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I/345                      Gaia DR2                   (Gaia Collaboration, 2018)

Gaia data release 2 (Gaia DR2). Gaia collaboration <Astron. Astrophys., in prep. (2018)> =2018A&A..in.prep...G =2018yCat.1345....0G
ADC_Keywords: Surveys ; Stars, standard ; Positional data ; Proper motions ; Photometry, photographic ; Cross identifications ; Radial velocities ; Stars, variable ; Minor planets Mission_Name: Gaia Keywords: catalogs - astrometry - techniques: radial velocities - stars: fundamental parameters - stars: variables: general - minor planets, asteroids: general Abstract: Gaia Data Release 2. Summary of the contents and survey properties: We present the second Gaia data release, Gaia DR2, consisting of astrometry, photometry, radial velocities, and information on as- trophysical parameters and variability, for sources brighter than magnitude 21. In addition epoch astrometry and photometry are provided for a modest sample of minor planets in the solar system. A summary of the contents of Gaia DR2 is presented, accompanied by a discussion on the differences with respect to Gaia DR1 and an overview of the main limitations which are still present in the survey. Recommendations are made on the responsible use of Gaia DR2 results. Methods. The raw data collected with the Gaia instruments during the first 22 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into this second data release, which represents a major advance with respect to Gaia DR1 in terms of completeness, performance, and richness of the data products. Gaia DR2 contains celestial positions and the apparent brightness in G for approximately 1.7 billion sources. For 1.3 billion of those sources, parallaxes and proper motions are in addition available. The sample of sources for which variability information is provided is expanded to 0.5 million stars. This data release contains four new elements: broad-band colour information in the form of the apparent brightness in the GBP (330-680nm) and GRP (630-1050nm) bands is available for 1.4 billion sources; median radial velocities for some 7 million sources are presented; for between 77 and 161 million sources estimates are provided of the stellar effective temperature, extinction, reddening, and radius and luminosity; and for a pre-selected list of 14000 minor planets in the solar system epoch astrometry and photometry are presented. Finally, Gaia DR2 also represents a new materialisation of the celestial reference frame in the optical, the Gaia-CRF2, which is the first optical reference frame based solely on extragalactic sources. There are notable changes in the photometric system and the catalogue source list with respect to Gaia DR1, and we stress the need to consider the two data releases as independent. Gaia DR2 represents a major achievement for the Gaia mission, delivering on the long standing promise to provide parallaxes and proper motions for over 1 billion stars, and representing a first step in the availability of complementary radial velocity and source astrophysical information for a sample of stars in the Gaia survey which covers a very substantial fraction of the volume of our galaxy. The catalogue of radial velocity standard stars (Soubiran et al., 2018A&A..in.prep...) The Radial Velocity Spectrometer (RVS) on board of Gaia having no calibration device, the zero point of radial velocities needs to be calibrated with stars proved to be stable at the level of 300m/s during the Gaia observations. A dataset of about 71000 ground-based radial velocity measurements from five high resolution spectrographs has been compiled. A catalogue of 4813 stars was built by combining these individual measurements. The zero point has been established using asteroids. The resulting catalogue has 7 observations per star on average on a typical time baseline of 6 years, with a median standard deviation of 15m/s. A subset of the most stable stars fulfilling the RVS requirements has been used to establish the zero point of the radial velocities provided in Gaia DR2. The stars not used for calibration are used for the RVS data validation. Description: Contents of Gaia DR2: The five-parameter astrometric solution - positions on the sky (alpha,delta), parallaxes, and proper motions - for more than 1.3 billion (109) sources, with a limiting magnitude of G=21 and a bright limit of G~=3. Parallax uncertainties are in the range of up to 0.04 milliarcsecond for sources at G<15, around 0.1mas for sources with G=17 and at the faint end, the uncertainty is of the order of 0.7mas at G=20. The corresponding uncertainties in the respective proper motion components are up to 0.06mas/yr (for G<15mag), 0.2mas/yr (for G=17mag) and 1.2mas/yr (for G=20mag). The Gaia DR2 parallaxes and proper motions are based only on Gaia data; they do no longer depend on the Tycho-2 Catalogue. Median radial velocities (i.e. the median value over the epochs) for more than 6 million stars with a mean G magnitude between about 4 and 13 and an effective temperature (Teff) in the range of about 3550 to 6900K. This leads to a full six-parameter solution: positions and motions on the sky with parallaxes and radial velocities, all combined with mean G magnitudes. The overall precision of the radial velocities at the bright end is in the order of 200-300m/s while at the faint end the overall precision is approximately 1.2km/s for a Teff of 4750K and about 2.5km/s for a Teff of 6500K. An additional set of more than 200 million sources for which a two-parameter solution is available: the positions on the sky (alpha,delta) combined with the mean G magnitude. These sources will have a positional uncertainty at G=20 of about 2mas, at J2015.5. G magnitudes for more than 1.5 billion sources, with precisions varying from around 1 milli-mag at the bright (G<13) end to around 20 milli-mag at G=20. Please be aware that the photometric system for the G band in Gaia DR2 will be different from the photometric system as used in Gaia DR1. GBP and GRP magnitudes for more than 1.1 billion sources, with precisions varying from a few milli-mag at the bright (G<13) end to around 200 milli-mag at G=20. Full passband definitions for G, BP and RP. These passbands are now available for download. A detailed description is given here. Epoch astrometry for more than 13,000 known asteroids based on more than 1.5 million CCD observations. 96% of the along-scan (AL) residuals are in the range -5 to 5mas, and 52% of the AL residuals are in the range of -1 to 1mas. The observations will be published in Gaia DR2 and also delivered to the Minor Planet Center (MPC). Subject to limitations the effective temperatures Teff for more than 150 million sources brighter than 17th magnitude with effective temperatures in the range 3000 to 10,000 K. For a subset of these sources also the line-of-sight extinction AG and reddening E(BP-RP) will be given, as well as the luminosity and radius. Lightcurves for more than 500,000 variable sources consisting of Cepheids, RR Lyrae, Mira and Semi-Regular Candidates as well as High-Amplitude Delta Scuti, BY Draconis candidates, SX Phoenicis Candidates and short time scale phenomena. Planned cross-matches between Gaia DR2 sources on the one hand and Hipparcos-2, Tycho-2, 2MASS PSC, SDSS DR9, Pan-STARRS1, GSC2.3, PPM-XL, AllWISE, and URAT-1 data on the other hand. Catalogue of radial velocity standard stars (Soubiran et al., 2018A&A..in.prep...): Individual and combined radial velocity measurements are presented for 4813 stars in rvstdcat.dat and rvstdmes.dat files. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file gaia2.sam 896 1000 GaiaSource DR2 data rvstdcat.dat 270 4813 Mean radial velocities on absolute scale rvstdmes.dat 76 71225 Original ground-based radial velocity measurements allwise.dat 39 555934 Allwise AGN Gaia DR2 cross-identification (auxallwiseagngdr2cross_id) iers.dat 28 2820 IERS GaiaDR2 cross-identification (auxiersgdr2crossid) cepheid.dat 435 9575 Cepheid stars (vari_cepheid) rrlyrae.dat 378 140784 RR Lyrae stars (vari_rrlyrae) lpv.dat 94 89617 Long Period Variable stars (varilongperiod_variable) varres.dat 70 363969 Variability classification results of all classifiers, identified by the classifierName column (variclassifierresult) shortts.dat 91 3018 Short-timescale sources (varishorttimescale) tsstat.dat 432 550737 Statistical parameters of time series, using only transits not rejected (varitimeseries_statistics) numtrans.dat 43 550737 Calibrated FoV transit photometry from CU5, consolidated and provided by CU7 for variable stars in Gaia DR2 (epoch_photometry, part 1) transits.dat 365 17712391 Calibrated FoV transit photometry for CU5, consolidated and provided by CU7 for variable stars in Gaia DR2 (epoch_photometry, part 2) rm.dat 137 147535 Rotation period in segment, part 1 (varirotationmodulation) rmseg.dat 276 583988 Rotation period in segment, part 2 (varirotationmodulation) rmout.dat 33 990561 Rotation period in segment, part 3 (varirotationmodulation) ssoobj.dat 59 14099 *Data related to Solar System objects observed by Gaia (sso_source) ssoorb.dat 181 14099 *Auxiliary information on asteroid orbits and basic photometric parameters (auxssoorbits) ssores.dat 155 1977702 *Residuals with respect to an orbital fit considering only the Gaia observations (auxssoorbit_residuals) ssoobs.dat 404 1977702 *Solar System object observations (sso_observation)
Note on ssoobj.dat: The quantities in the table are derived from data reduction and are associated to single objects. Note on ssoorb.dat: from the astorb database (Cat. B/astorb). Note on ssores.dat: Each entry has a corresponding record in the table ssoobs.dat. A flag is given, indicating if the observation has been rejected by the fit procedure. Note on ssoobs.dat: Each table line contained data obtained during the transit of the source on a single CCD, during a single transit. The corresponding epoch is provided. Data not varying within the transit are repeated identically for all single observations of that transit.
