Gamma-ray Observations of Pulsars in the Fermi Era Paul S. Ray - - PowerPoint PPT Presentation

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gamma ray observations of pulsars in the fermi era
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Gamma-ray Observations of Pulsars in the Fermi Era Paul S. Ray - - PowerPoint PPT Presentation

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Gamma-ray Observations of Pulsars in the Fermi Era Paul S. Ray (NRL) for the Fermi LAT Collaboration, Fermi Pulsar Timing Consortium and Fermi Pulsar Search Consortium Pablo Saz Parkinson Santa Cruz Institute for Particle Physics (SCIPP),

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Gamma-ray Observations of Pulsars in the Fermi Era

Paul S. Ray (NRL) for the Fermi LAT Collaboration, Fermi Pulsar Timing Consortium and Fermi Pulsar Search Consortium Pablo Saz Parkinson Santa Cruz Institute for Particle Physics (SCIPP), UCSC 2013 July 8 FAN4 - University of Hong Kong

Thursday, July 11, 13

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Fermi Gamma-ray Space Telescope

Large area: 8000 cm2 area (at 1 GeV) Broad band: 20 MeV to >300 GeV Good localization: 0.6–0.8 deg radius PSF (1 GeV) Continuous sky survey mode of operation with wide FOV

(Atwood et al. 2009, ApJ, 697, 1071)

Key LAT Features for Pulsars

Gamma-ray Burst Monitor (GBM) NaI and BGO Detectors 8 keV - 40 MeV

Large AreaTelescope (LAT) 20 MeV - >300 GeV

Thursday, July 11, 13

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Fermi in Space

Launch from Cape Canaveral 11 June 2008. Circular orbit, 565 km altitude (96 min period), 25.6 deg inclination. Soon to complete 5 years of survey observations, with a planned mission of 10 years. Usual mode of operation is scanning, so that the entire sky is viewed every two orbits.

Thursday, July 11, 13

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LAT Gamma-ray Candidate Event

For each event, the ground-based reconstruction algorithms measures three quantities: arrival direction, energy, and arrival time.

LAT is a pair conversion telescope

Thursday, July 11, 13

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5

Four years of LAT survey data

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Three+ Ways to Detect Pulsars with the LAT

  • Folding gamma-ray photons according to a known pulsar timing model,

from radio or X-rays All 6 EGRET pulsars were detected this way (but Geminga, Crab and Vela could have been discovered in blind searches; Ziegler 2008, Chandler et al. 2001)

  • Blind searches for pulsations directly in the gamma-ray data

Spectacularly successful for young pulsars Really hard for MSPs!

  • Radio pulsar searches of LAT unidentified sources

Sensitivity to MSPs, binaries, very noisy pulsars

+ New: Optical studies of LAT source locations to find binary pulsar counterparts

Still need a blind frequency search to detect pulsations

Thursday, July 11, 13

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Folding With Ephemerides

Large campaign to provide radio and X-ray timing models for all (~200) pulsars with Ė > 1 x 1034 erg/s (Smith et al. 2008 A&A, 492, 923) Thanks to all members of the Pulsar Timing Consortium! Folded LAT photons for 762 pulsars About 40 new γ-ray pulsars discovered in this way

Thursday, July 11, 13

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Bright gamma-ray pulsars with Fermi

High signal-to-noise and good timing models allow study of fine features in the light curve and evolution of profile shapes with energy Phase-resolved spectroscopy reveals rapid changes is spectral parameters (e.g. cutoff energy) within gamma-ray peaks Many pulsars have sub-exponential phase- averaged spectra from superposition of range of exponential cutoffs. Phase resolved spectroscopy is important for proper modeling.

Preliminary

(DeCesar et al. 2012)

Thursday, July 11, 13

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from 1 to 8 MSP γ-ray profiles

Most MSP profiles (peak separation & radio lags) look very much like the young pulsars

(Abdo et al. 2009, Science, 325, 848) Kuiper et al. 2000, A&A, 359, 615

Thursday, July 11, 13

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from 8 to many γ-ray MSPs

  • Fig. 1. MLR map for energies

MeV of a sky region centered

Kuiper et al. 2000, A&A, 359, 615

Thursday, July 11, 13

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where to search for more ?

in globular clusters toward LAT unidentified sources: radio/blind searches toward “pulsar-like” LAT sources toward potential X-ray/opt counterparts

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γ-ray MSPs in Globular Clusters

in M28: B1821-24 + NMSP ∼ 50 in NGC6624: J1823–3021A + NMSP < 32

Counts

20 40 60 80 100 120 140 160

Counts

20 40 60 80 100 120 140 160

> 0.1 GeV J1823-3021A

Counts

5 10 15 20 25 30 35 40

> 1.0 GeV > 3.0 GeV

Counts

20 40 60 80 100 120

0.1 - 1.0 GeV

Pulsar Phase

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Radio Flux (au)

0.2 0.4 0.6 0.8 1

1.4 GHz

see also Wu et al. arXiV:1302.0610v1

highest Lγ ∼ 8.4 1034 erg/s at 8.4 kpc

Freire+ 2010 Science, 334, 1107

high Lγ ∼ 3 1034 erg/s at 5.5 kpc

Thursday, July 11, 13

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radio searches in γ-ray Globular Clusters

in NGC6652: J1839–3259

LAT glob. clusters with no known radio MSP Long S-band GBT observations, using coherent dedispersion mode of GUPPI DM 63.35 pc cm–3, much less than expected from NE2001 highly (e ∼0.95) eccentric 9.25 day

  • rbit, confirming association (rare

eccentric binaries in the field)

Thursday, July 11, 13

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Using LAT to Find Radio Pulsars

2FGL Catalog (Nolan et al. 2012)

575 unassociated 2FGL sources pulsar likeness low variability expo-cut-off spectra multiple techniques for ranking sources + patience ! ∼ a year to get

  • rbit, position, Pdot, longer to

evaluate pulsar timing array potential and get proper motions (Shlovskii effect)

Ackermann et al., ApJ 753, 83 (2012) Lee et al., MNRAS 424, 2832 (2012)

Thursday, July 11, 13

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Success! >48 MSPs found!

