Timing studies and PSR J0437-4715 analysis Till Eifert, HU Berlin April, 2005

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Transcript of Timing studies and PSR J0437-4715 analysis Till Eifert, HU Berlin April, 2005

  • Timing studies and PSR J0437-4715 analysisTill Eifert, HU Berlin

    April, 2005

  • OutlineAnalysis of pulsar timing dataImprovement of barycenter correctionImplementation of binary correctionPSR J0437-4715Data analysis, first resultsConclusion / Outlook

  • Analysis of pulsar timing data

    Given: GPS event time stamp from CentralTriggerintrinsic accuracy of GPS 10 s ~ 30 s from peak jitter of optical pulsar measurements

    Phase of a pulsar waveform depends on:Spin-down ( ATNF PSR DB)Motion of Earth within the solar system ( barycenter correction)Orbital motion of the pulsar ( binary correction)

    Crosscheck with TEMPO:Standard tool from radio astronomersEvolving since 1972Accuracy < s range, proved by extensive tests with 6 years of data.

  • Barycenter correctiont = toa in TDT (UTC + leap seconds) system tb units: Barycentric Dynamical Time (TDB)

    tSSB correction to solar system barycenter (Roemer time delay)tE solar system Einstein delay (gravitational redshift & time dilation due to motions of the Earth = TDB correction)tS Shapiro delay (caused by propagation of the pulsar signal through curved spacetime)

    Taken from F. Schmidt

  • CRASH vs. TEMPOCRASH vs. TEMPO timing corrections:tE (TDB) (< 25 s)tS + tSSB (< 0.12 ms)proper motion, parallax not used for phase calculation in old Crash!

    Good enough?For young PSR: Yes!

    What about ms PSR?

    TDB (Crash Tempo)SSB + Shapiro (Crash Tempo)

  • CRASH vs. TEMPOPSR J0437 ephemeris(P ~ 5.7ms, proper motion ~ 100 mas/yr, parallax ~ 7 mas)

    tb < 2 ms

    Thus, CRASH not applicable for analysis over long observation period of close ms PSR!

    tbary (Crash Tempo)p (Crash Tempo)

  • ImprovementsNew in Crash module:New TDB algorithmNew barycenter algorithm, taking into account:Shapiro delayProper motionParallaxNew routines to read in TEMPO and GRO parameter filesTwo binary models addedtbary (Crash Tempo)p (Crash Tempo)

  • Improvements (zoomed)New in Crash module:New TDB algorithmNew barycenter algorithm, taking into account:Shapiro delayProper motionParallaxNew routines to read in TEMPO and GRO parameter filesTwo binary models addedtbary (Crash Tempo)p (Crash Tempo)

  • Binary modelsPSR in binary system significant acceleration

    Blandford-Teukolsky (BT) model: Keplerian ellipseNewtonian dynamics Einstein delay patched into model afterwards additional effects are accommodated by nonzero time derivativesDamour-Deruelle (DD) model: more generalRoemer time delayOrbital Einstein and Shapiro delayAberration caused by rotation

  • Checking BT model correction against TEMPOtbinary < 10-9 s

  • Checking DD model correction against TEMPOtbinary < 10-10 s

  • OutlineAnalysis of pulsar timing dataImprovement of barycenter correctionImplementation of binary correctionPSR J0437-4715Data analysis, first resultsConclusion / Outlook

    New code: good agreement (

  • PSR J0437-4715Distance ~ 140 pcP ~ 5.75 ms, dP/dt ~ 10-20Low B ~ 108 -1010GBinary orbit ~ 5.74 daysLow mass companion ~ 0.2 MNot eclipsingNo optical brightness variationPulsed emission visible in radio, X-rays

    Harding, A.K., Usov, V. V., Muslimov, A. G., 2005, ApJ, 622, 531Polar Cap model prediction

  • PSR J0437-4715Two phase cycles!Radio observation at ParkesROSAT High Resolution Imager (HRI) ROSAT Position Sensitive Proportional Counter (PSPC)Chandra High Resolution Camera (HRC)

  • Data analysisData from October 200422 runs with 4 telescopes (passed quality check), ~ 9.1 h livetimeZenith angle range: 23.9 30 degEnergy threshold ~ 200 GeV

    Std. Hd Cuts: desert/phase1_0510_southBackground model: SevenBackgroundMaker

    PSR analysis: ephemeris from ATNFStatistical tests: Z2, H

  • DC analysisStd. Hd cuts9.1 h livetime

    Significance: 0.4

    What about AC?