See also: B/astorb : Orbits of Minor Planets (Bowell+ 2014) II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) II/328 : AllWISE Data Release (Cutri+ 2013) I/337 : Gaia DR1 (Gaia Collaboration, 2016) Byte-by-byte Description of file: gaia2.sam
Bytes Format Units Label Explanations
1- 28 A28 --- DR2Name Unique source designation (unique across all Data Releases) (Gaia DR2 NNNNNNNNNNNNNNNNNNN) (designation) (1) 30- 44 F15.11 deg RAdeg Barycentric right ascension (ICRS) at Ep=2015.5 (ra) 46- 60 F15.11 deg DEdeg Barycentric declination (ICRS) at Ep=2015.5 (dec) 62- 80 I19 --- SolID Solution Identifier (solution_id) (G1) 82-100 I19 --- Source Unique source identifier (unique within a particular Data Release) (source_id) (G2) 102-111 I10 --- RandomI Random index used to select subsets (random_index) (2) 113-118 F6.1 yr Epoch [2015.5] Reference epoch (ref_epoch) 120-126 F7.4 mas e_RAdeg Standard error of right ascension (e_RA*cosDE) (ra_error) 128-134 F7.4 mas e_DEdeg Standard error of declination (dec_error) 136-145 F10.4 mas Plx ? Absolute stellar parallax (parallax) 147-152 F6.4 mas e_Plx ? Standard error of parallax (parallax_error) 154-163 F10.4 --- RPlx ? Parallax divided by its error (parallaxovererror) 165-173 F9.3 mas/yr pmRA ? Proper motion in right ascension direction (pmRA*cosDE) (pmra) (3) 175-179 F5.3 mas/yr e_pmRA ? Standard error of proper motion in right ascension direction (pmra_error) 181-189 F9.3 mas/yr pmDE ? Proper motion in declination direction (pmdec) (4) 191-195 F5.3 mas/yr e_pmDE ? Standard error of proper motion in declination direction (pmdec_error) 197-203 F7.4 --- RADEcor Correlation between right ascension and declination (radeccorr) 205-211 F7.4 --- RAPlxcor ? Correlation between right ascension and parallax (raparallaxcorr) 213-219 F7.4 --- RApmRAcor ? Correlation between right ascension and proper motion in right ascension (rapmracorr) 221-227 F7.4 --- RApmDEcor ? Correlation between right ascension and proper motion in declination (rapmdeccorr) 229-235 F7.4 --- DEPlxcor ? Correlation between declination and parallax (decparallaxcorr) 237-243 F7.4 --- DEpmRAcor ? Correlation between declination and proper motion in right ascension (decpmracorr) 245-251 F7.4 --- DEpmDEcor ? Correlation between declination and proper motion in declination (decpmdeccorr) 253-259 F7.4 --- PlxpmRAcor ? Correlation between parallax and proper motion in right ascension (parallaxpmracorr) 261-267 F7.4 --- PlxpmDEcor ? Correlation between parallax and proper motion in declination (parallaxpmdeccorr) 269-275 F7.4 --- pmRApmDEcor ? Correlation between proper motion in right ascension and proper motion in declination (pmrapmdeccorr) 277-280 I4 --- NAL Total number of observations AL (astrometricnobs_al) (6) 282-285 I4 --- NAC Total number of observations AC (astrometricnobs_ac) (7) 287-290 I4 --- NgAL Number of good observations AL (astrometricngoodobsal) (8) 292-294 I3 --- NbAL Number of bad observations AL (astrometricnbadobsal) (9) 296-304 F9.4 --- gofAL Goodness of fit statistic of model wrt along-scan observations (astrometricgofal) (10) 306-316 F11.2 --- chi2AL AL chi-square value (astrometricchi2al) (11) 318-323 F6.3 mas epsi Excess noise of the source (astrometricexcessnoise) (12) 325-334 E10.3 --- sepsi Significance of excess noise (astrometricexcessnoise_sig) (13) 336-337 I2 --- Solved Which parameters have been solved for? (astrometricparamssolved) (14) 339 I1 --- APF Primary or secondary (astrometricprimaryflag) (15) 341-348 F8.4 mas-2 WAL Mean astrometric weight of the source (astrometricweightal) (16) 350-356 F7.4 um-1 pscol ? Astrometrically determined pseudocolour of the source (astrometricpseudocolour) (17) 358-363 F6.4 um-1 e_pscol ? Standard error of the pseudocolour of the source (astrometricpseudocolour_error) 365-370 F6.3 --- fvarpi Mean Parallax factor AL (meanvarpifactor_al) 372-374 I3 --- MatchObsA Matched FOV transits used in the AGIS solution (astrometricmatchedobservations) (18) 376-377 I2 --- Nper Number of visibility periods used in Astrometric solution (visibilityperiodsused) 379-389 E11.6 mas amax The longest semi-major axis of the 5-d error ellipsoid (astrometricsigma5dmax) (19) 391 I1 --- type [0/3] The type of the source mainly used for frame rotation (framerotatorobject_type) (20) 393-395 I3 --- MatchObs The total number of FOV transits matched to this source (matched_observations) 397 I1 --- Dup [0/1] Source with duplicate sources (duplicated_source) (21) 399-402 I4 --- o_Gmag Number of observations contributing to G photometry (photgn_obs) (22) 404-414 E11.5 e-/s FG G-band mean flux (photgmean_flux) 416-426 E11.5 e-/s e_FG Error on G-band mean flux (photgmeanfluxerror) 428-436 F9.3 --- RFG G-band mean flux divided by its error (photgmeanfluxover_error) 438-446 F9.6 mag Gmag G-band mean magnitude (Vega) (photgmean_mag) (23) 448-450 I3 --- o_BPmag Number of observations contributing to BP photometry (photbpn_obs) (24) 452-462 E11.5 e-/s FBP ? Mean flux in the integrated BP band (photbpmean_flux) 464-474 E11.5 e-/s e_FBP ? Error on the integrated BP mean flux (photbpmeanfluxerror) (25) 476-484 F9.3 --- RFBP ? Integrated BP mean flux divided by its error (photbpmeanfluxover_error) 486-494 F9.6 mag BPmag ? Integrated BP mean magnitude (Vega) (photbpmean_mag) (26) 496-498 I3 --- o_RPmag ? Number of observations contributing to RP photometry (photrpn_obs) (27) 500-510 E11.5 e-/s FRP ? Mean flux in the integrated RP band (photrpmean_flux) 512-522 E11.5 e-/s e_FRP ? Error on the integrated RP mean flux (photrpmeanfluxerror) (28) 524-532 F9.3 --- RFRP ? Integrated RP mean flux divided by its error (photrpmeanfluxover_error) 534-542 F9.6 mag RPmag ? Integrated RP mean magnitude (Vega) (photrpmean_mag) (29) 544-548 F5.3 --- E(BR/RP) ? BP/RP excess factor (photbprpexcessfactor) 550 I1 --- Mode Photometry processing mode (photprocmode) 552-560 F9.6 mag BP-RP ? BP-RP colour (photBpMeanMag-photRMeanMag) (bp_rp) 562-570 F9.6 mag BP-G ? BP-G colour (photBpMeanMag-photGMeanMag) (bp_g) 572-580 F9.6 mag G-RP ? G-RP colour (photGMeanMag-photRpMeanMag) (g_rp) 582-588 F7.2 km/s RV ? Spectroscopic radial velocity in the solar barycentric reference frame (radial_velocity) 590-594 F5.2 km/s e_RV ? Radial velocity error (radialvelocityerror) (30) 596-598 I3 --- o_RV Number of transits used to compute radial velocity (rvnbtransits) 600-605 F6.1 K Tefftemp ? Teff of the template used to compute radial velocity (rvtemplateteff) (36) 607-610 F4.1 [cm/s2] loggtemp ? logg of the template used to compute radial velocity (rvtemplatelogg) (36) 612-615 F4.1 --- [Fe/H]temp ? Fe/H of the template used to compute radial velocity (rvtemplatefe_h) (36) 617-629 A13 --- Var Photometric variability flag (photvariableflag) (31) 631-644 F14.10 deg GLON Galactic longitude (l) (32) 646-659 F14.10 deg GLAT Galactic latitude (b) (32) 661-674 F14.10 deg ELON Ecliptic longitude (ecl_lon) (33) 676-689 F14.10 deg ELAT Ecliptic latitude (ecl_lat) (33) 691-696 I6 --- fPriam ? Flags for the Apsis-Priam results (priam_flags) (34) 698-704 F7.2 K Teff ? Stellar effective temperature (estimate from Apsis-Priam) (teff_val) 706-712 F7.2 K b_Teff ? Uncertainty (lower) on Teff estimate from Apsis-Priam (16th percentile) (teffpercentilelower) 714-720 F7.2 K B_Teff ? Uncertainty (upper) on Teff estimate from Apsis-Priam (84th percentile) (teffpercentileupper) 722-727 F6.4 mag AG ? Estimate of extinction in the G band from Apsis-Priam (agval) 729-734 F6.4 mag b_AG ? Uncertainty (lower) on AG estimate from Apsis-Priam (16th percentile) (agpercentile_lower) 736-741 F6.4 mag B_AG ? Uncertainty (upper) on AG estimate from Apsis-Priam (84th percentile) (agpercentile_upper) 743-748 F6.4 mag E(BP-RP) ? Estimate of redenning E(BP-RP) from Apsis-Priam (ebpminrpval) 750-755 F6.4 mag b_E(BP-RP) ? Uncertainty (lower) on E(BP-RP) estimate from Apsis-Priam (16th percentile) (ebpminrppercentile_lower) 757-762 F6.4 mag B_E(BP-RP) ? Uncertainty (upper) on E(BP-RP) estimate from Apsis-Priam (84th percentile) (ebpminrppercentile_upper) 764-769 I6 --- fFLAME ? Flags for the Apsis-FLAME results (flame_flags) (35) 771-776 F6.2 solRad Rad ? Estimate of radius from Apsis-FLAME (radius_val) 778-783 F6.2 solRad b_Rad ? Uncertainty (lower) on radius estimate from Apsis-FLAME (16th percentile) (radiuspercentilelower) 785-791 F7.2 solRad B_Rad ? Uncertainty (upper) on radius estimate from Apsis-FLAME (84th percentile) (radiuspercentileupper) 793-801 F9.3 solLum Lum ? Esimate of luminosity from Apsis-FLAME (lum_val) 803-811 F9.3 solLum b_Lum ? Uncertainty (lower) on luminosity estimate from Apsis-FLAME (16th percentile) (lumpercentilelower) 813-821 F9.3 solLum B_Lum ? Uncertainty (upper) on luminosity estimate from Apsis-FLAME (84th percentile) (lumpercentileupper) 823-837 F15.11 deg RAJ2000 Barycentric right ascension (ICRS) at Ep=2000.0 (added by CDS) (ra_epoch2000) 839-845 F7.4 mas e_RAJ2000 Standard error of right ascension (e_RA*cosDE) (added by CDS) (raepoch2000error) 847-861 F15.11 deg DEJ2000 Barycentric declination (ICRS) at Ep=2000.0 (added by CDS) (dec_epoch2000) 863-869 F7.4 mas e_DEJ2000 Standard error of declination (added by CDS) (decepoch2000error) 871-878 F8.6 mag e_Gmag Standard error of G-band mean magnitude (Vega) (added by CDS) (photgmeanmagerror) (37) 880-887 F8.6 mag e_BPmag ? Standard error of BP mean magnitude (Vega) (added by CDS) (photbpmeanmagerror) (37) 889-896 F8.6 mag e_RPmag ? Standard error of RP mean magnitude (Vega) (added by CDS) (photrpmeanmagerror) (37)
Note (1): A source designation, unique across all Gaia Data Releases, that is constructed from the prefix "Gaia DRx" followed by a string of digits corresponding to source_id (3 space-separated words in total). Note that the integer source identifier source_id is NOT guaranteed to be unique across Data Releases; moreover it is not guaranteed that the same astronomical source will always have the same source_id in different Data Releases. Hence the only safe way to compare source records between different Data Releases in general is to check the records of proximal source(s) in the same small part of the sky. Note (2): Random index which can be used to select smaller subsets of the data that are still representative. The column contains a random permutation of the numbers from 0 to N-1, where N is the number of rows. The random index can be useful for validation (testing on 10 different random subsets), visualization (displaying 1% of the data), and statistical exploration of the data, without the need to download all the data. Note (3): Proper motion in right ascension µα*~µαcosδ of the source in ICRS at the reference epoch ref_epoch. This is the tangent plane projection of the proper motion vector in the direction of increasing right ascension. Note (4): Proper motion in declination µ_δ of the source at the reference epoch ref_epoch. This is the tangent plane projection of the proper motion vector in the direction of increasing declination. Note (6): Total number of AL observations (= CCD transits) used in the astrometric solution of the source, independent of their weight. Note that some observations may be strongly downweighted (see astrometricNBadObsAl). Note (7): Total number of AC observations (= CCD transits) used in the astrometric solution of the source, independent of their weight. Note that some observations may be strongly downweighted (see astrometricNBadObsAc). Nearly all sources having G<13 will have AC observations from 2d windows, while fainter than that limit only ∼1% of transit observations (the so-called "calibration faint stars") are assigned 2d windows resulting in AC observations. Note (8): Number of AL observations (= CCD transits) that were not strongly downweighted in the astrometric solution of the source. Strongly downweighted observations (with downweighting factor w<0.2) are instead counted in astrometricNBadObsAl. The sum of astrometricNGoodObsAl and astrometricNBadObsAl equals astrometricNObsAl, the total number of AL observations used in the astrometric solution of the source. Note (9): Number of AL observations (= CCD transits) that were strongly downweighted in the astrometric solution of the source, and therefore contributed little to the determination of the astrometric parameters. An observation is considered to be strongly downweighted if its downweighting factor w<0.2, which means that the absolute value of the astrometric residual exceeds 4.83 times the total uncertainty of the observation, calculated as the quadratic sum of the centroiding uncertainty, excess source noise, and excess attitude noise. Note (10): Goodness-of-fit statistic of the astrometric solution for the source in the along-scan direction. This is the 'gaussianized chi-square', which for good fits should approximately follow a normal distribution with zero mean value and unit standard deviation. Values exceeding, say, +3 thus indicate a bad fit to the data. This statistic is computed according to the formula astrometricGofAl=(9ν/2)1/2 [(χ2/ν)1/3^ + 2/(9ν)-1] where χ2=astrometricChi2Al is theAL chi-square statistic and ν=astrometricNGoodObsAl-N is the number of degrees of freedom for a source update. Here N=5 is the number of astrometric parameters. Note that only "good" (i.e. not strongly downweighted) observations are included in χ2 and ν. The above formula is the well-known cube-root transformation of the chi-square variable (E.B. Wilson & M.M. Hilferty 1931, Proc. National Academy of Science, 17, 684). It is usually quoted to be valid for ν>30, but is in fact useful for much smaller ν. This transformation of (χ2, ν) eliminates the inconvenience of having the distribution (and hence the significance levels) depend on the additional variable ν, which is generally not the same for different sources. An alternative indicator of bad fits is the astrometricExcessNoise. In AGIS the source update deals with bad fits by adding astrometricExcessNoise to the formal observation noise. This reduces the weight of the observations and inflates the covariance of the estimated astrometric parameters correspondingly. However, the chi-square values used to calculate astrometricGofAl do not take into account the astrometricExcessNoise, and astrometricGofAl can therefore always be used as a goodness-of-fit indicator of the source solution in AGIS. Note (11): Description:Astrometric goodness-of-fit (χ2) in the AL direction. χ2 values were computed for the 'good' AL observations of the source, without taking into account the astrometricExcessNoise (if any) of the source. They do however take into account the attitude excess noise (if any) of each observation. Note (12):This is the excess noise εi of the source. It measures the disagreement, expressed as an angle, between the observations of a source and the best-fitting standard astrometric model (using five astrometric parameters). The assumed observational noise in each observation is quadratically increased by εi in order to statistically match the residuals in the astrometric solution. A value of 0 signifies that the source is astrometrically well-behaved, i.e. that the residuals of the fit statistically agree with the assumed observational noise. A positive value signifies that the residuals are statistically larger than expected. The significance of εi is given by astrometricExcessNoiseSig (D). If D≤2 then εi is probably not significant, and the source may be astrometrically well-behaved even if εi is large. The excess noise εi may absorb all kinds of modelling errors that are not accounted for by the observational noise (image centroiding error) or the excess attitude noise. Such modelling errors include LSF and PSF calibration errors, geometric instrument calibration errors, and part of the high-frequency attitude noise. These modelling errors are particularly important in the early data releases, but should decrease as the astrometric modelling of the instrument and attitude improves over the years. Additionally, sources that deviate from the standard five-parameter astrometric model (e.g. unresolved binaries, exoplanet systems, etc.) may have positive εi. Given the many other possible contributions to the excess noise, the user must study the empirical distributions of εi and D to make sensible cutoffs before filtering out sources for their particular application. Note (13): Adimensionless measure (D) of the significance of the calculated astrometricExcessNoise (εi). A value D>2 indicates that the given εi is probably significant. For good fits in the limit of a large number of observations, D should be zero in half of the cases and approximately follow the positive half of a normal distribution with zero mean and unit standard deviation for the other half. Consequently, D is expected to be greater than 2 for only a few percent of the sources with well-behaved astrometric solutions. In the early data releases εi will however include instrument and attitude modelling errors that are statistically significant and could result in large values of εi and D. The user must study the empirical distributions of these statistics and make sensible cutoffs before filtering out sources for their particular application. Note (14): This is a binary code indicating which astrometric parameters were estimated for the source. A set bit means the parameter was estimated. The least-significant bit represents α, the next bits δ, ϖ, µα*, and µδ. For Gaia DR2the only relevant values are - astrometricParamsSolved=31 (binary 11111): all five astrometric parameters were estimated - astrometricParamsSolved=3 (binary 11): only position (α, δ) was estimated Note (15): Flag indicating if this source was used as a primary source (true) or secondary source (false). Only primary sources contribute to the estimation of attitude, calibration, and global parameters. The estimation of source parameters is otherwise done in exactly the same way for primary and secondary sources. Note (16): Mean astrometric weight of the source in the AL direction. The mean astrometric weight of the source is calculated as per Eq. (119). Note (17): Colour of the source assumed in the final astrometric processing. The astrometricPseudoColour is defined to be equivalent to the effective wavenumber of the photon flux distribution in the astrometric (G) band, and is measured in um-1. The value given in this field was astrometrically determined in a preliminary solution, using the chromatic displacement of image centroids calibrated by means of the effective wavenumbers (νeff) of primary sources calculated from BP and RP magnitudes. The field is empty when no such determination was possible, in which case a default value of 1.6um-1 was assumed. Note (18): The number of FOV transits matched to this source, counting only the transits containing CCD observations actually used to compute the astrometric solution. This number will always be equal to or smaller than the matchedObservations, the difference being the FOV transits that were not used in the astrometric solution because of bad data or excluded time intervals. Note (19): The longest principal axis in the 5-dimensional error ellipsoid. This is a 5-dimensional equivalent to the semi-major axis of the position error ellipse and is therefore useful for filtering out cases where one of the five parameters, or some linear combination of several parameters, is particularly ill-determined. It is measured in mas and computed as the square root of the largest singular value of the scaled 5x5 covariance matrix of the astrometric parameters. The matrix is scaled so as to put the five parameters on a comparable scale, taking into account the maximum along-scan parallax factor for the parallax and the time coverage of the observations for the proper motion components. If C is the unscaled covariance matrix, the scaled matrix is SCS, where S=diag(1,1,sinξ,T/2,T/2), ξ=45° is the solar aspect angle in the nominal scanning law, and T the time coverage of the data used in the solution. T=1.75115 yr for Gaia DR2. astrometricSigma5dMax is given for both 5-parameter and 2-parameter solutions, as its size is one of the criteria for accepting or rejecting the 5-parameter solution. In case of a 2-parameter solution (astrometricParamsSolved=3) it gives the value for the rejected 5-parameter solution, and can then be arbitrarily large. Note (20): This field is non-zero if the source was used to define the reference frame of the positions and proper motions. The values used are: 0 = An ordinary source not used for the reference frame determination 2 = The optical counterpart of an extragalactic radio source with accurately known VLBI position in ICRF. This is used to determine the orientation of the reference frame at the reference epoch, but also contributes to the determination of a non-rotating frame. 3 = An extragalactic source (AGN or quasar) that was used to determine a kinematically non-rotating celestial frame. Note (21): During data processing, this source happened to be duplicated and only one source identifier has been kept. Observations assigned to the discarded source identifier(s) were not used. This may indicate observational, cross-matching or processing problems, or stellar multiplicity, and probable astrometric or photometric problems in all cases. In Gaia DR1 and DR2, for close doubles with separations below some 2 arcsec, truncated windows have not been processed, neither in astrometry nor photometry. The transmitted window is centred on the brighter part of the acquired window, so the brighter component has a better chance to be selected, even when processing the fainter transit. If more than two images are contained in a window, the result of the image parameter determination is unpredictable in the sense that it might refer to either (or neither) image, and no consistency is assured. Note (22): Number of observations (CCD transits) that contributed to the G mean flux and mean flux error. Note (23): This is computed from the G-band mean flux applying the magnitude zero-point in the Vega scale. No error is provided for this quantity as the error distribution is only symmetric in flux space. This converts to an asymmetric error distribution in magnitude space which cannot be represented by a single error value. Note (24): Number of observations (CCD transits) that contributed to the integrated BP mean flux and mean flux error. Note (25): Error on the mean flux in the integrated BP band (errors are computed from the dispersion about the weighted mean of input calibrated photometry). Note (26): Mean magnitude in the integrated BP band. This is computed from the BP-band mean flux applying the magnitude zero-point in the Vega scale. No error is provided for this quantity as the error distribution is only symmetric in flux space. This converts to an asymmetric error distribution in magnitude space which cannot be represented by a single error value. Note (27): Number of observations (CCD transits) that contributed to the integrated RP mean flux and mean flux error. Note (28): Error on the mean flux in the integrated RP band (errors are computed from the dispersion about the weighted mean of input calibrated photometry). Note (29): Mean magnitude in the integrated RP band. This is computed from the RP-band mean flux applying the magnitude zero-point in the Vega scale. No error is provided for this quantity as the error distribution is only symmetric in flux space. This converts to an asymmetric error distribution in magnitude space which cannot be represented by a single error value. Note (30): The radialVelocityError is the error on the median to which a constant noise floor of 0.11km/s has been added in quadrature to take into account the calibration contribution. In detail, radialVelocityError=sqrt(σ^2{Vrad}+0.11^2) where σ{Vrad} is the error on the median: σ{Vrad} = sqrt(π/2).σ(V_rad^t)/sqrt(nbtransits) where σ(V_rad^t) is the standard deviation of the epoch radial velocities and rvNbTransits the number of transits for which a V_rad^t has been obtained. Note (31): Flag indicating if variability was identified in the photometric data: - "NOT_AVAILABLE" = source not processed and/or exported to catalogue - "CONSTANT" = Source not identified as variable - "VARIABLE" = source identified and processed as variable, see Vari* tables (cepheid.dat, rrlyrae.dat, lpv.dat, shortts.dat) Note that for this data release only a subset of (variable) sources was processed and/or exported, so for many (known) variable sources this flag is set to "NOT AVAILABLE". No "CONSTANT" sources were exported either. Note (32): Galactic longitude and latitude of the object at reference epoch refEpoch, see Section [ssec:cu3astintrogalactic] of the release documentation for conversion details. Note (33): Ecliptic longitude and latitude of the object at reference epoch refEpoch, obtained from the equatorial coordinates using the transformation defined in Section 1.5.3 of "The Hipparcos and Tycho Catalogues", ESA SP-1200, Volume 1 (ESA, 1997). Note (34): Flags describing the status of the astrophysical parameters Teff, AG and E[BP-RP] (i.e. those determined by Apsis-Priam). They are described in Chapter [chap:cu8par] of the release documentation. Note (35): Flags describing the status of the astrophysical parameters radius and luminosity (i.e. those determined by Apsis-FLAME). They are described in Chapter [chap:cu8par] of the release documentation. Note (36): The purpose of these parameters is to provide information on the synthetic spectrum used to determine radial_velocity, and not to provide an estimation of the star parameter. Note (37): The single-valued errors added by CDS do not always reflect accurately the magnitude errors. Indeed, the errors are only symmetric in flux space and ideally a +1 sigma and -1 sigma would be needed to properly describe the magnitude uncertainties. For the G-band this effect is probably not very severe, but for BP and RP this may become significant at the faint end.
