J/A+A/674/A25ivo://CDS.VizieR/J/A+A/674/A25doi:10.26093/cds/vizier.36740025CDSHoll B.Fabricius C.Portell J.Lindegren L.Panuzzo P.Bernet M.,Castaneda J.Jevardat de Fombelle G.Audard M.Ducourant C.,Harrison D.L.Evans D.W.Busso G.Sozzetti A.Gosset E.Arenou F.,De Angeli F.Riello M.Eyer L.Rimoldini L.Gavras P.Mowlavi N.,Nienartowicz K.Lecoeur-Taibi I.Garcia-Lario P.Pourbaix D.2024-11-06T20:04:45Z2023-06-16T13:11:48ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frsurveysvariable-starsphotometryvisible-astronomyradial-velocityGaia DR3 time series data may contain spurious signals related to the time-dependent scan angle. We aim to explain the origin of scan-angle dependent signals and how they can lead to spurious periods, provide statistics to identify them in the data, and suggest how to deal with them in Gaia DR3 data and in future releases. Using real Gaia (DR3) data, alongside numerical and analytical models, we visualise and explain the features observed in the data. We demonstrated with Gaia (DR3) data that source structure (multiplicity or extendedness) or pollution from close-by bright objects can cause biases in the image parameter determination from which photometric, astrometric and (indirectly) radial velocity time series are derived. These biases are a function of the time-dependent scan direction of the instrument and thus can introduce scan-angle dependent signals, which due to the scanning law induced sampling of Gaia can result in specific spurious periodic signals. Numerical simulations in which period search is performed on Gaia time series with a scan-angle dependent signal qualitatively reproduce the general structure observed in the spurious period distribution of photometry and astrometry, as well as the associated spatial distributions on the sky. A variety of statistics allows for the deeper understanding and identification of affected sources. The origin of the scan-angle dependent signals and subsequent spurious periods is well-understood and is in majority caused by fixed-orientation optical pairs with separation <0.5" (amongst which binaries with P>>5y) and (cores of) distant galaxies. Though the majority of sources with affected derived parameters have been filtered out from the Gaia archive nss_two_body_orbit and several vari-tables, there remain Gaia DR3 data that should be treated with care (note that no sources were filtered from gaia_source). Finally, the various statistics discussed in the paper can not only be used to identify and filter affected sources, but alternatively reveal new information about them not available through other means, especially in terms of binarity on sub-arcsecond scale.2023A&A...674A..25Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/674/A25CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/355 : Gaia DR3 Part 1: Main sourcesI/356 : Gaia DR3 Part 2: Extra-galacticI/357 : Gaia DR3 Part 3: Non-single starsI/358 : Gaia DR3 Part 4: VariabilityI/359 : Gaia DR3 Part 5: Solar SystemI/360 : Gaia DR3 Part 6: Performance verificationhttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/674/A25https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/674/A25http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/674/A25https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/674/A25https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/674/A25http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/674/A25GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/674/A25/vspursig (Spurious signals (vari\_vari\_spursign))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/674/A25/vspursig?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/674/A25/vspursig?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/674/A25/vspursig?GETtext/xml+votable180.050000true45.176533304080.26083015860.005555555555555556Gaia0/0-11 6/https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/674/A25?format=asciiOpticaldefaultJ/A+A/674/A25/vspursigSpurious signals (vari\_vari\_spursign)SourceSource Identifier (source_id)meta.id;meta.mainindexedRA_ICRSRight ascension (ICRS) at Ep=2016.0 (ra)degpos.eq.ra;meta.mainDE_ICRSDeclination (ICRS) at Ep=2016.0 (dec)degpos.eq.dec;meta.mainVarFlagPhotometric variability flag (phot_variable_flag)meta.code;src.varcharAnd[0/1] Flag indicating that the source is present in the Gaia Andromeda Photometric Survey (GAPS) (in_andromeda_survey)meta.code.statusintNobsAllNumber of observations in common for G, BP and RP bands, used in computation of the Spearman correlation excess factor fields (num_obs_common_all_bands)meta.numberintNobsgFoVNumber of selected observations of G FoV transits, used in the frequency fields (num_obs_g_fov)meta.numberintGLSFreqgFoVFrequency identified by Generalised Least Squares period search on G FoV