-ray pulsars Fermi observations of -ray pulsars Fermi - - PowerPoint PPT Presentation

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-ray pulsars Fermi observations of -ray pulsars Fermi observations of Pablo M. Saz Parkinson Pablo M. Saz Parkinson Santa Cruz Institute for Particle Physics Santa Cruz Institute for Particle Physics (University of California)

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SciNeGHE08 Workshop, Abano Terme, Italy Thursday, 9 October 2008

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Fermi observations of Fermi observations of γ γ-ray pulsars

  • ray pulsars

Pablo M. Saz Parkinson Pablo M. Saz Parkinson

Santa Cruz Institute for Particle Physics Santa Cruz Institute for Particle Physics (University of California) (University of California) for for the Fermi-LAT Collaboration

the Fermi-LAT Collaboration

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SciNeGHE08 Workshop, Abano Terme, Italy Thursday, 9 October 2008

The Fermi (formerly GLAST) LAT

  • 20 MeV – 300 GeV
  • 2.5 sr FOV
  • All-sky every 3 hours
  • ~ 25 times EGRET

sensitivity

  • Angular resolution:

~3-6 deg. @ 100 MeV ~0.1-0.2 deg. @ 10 GeV

  • Many science targets:

e.g. AGN, Dark Matter, GRB, Pulsars ... (NB: in alphabetical order)

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SciNeGHE08 Workshop, Abano Terme, Italy Thursday, 9 October 2008

Gamma-ray pulsars

  • Number gamma-ray

pulsars pre-Fermi= 7 (6 by EGRET)

  • Number of “Gemingas” = 1

(Geminga)

  • The “Geminga fraction”

can tell us about the different mechanisms responsible for radio and gamma-ray pulsations

Gonthier, Van Guilder, & Harding (2004) Credit: D. Thompson

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Fermi searches for γ-ray pulsars

  • Two types of searches for γ-ray pulsars

– Using known ephemerides of radio/X-ray pulsars – “Blind” searches for Geminga-type pulsars

SciNeGHE08 Workshop, Abano Terme, Italy Thursday, 9 October 2008

Folded light curve of Geminga using 13 days of “Survey” data

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SciNeGHE08 Workshop, Abano Terme, Italy Thursday, 9 October 2008

Searches for known pulsars

  • Pulsars being timed by a large collaboration
  • f radio and X-ray astronomers and the

Fermi-LAT team

  • Number of pulsars on the list is large (and

increasing)

  • Coordinator: David Smith (CENBG, France)
  • See M. Razzano talk on Vela pulsar
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SciNeGHE08 Workshop, Abano Terme, Italy Thursday, 9 October 2008

Search for unknown pulsars

  • Spin parameters (F0,F1,F2) unknown
  • Locations used are from promising “Geminga

candidates” and from the LAT catalog

  • The low event rates and long observation

periods make traditional FFT search techniques prohibitively expensive computationally

  • An efficient time-differencing technique makes

it feasible to search a large number of pulsar candidates

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Time Differencing Technique

t1

∆t2 ∆t3 ∆t4 ∆t5 ∆t6

Photon arrival time

∆t1

t3 t2 t4

A Periodic signal will also show up in the differences of the arrival times => Calculate FT based on the time differences

# of FFT bins = f * tmax_diff * 2 PC with 2GB can handle 33 x 106 bin FFT Atwood et. al., ApJ Lett., 652, 49 (2006) Ziegler et. al., ApJ 680, 620 (2008)

SciNeGHE08 Workshop, Abano Terme, Italy Thursday, 9 October 2008

Credit: M. Ziegler

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SciNeGHE08 Workshop, Abano Terme, Italy Thursday, 9 October 2008

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Sources of interest in our searches

  • Unidentified Fermi-LAT sources
  • List of known pulsars, e.g.:

–EGRET Pulsars –Pulsars coincident with EGRET sources

  • List of “Geminga Candidates”, e.g.:

–3EG J1835+5918 (aka the “next” Geminga) –CTA1 –Compact objects of PWNe –Milagro sources (e.g. MGROJ2019+37)

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SciNeGHE08 Workshop, Abano Terme, Italy Thursday, 9 October 2008

EGRET Pulsars

  • EGRET pulsars were found in blind search within the 60-day

launch and early operations (L&EO) period.

Geminga PSR B1706-44 PSR B1951+32

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SciNeGHE08 Workshop, Abano Terme, Italy Thursday, 9 October 2008

Detection of glitch in PSR B1706-44

Pre-glitch ephemeris Post-glitch ephemeris

  • A search around a narrow range of

frequencies centered on known ephemeris results in two peaks in power spectrum

  • Glitch occurred between 14-15 August
  • Known to glitch (e.g. 1992, 1995)
  • Radio observations are planned
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SciNeGHE08 Workshop, Abano Terme, Italy Thursday, 9 October 2008

A radio-quiet pulsar in CTA1

P ~ 317 ms Pdot ~ 3.6E-13 Edot = 4.5E35 Characteristic age ~ 10,000 yrs Location of EGRET source 3EG J0010+7309, the Fermi-LAT source, and the central X-ray source RX J0007.0+7303

SciNeGHE08 Workshop, Abano Terme, Italy Thursday, 9 October 2008

To appear in Science

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SciNeGHE08 Workshop, Abano Terme, Italy Thursday, 9 October 2008

Conclusions

  • GLAST was successfully launched on 11

June 2008 (subsequently renamed Fermi)

  • The 60-day L&EO verification period was

successfully completed. In addition to tuning, testing, and calibrating the instrument ... science was being carried out.

  • Fermi is looking for gamma-ray pulsations

from known and unknown pulsars

  • A new radio-quiet gamma-ray pulsar has been

discovered ... and more are on the way.

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SciNeGHE08 Workshop, Abano Terme, Italy Thursday, 9 October 2008

Grazie!