Byte-by-byte Description of file: rvstdcat.dat
Bytes Format Units Label Explanations
2- 23 A22 --- ID Star ID (HIP, TYC or 2MASS) 25- 32 F8.3 km/s RV [-382.272/339.061] Mean Radial Velocity 35- 41 F7.4 km/s eRV [0.0001/0.2157] Internal error of RV 44- 50 F7.4 km/s s_RV [0/1.6164] Standard deviation of RV 53- 59 F7.4 km/s e_RV [0.0001/0.6374] Uncertainty of RV 61- 65 I5 d Tbase Time baseline of the N observations 67- 71 I5 d JDm Mean Julian Day of observations (JD-2400000) 73- 75 I3 --- N Number of ground-based radial velocities 79- 97 I19 --- Source ?=0 Source ID in Gaia DR2 99-102 A4 --- Flag Calibration or validation status (1) 104-110 F7.2 km/s RVS [-382.02/339.66]?=-999.99 Gaia DR2 Radial Velocity 112-116 F5.2 km/s e_RVS [0.11/19.07]?=-9.99 Gaia DR2 Radial Velocity error 118-120 I3 --- o_RVS [0/92] Number of RVS transits 122-143 A22 --- 2MASS ? 2MASS ID (2MASSJHHMMSSss+DDMMSSS) 145-151 F7.3 mag Jmag ?=-9.999 2MASS J magnitude 153-159 F7.3 mag Hmag ?=-9.999 2MASS H magnitude 161-167 F7.3 mag Kmag ?=-9.999 2MASS K magnitude 169-175 F7.3 mag e_Jmag ?=-9.999 2MASS J magnitude error 177-183 F7.3 mag e_Hmag ?=-9.999 2MASS H magnitude error 185-191 F7.3 mag e_Kmag ?=-9.999 2MASS K magnitude error 193-195 A3 --- Qflag 2MASS Qflag 199-208 F10.6 deg RAdeg Right ascension (ICRS) (2) 211-219 F9.5 deg DEdeg Declination (ICRS) (2) 221 A1 --- --- [J] 222-227 F6.1 yr Epoch Epoch for RAdeg and DEdeg 229-233 F5.2 mag Bmag ? Simbad B magnitude 235-239 F5.2 mag Vmag ? Simbad V magnitude 241-255 A15 --- SpType ? Simbad spectral type 257-270 A14 --- otype Simbad object type
Note (1): Flag as follows: CAL1 = calibrator for DR2 and DR3 CAL2 = calibrator for DR2 not for DR3 CAL3 = calibrator for DR3 not for DR2 VAL = validation star Note (2): RA and DEC come from Gaia DR2 (ICRS, Epoch=J2015.5) when available (source_id>0) or from Simbad (ICRS, Epoch=J2000.0).
Byte-by-byte Description of file: rvstdmes.dat
Bytes Format Units Label Explanations
2- 23 A22 --- ID Star ID (HIP, TYC or 2MASS) 25 A1 --- Instr Instrument (1) 27- 31 I5 d JD Julian Day of observation (JD-2400000) 33- 40 F8.3 km/s RV Radial Velocity 42- 48 F7.4 km/s e_RV Radial Velocity error 50- 51 A2 --- Mask Spectral type of the mask used for the CCF (2) 53- 76 A24 --- Idspec ? Identification number in public archive (3)
Note (1): Instrument code as follows: S = SOPHIE E = ELODIE C = CORALIE N = NARVAL H = HARPS Note (2): Mask is unknown when the measurement comes from the AMBRE-HARPS catalogue (de Pascale et al., 2014A&A...570A..68D) Note (3): Internal sequence number in SOPHIE archive (seq), or running number (immanum) and dataset in ELODIE archive, or original file name (ORIGFILE) in ESO-HARPS archive.
Byte-by-byte Description of file: allwise.dat
Bytes Format Units Label Explanations
1- 19 A19 --- Allwise WISE All-Sky Release Catalog name, based on J2000 position (allwise_name) 21- 39 I19 --- Source Gaia source identifier (source_id)
Byte-by-byte Description of file: iers.dat
Bytes Format Units Label Explanations
1- 8 A8 --- IERS International Earth Rotation and Reference Systems Service name (HHMM+DDd, B1950 equinox) (iers_name) 10- 28 I19 --- Source Gaia source identifier (source_id) (G3)
Byte-by-byte Description of file: cepheid.dat
Bytes Format Units Label Explanations
1- 5 A5 --- TBest Best type classification estimate (typebestclassification) (1) 7- 12 A6 --- TBest2 Best subclassification estimate (type2bestsub_classification) (2) 14- 27 A14 --- Mbest Best mode classification estimate (modebestclassification) (3) 29- 33 A5 --- Mbest2 Best multi mode DCEP classification (multimodebest_classification) (4) 35- 52 I18 --- SolID Solution Identifier (solution_id) (G1) 54- 72 I19 --- Source Unique source identifier (source_id) (G2) 74- 85 F12.8 d Pf ? Period corresponding to the fundamental pulsation mode (for multi mode pulsators) in the G band time series (pf) (G5) 87- 96 F10.8 d e_Pf ? Uncertainty of the Pf period (pf_error) (G6) 98-107 F10.8 d P1O ? Period corresponding to the first overtone pulsation mode (for multi mode pulsators) in the G band time series (p1_o) (G7) 109-118 F10.8 d e_P1O ? Uncertainty of the P2O period (p1oerror) (G6) 120-129 F10.8 d P2O ? Period corresponding to the second overtone pulsation mode (for multi mode pulsators) in the G band time series (p2_o) (G8) 131-140 F10.8 d e_P2O ? Uncertainty of the P2O period (p2oerror) (G6) 142-151 F10.8 d P3O ? Period corresponding to the third overtone pulsation mode (for multi mode pulsators) in the G band time series (p3_o) (G9) 153-162 F10.8 d e_P3O ? Uncertainty of the P3O period (p3oerror) (G6) 164-176 F13.8 d EpG Epoch of the maximum of the light curve in the G band (JD=2455197.5) (epoch_g) (G10) 178-187 F10.8 d e_EpG Uncertainty on the epoch parameter epoch G (epochgerror) 189-201 F13.8 d EpBP Epoch of the maximum of the light curve in the BP band (JD=2455197.5) (epoch_bp) (G10) 203-212 F10.8 d e_EpBP Uncertainty on the epoch parameter epoch BP (epochbperror) 214-226 F13.8 d EpRP Epoch of the maximum of the light curve in the RP band (JD=2455197.5) (epoch_rp) (G10) 228-237 F10.8 d e_EpRP Uncertainty on the epoch parameter epoch RP (epochrperror) 239-247 F9.6 mag Gmag Intensity-averaged magnitude in the G band (intaverageg) 249-256 F8.6 mag e_Gmag Uncertainty on Intensity-averaged magnitude in the G band (intaverageg_error) (G11) 258-266 F9.6 mag BPmag ? Intensity-averaged magnitude in the BP band (intaveragebp) 268-275 F8.6 mag e_BPmag ? Uncertainty on Intensity-averaged magnitude in the BP band (intaveragebp_error) (G11) 277-285 F9.6 mag RPmag ? Intensity-averaged magnitude in the RP band (intaveragerp) 287-294 F8.6 mag e_RPmag ? Uncertainty on Intensity-averaged magnitude in the RP band (intaveragerp_error) (G11) 296-303 F8.6 mag AmpG Peak-to-peak amplitude of the G band light curve (peaktopeak_g) (G12) 305-312 F8.6 mag e_AmpG Uncertainty on the AmpG parameter (peaktopeakgerror) (G13) 314-321 F8.6 mag AmpBP ? Peak-to-peak amplitude of the BP band light curve (peaktopeak_bp) (G12) 323-330 F8.6 mag e_AmpBP ? Uncertainty on the AmpBP parameter (peaktopeakbperror) (G13) 332-339 F8.6 mag AmpRP ? Peak-to-peak amplitude of the RP band light curve (peaktopeak_rp) (G12) 341-348 F8.6 mag e_AmpRP ? Uncertainty on the AmpRP parameter (peaktopeakrperror) (G13) 350-354 F5.2 [-] [Fe/H] ? Metallicity of the star from the Fourier parameters of the light curve (metallicity) (G14) 356-359 F4.2 [-] e_[Fe/H] ? Uncertainty of the metallicity parameter (metallicity_error) 361-367 F7.5 --- R21G ? Fourier decomposition parameter r21G: A2/A1 (for G band) (r21_g) (G15) 369-375 F7.5 --- e_R21G ? Uncertainty on the r21G parameter: A2/A1 (for G band) (r21gerror) (G16) 377-383 F7.5 --- R31G ? Fourier decomposition parameter A3/A1 (for G band) (r31_g) (G15) 385-391 F7.5 --- e_R31G ? Uncertainty on the r31G parameter: A3/A1 (for G band) (r31gerror) (G16) 393-399 F7.5 rad phi21G ? Fourier decomposition parameter phi21G: phi2-2*phi1 (for G band) (phi21_g) (G17) 401-407 F7.5 rad e_phi21G ? Uncertainty on the phi21G parameter (for G band) (phi21gerror) (G18) 409-415 F7.5 rad phi31G ? Fourier decomposition parameter phi31G: phi3-3*phi1 (for G band) (phi31_g) (G17) 417-423 F7.5 rad e_phi31G ? Uncertainty on the phi31G parameter (for G band) (phi31gerror) (G18) 425-427 I3 --- o_EpG Number of G FoV epochs used in the fitting algorithm (numcleanepochs_g) 429-431 I3 --- o_EpBP Number of BP epochs used in the fitting algorithm (numcleanepochs_bp) 433-435 I3 --- o_EpRP Number of RP epochs used in the fitting algorithm (numcleanepochs_rp)
Note (1): Classification of a Cepheid into "DCEP", "T2CEP" or "ACEP" using the period-luminosity relations, which are different for the three different types of Cepheids. Note (2): Sub-classification of a T2CEP Cepheids into BL Herculis ("BL_HER"), W Virginis ("W_VIR") or RV Tauris ("RV_TAU") sub-types depending on the source periodicity. Note (3): Best mode classification estimate: "FUNDAMENTAL": fundamental mode for typeBestClassification="DCEP" or "ACEP" "FIRST_OVERTONE": first overtone for typeBestClassification="DCEP" or "ACEP" "SECOND_OVERTONE": second overtone for typeBestClassification="DCEP" "MULTI": multi-mode pulsators for typeBestClassification="DCEP" "UNDEFINED": if mode could not be clearly determined for typeBestClassification="DCEP" or "ACEP" "NOT_APPLICABLE": when typeBestClassification="T2CEP" The Cepheid pulsation mode is assigned using the period-luminosity and period-Wesenheit relations, which are different for the various pulsation modes as well as analysing the Fourier parameters vs period plots. The type "MULTI" is assigned to stars pulsating in two or more modes simultaneously. Note (4): Sub-classification of multi mode DCEP variables according to their position in the "Petersen diagram" (see e.g. Fig. 1 in Soszynski et al., 2015AcA....65..329S). F,1O,2O and 3O mean fundamental, first, second and third overtone, respectively.
