Impact of planetary ephemerides on Pulsar Timing Arrays results

G. Theureau (USN/LPC2E), S. Babak (APC), A. Petteau (APC), L. Guillemot (LPC2E), S. Chen (LPC2E)

MODE-SNR-PWN Orléans 2019

Aurélien Chalumeau (APC/USN/LPC2E)

● Rotational params● Astrometric params● Orbital params● ISM effects● Clock correction● Transformation to the SSB● ...

The pulsar tming process

MODE-SNR-PWN Orléans 20192A. Chalumeaucf. Lorimer & Kramer 2005

Observational TOAs Timing model

Residuals

● Rotational params● Astrometric params● Orbital params● ISM effects● Clock correction● Transformation to the SSB● ...

Observational TOAs

The pulsar tming process

MODE-SNR-PWN Orléans 20193A. Chalumeau

Timing model

Residuals

cf. Lorimer & Kramer 2005

TOA transformaton to the SSB

MODE-SNR-PWN Orléans 20194A. Chalumeau

From the topocentric to the quasi-inertial solar system barycenter frame

cf. Lorimer & Kramer 2005

Römer delay Parallax

Shapiro

Einstein delay

Orbits of solar system bodies needed !

TOA transformaton to the SSB

MODE-SNR-PWN Orléans 20195A. Chalumeau

From the topocentric to the quasi-inertial solar system barycenter frame

cf. Lorimer & Kramer 2005

Predict positions and velocities of solar system bodies

Numerical integration of planetary motion fitted to the observational data

SSE produced by JPL, IMCCE, ….INPOP17a vs. DE436

Solar system ephemeris (SSEs)

MODE-SNR-PWN Orléans 20196A. Chalumeau

MODE-SNR-PWN Orléans 20197A. Chalumeau

A possible study : use PTA to constraint SSEs

cf. Caballero et al. 2018

➔ Mass constraints :● Planetary systems● Asteroid-belt objects

➔ Limits on unmodelled object masses

➔ ULs on putatve exotc object mass

MODE-SNR-PWN Orléans 20198A. Chalumeau

Impact of SSEs on PTA results

cf. Arzoumanian et al. 2018

Systematc biases larger than the statstcal uncertainty of the limits

SSE errors can mimic a GWB signal !

BAYESEPHEM model (11 parameters) to marginalize AGWB over ephemeris uncertaintiesGWB constraint gets robust against SSE errors

Problem : Modelling SSE errors can absorb some of the GWB signal

MODE-SNR-PWN Orléans 20199A. Chalumeau

Impact of SSEs on PTA resultsCharacterizaton of the impact of SSE errors

DE200INPOP17a

● Producton of perturbated SSEs

● Input perturbated SSEs in tming process

● Same for the full GWB search process

Using INPOP data with a direct expert support (cf. A. Fienga (Géoazur))

MODE-SNR-PWN Orléans 201910A. Chalumeau

Impact of SSEs on PTA resultsCharacterizaton of the impact of SSE errors

● Producton of perturbated SSEs

● Input perturbated SSEs in tming process

● Same for the full GWB search process

Using INPOP data with a direct expert support (cf. A. Fienga (Géoazur))

DE200INPOP17a

MODE-SNR-PWN Orléans 201911A. Chalumeau

Impact of SSEs on PTA resultsProducton of perturbated SSEs

Orbital elementsReference (P,V) Partal matrices Covariance matrix

MODE-SNR-PWN Orléans 201912A. Chalumeau

Conclusion

● PTA sensitvity limited by SSE imperfectons

● BAYESEPHEM corrects SSE systematcs but could subtract the sensitvity➔ Essental to characterize properly the impact on PTA results

● Perturbated SSE produced thanks to A. Fienga – PTA-France group collaboraton

● Next steps : ➔ Study the efects on tming residuals and pulsar parameters➔ Characterize properly the efects on GW search results

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