1. LZ - Crab Pulsar - Bled, 27/03/2008 An Aqueye view of the Crab Pulsar L. Zampieri & C. Germana' X-ray: NASA/CXC/ASU/J.Hester et al.; Optical: NASA/ESA/ASU/J.Hester & A.Loll; Infrared: NASA/JPL- Caltech/Univ. Minn./R.Gehrz

2. LZ - Crab Pulsar - Bled, 27/03/20082 Outline Historical notes Basic physics Parameters of the Crab pulsar Xronos timing software Tests: simulated signal and ROSAT data Aqueye observations Problems and future goals

3. 3 Crab pulsar: Historical notes Hosted in the Crab nebula in Taurus (M1), remnant of a bright supernova recorded by Chinese and Arab astronomers in 1054‏ Central star identified by Minkowski (1942); radio emission discovered in 1949 (Bolton et al. 1949) Pulsating radio emission discovered in 1968 (Staelin & Reifenstein 1968, Comella et al. 1969; one year after the detection of the first pulsar by Bell & Hewish in Cambridge), providing strong evidence for the connection with supernova explosions X-ray and gamma-ray emission discovered in 1963 (Bowyer et al. 1964) and 1967 (Haymes et al. 1968) Optical and X-ray pulsations discovered in 1969 (Cocke et al.; Fitz et al.) Overwhelming evidence that pulsars are rotating neutron stars (Pacini 1967; Gold 1968, 1969): * shortness (~ms-s), stability (1:10 8 ) and gradual slowing down of the period P * (dE/dt) nebula = - (dE/dt) pulsar

4. 4 Basic physics Limiting period above which F c >F g (break-up period): shortest period observed P=1.6074 ms (PSR B1957+20) Rotation power and magnetic dipole radiation (Ghosh 2007):

5. Basic physics Rotational energy goes into intense low-frequency radiation and into accelerating charged particles (relativistic wind), that power the nebula Crossing magnetic field lines, they emit synchrotron radiation Only a small fraction (10 -5 - 10 -7 ) of E rot goes into beamed, narrow radio pulses Pulses usually have single components and small duty cycles (10 0 ). But the pulse shape of the Crab has two sharp peaks separated by 140 0 in phase, similar at all wavelengths  emission of the two polar beams from an almost orthogonal rotator

6. 6 Parameters of the Crab pulsar The Crab pulsar is a fast rotating, young neutron star with (Ghosh 2007): E rot =2.0x10 49 erg dE rot /dt=-5.0x10 38 erg/s B 12 =7 Period P Ein =33.235427(70) ms on Sep 14, 1979 (Einstein; Harnden & Seward 1984) P XMM =33.5341004590(5) ms on March 7, 2002 (XMM; Kirsh et al. 2006) P XMM - P Ein =0.298673 ms  dP/dt=36 ns/day  dP/dt=4.2x10 -13 P today =33.61 ms

7. 7 Xronos timing software General purpose timing analysis software, developed since 1987 to analyse EXOSAT data but designed to be detector and wavelength-independent Developed on Unix/Linux platforms; present release (v. 5.18) fully integrated within the HEAsoft distribution (HEASARC) Consists of a number of independent programs: autocor, crosscor, efold, efsearch, lcurve, powspec Primary input/output format is FITS (Flexible Image Transport System). ASCII-to-FITS conversion routines available. BIN INTERVAL FRAME

8. LZ - Crab pulsar - Bled, 27/3/20088 Xronos timing software: programs autocor/crosscor: autocorrelation/crosscorrelation for one/two- simultaneous time series, computed by a FFT algorithm (or a direct Fourier algorithm) lcurve/efold: lightcurve vs. time/folded lightcurve vs. phase efsearch: after folding data over a range of periods, determines chi-square of the folded light curve wrt a constant powspec: power spectral density for one time series, computed by a FFT algorithm (or a direct Fourier algorithm)  We are developing our own software to automatically search for powers exceeding a certain detection level and quantify the signal power in terms of a relative rms variation

9. 9 Tests Simulated periodic (P=30 ms) signal with a superimposed Poissonian noise (S/N~5)

10. Tests PSPC/ROSAT observation of the Crab pulsar performed on March 1, 1991 (667 counts/s, including part of the nebula) Standard reduction applied and photon extracted from a 2’ circular region centered on the source position 660 s P ROSAT =P Ein +(dP/dt)*Dt=33.386 ms

11. LZ - Crab Pulsar - Bled, 27/3/200811 Aqueye observations of the Crab Aqueye observation started at 23:51 on Dec 19, 2007 and lasted ~1 hour Binned ASCII data file (received from Tommaso) Processing chain:  data divided in 6 segments of ~9 m (file size < 50 MBytes)  converted in FITS format  corrected for arrival time at the solar system barycenter (~0.1 s difference in photon arrival time in a 1 hour observation due to the Earth motion)  sequence of Xronos programs launched using a python ‘interface’

12. LZ - Crab pulsar - Bled, 27/3/200812 Aqueye: Crab period f=32.5 Hz P=30.77 ms Ptoday=33.61 ms

13. LZ - Crab pulsar - Bled, 27/3/200813 Aqueye: Crab folded light curve 3 s 30 s 300 s

14. LZ - Crab pulsar - Bled, 27/3/200814 Problems and future goals Crab crucial test for timing accuracy Xronos reliable package for the timing analysis Development of other timing software to perform additional analyses Main problem: stability of the internal Aqueye ATFU  error in determining P and lack of coherence in the folded lighcurve Timing accuracy needed for calculating stable Crab pulse profiles up to 10 m < 1 microsec Choice of data format for distribution: binned vs. unbinned data