Byte-by-byte Description of file: rrlyrae.dat
Bytes Format Units Label Explanations
1- 4 A4 --- TBest Best type classification estimate (best_classification) (1) 6- 23 I18 --- SolID Solution Identifier (solution_id) (G1) 25- 43 I19 --- Source Unique source identifier (source_id) (G2) 45- 56 F12.8 d Pf ? Period corresponding to the fundamental pulsation mode (for multi mode pulsators) in the G band time series (pf) (G5) 58- 67 F10.8 d e_Pf ? Uncertainty of the Pf period (pf_error) (G6) 69- 78 F10.8 d P1O ? Period corresponding to the first overtone pulsation mode (for multi mode pulsators) in the G band time series (p1_o) (G7) 80- 89 F10.8 d e_P1O ? Uncertainty of the P2O period (p1oerror) (G6) 91-103 F13.8 d EpG Epoch of the maximum of the light curve in the G band (JD=2455197.5) (epoch_g) (G10) 105-114 F10.8 d e_EpG Uncertainty on the epoch parameter epoch G (epochgerror) 116-128 F13.8 d EpBP Epoch of the maximum of the light curve in the BP band (JD=2455197.5) (epoch_bp) (G10) 130-139 F10.8 d e_EpBP Uncertainty on the epoch parameter epoch BP (epochbperror) 141-153 F13.8 d EpRP Epoch of the maximum of the light curve in the RP band (JD=2455197.5) (epoch_rp) (G10) 155-164 F10.8 d e_EpRP Uncertainty on the epoch parameter epoch RP (epochrperror) 166-174 F9.6 mag Gmag Intensity-averaged magnitude in the G band (intaverageg) 176-183 F8.6 mag e_Gmag Uncertainty on Intensity-averaged magnitude in the G band (intaverageg_error) (G11) 185-193 F9.6 mag BPmag ? Intensity-averaged magnitude in the BP band (intaveragebp) 195-202 F8.6 mag e_BPmag ? Uncertainty on Intensity-averaged magnitude in the BP band (intaveragebp_error) (G11) 204-212 F9.6 mag RPmag ? Intensity-averaged magnitude in the RP band (intaveragerp) 214-221 F8.6 mag e_RPmag ? Uncertainty on Intensity-averaged magnitude in the RP band (intaveragerp_error) (G11) 223-230 F8.6 mag AmpG Peak-to-peak amplitude of the G band light curve (peaktopeak_g) (G12) 232-239 F8.6 mag e_AmpG Uncertainty on the AmpG parameter (peaktopeakgerror) (G13) 241-249 F9.6 mag AmpBP ? Peak-to-peak amplitude of the BP band light curve (peaktopeak_bp) (G12) 251-258 F8.6 mag e_AmpBP ? Uncertainty on the AmpBP parameter (peaktopeakbperror) (G13) 260-267 F8.6 mag AmpRP ? Peak-to-peak amplitude of the RP band light curve (peaktopeak_rp) (G12) 269-277 F9.6 mag e_AmpRP ? Uncertainty on the AmpRP parameter (peaktopeakrperror) (G13) 279-283 F5.2 [-] [Fe/H] ? Metallicity of the star from the Fourier parameters of the light curve (metallicity) (G14) 285-289 F5.2 [-] e_[Fe/H] ? Uncertainty of the metallicity parameter (metallicity_error) 291-297 F7.5 --- R21G ? Fourier decomposition parameter r21G: A2/A1 (for G band) (r21_g) (G15) 299-305 F7.5 --- e_R21G ? Uncertainty on the r21G parameter: A2/A1 (for G band) (r21gerror) (G16) 307-313 F7.5 --- R31G ? Fourier decomposition parameter A3/A1 (for G band) (r31_g) (G15) 315-321 F7.5 --- e_R31G ? Uncertainty on the r31G parameter: A3/A1 (for G band) (r31gerror) (G16) 323-329 F7.5 rad phi21G ? Fourier decomposition parameter phi21G: phi2-2*phi1 (for G band) (phi21_g) (G17) 331-338 F8.5 rad e_phi21G ? Uncertainty on the phi21G parameter (for G band) (phi21gerror) (G18) 340-346 F7.5 rad phi31G ? Fourier decomposition parameter phi31G: phi3-3*phi1 (for G band) (phi31_g) (G17) 348-354 F7.5 rad e_phi31G ? Uncertainty on the phi31G parameter (for G band) (phi31gerror) (G18) 356-358 I3 --- o_EpG Number of G FoV epochs used in the fitting algorithm (numcleanepochs_g) 360-362 I3 --- o_EpBP Number of BP epochs used in the fitting algorithm (numcleanepochs_bp) 364-366 I3 --- o_EpRP Number of RP epochs used in the fitting algorithm (numcleanepochs_rp) 368-372 F5.2 mag Gabs ? Interstellar absorption in the G-band (g_absorption) 374-378 F5.2 mag e_Gabs ? Error on the interstellar absorption in the G-band (gabsorptionerror)
Note (1): Classification of an RR Lyrae star according to the pulsation mode: RRc ("RRC") for first overtone, RRab ("RRAB") for fundamental mode, and RRd ("RRD") for double modes, obtained using the period-amplitude diagram in the G-band; the plots of the Fourier parameters R21 and Phi2 vs period and the Petersen diagram.
Byte-by-byte Description of file: lpv.dat
Bytes Format Units Label Explanations
1- 18 I18 --- SolID Solution Identifier (G1) (solution_id) 20- 38 I19 --- Source Unique source identifier (G2) (source_id) 40- 47 F8.4 mag MBOL [-23.1415/10.8172]? Absolute bolometric magnitude of the star (absmagbol) 49- 58 F10.4 mag e_MBOL [0.0518/56681.7485]? Error of absolute bolometric magnitude (absmagbol_error) 60 I1 --- Flag Red supergiant flag (marks stars that are probably red supergiants) (rsg_flag) 62- 68 F7.4 mag BolCorr [-9.1792/-0.2194] Bolometric correction for LPVs (bolometric_corr) (1) 70- 75 F6.4 mag e_BolCorr [0.005/5.9739] Error of the bolometric correction (bolometriccorrerror) (2) 77- 84 F8.6 d-1 Freq [0.000011/0.016666] Frequency of the LPV (frequency) 86- 94 F9.6 d-1 e_Freq [0.000027/65.899389] Error on the frequency (frequency_error)
Note (1): This parameter gives the bolometric correction for the case of LPVs; details of the calculation can be found in Chapter [chap:cu7var] of the release documentation. For DR2, the bolometric correction was fixed to a specific value in three cases. First for red supergiant LPVs, identified with, the value was set to -0.71mag. Second, the value was set to -2.2mag for LPVs with G amplitude variations >3mag, where the variability amplitude is computed as the 5-95% trimmed range using the LEGACY strategy of commons-math to compute the percentiles. Third, for all cases for which the uncertainty in BP or in RP was larger than 4mag, the BP-RP color was assumed to be 3.25mag, at which value the bolometric correction is -1.729mag. Note (2): This parameter gives the error of the bolometric correction for the case of LPVs. For DR2, the bolometric correction was fixed to a specific value in three cases. First for red supergiant LPVs, identified with, the value was set to 0.3mag. Second, the value was set to 0.005mag for LPVs with G amplitude variations >3mag, where the variability amplitude is computed as the 5-95% trimmed range using the LEGACY strategy of commons-math to compute the percentiles. Third, for all cases for which the uncertainty in BP or in RP was larger than 4mag, the BP-RP color was assumed to be 3.25mag and the error on BP-RP assumed to be 2mag, at which values the bolometric correction error is 1.892mag.