  • Timing analysisQuestion: just a fluctuation or possible hint for pulsed TeV emission?(note: fluctuation is on the right phase position!)On regionZ21 = 5.6 (Prob. 0.06)Z22 = 5.7 (Prob. 0.23)H = 5.6OFF region with highest H = 3.8All energies, DC: 0.4 OFF regions (summed)~ flat

  • Timing analysis, energy binsOn regionZ21 = 6.4 (Prob. 0.04)Z22 = 6.7 (Prob. 0.15)H = 6.4All energies < 0.5 TeV, DC: 0.5 OFF regions flatAll energies > 0.5 TeV, DC: -0.2 On regionZ21 = 0.2 (Prob. 0.92)Z22 = 2.2 (Prob. 0.70)H = 0.2

  • Zenith angleDC SignificanceEnergy < 0.5 TeV

    Maximize signal/noise ratio for low energy by using very small zenith angles only

    Chart1

    0.5

    0.5

    0.7

    1

    1.5

    2

    2.6

    Zenith angle [deg]

    DC Significance [sigma]

    Sheet1

    Zenith angleSignificance

    300.5

    290.5

    280.7

    271

    261.5

    252

    24.52.6

    Sheet2

    Sheet3

  • Timing analysisAll energies < 0.5 TeV, zenith angle < 25 degOn regionDC: 2.0 5.6 h livetime

    Z21 = 9.4 (Prob. 0.009)Z22 = 11.3 (Prob. 0.02)H = 9.4

    OFF regions flat (max H = 2.2)

    with std. HD cuts !

  • Conclusion / OutlookWe have developed and tested the tools to analyse ms PSR (sub s agreement with TEMPO)It is difficult to ignore the fluctuation at the right phase positionOptimizing cuts on MC with exp. cut-off spectraCross-check with Mathieus model analysisWe need more data with very low zenith angle

  • Leap seconds in UTC|UT1-UTC| < 0.9 seconds leap seconds

    UT1: time scale based on the Earths rotation (irregular fluctuations, general slowing down)UTC: TAI (International Atomic Time) + leap seconds

    Taken from Earth Orientation Center

  • Data analysisOn regionZ21 = 9.1 (Prob. 0.01)Z22 = 9.3 (Prob. 0.05)H = 9.1All energies: 0.2 - 0.45 TeV, all zenith angle

    I have divided my talk into two distinct parts:

    First: checking, improving, and implementation of time of arrival correctionsSecond: Analysis and first results of the ms PSR J0437

    Folge nach dem erfolgreichen implementieren In order to do timing analysis, we start off with the time stamp from the CentralTrigger.

    The intrinsic accuracy of GPS is in the order of 10 us.On the other hand, we know from optical Crab measurements that the main peak jitters over month in the order of 30 us.(kuerzer)

    Next, we are interested in the phase of the events. This phase strongly depends on:Pulsar specific parameters, for example the spin-down. Those parameters are provided, in so called ephemeris files, by the Australian Telescope National Facility Pulsar Database.The motion of the earth within the solar system. This effect has to be corrected by our software!If the pulsar is in a binary system, we again have to correct acceleration effects.

    Now, how do we know our software corrections are working properly? One can crosscheck with existing tools!Luckily, there is a standard tool from the radio astronomers, called TEMPO.TEMPO is widely used by radio astronomers doing pulsar analysis.Radio astronomers claim, TEMPO has accuracy in the sub us range.

    Lets start with the corrections in our solar system, due to the motion of earth:

    There are three essential correction terms, I am going to briefly explain:We start with the arrival time, transformed to the Terrestrial Dynamical Time.First term corrects the arrival time to the solar system barycenter. Thats just Newtonian physics.Second term corrects clocks on earth. Thats SR and GR physics. This is independent of the source direction.Last term is a GR correction to the signal.

    Now, how do these correction terms compare to TEMPO.

    You see the difference of the correction terms between H.E.S.S. and TEMPO for the year 2004.The upper plot shows the TDB term, that is the solar system Einstein delay. The maximum deviation is 25 us.The lower plot shows the Solar system barycenter and the Shapiro delay term. The maximum deviation which is due to the Shapiro delay, is 0.12 ms.

    Of course, you have seen phasogramms from optical Crab measurements. Additionally, there have been young PSR studies. They are not effected! But maybe the 30 us jitter was due to those corrections.

    It gets worse if I take close ms PSR, with proper motion and parallax as I will show on the next slide.These two plots show again the timing and phase difference of H.E.S.S and TEMPO over the year 2004. This time I have used the ephemeris for J0437, including proper motion and parallax, which not negligible because of the small distance of only 140 pc.

    The upper plot shows the time difference for the whole barycenter correction. The maximal deviation is about 2 ms.The lower plot shows the corresponding difference in the phase using the 6 ms period of J0437.

    As you can easily see, the old H.E.S.S. software did not satisfy the needs for a long observation of a ms PSR!

    So, we implemented new algorithms.Here you see exactly the same plots with the same scale again, but now using the new algorithms we have developed.

    New is: the algorithms for all three barycenter correction termsMethods to read-in TEMPO and GRO parameter filesTwo binary models, I will talk about in a minute.

    Back to the plots, lets see zoom in, until we see a deviation.

    Thats it: zoomed in by a factor of 1000.

    So the new softwares barycenter correction is in agreement with TEMPO below 1 us!In the case of binary systems, there is significant acceleration, which has to be corrected too.

    There are many binary models around. We have decided to implement the two most important ones. This enables us to use most binray ephemerides.

    First, the Blandford-Teukolsy model. This model assumes a Keplerian ellipse but also accommodates additional effects.Second, the Damour-Deruelle model. This model is more general. The corre