timing studies and psr j0437-4715 analysis
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Timing studies and PSR J0437-4715 analysis. Till Eifert, HU Berlin April, 2005. Outline. Analysis of pulsar timing data Improvement of barycenter correction Implementation of binary correction PSR J0437-4715 Data analysis, first results Conclusion / Outlook. - PowerPoint PPT PresentationTRANSCRIPT
Timing studies and PSR J0437-4715 analysis
Till Eifert, HU Berlin
April, 2005
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 2
Outline
○ Analysis of pulsar timing data
• Improvement of barycenter correction
• Implementation of binary correction
○ PSR J0437-4715
• Data analysis, first results
○ Conclusion / Outlook
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 3
Analysis of pulsar timing data
Given: GPS event time stamp from CentralTrigger
intrinsic accuracy of GPS 10 μs
~ 30 μs 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 astronomers
○ Evolving since 1972
○ Accuracy < μs range, proved by extensive tests with 6 years of data.
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 4
Barycenter correction
t = 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
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 5
CRASH vs. TEMPO
CRASH vs. TEMPO timing corrections:
○ ∆tE (TDB) (< 25 μs)
○ ∆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)
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 6
CRASH vs. TEMPO
PSR 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)
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 7
Improvements
New in Crash module:
○ New TDB algorithm
○ New barycenter algorithm,
taking into account:
• Shapiro delay
• Proper motion
• Parallax
○ New routines to read in
TEMPO and GRO parameter
files
○ Two binary models added
∆tbary (Crash – Tempo)
∆p (Crash – Tempo)
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 8
Improvements (zoomed)
New in Crash module:
○ New TDB algorithm
○ New barycenter algorithm,
taking into account:
• Shapiro delay
• Proper motion
• Parallax
○ New routines to read in
TEMPO and GRO parameter
files
○ Two binary models added
∆tbary (Crash – Tempo)
∆p (Crash – Tempo)
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 9
Binary models
PSR in binary system → significant acceleration
Blandford-Teukolsky (BT) model:
○ Keplerian ellipse
○ Newtonian dynamics
○ Einstein delay patched into model afterwards
○ additional effects are accommodated by nonzero time derivatives
Damour-Deruelle (DD) model:
○ more general
○ Roemer time delay
○ Orbital Einstein and Shapiro delay
○ Aberration caused by rotation
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 10
Checking BT model correction against TEMPO
∆tbinary < 10-9 s
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 11
Checking DD model correction against TEMPO
∆tbinary < 10-10 s
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 12
Outline
○ Analysis of pulsar timing data
• Improvement of barycenter correction
• Implementation of binary correction
○ PSR J0437-4715
• Data analysis, first results
○ Conclusion / Outlook
→ New code: good agreement (<μs) with TEMPO
Code will be merged with CVS head soon
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 13
PSR J0437-4715
○ Distance ~ 140 pc
○ P ~ 5.75 ms, dP/dt ~ 10-20
○ Low B ~ 108 -1010G
○ Binary orbit ~ 5.74 days
○ Low mass companion ~ 0.2 M
○ Not eclipsing
○ No optical brightness variation
○ Pulsed emission visible in radio,
X-rays Harding, A.K., Usov, V. V., Muslimov, A. G., 2005, ApJ, 622, 531
Polar Cap model prediction
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 14
PSR J0437-4715
Radio observation at Parkes
Two phase cycles!
ROSAT High Resolution Imager (HRI)
ROSAT Position Sensitive Proportional Counter (PSPC)
Chandra High Resolution Camera (HRC)
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 15
Data analysis
○ Data from October 2004
○ 22 runs with 4 telescopes (passed quality check), ~ 9.1 h livetime
○ Zenith angle range: 23.9 – 30 deg
○ Energy threshold ~ 200 GeV
○ Std. Hd Cuts: desert/phase1_0510_south
○ Background model: SevenBackgroundMaker
○ PSR analysis: ephemeris from ATNF
○ Statistical tests: Z2, H
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 16
DC analysis
Std. Hd cuts
9.1 h livetime
Significance: 0.4 σ
…
What about AC?
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 17
Timing analysis
Question: just a fluctuation or possible hint for pulsed TeV emission?
(note: fluctuation is on the right phase position!)
On region
Z21 = 5.6 (Prob. 0.06)
Z22 = 5.7 (Prob. 0.23)
H = 5.6
OFF region with highest H = 3.8
All energies, DC: 0.4 σ
OFF regions (summed)
~ flat
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 18
Timing analysis, energy bins
On region
Z21 = 6.4 (Prob. 0.04)
Z22 = 6.7 (Prob. 0.15)
H = 6.4
All energies < 0.5 TeV, DC: 0.5 σ
OFF regions flat
All energies > 0.5 TeV, DC: -0.2 σ
On region
Z21 = 0.2 (Prob. 0.92)
Z22 = 2.2 (Prob. 0.70)
H = 0.2
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 19
Zenith angle
0
0.5
1
1.5
2
2.5
3
24 25 26 27 28 29 30 31
Zenith angle [deg]
DC
Sig
nif
ican
ce [
sig
ma]
DC SignificanceEnergy < 0.5 TeV
Maximize signal/noise ratio for low energy by using very small
zenith angles only
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 20
Timing analysis All energies < 0.5 TeV, zenith angle < 25 deg
On regionDC: 2.0 σ 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 !
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 21
Conclusion / Outlook
○ We have developed and tested the tools to analyse
ms PSR (sub μs agreement with TEMPO)
○ It is difficult to ignore the fluctuation at the right
phase position
○ Optimizing cuts on MC with exp. cut-off spectra
○ Cross-check with Mathieu’s model analysis
○ We need more data with very low zenith angle
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 22
Leap seconds in UTC
|UT1-UTC| < 0.9 seconds
→ leap seconds
UT1: time scale based on the Earth’s rotation (irregular fluctuations, general
slowing down)
UTC: TAI (International Atomic Time) + leap seconds
Taken from Earth Orientation Center
H.E.S.S. Collaboration Meeting, Palaiseau , 2005 Till Eifert, HU Berlin p. 23
Data analysis
On region
Z21 = 9.1 (Prob. 0.01)
Z22 = 9.3 (Prob. 0.05)
H = 9.1
All energies: 0.2 - 0.45 TeV, all zenith angle