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1、TEMPO2 tutorial,George Hobbs (饺子), Research Scientist CSIRO Australia Telescope National Facility, International Young Scientist of NTSC george.hobbscsiro.au,Content,TEMPO2 is a software package. It implements “pulsar timing” algorithms.Section 1: What TEMPO2 has been used for. Overview of TEMPO2 Se
2、ction 2: How to use TEMPO2 Section 3: How to develop TEMPO2Major TEMPO2 developers (software and algorithms): G. Hobbs, R. Edwards, R. Manchester, W. Coles, X. You, M. Keith, F. Jenet, D. Yardley, J. Verbiest, ,CSIRO. TEMPO2,What has tempo2 been used for in 2010/2011?,Searching for gravitational wav
3、e signals (e.g., Yardley et al. 2011, Yardley et al. 2010, Abbott et al. 2010, van Haasteren et al. 2010) Using pulsars as navigational aids (Ruggiero 2011) Statistical analysis of timing residuals (e.g., Na, X. S. et al., 2011, Hobbs et al. 2010) Studying emission geometry (e.g., Noutsos et al., 20
4、11) Searching for gamma-ray pulsars (Ray et al., 2010) Determining pulsar masses (Demorest et al. 2010) Studying pulsations from main-sequence stars (Ravi et al. 2010) Tests of relativity (Weisberg et al. 2010) Measuring Jupiters mass (Champion et al. 2010) Observations of glitches (Chukwude et al.
5、2010) Analysis of accreting millisecond X-ray pulsar (Patruno et al. 2010) Relativistic spin precession (Manchester et al. 2010),CSIRO. TEMPO2,What does tempo2 do?,USAGE 1: Start with file of pulse arrival times Start with model of a pulsars spin, astrometric and orbital parameters - pulsar timing r
6、esidualsUSAGE 2: Start with pulsar timing model - predict the pulse phase and frequency at a given observatory at a given time,CSIRO. TEMPO2,A parameter file (.par),CSIRO. TEMPO2,Pulsar name, astrometric, rotational, dispersion measure and orbital parameters,Realisation of terrestrial time,Solar sys
7、tem ephemeris,Weighted fit?,Fit for this parameter?,An arrival time file (.tim),CSIRO. TEMPO2,States that this is a tempo2 format file,Filename or identifier,Observing frequency (MHz),Site arrival time (MJD),Uncertainty on arrival time (us),Telescope code,User defined flags,How does tempo2 work?,The
8、 algorithms are based on those implemented in TEMPO1 Details in Hobbs, Edwards & Manchester (2006) and Edwards, Hobbs & Manchester (2006),CSIRO. TEMPO2,Conversion of site-arrival-time to pulse emission time,Clock corrections,Atmospheric delays,Einstein delay,Shapiro delay,Roemer delay,Secular motion
9、 (e.g., radial velocity),Dispersive delay,Orbital motion,Details: clock correction,Must convert from the observatory time standard to a realisation of terrestrial time TT. Use set of text files containing the difference between two time standards: pks2gps.clk, gps2utc.clk, utc2tai.clk, tai2tt_bipm20
10、11.,CSIRO. TEMPO2,Youll find these files in $TEMPO2/clock directory,Details: Einstein delay,Pulse arrival times (in terrestrial time) must be converted to the frame of the Solar System Barycentre. TEMPO2 uses the tabulated results of Irwin & Fukushima (1999),CSIRO. TEMPO2,Details: Roemer delay,The R
11、oemer delay is the vacuum light travel time between the pulse arriving at the observatory and the equivalent arrival time at the SSB.,CSIRO. TEMPO2,R,k,SSB,Earth,pulsar,K = Unit vector pointing at pulsar. Obtained from RA, DEC, PMRA, PMDEC,R is vector from observatory to SSB. Use JPL ephemeris, obse
12、rvatory coordinates and earth orientation parameters,Use observatory coordinate file to know position of observatory,Roemer delay,CSIRO. Gravitational wave detection,Pulsar in ecliptic,Ecliptic latitude = 90 deg,Details: Shapiro delay,Time delay caused by the passage of the pulse through large gravi
13、tational fields. Tempo2 includes delay caused by Sun ( 110us), Jupiter (180ns), Saturn (58ns), Neptune (12ns) and Uranus (10ns),CSIRO. TEMPO2,Details: dispersive delay,D is the dispersion constant. DM (cm-3pc) = 2.410 x 10-16 D f is the frequency of the radiation at the Solar System barycentre,CSIRO
14、. TEMPO2,Details: binary system,For pulsars in binary systems, tempo2 includes parameters describing the orbital motion. Various binary models exist. Suggest using “T2” model that combines most earlier binary models,CSIRO. TEMPO2,Using the pulsar timing model,Have pulse emission time in the pulsar f
15、rame. Predict using the pulsar timing modelCan also include simple model of glitch events,CSIRO. TEMPO2,Phase of pulse sequence,Pulse frequency (and time derivatives),Pulse emission time,Time at which df/dt = n,Reference phase,Timing residuals,CSIRO. TEMPO2,Timing residual for ith observation,Pulse
16、phase,Nearest integer to fi,Pulse frequency,Example,CSIRO. TEMPO2,Time,Measured arrival time with observatory clock,Measured arrival time in terrestrial time (Dc),Measured arrival time in pulsar frame,1,3,4,2,5,Predicted arrival times in pulsar frame,Timing residual,Pulsar timing residuals,If pulsar
17、 model predicts the observations perfectly (and the conversion from the observatory to pulsar frame is perfect) then R = 0 (within measurement uncertainty). If R != 0 then the pulsar model is (1) not accurate or (2) does not include a physical process that affects the measured arrival times or (3) the correction from the observatory to pulsar frame is not correct.,