Byte-by-byte Description of file: varres.dat
Bytes Format Units Label Explanations
1- 18 I18 --- SolID Solution Identifier (meta.version) (G1) 20- 38 I19 --- Source Unique source identifier (source_id) (G2) 40- 51 A12 --- Classifier Name of the classifier used to produce this result (classifier_name) (1) 53- 62 A10 --- BClass Name of best class, see table VariClassifierDefinition for details of the class (bestclassname) (2) 64- 70 F7.5 --- BClassScore [0/1] Score of the best class (bestclassscore) (3)
Note (1): nTransits:2+ : Multi-stage Random Forest semi-supervised classifier applied to time series with 2 or more field-of-view transits in the G band (solID=369295546864633574) Note (2): Best classes as follows: ACEP = Anomalous Cepheids ARRD = Anomalous double-mode RR Lyrae stars CEP = Classical (delta) Cepheids DSCT_SXPHE = Variable stars of types delta Scuti (DSCT) and SX Phoenicis (SXPHE) MIRA_SR = Long period variable stars including omicron Ceti (MIRA) and semiregular (SR) variables RRAB = Fundamental-mode RR Lyrae stars RRC = First-overtone RR Lyrae stars RRD = Double-mode RR Lyrae stars T2CEP = Type-II Cepheids Note (3): It describes a quantity between 0 and 1 which is related to the confidence of the classifier in the identification of the best class (classBestName) by a monotonically increasing function (depending on class).
Byte-by-byte Description of file: shortts.dat
Bytes Format Units Label Explanations
1- 18 I18 --- SolID Solution Identifier (solution_id) (G1) 20- 38 I19 --- Source Unique source identifier (source_id) (G2) 40- 47 F8.6 mag Amp Amplitude estimate of all per CCD G-band photometry (quantile(95%)-quantile(5%)) (amplitude_estimate) 49- 51 I3 --- Nfov [14/109] Number of FoV transits with more than 7 CCD measurements after time series cleaning (numberoffov_transits) 53- 60 F8.6 --- abbe Mean of per-FOV Abbe values derived from CCD G-band photometry (meanoffovabbevalues) (1) 62 I1 --- Nvario Number of points in the variogram (variogramnumpoints) 64- 71 F8.6 d Tvario Characteristic time scales of variability (variogramchartimescales) 73- 80 F8.6 mag+2 Vvario Variogram values associated with the variogramCharTimescales (variogram_values) 82- 91 F10.6 d-1 Freq [1.006922/143.926266] Frequency search result for either G CCD, G FoV, BP or RP photometry (frequency) (2)
Note (1): This parameter is filled by the mean of per-FoV Abbe values derived from per-CCD G-band photometry. Considering a given source, for each of its FoV transits containing more than one per-CCD measurement, the associated Abbe value from per-CCD G-band photometry is derived as abbe = ∑(mag(t{i+1})-mag(ti))^{2}/2∑(mag(ti)-<mag(ti)>)^{2} where <mag(ti)> is the mean of the per-CCD measurements of the transit. The value of meanOfFovAbbeValues is calculated as the mean of these per-FoV Abbe values. Note (2): The parameter is filled by the frequency value resulting from the period search (method LOMB_SCARGLE for DR2) performed either on the per-CCD G-band photometry, per-FoV G-band photometry, BP photometry or RP photometry, if periodicity has been detected. Otherwise it is set to NULL.
Byte-by-byte Description of file: tsstat.dat
Bytes Format Units Label Explanations
1- 18 I18 --- SolID Solution Identifier (G1) (solution_id) 20- 38 I19 --- Source Unique source identifier (G2) (source_id) 40- 42 I3 --- NGmag [5/242] Total number of G FOV transits selected for variability analysis (numselectedg_fov) 44- 56 F13.8 d TimeGmag Mean observation time for G FoV transits (meanobstimegfov) 58- 69 F12.8 d DurGmag Time duration of the time series for G FoV transits (timedurationg_fov) 71- 79 F9.6 mag b_Gmag Minimum G FoV magnitude (minmagg_fov) 81- 89 F9.6 mag B_Gmag Maximum G FoV magnitude (maxmagg_fov) 91- 99 F9.6 mag Gmag Mean G FoV magnitude (meanmagg_fov) 101-109 F9.6 mag GmagMed Median G FoV magnitude (medianmagg_fov) 111-119 F9.6 mag RangeGmag Difference between the highest and lowest G FoV magnitudes (rangemagg_fov) 121-129 F9.6 mag stddevGmag Square root of the unweighted G FoV magnitude variance (stddevmaggfov) 131-136 F6.3 --- SkeGmag Standardized unweighted G FoV magnitude skewness (skewnessmagg_fov) 138-143 F6.3 --- KurGmag Standardized unweighted G FoV magnitude kurtosis (kurtosismagg_fov) 145-152 F8.6 mag MADGmag Median Absolute Deviation (MAD) for G FoV transits (madmagg_fov) 154-158 F5.3 --- AbbeGmag Abbe value for G FoV transits (abbemagg_fov) 160-168 F9.6 mag IQRGmag Interquartile range for G FoV transits (iqrmagg_fov) 170-172 I3 --- NBPmag Total number of BP FOV transits selected for variability analysis (numselectedbp) 174-186 F13.8 d TimeBPmag ? Mean observation time for BP FoV transits (meanobstime_bp) 188-199 F12.8 d DurBPmag ? Time duration of the time series for BP FoV transits (timedurationbp) 201-209 F9.6 mag b_BPmag ? Minimum BP FoV magnitude (minmagbp) 211-219 F9.6 mag B_BPmag ? Maximum BP FoV magnitude (maxmagbp) 221-229 F9.6 mag BPmag ? Mean BP FoV magnitude (meanmagbp) 231-239 F9.6 mag BPmagMed ? Median BP FoV magnitude (medianmagbp) 241-249 F9.6 mag RangeBPmag ? Difference between the highest and lowest BP FoV magnitudes (rangemagbp) 251-259 F9.6 mag stddevBPmag ? Square root of the unweighted BP FoV magnitude variance (stddevmag_bp) 261-267 F7.3 --- SkeBPmag ? Standardized unweighted BP FoV magnitude skewness (skewnessmagbp) 269-275 F7.3 --- KurBPmag ? Standardized unweighted BP FoV magnitude kurtosis (kurtosismagbp) 277-284 F8.6 mag MADBPmag ? Median Absolute Deviation (MAD) for BP FoV transits (madmagbp) 286-290 F5.3 --- AbbeBPmag ? Abbe value for BP FoV transits (abbemagbp) 292-300 F9.6 mag IQRBPmag ? Interquartile range for BP FoV transits (iqrmagbp) 302-304 I3 --- NRPmag ? Total number of RP FOV transits selected for variability analysis (numselectedrp) 306-318 F13.8 d TimeRPmag ? Mean observation time for RP FoV transits (meanobstime_rp) 320-331 F12.8 d DurRPmag ? Time duration of the time series for RP FoV transits (timedurationrp) 333-341 F9.6 mag b_RPmag ? Minimum RP FoV magnitude (minmagrp) 343-351 F9.6 mag B_RPmag ? Maximum RP FoV magnitude (maxmagrp) 353-361 F9.6 mag RPmag ? Mean RP FoV magnitude (meanmagrp) 363-371 F9.6 mag RPmagMed ? Median RP FoV magnitude (medianmagrp) 373-381 F9.6 mag RangeRPmag ? Difference between the highest and lowest RP FoV magnitudes (rangemagrp) 383-391 F9.6 mag stddevRPmag ? Square root of the unweighted RP FoV magnitude variance (stddevmag_rp) 393-399 F7.3 --- SkeRPmag ? Standardized unweighted RP FoV magnitude skewness (skewnessmagrp) 401-407 F7.3 --- KurRPmag ? Standardized unweighted RP FoV magnitude kurtosis (kurtosismagrp) 409-416 F8.6 mag MADRPmag ? Median Absolute Deviation (MAD) for RP FoV transits (madmagrp) 418-422 F5.3 --- AbbeRPmag ? Abbe value for RP FoV transits (abbemagrp) 424-432 F9.6 mag IQRRPmag ? Interquartile range for RP FoV transits (iqrmagrp)
Byte-by-byte Description of file: numtrans.dat
Bytes Format Units Label Explanations
1- 19 I19 --- SolID Solution Identifier (solution_id) (G1) 21- 39 I19 --- Source Source Identifier (source_id) (G2) 41- 43 I3 --- Ntrans [5/277] Number of Gaia transits, in all bands, in transits.dat file (n_transits)
Byte-by-byte Description of file: transits.dat
Bytes Format Units Label Explanations
1- 19 I19 --- Source Source Identifier (source_id) (G2) 21- 37 I17 --- TransitID Transit Identifier as defined in JP-011 and received by DPCI from IDT (transit_id) 39- 51 F13.8 d TimeG ? Transit averaged G band observation time (JD-2455197.5) (gtransittime) (1) 53- 69 E17.9 e-/s FG ? Transit averaged G band flux (gtransitflux) (2) 71- 88 E18.9 e-/s e_FG ? Error on the transit averaged G band flux (gtransitflux_error) 90-107 E18.9 --- RFG ? Transit averaged G band flux divided by its error (gtransitfluxovererror) 109-117 F9.6 mag Gmag ? Transit averaged G band magnitude (converted from transit averaged G band flux) (gtransitmag) 119-127 F9.6 mag e_Gmag ? Error on transit averaged G band magnitude, added by CDS (gtransitmag_error) 129-141 F13.8 d TimeBP ? BP CCD transit observation time (JD-2455197.5) (bpobstime) (1) 143-159 E17.9 e-/s FBP ? BP band flux (bp_flux) 161-177 E17.9 e-/s e_FBP ? Error on the BP band flux (bpfluxerror) 179-195 E17.9 --- RFBP ? BP band flux divided by its error (bpfluxover_error) 197-205 F9.6 mag BPmag ? BP band magnitude (converted from BP band flux) (bp_mag) 207-219 E13.6 mag e_BPmag ? Error on the BP band magnitude, added by CDS (bpmagerror) 221-233 F13.8 d TimeRP ? RP CCD transit observation time (JD-2455197.5) (rpobstime) (1) 235-251 E17.9 e-/s FRP ? RP band flux (rp_flux) 253-269 E17.9 e-/s e_FRP ? Error on the RP band flux (rpfluxerror) 271-287 E17.9 --- RFRP ? RP band flux divided by its error (rpfluxover_error) 289-297 F9.6 mag RPmag ? RP band magnitude (converted from RP band flux) (rp_mag) 299-309 E11.6 mag e_RPmag ? Error on the RP band magnitude, added by CDS (rpmagerror) 311 I1 --- noisy [0/1] G band flux scatter larger than expected by photometry processing (all CCDs considered) (photometryflagnoisy_data) 313 I1 --- smu [0/1] SM transit unavailable by photometry processing (photometryflagsm_unavailable) 315 I1 --- af1u [0/1] AF1 transit unavailable by photometry processing (photometryflagaf1_unavailable) 317 I1 --- af2u [0/1] AF2 transit unavailable by photometry processing (photometryflagaf2_unavailable) 319 I1 --- af3u [0/1] AF3 transit unavailable by photometry processing (photometryflagaf3_unavailable) 321 I1 --- af4u [0/1] AF4 transit unavailable by photometry processing (photometryflagaf4_unavailable) 323 I1 --- af5u [0/1] AF5 transit unavailable by photometry processing (photometryflagaf5_unavailable) 325 I1 --- af6u [0/1] AF6 transit unavailable by photometry processing (photometryflagaf6_unavailable) 327 I1 --- af7u [0/1] AF7 transit unavailable by photometry processing (photometryflagaf7_unavailable) 329 I1 --- af8u [0/1] AF8 transit unavailable by photometry processing (photometryflagaf8_unavailable) 331 I1 --- af9u [0/1] AF9 transit unavailable by photometry processing (photometryflagaf9_unavailable) 333 I1 --- bpu [0/1]? ABP transit unavailable by photometry processing (photometryflagbp_unavailable) 335 I1 --- rpu [0/1]? ABP