observation of radio loud pulsars with the fermi … · observation of radio loud pulsars with the...

OBSERVATION of RADIO LOUD PULSARS

with the Fermi-LATγ-ray telescope

Thierry ReposeurCENBG Bordeaux, France

on behalf ofthe Fermi-LAT Collaboration and

the Pulsar Timing Consortium

Orange Pulsar Meeting27-28 September 2010 Orange, NSW, Australia

pre-Fermi era

7 pulsars known to radiate γ-rays (6 EGRET, 1 COMPTEL)

Vela, the brightest Geminga, 1st radio quiet B1952, no cutoff

A too small population for an extensive study

Fermi-LAT sensitity about 25x EGRET's → expect many more pulsars.

BUT very few gamma-rays per rotation (at GeV energies, Vela gives 1 photon every 100 rotations)typically 1000 “pulsed” gammas a year

Radio observatories are very well suited to provide good timing solutions over a long period of time

→ we can fold our γ's, see what comes out→ Pulsar Timing Consortium

(for the radio quiet pulsars → Marianne's talk)Thierry Reposeur, Orange Pulsar Meeting, 27-28 September 2010. Orange, NSW, Australia

The Pulsar Timing Consortium (PTC) one contact: smith at cenbg.in2p3.fr

Agreement (MoU) between several telescopes and the Fermi-LAT collaboration.(Parkes, GBT, Nançay, Jodrell + RXTE...)

Initially, sources with dE/dt > 1034 erg/s are monitored

→ 214 pulsars being « officially » followed (red)

but our 1st ms pulsar J0030+0451, has Edot=31033 erg/s

→ gently ask for ephemerides not in the MoU

→ more than 750 ephemerides (blue) available at that time (mostly from Nançay and Jodrell)

Note: Parkes alone in the Southern hemisphere → great for the TeV PWN HESS connection (See Marie-Hélène's talk here)

Also The LAT Pulsar Search Consortium to search for radio pulsar in the Fermi-LAT sources (see Mike's talk)

Thierry Reposeur, Orange Pulsar Meeting, 27-28 September 2010. Orange, NSW, Australia

Thierry Reposeur, Orange Pulsar Meeting, 27-28 September 2010. Orange, NSW, Australia

The exemple of J1048-5832Abdo et al., ApJ, 706(2009)1331-1340hardly seen by EGRET

The exemple of J1952+3252Abdo et al., ApJ, 720(2010)26-40

energy cutoff !

No way without radio timing !

Thierry Reposeur, Orange Pulsar Meeting, 27-28 September 2010. Orange, NSW, Australia

The official map

More up to date (not yet released)

The LAT has detected 71 γ-ray pulsars in three (nearly equal) categories

Young radio-loud pulsars Young radio-quiet pulsars Radio-loud MSPs

→ First population study (Abdo et al., ApJS 187(2010)460-494)

Pulsars in the first catalogue MSPs / blind search / radio selected / non detected

MSPs and “normal” have similar BLC

→ same emission mechanisms (?)

apart from MSPs we observe mainly young pulsarssmall agelarge BLarge Edotsmall P

Thierry Reposeur, Orange Pulsar Meeting, 27-28 September 2010. Orange, NSW, Australia

Thierry Reposeur, Orange Pulsar Meeting, 27-28 September 2010. Orange, NSW, Australia

Power law + exponential cutoff energy spectra

spectral energy cutoff not correlated with the surface magnetic field → disfavors the Polar Cap model (γ−B cascades)

slight correlation with BLC

→ emission at “high altitude”

non evidence of hyper-exponential cutoff → “high altitude” emission

low altitude emission visible from one hemisphere and higher altitude (r > r

NC)

emission visible from the other. This isthe “two pole caustic” (TPC) model (Dyks and Rudak 2003)→ intermediate between the polar cap (PC) and the Outer Gap (OG) picture

← “Déjà vu...”

Thierry Reposeur, Orange Pulsar Meeting, 27-28 September 2010. Orange, NSW, Australia

Correlation between radio/gamma peak separation is observed as predicted by outer magnetosphere models (Outer Gap, Slot Gap).

The 0.2 range favors Outer Gap models the 0.4-0.5 range argues for Two Pole

Caustic models

2 populations Δ=0.2, Δ=0.4-0.5No dependence with EdotA full comparison will require detailed population models, which are being created.

9

γ luminosity: Lγ = 4πf

Ωhd2

Lγ≈Edot ↔ 100% efficiency, L

γ≈ Edot1/2 ↔ constant voltage line

Seems to be Lγ≈ Edot1/2 for Edot>10e36 erg/s

but still a big dispersion, errors due to 1) assumption on fΩ , 2) distances

Thierry Reposeur, Orange Pulsar Meeting, 27-28 September 2010. Orange, NSW, Australia

fΩ here assumed = 1 (geometry,

what about MSPs ?)

h energy flux measured by Fermi

d distance to Earth, may have large uncertainties when evaluated from DM

10

numerous pulsars are

unidentified EGRET's associated with SNR/PWNe associated with TeV sources

Thierry Reposeur, Orange Pulsar Meeting, 27-28 September 2010. Orange, NSW, Australia

Why don't we see some young energetic pulsars ?Large background regionbroad lightcurve?

The LAT will continue to find new pulsars, but at a slower rate (sensitivity x2.2 after 5 years)

New categories? High B-field pulsars Radio-quiet MSPs Young binary pulsars Individual MSPs in GCs

QUESTIONS

Thierry Reposeur, Orange Pulsar Meeting, 27-28 September 2010. Orange, NSW, Australia

Thierry Reposeur, Orange Pulsar Meeting, 27-28 September 2010. Orange, NSW, Australia

CONCLUSIONS

The LAT has detected 71 γ-ray pulsars (not all published yet)

1/3 are young radio-loud pulsars 1/3 are young radio-quiet pulsars 1/3 are radio-loud MSPs

21 radio MSPs found in Fermi-LAT unidentified sources, some turn out to be also γ-ray emitters (pulsed !)

LAT statistics on γ-ray pulsars enabling population studies (phase resolved spectra)

Hight altitude emission processes are favored (OG, SG)→ γ-ray beams scan over a large portion of the sky

but Polar Cap still compatible with a few individuals (Marie-Hélène's PSR B1509-58)

send ephem files for your favorite pulsars if you think it is worth looking at it in γ-rays