gamma-ray pulsarsgamma-ray pulsars: spin down vs luminosity & the distance problem peter r. den...

Gamma-ray Pulsars:

spin down vs luminosity &

the distance problem

Peter R. den HartogStanford University (HEPL/KIPAC)

[email protected]

Parkes 50 years, Parkes, NSW, Australia, November 2 , 2011

obo LAT-collaboration, pulsar timing consortium and pulsar search consortium

in preparation for Fermi LAT 2nd Pulsar Catalog

Tuesday, November 29, 2011

mailto:[email protected]

mailto:[email protected]

EMBARGO

This talk contains EMBARGOED material

Please do not cite (tweet, blog) any details of this talk until TOMORROW afternoon EST

There will be a NASA press conference on the announcement of the

100th Fermi gamma-ray pulsar


Fermi Gamma-ray Space TelescopeTwo instruments:• Large Area Telescope (LAT)• Gamma-ray Burst Monitor (GBM).

International collaboration: USA, France, Germany, Italy, Japan, Sweden.

Lifetime 5 to 10 years.

LAT • Energy range: 20 MeV to >300 GeV. • Large FOV of 2.4 sr.• Survey observation mode (with a few exceptions).

Whole sky seen in two orbits (eight times per day).• Effective area at 1 GeV ~7000 cm2 • Angular resolution: ~ 3.5° at 0.1 GeV, 0.6° at 1 GeV• Point-source location accuracy ~1’ @ 1GeV


0 0.05 0.15 0.35 0.74 1.5 3.1 6.2 13 25 50

Gamma-ray sources: From EGRET to Fermi

Second Fermi LAT catalog (2FGL)Fermi LAT all-sky gamma-ray map >100 MeV

271 sources (9 years)6 Pulsars

1873 sources (2 years)87 Pulsars

J0534+2200 (Crab)J0633+1746 (Geminga)J0835-4510 (Vela)J1057-5226J1709-4429J1952+3252

Few ‘marginal’ detections including 1 millisecond PSR (PSR-J0218+4232; Kuiper et al. 2000)

Abdo et al. 2011 arxiv.org/abs/1108.1435v1


Gamma-ray sources: From EGRET to Fermi

Second Fermi LAT catalog (2FGL)Fermi LAT all-sky gamma-ray map >100 MeV

J0534+2200 (Crab)J0633+1746 (Geminga)J0835-4510 (Vela)J1057-5226J1709-4429J1952+3252

Few ‘marginal’ detections including 1 millisecond PSR (PSR-J0218+4232; Kuiper et al. 2000)

Abdo et al. 2011 arxiv.org/abs/1108.1435v1


Pulsar Timing consortiumCampaign to time 224 high E pulsars.(best gamma-ray candidates, but unstable spin-down rate.)

Nançay and Jodrell Bank provide us with another 500 ephemerides!

.

Parkes (Australia)

Nançay (France)

Jodrell Bank (England)

RXTE

Green Bank Telescope (USA)

Arecibo (Puerto Rico)

Smith et al. A&A 492, 293 (2008)


Pulsar Timing consortiumCampaign to time 224 high E pulsars.(best gamma-ray candidates, but unstable spin-down rate.)

Nançay and Jodrell Bank provide us with another 500 ephemerides!

.

Parkes (Australia)

Nançay (France)

Jodrell Bank (England)

RXTE

Green Bank Telescope (USA)

Arecibo (Puerto Rico)

Smith et al. A&A 492, 293 (2008) FERMI


Current γ-ray pulsar population

Counter now at 101 Fermi γ-ray PSRs. (Tomorrow special press event for 100th Fermi PSR!)1/3 gamma-selected pulsars. Previously unknown pulsars discovered in blind searches + Geminga1/3 millisecond pulsars, More to come from recent discovered MSPs in Fermi Unassociated sources1/3 radio-selected discovered using radio ephemerides


Filling in the P - Pdot

E = 1035 erg s-1.

Abdo et al., ApJS 187, p460, 2010


Filling in the P - Pdot

E = 1033 erg s-1.

E = 1035 erg s-1.


Emission mechanism & geometry

Different theoretical models exist to explain the observed gamma-ray emission.They assume different emission processes and origins in the magnetosphere → different emission geometry.

Different models predict different light curves (e.g. number of peaks, separation, radio/gamma lag, ratio of radio-loud/radio-quiet).

Different γ-ray spectra are expected (i.e. exponential cutoff vs super-exponential cutoff)

Some answers thanks to Fermi:• The gamma-ray emission from the bulk of the gamma-ray pulsars is outer magnetospheric

• There are many gamma-ray millisecond pulsars

• The fraction of radio-loud to radio-quiet gamma-ray pulsars is 2:1

Stick around for the next talk by Matthew Kerr


δ radio-gamma offset

Δ Separation between γ peaks

Interpreting light curves

Abdo et al. 2009, ApJ, 700, 1059

Determine: Δ, δ, finda) which model best matches (if any)b) for which α, ζ valuesc) Determine fΩ and refine Lγ .