transit unavailable by photometry processing (photometryflagrp_unavailable) 337 I1 --- smr [0/1] SM transit rejected by photometry processing(photometryflagsm_reject) 339 I1 --- af1r [0/1] AF1 transit rejected by photometry processing (photometryflagaf1_reject) 341 I1 --- af2r [0/1] AF2 transit rejected by photometry processing (photometryflagaf2_reject) 343 I1 --- af3r [0/1] AF3 transit rejected by photometry processing (photometryflagaf3_reject) 345 I1 --- af4r [0/1] AF4 transit rejected by photometry processing (photometryflagaf4_reject) 347 I1 --- af5r [0/1] AF5 transit rejected by photometry processing (photometryflagaf5_reject) 349 I1 --- af6r [0/1] AF6 transit rejected by photometry processing (photometryflagaf6_reject) 351 I1 --- af7r [0/1] AF7 transit rejected by photometry processing (photometryflagaf7_reject) 353 I1 --- af8r [0/1] AF8 transit rejected by photometry processing (photometryflagaf8_reject) 355 I1 --- af9r [0/1] AF9 transit rejected by photometry processing (photometryflagaf9_reject) 357 I1 --- bpr [0/1]? BP transit rejected by photometry processing (photometryflagbp_reject) 359 I1 --- rpr [0/1]? RP transit rejected by photometry processing (photometryflagrp_reject) 361 I1 --- VarGr [0/1]? Average G transit photometry rejected by variability processing (variabilityflagg_reject) (3) 363 I1 --- VarBPr [0/1]? Average BP transit photometry rejected by variability processing (variabilityflagbp_reject) (3) 365 I1 --- VarRPr [0/1]? Average RP transit photometry rejected by variability processing (variabilityflagrp_reject) (3)
Note (1): Field-of-view transit averaged observation time in units of Barycentric JD (in TCB) in days -2455197.5, computed as follows. First the observation time is converted from On-board Mission Time (OBMT) into Julian date in TCB (Temps Coordonnee Barycentrique). Next a correction is applied for the light-travel time to the Solar system barycentre, resulting in Barycentric Julian Date (BJD). Finally, an offset of 2455197.5 days is applied (corresponding to a reference time T0 at 2010-01-01T00:00:00) to have a conveniently small numerical value. Units: (Barycentric JD in TCB - 2455197.5 (day)). For TimeG: Although the centroiding time accuracy of the individual CCD observations is (much) below 1ms, this per-FoV observation time is averaged over typically 9 CCD observations taken in a time range of about 44 sec. Note (2): The average G flux value for the FoV transit. The calculation only uses accepted transits. This could include SM and AF fluxes. Note (3): Flag as follows: 1 = rejected 0 = processed
Byte-by-byte Description of file: rm.dat
Bytes Format Units Label Explanations
1- 12 F12.9 d ProtB Best rotation period (bestrotationperiod) (1) 14- 24 F11.9 d e_ProtB Error on best rotation period (bestrotationperiod_error) 26- 32 F7.5 mag AImax Activity Index in segment (maxactivityindex) (2) 34- 40 F7.5 mag e_AImax Error on Activity index in segment (maxactivityindex_error) (3) 42- 49 F8.5 mag Gunsp The unspotted G magnitude in segment (g_unspotted) (4) 51- 57 F7.5 mag e_Gunsp The unspotted G mag uncertainties in segment (gunspottederror) 59- 66 F8.5 mag BPunsp ? The unspotted BP magnitude in segment (bp_unspotted) 68- 74 F7.5 mag e_BPunsp ? The unspotted BP magnitude uncertainty in segment (bpunspottederror) 76- 83 F8.5 mag RPunsp ? The unspotted RP magnitude in segment (rp_unspotted) 85- 91 F7.5 mag e_RPunsp ? The unspotted RP magnitude uncertainty in segment (rpunspottederror) 93-111 I19 --- SolID Solution Identifier (solution_idR) (G1) 113-131 I19 --- Source Source Identifier (source_id) (G2) 133-134 I2 --- Nseg Number of segments (num_segments) (5) 136-137 I2 --- Nout Number of outliers (num_outliers) (6)
Note (1): this field is an estimate of the stellar rotation period and is obtained by averaging the periods obtained in the different segments Note (2): this array stores the activity indexes measured in the different segments. In a given segment the amplitude of variability A is taken as an index of the magnetic activity level. The amplitude of variability is measured by means of the equation: A=mag95-mag5 where mag95 and mag5 are the 95-th and the 5-th percentiles of the G-band magnitude values. Note (3): error associated with the activity indexes in the G band. In a given segment the error on the activity index A is computed by means of the equation: sigmaA=sqrt{sigmamag952 + sigmamag52} where sigmamag95 and sigmamag5 are the uncertainties of the measurements associated with the 95th and 5th percentiles of the G-band magnitude values, respectively Note (4): in a given segment the G magnitude corresponding to the unspotted state is estimated by taking the minimum G value in the segment. Note (5): This is the number of time intervals (segments) in which the magnitude and colour time-series are splitted. The segmentation of time-series is needed because the spots due to the stellar magnetic activity have a life-time shorter than the whole Gaia time-series. The rotational modulation induced by spots can therefore be detected only in segments whose duration is comparable with the spots life-time Note (6): the number of outliers detected by the robust linear regression procedure.
Byte-by-byte Description of file: rmseg.dat
Bytes Format Units Label Explanations
1- 19 I19 --- Source Unique source identifier (source_id) (G2) 21- 36 F16.12 d SProt ? Rotation period in segment (segmentsrotationperiod) (1) 38- 54 E17.12 d e_SProt ? Rotation period uncertainty in segment (segmentsrotationperiod_error) 56- 72 E17.12 % FAPsPRot FAP on rotation period in segment (segmentsrotationperiod_fap) (2) 74- 82 F9.6 mag Scos ? Coefficient of cosine term of linear fit in segment (segmentscosterm) (3) 84- 91 F8.6 mag e_Scos ? Error on cosin term (segmentscosterm_error) 93-101 F9.6 mag Ssin ? Coefficient of sin term of linear fit in segment (segmentssinterm) (3) 103-110 F8.6 mag e_Ssin ? Error on sine term (segmentssinterm_error) 112-120 F9.6 mag Sa0 ? Constant term (A0) of linear fit in segment (segmentsa0term) (3) 122-129 F8.6 mag e_Sa0 ? Error on constant term (segmentsa0term_error) 131-137 F7.5 mag SAI Activity Index in segment (segmentsactivityindex) (4) 139-145 F7.5 mag e_SAI Error on Activity index in segment (segmentsactivityindex_error) (5) 147-154 F8.5 mag SGunsp The unspotted G magnitude in segment (segmentsgunspotted) 156-162 F7.5 mag e_SGunsp The unspotted G magnitude uncertainty in segment (segmentsgunspotted_error) 164-171 F8.5 mag SBPunsp ? The unspotted BP magnitude in segment (segmentsbpunspotted) 173-179 F7.5 mag e_SBPunsp ? The unspotted BP magnitude uncertainty in segment (segmentsbpunspotted_error) 181-188 F8.5 mag SRPunsp ? The unspotted RP magnitude in segment (segmentsrpunspotted) 190-196 F7.5 mag e_SRPunsp ? The unspotted RP magnitude uncertainty in segment (segmentsrpunspotted_error) 198-210 F13.8 d STimeS Time at which segments start (JD-2455197.5) (segmentsstarttime) (6) 212-224 F13.8 d STimeE Time at which segments end (JD-2455197.5) (segmentsendtime) (6) 226-234 F9.3 --- ScolI Colour-Magnitude Intercept in segment (segmentscolourmag_intercept) (7) 236-242 F7.3 --- e_ScolI Colour-Magnitude Intercept uncertainty in segment (segmentscolourmagintercepterror) 244-251 F8.4 --- ScolM Colour-Magnitude Slope in segments (segmentscolourmag_slope) (7) 253-259 F7.4 --- e_ScolM Colour-Magnitude Slope uncertainty in segment (segmentscolourmagslopeerror) 261-268 F8.5 --- Scor Correlation coefficient in segment (segmentscorrelationcoefficient) (8) 270-276 F7.5 --- Ssigni Correlation coefficient significance in segment (segmentscorrelationsignificance) (9)
Note (1): A period search algorithm is applied to the different time-series segments. If the star is a solar-like variable the detected period is a measure of the stellar rotation period. This array is filled with the periods detected in the different segments (for each segment the period with the highest statistical significance is stored). Note (2): False Alarm Probability = Probability that that a white noise sequence produces a peak similar or higher than the computed one; i.e.; small FAP = little probability of noise;high FAP = noise is an acceptable explanation for the peak. Note (3): if a significative period T0 is detected in a time-series segment; then the points of the time-series segment are fitted with the function mag(t)=mag0+Acos(2π/T0t) + Bsin(2π/T0t). This array stores the A terms obtained by the fitting procedure in the different segments. Note (4): this array stores the activity indexes measured in the different segments. In a given segment the amplitude of variability A is taken as an index of the magnetic activity level. The amplitude of variability is measured by means of the equation: A=mag95-mag5 where mag95 and mag5 are the 95-th and the 5-th percentiles of the G-band magnitude values. Note (5): this array stores the errors associated with the activity indexes in the G band. In a given segment the error on the activity index A is computed by means of the equation: sigmaA=sqrt{sigmamag952+sigmamag52} where sigmamag95and sigmamag5 are the uncertainties of the measurements associated with the 95th and 5th percentiles of the G-band magnitude values, respectively. Note (6): an array filled with the starting (ending) times of segments in Barycentric JD in TCB - 2455197.5 unit. Note (7): a robust linear regression is applied to the points (BP-RP;G) in each segment. This array is filled with the intercepts given by the fitting procedure in the different segments. Note (8): The Pearson correlation coefficient r between BP-RP and G is computed in each segment. The higher is the Pearson coefficient the higher is the probability that the stellar variability is due to rotational modulation. This array is filled with the Pearson coefficients obtained in the different segments. Note (9): this array is filled with the statistical significances associated with the Pearson coefficients computed in the different segments. The significance p associated with a given r=r0 gives the probability P(r≥r0) that two sets of uncorrelated measurements have a Pearson coefficient ≥r0.
