behaviour- RL MS pulsars have a more uniform behaviour (geometry?) than RL ones (Our work is just a starting point)

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