44 th Rencontres de Moriond 1 Blind Period Search gamma-ray pulsar by Fermi-LAT F. Giordano Dipartimento Interateneo di Fisica and INFN Sez. Bari for the Fermi LAT collaboration

44 th Rencontres de Moriond 2 PSR B –Flux ~1.1 ∙10 -6 ph/cm 2 s PSR B & PSR B –Flux for E>100MeV ~10 -7 ph/cm 2 s Vela, Crab & Geminga are the brightest sources in the Gamma-ray sky Their Flux for E>100MeV ÷10 -6 ph/cm 2 s Where we were: the EGRET Pulsars

44 th Rencontres de Moriond 3 Geminga Geminga (16 days) Crab Crab (16 days) Vela Vela (16 days) PSR B PSR B (25 days) PSR B PSR B (25 days) PSR B PSR B (25 days) Where we started…

44 th Rencontres de Moriond 4 Pulses at 1/10 th true rate Where we are…

44 th Rencontres de Moriond 5 1. Radio-quiet gamma-ray sources list generated pre-Launch, with very accurate source locations from other wavelengths. a. 3EG J (possibly the “next Geminga”) b. CTA1 (recently published in Science) c. Compact objects of Pulsar Wind Nebulae (PWNe) d. Milagro sources (e.g. MGROJ ) 2. Fermi-LAT sources – a list of gamma-ray sources generated post- Launch with a Fermi localization Search for new  -ray pulsars The Geminga candidates

44 th Rencontres de Moriond 6 The Blind Period Search The spin parameters (frequency, spin-down) are unknown, so to resolve the phase plot, a search over f, df/dt parameter space has to be implemented to find the timing solution. Limitations: 1. Gamma-ray photon data is exceptionally sparse (10 3  10 4 photons per yr ). 2. Such long datasets make fully coherent methods like FFTs require large numbers of fdot trials to prevent smearing of the signal. This large number of trials would also greatly reduce the significance of the signal. 3. FFTs of this magnitude require large amounts of memory: 1 64 Hz = 331 million bins = 5.3 GB of memory! 4. If the pulsar were to glitch (suddenly change its frequency), then the signal power would diminish greatly.

44 th Rencontres de Moriond 7 The “Time-Differencing” Technique Periodicity in photon arrival times will also show up in differences of photon arrival times. Time differences cancel out long term phase slips because differencing starts the "clock" over (and over, and over...) Despite the reduced frequency resolution (and therefore number of bins), the sensitivity is not much reduced because of a compensating reduction in the number of fdot trials

44 th Rencontres de Moriond 8 The First Candidate

44 th Rencontres de Moriond 9 CTA 1 pulsar (2 cycles, P= ms)  -ray source at l,b = , ; 95% error circle radius =0.038° contains the X-ray source RX J , central to the PWN superimposed on the radio map at 1420 MHz. Pulsar off-set from center of radio SNR; rough estimate of the lateral speed of the pulsar is ~450 km/s Exhibits all characteristics of a young high- energy pulsar (characteristic age ~1.4 x 10 4 yr), which powers a synchrotron pulsar wind nebula embedded in a larger SNR. Spin-down luminosity ~10 36 erg s -1, sufficient to supply the PWN with magnetic fields and energetic electrons. The  -ray flux from the CTA 1 pulsar corresponds to about 1-10% of E rot (depending on beam geometry) 9 The First discovery Science, Volume 322, Issue 5905, pp (2008). P ms Pdot3.61× s/s

44 th Rencontres de Moriond 10 EG UnID sources 3EG (Taz) 3EG J (Eel) 3EG J (Rabbit) 3EG J EG J EG J EGJ2020 Gamma-Cigny 3EG J EG J

44 th Rencontres de Moriond 11 More Blind Search Pulsars (not in 3EG ) PSR J PSR J MGRO + 2 new Fermi Sources PSR J MGRO J

44 th Rencontres de Moriond 12 First population study Blind search pulsars ATNF pulsars Flux (Ph/cm 2 s) P1 P0 B Strength (Gauss) Edot (erg/s) Age (yr) Age (yr)

44 th Rencontres de Moriond 13 Conclusions - 13 new (potentially radio-quiet) gamma-ray pulsars have been discovered in 3 months of Fermi-LAT data - 10 out of 13 of these blind period search pulsars have an EGRET source location (3EG). Since two-thirds of EGRET sources remain unidentified, and this is a good step in identifying them. - These pulsars have an age distribution 10 kyr Myr and spin-down luminosity distribution: erg/s erg/s - These new pulsar discoveries will enable a population study of radio- quiet vs. radio-loud pulsars which will provide new information on the emission geometry in these sources and the galactic populations of these high energy emitters. - Deep radio pulsar searches of the new gamma-ray only pulsars have begun, in order to get strong constraints on the radio luminosity.

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