Watters et al. 2009, ApJ 695, 1289Romani & Watters 2010, ApJ 714, 810

20 30 40 50 60 70 80 90

TPC eps=+0.2

80

OG eps=-0.280604020

60

40

20

OG eps=0.0 OG eps=+0.2

TPC eps=-0.2 TPC eps=0.0


b=1 high-altitude emission.Strong magnetic fields would attenuate gamma rays if the emission were close to the surface b>1 (super-exponential)

Spectral index Γ~1.5Cutoff E0 ~2.5 GeVEnergy flux > 100 MeV ~ 4.3e-10 ergs cm-2s-1

b

Spectral shape: Power Law + Exponential Cutoff

LAT spectra for PSR J2021+3651Abdo et al. 2009, ApJ, 700, 1059

● young, radio-selected young, gamma-selected▲ millisecond pulsar

Abdo et al., ApJS 187, p460, 2010


0

1

2

3

4

5

6

7

8

Pulsar Phase0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

)M

eVlo

g(E

1.5

2

2.5

3

3.5

4

4.5

5

0

1

2

3

4

5

6

7

8

0

1

2

3

4

5

6

7

8

0

1

2

3

4

5

6

7

8

Cutoff energy and spectral index vs. pulse phase. 203 fixed-counts (750) phase bins.

Vela (PSR J0835−4510)

Cou

nts

0

5000

10000 >0.02 GeVP1

P3

P2

Cou

nts

0

5

10

15 >20.0 GeV

Cou

nts

0

50

8.0 20.0 GeV

Cou

nts

0

200

4003.0 8.0 GeV

Cou

nts

0

1000

2000 1.0 3.0 GeV

Cou

nts

0

2000

4000 0.3 1.0 GeV

Cou

nts

0

1000

2000

3000 0.1 0.3 GeV

Pulsar Phase0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Cou

nts

0

50

1000.02 0.1 GeV

Cou

nts

0

5000

10000 >0.02 GeVP1

P3

P2

Cou

nts

0

5

10

15 >20.0 GeV

Cou

nts

0

50

8.0 20.0 GeV

Cou

nts

0

200

4003.0 8.0 GeV

Cou

nts

0

1000

2000 1.0 3.0 GeV

Cou

nts

0

2000

4000 0.3 1.0 GeV

Cou

nts

0

1000

2000

3000 0.1 0.3 GeV

Pulsar Phase0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Cou

nts

0

50

1000.02 0.1 GeV

Energy (GeV)110 1 10

)1 s2

dN/d

E (e

rg c

m2 E

1010

910

810

0.135 0.133

0.05± = 1.820.67 GeV± = 3.98CE


)1 s2

dN/d

E (e

rg c

m2 E

1010

910

810

0.226 0.220

0.08± = 1.170.17 GeV± = 1.51CE


)1 s2

dN/d

E (e

rg c

m2 E

1010

910

810

0.324 0.315

0.05± = 1.330.48 GeV± = 4.05CE


)1 s2

dN/d

E (e

rg c

m2 E

1010

910

810

0.563 0.562

0.04± = 1.550.66 GeV± = 4.89CE

Abdo et al., ApJ 696, 1084, 2009;Abdo et al., ApJ 713, 154, 2010 Spectra from four phase bins

Pulse profile as function of phase


Pulsar detectability

Abdo et al., ApJS 187, p460, 2010

Fermi LAT pulsar catalog I contained 46 γ-ray pulsars: 17 γ-ray-selected, 21 radio-selected, 8 MSPs

The high E pulsars seem to favour L∝E0.5 while lower E pulsars may favour L∝E...

Luminosity determinations depend very sensitive on distance estimates and uncertainties.Note 8 out of 17 γ-ray-selected PSRs with distance estimates.

... .


PSRCATII distances status

For all radio pulsars we have DM (they are in pretty good condition)DM distances for: ~66% (not necessarily used in PSRCATII)

~33% Pulsars with other estimate(s) How reliable are they?Work in progress

The Gamma-ray only pulsars are a problem..(arguably the more interesting ones)~25% of all pulsars without any distance estimate. Also work in progress


PSRCATII distances status

Parallax: 13 Fermi PSRs with parallax measurements, however 5 of them <5σ

DM distances: have now 20% errors.Arguably some are less reliable. Identify problem regions and maybe assign a larger error?

Associations: continue trying to find them in literature/ archives/ surveys/ X-ray / WDs Long process. In general it takes several hours per pulsar.


PSRCATII distances

Parallax:Programs have started to measure parallaxes of Fermi PSRs. Maybe some good numbers of new distances for Fermi Pulsar Catalog III.

NE201X: (Cordes et al.)Hard work is going on for new Galactic electron-density model to replace NE2001. Looking good for PSRCATIII


Fermi collaboration birthday wishes

Happy 50th birthday PARKES

Thank you for all the hard work,

awesome science and great collaborations


gamma-ray pulsarsgamma-ray pulsars: spin down vs luminosity & the distance problem peter r. den...

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