Nançay (France) GMRT (India) GreenBank (USA) Parkes (Asutralia) Effelsberg (Germany)

Ray+‘arXiv 1205.3089

Thursday, July 11, 13

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blind searches

Einstein@Home 300,000 people have contributed perfect for LAT MSP searches (tiny data volumes, repetitive computing

  • nly sensitive to isolated MSP (1/4
  • f the total population)

currently searching 100 best LAT candidates up to 1200 Hz “guided” searches toward LAT sources X-ray, optical counterparts binary orbital parameters

flux >

Romani+ 2012 ApJL 754, 25

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X-ray + Optical Studies of bright UNIDs

deep X-ray, optical and radio imaging

  • bservations to look for likely counterparts
  • nly a handful remain to explore

Orbital periods identified in optical J2339–0533 : Porb = 4.6 hours J1311–3430 : Porb = 1.56 hours

2 Romani

  • FIG. 1.— HET/SSO/WIYN measurements of J2339
  • 0533. Upper panel:

Romani et al. 2011, ApJL, 743, 26

J2339–0533

Thursday, July 11, 13

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Blind Search MSP Discovery!

Optical: orbital Porb and Tasc Search space (free trials): pulsation F0 (108), F1 (102), X, and orbit Porb and Tasc: (107) extreme black widow

Weighted counts > 0.1 GeV 50 100 150 200 250

  • W. counts

< 0.3 GeV 20 40 60 80

  • W. counts

0.3 − 1 GeV 30 60 90

  • W. counts

1 − 3 GeV 10 30 50 70

  • W. counts

3 − 7 GeV 3 6 9 12

  • W. c.

> 7 GeV Pulse phase 0.5 1 1.5 2 1 3 5

PSR J1311-3430

Pletsch et al. 2012

Porb = 1.56 hr Mcomp > 8 MJupiter

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But Not Radio Quiet...

Ray et al. (2013)

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Breaking News: J2339–0533!

2.88 ms pulsations discovered in 1.6hr GBT observation at 820 MHz DM 8.72 gives D = 450 pc Measured semimajor axis 0.611 lt-s, larger than expected MC > 0.26 M⊙◉☊ Redback, not black widow Often not visible LAT pulsations now detected

(Ray et al. 2013, in prep)

Thursday, July 11, 13

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Black Widows & Redbacks

Characterize the `weather’ in the system Eclipse mechanism? Understand evolutionary paths Connection to isolated millisecond pulsars?

Thursday, July 11, 13

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Black Widows & Redbacks

ablated companions transition LMXB → MSP

Characterize the `weather’ in the system Eclipse mechanism? Understand evolutionary paths Connection to isolated millisecond pulsars?

Thursday, July 11, 13

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Selecting for Energetic MSPs?

Many of these are isolated

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Second LAT Pulsar Catalog (2PC) (ApJS, accepted: arXiv: 1305.4385)

117 pulsars in 2PC

PRELIMINARY

2PC, LAT collaboration, in preparation

117 pulsars in 3-yr data light curve, spectra, distances,

  • ff-pulse flux, X-ray data,

Schlovskii corrections, etc… available online

Thursday, July 11, 13

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Second LAT Pulsar Catalog (2PC) (ApJS, accepted: arXiv: 1305.4385)

1/3 MSPs 1/3 young + radio-loud 1/3 young + radio-quiet

117 pulsars in 2PC

PRELIMINARY

2PC, LAT collaboration, in preparation

117 pulsars in 3-yr data light curve, spectra, distances,

  • ff-pulse flux, X-ray data,

Schlovskii corrections, etc… available online

Thursday, July 11, 13

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Second LAT Pulsar Catalog (2PC) (ApJS, accepted: arXiv: 1305.4385)

1/3 MSPs 1/3 young + radio-loud 1/3 young + radio-quiet

117 pulsars in 2PC

PRELIMINARY MSP in globular cluster double pulsar

▲

2PC, LAT collaboration, in preparation

117 pulsars in 3-yr data light curve, spectra, distances,

  • ff-pulse flux, X-ray data,

Schlovskii corrections, etc… available online

Thursday, July 11, 13

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radio silent, quiet, faint … loud γ-ray pulsars

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the older, the more efficient, the harder

PRELIMINARY

+Xray

PRELIMINARY

2PC, LAT Colllaboration‘2013, in preparation

evolutionary trends in 2PC

2PC, LAT Colllaboration‘2013, in prep

Thursday, July 11, 13

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radiation pattern trends in 2PC

suggestive of

  • ne pole seen in γ rays
  • pposite pole in radio

no marked evolution of peak separation Δ with Ė

2PC, LAT Colllaboration‘2013, in preparation

Thursday, July 11, 13

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Going forward

125 publicly-announced detected pulsars Follow up timing by PSC Re-observe because of eclipses, scintillation, unknown spectra, RFI, etc... more blind searches Ongoing searches of LAT unidentified sources new catalog analyses yield new targets Radio flux not correlated with γ-ray so plenty more to find how to reach the long-Porb ones?

https://confluence.slac.stanford.edu/display/GLAMCOG/Public+List+of+LAT-Detected+Gamma-Ray+Pulsars

⇒

2PC, LAT Colllaboration+‘2013, in prep

more radio pulsars to soon cross the 5-σ threshold

Thursday, July 11, 13

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Fermi LAT pathfinder

+3FGL on the way !

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