timeseries (gls_freq_g_fov)d**-1stat.valuedoubleGLSFreqAmplgFoVNormalised amplitude of the frequency identified by Generalised Least Squares period search on G FoV timeseries (gls_freq_ampl_g_fov)stat.valuedoubleGLSFreqSDEgFoVSignal Detection Efficiency (SDE) of the frequency identified by Generalised Least Squares period search on G FoV timeseries (gls_freq_sde_g_fov)stat.snrdoubleGLSFreqFAPgFoVFalse Alarm Probability (FAP) of the frequency identified by Generalised Least Squares period search on G FoV timeseries (double) (gls_freq_fap_g_fov)stat.probabilitydoubleNHMFundFreqgFoV? Fundamental frequency identified by non-linear harmonic modelling on G FoV timeseries, initialised by the Generalised Least Squares frequency (nhm_fund_freq_g_fov)d**-1stat.valuedoublenullablee_NHMFundFreqgFoV? Uncertainty of the fundamental frequency identified by non-linear harmonic modelling on G FoV timeseries (nhm_fund_freq_error_g_fov)d**-1stat.errordoublenullablespearmanCorrExfgFoV? G-band FoV photometry Spearman correlation with corrected flux excess factor (spearman_corr_exf_g_fov)stat.correlationdoublenullableNobs-EPSLgFoVNumber of G-band FoV photometry observations excluding EPSL, used for the IPD correlation and scan angle modelling in the G band (num_obs_excl_epsl_g_fov)meta.numberintspearmanCorrIPDgFoV? G-band FoV photometry Spearman correlation with IPD model (spearman_corr_ipd_g_fov)stat.correlationdoublenullableSAMoffsetgFoV? Magnitude offset of the scan angle model fit to G-band FoV photometry (scan_angle_model_offset_g_fov)magstat.fit.paramdoublenullableSAMamplgFoV? Amplitude of the scan angle model fit to G-band FoV photometry (scan_angle_model_ampl_g_fov)magstat.fit.paramdoublenullableSAMamplSignigFoV? Significance of the amplitude of the scan angle model fit to G-band FoV photometry (scan_angle_model_ampl_sig_g_fov)stat.fit.goodnessdoublenullableSAMphasegFoV? Phase of the scan angle model fit to G-band FoV photometry (scan_angle_model_phase_g_fov)degstat.fit.paramdoublenullableSAMredchi2gFoV? Reduced Chi2 of the scan angle model fit to G-band FoV photometry (scan_angle_model_red_chi2_g_fov)stat.fit.goodnessdoublenullableSAMf2gFoV? F2 goodness-of-fit of the scan angle model fit to G-band FoV photometry (scan_angle_model_f2_g_fov)stat.fit.goodnessdoublenullablespearmanCorrExfBP? BP-band photometry Spearman correlation with corrected flux excess factor (spearman_corr_exf_bp)stat.correlationdoublenullableNobs-epslBPNumber of BP-band photometry observations excluding EPSL, used for the IPD correlation and scan angle modelling in the BP band (num_obs_excl_epsl_bp)meta.numberintspearmanCorrIPDBP? BP-band Spearman correlation with IPD model (spearman_corr_ipd_bp)stat.correlationdoublenullableSAMoffsetBP? Magnitude offset of the scan angle model fit to BP-band photometry (scan_angle_model_offset_bp)magstat.fit.paramdoublenullableSAMamplBP? Amplitude of the scan angle model fit to BP-band photometry (scan_angle_model_ampl_bp)magstat.fit.paramdoublenullableSAMamplSigniBP? Significance of the amplitude of the scan angle model fit to BP-band photometry (scan_angle_model_ampl_sig_bp)stat.fit.goodnessdoublenullableSAMphaseBP? Phase of the scan angle model fit to BP-band photometry (scan_angle_model_phase_bp)degstat.fit.paramdoublenullableSAMredchi2BP? Reduced Chi2 of the scan angle model fit to BP-band photometry (scan_angle_model_red_chi2_bp)stat.fit.goodnessdoublenullableSAMf2BP? F2 goodness-of-fit of the scan angle model fit to BP-band photometry (scan_angle_model_f2_bp)stat.fit.goodnessdoublenullablespearmanCorrExfRP? RP-band photometry Spearman correlation with corrected flux excess factor (spearman_corr_exf_rp)stat.correlationdoublenullableNobs-epslRPNumber of RP-band photometry observations excluding EPSL, used for the IPD correlation and scan angle modelling in the RP band (num_obs_excl_epsl_rp)meta.numberintspearmanCorrIPDRP? RP-band Spearman correlation with IPD model (spearman_corr_ipd_rp)stat.correlationdoublenullableSAMoffsetRP? Magnitude offset of the scan angle model fit to RP-band photometry (scan_angle_model_offset_rp)magstat.fit.paramdoublenullableSAMamplRP? Amplitude of the scan angle model fit to RP-band photometry (scan_angle_model_ampl_rp)magstat.fit.paramdoublenullableSAMamplSigniRP? Significance of the amplitude of the scan angle model fit to RP-band photometry (scan_angle_model_ampl_sig_rp)stat.fit.goodnessdoublenullableSAMphaseRP? Phase of the scan angle model fit to RP-band photometry (scan_angle_model_phase_rp)degstat.fit.paramdoublenullableSAMredchi2RP? Reduced Chi2 of the scan angle model fit to RP-band photometry (scan_angle_model_red_chi2_rp)stat.fit.goodnessdoublenullableSAMf2RP? F2 goodness-of-fit of the scan angle model fit to RP-band photometry (scan_angle_model_f2_rp)stat.fit.goodnessdoublenullable