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