Ephemeris errors and precision 4ming€¦ · Saturn of 3x10-10 solar masses, and consistent with signal observed in data Acons • IPTA joint analysis (globally search for M sat)

RyanM.ShannonICRAR-Cur(n&CSIROAstronomyandSpaceScience

Ephemeriserrorsandprecision4ming

Updatestotempo2*•  Newversionsofjplephlibraries/func4ons

•  Readephemeridesusingcalcephlibraries•  Consistentresultsusing“newandoldephemerisreadingmethods

•  Examineddifferencesinrealisa4onsofTT|differentephemerides•  DifferencesinTTsmall

•  CompareINPOP,NASA,andEPMephemerisseries

•  Grossdifferencesinephemerides•  Coordinatetransforma4ons(lesssoinlatestephemerides)•  SignificantnoiseinDE200andDE405

*(notyetcommiVedtobitbucketrepoL)

Ephemeriserrors|RyanShannon2|

Comparisonof1909datasets

•  PPTAJ1909-374410cmobserva4ons•  (12yr–throughMarch2016)

•  ProcessedusingDR1(Manchesteretal.2013)pipeline

•  Timingmodelincludesusualparameters+DM1

• Modelsshowdifferentgoodnessoffit•  DE414/418104ns->112ns(DE421)->123ns(DE430-435)•  Excessnoiserednoise(evidentwhenresidualsaveragedtogether)

•  DifferenceisassociatedwithchangeinhowSaturnismodelled •  Changeinmassby3e-10coincidentwithCassinimeasurements



Blue: DE421 Red: DE418


Simulated arrival times over > 40 years Simulated in DE418 and measured in DE421

After fitting for Msat, RA, DEC ΔMsat = 3x10-10 Msun

DifferencebetweenDE418andDE421

Ephemerides

•  Noisedifferent(levelandcolour)differbetweenephemerides

•  BothJPLandINPOPephemerideshavethesametrends•  Degrada4onin4mingprecisionwithephemeridespost-2008

•  Jacobsenetal.CassinimeasurementsofSaturniansystem


Chooseyourownephemeraladventure




In DE421 change in mass of Jupiter is favored over red noise by log(Evidence) of > 3



Published in March 2016 to correct Saturn’s position


DE430andSaturn Systematic offsets between ephemerides

Summaryandnextsteps

•  Systema4cdifferencesbetweenephemeridesmeasureableinourdatasets•  Poorer4mingprecisionmeasuredinmodernephemeridesinbothINPOPandJPLseries

•  DifferencesbetweenDE421andDE418consistentwithachangeinmassofSaturnof3x10-10solarmasses,andconsistentwithsignalobservedindata

Ac4ons•  IPTAjointanalysis(globallysearchforMsat)•  LiaisewithephemerisbuilderstobeVerunderstandtheeffects(ongoing)•  LiaisewithCassinicrewtoseeiftheyhaveanupdatedSaturnmass


Comparisonofdatasets (DFB4throughJune2015)

•  DR1–DM2(212.69/167=1.27357)•  DR2–DM2(222.56/167=1.33269)

•  DR1-DM1(213.06/168=1.26824)•  DR2-DM1(222.88/168=1.32669)

•  DR1-DM0(220.65/169=1.30563)•  DR2-DM0(222.98/169=1.31938)•  DR1:-14.79•  DR2:-14.67

•  EQUADslightlylargerinDR2•  EQUADincreaseswithDR2


(AllthroughJune2015)

•  DR1-DM0(516.72/320=1.61475)•  DR1-DM1(513.17/319=1.60869)•  DR1-DM2(510.28/318=1.60466)

•  DR2-DM0(0.114,544.76/320=1.70236)•  DR2-DM1(0.114,544.67/319=1.70742)•  DR2-DM2(0.114,543.44/318=1.70892)

Evidencecomparison

MarginalevidenceinfavourofSaturnoverrednoise

•  DE418(withPS,RN)(6665.6)•  DE418(noPS,RN)(6665.1)•  DE421(withPS,RN)(6660.7)•  DE421(withPS,RN,Saturn)(6663.2)•  DE421(withPS,noRN,Saturn)(6661.8)


Documents

Ephemeris errors and precision 4ming€¦ · Saturn of 3x10-10 solar masses, and consistent with signal observed in data Acons • IPTA joint analysis (globally search for M sat)