Byte-by-byte Description of file: rmout.dat
Bytes Format Units Label Explanations
1- 19 I19 --- Source Unique source identifier (source_id) (G2) 21- 33 F13.8 d TimeOutliers Times at which outliers occurs (JD-2455197.5 ) (outliers_time) (1)
Note (1): times at which the detected outliers occurred in Barycentric JD in TCB-2455197.5 unit.
Byte-by-byte Description of file: ssoobj.dat
Bytes Format Units Label Explanations
1- 19 I19 --- SolID Solution Identifier (solution_id) (G1) 21- 31 I11 --- Source Unique source identifier (source_id) (G3) 33- 35 I3 --- Nobs [15/591] Number of CCD-level observations of the asteroid that appear in the SsoObservation (ssoobs.dat) table (numofobs) 37- 42 I6 --- MPC Minor planet number attributed by MPC (number_mp) 44- 59 A16 --- Name MPC name or preliminary designation (denomination)
Byte-by-byte Description of file: ssoorb.dat
Bytes Format Units Label Explanations
1- 19 I19 --- SolID Solution Identifier (solution_id) (G1) 21- 26 I6 --- MPC Asteroid number assigned by MPC (number_mp) 28- 43 A16 --- Name MPC name or preliminary designation (designation) 45- 49 F5.2 mag Hmag Absolute magnitude H for the asteroid (mag_h) (2) 51- 54 F4.2 --- Slopeg Slope parameter of the magnitude-phase law (slope_g) 56- 62 I7 --- Code Object specific flags (code) (3) 64- 68 I5 d Obs.arc Time interval of the observations used to compute the orbit (obs_arc) 70- 73 I4 --- Obs.num Number of observations used to compute the orbit (obs_num) 75- 82 A8 "YYYYMMDD" Obs.epoch Epoch of osculation, yyyymmdd (TDT) (osc_epoch) (4) 84- 93 F10.6 deg Orb.m Orbital element: Mean anomaly (orb_m) 95-104 F10.6 deg Omega Argument of perihelion at equinox J2000.0 (omega) (5) 106-115 F10.6 deg Node.omega Longitude of the ascending node at equinox J2000.0 (node_omega) (5) 117-125 F9.6 deg Incl Orbit inclination (J2000.0) (inclination) 127-136 F10.8 --- Eccen Orbit eccentricity (eccentricity) 138-148 F11.8 AU a Semimajor axis of the orbit (a) 150-157 A8 "YYYYMMDD" Orb.Date Date of orbit computation (MST, = UTC - 7 hr) (orb_date) 159-164 F6.4 arcsec CEU Absolute value of the current 1-sigma ephemeris uncertainty (ceu) 166-172 F7.4 mas/s CEU.rate Rate of change of the orbit uncertainty (ceu_rate) (6) 174-181 A8 "YYYYMMDD" CEU.epoch Date of CEU (0 hr UT) (ceu_epoch)
Note (2): Number of decimal places depending on accuracy (zero to 2), except for unnumbered asteroids (2 decimals even if H is poorly known) Note (3): See ftp://cdsarc.u-strasbg.fr/pub/cats/B/astorb/astorb.html for a full description Note (4): The epoch is the Julian date ending in 00.5 nearest the date the orbit data set was compiled. Note (5): Note this is not ICRS because these orbits are heliocentric and all angles are referred to the nodal point defined at equinox J2000.0) Note (6): Note that in astorb it is given in arcsec/day.
Byte-by-byte Description of file: ssores.dat
Bytes Format Units Label Explanations
1- 11 I11 --- Source Unique source identifier (source_id) (G3) 13- 29 I17 --- Transit Transit Identifier (transit_id) (2) 31- 48 I18 --- Obs.ID Observation Identifier (observation_id) (3) 50- 55 I6 --- MPC Minor Planet number attributed by MPC (number_mp) 57- 74 F18.13 d Epoch Gaiacentric epoch TCB(Gaia) (epoch) (G4) 76- 94 E19.13 mas Res.RA Post-orbital fit residual in RA*cos(DE) direction (residual_ra) 96-114 E19.13 mas Res.DE Post-orbital fit residual in DE direction (residual_dec) 116-133 E18.13 mas Res.AL Post-orbital fit residual in AL (Along Scan) direction (residual_al) 135-153 E19.13 mas Res.AC Post-orbital fit residual in AC (Across Scan) (residual_ac) 155 I1 --- Select [0/1] Flag for observation not rejected by orbital fit (selected) (5)
Note (2): The Transit Id is a number obtained from the combination of data fields from the telemetry. More specifically, from AF1 refacquisitiontime, AF1 ac, FOV and CCD Row. It uniquely identifies the transit of a source on the focal plane. Note (3): Identifier at single CCD level of the observation of a Solar System object. It is unique, and obtained from a combination of transitId and an integer number representing the CCD strip. Note (5): Post-fit residuals are then computed. Rejection of single observations may occur in this process. This flag is 1 when no observation is rejected.
Byte-by-byte Description of file: ssoobs.dat
Bytes Format Units Label Explanations
1- 19 I19 --- SolID Solution Identifier (solution_id) (G1) 21- 31 I11 --- Source Unique source identifier (source_id) (G3) 33- 50 I18 --- Obs.Id Observation Identifier (observation_id) 52- 57 I6 --- MPC Minor Planet number attributed by MPC (number_mp) 59- 76 F18.13 d Epoch Gaiacentric epoch TCB(Gaia) (JD-2455197.5) (epoch) (G4) 78- 86 E9.3 d e_Epoch Error in Gaiacentric epoch (for both Epoch and EpochUTC) (epoch_err) 88-105 F18.13 d EpochUTC Gaiacentric epoch UTC (epoch_utc) (JD-2455197.5) (1) 107-129 F23.19 deg RAdeg ICRS Right Ascension of the source as observed by Gaia at epoch EpochUTC (ra) 133-155 E23.19 deg DEdeg ICRS Declination of the source as observed by Gaia at epoch EpochUTC (dec) 157-163 F7.4 mas e_RAdeg Standard error of right ascension - systematic component (e_RA*cosDE) (raerrorsystematic) 165-171 F7.4 mas e_DEdeg Standard error of declination - systematic component (decerrorsystematic) 173-179 F7.4 --- RADEcors Correlation of RA and DE errors - systematic component (radeccorrelation_systematic ) 181-188 F8.4 mas eRAdeg Standard error of right ascension - random component (e_RA*cosDE) (raerrorrandom) 190-197 F8.4 mas eDEdeg Standard error of declination - random component (decerrorrandom) 199-205 F7.4 --- RADEcorr Correlation of RA and DE errors - random component (radeccorrelation_random) 207-215 F9.6 mag Gmag ? Calibrated G magnitude (corrected G magnitude based on refined signal analysis) (g_mag) 217-234 E18.14 e-/s FG ? Average calibrated G flux for the transit (g_flux) 236-253 E18.14 e-/s e_FG ? Error on the G flux (gfluxerror) 255-276 E22.17 AU Xpos Barycentric equatorial J2000 (ICRS) x position of Gaia at the epoch of observation (x_gaia) 278-299 E22.17 AU Ypos Barycentric equatorial J2000 (ICRS) y position of Gaia at the epoch of observation (y_gaia) 301-322 E22.17 AU Zpos Barycentric equatorial J2000 (ICRS) z position of Gaia at the epoch of observation (z_gaia) 324-345 E22.17 AU/d VX Barycentric equatorial J2000 (ICRS) x velocity of Gaia at the epoch of observation (vx_gaia) 347-368 E22.17 AU/d VY Barycentric equatorial J2000 (ICRS) y velocity of Gaia at the epoch of observation (vy_gaia) 370-391 E22.17 AU/d VZ Barycentric equatorial J2000 (ICRS) z velocity of Gaia at the epoch of observation (vz_gaia) 393-402 F10.6 deg PA Position angle of the scanning direction (positionanglescan) (2) 404 I1 % ConfLevel [0] Level of confidence of the identification (levelofconfidence) (3)
Note (1): Gaiacentric epoch in UTC in JD-2455197.5 corresponding to right ascension and declination. Note (2): Position angle of the scan direction at the epoch of observation in the equatorial reference frame. 0 = North direction, pi/2 = increasing right ascension, pi = South, 3pi/2 = decreasing right ascension. It is defined as the angle between the AL direction and the direction to the North Pole, at the SSO position, after applying the correction for aberration. As a consequence of this correction for aberration, the AC direction is no longer strictly perpendicular to the AL direction. Note (3): Level of confidence in the identification of the given SSO source_id with this observation as follows: 0 = completely unambiguous 100 = no identification
Global notes: Note (G1): All Gaia data processed by the Data Processing and Analysis Consortium comes tagged with a solution identifier. This is a numeric field attached to each table row that can be used to unequivocally identify the version of all the subsystems that where used in the generation of the data as well as the input data used. It is mainly for internal DPAC use but is included in the published data releases to enable end users to examine the provenance of processed data products. To decode a given solution ID visit. Note (G2): Unique source identifier (unique within a particular Data Release) Long Description: A unique numerical identifier of the source, encoding the approximate position of the source (roughly to the nearest arcmin), the provenance (data processing centre where it was created), a running number, and a component number. The approximate equatorial (ICRS) position is encoded using the nested HEALPix scheme at level 12 (Nside = 4096), which divides the sky into ∼200 million pixels of about 0.7 arcmin2. The source ID consists of a 64-bit integer, least significant bit = 1 and most significant bit = 64, comprising: - a HEALPix index number (sky pixel) in bits 36 - 63; by definition the smallest HEALPix index number is zero. - a 3-bit Data Processing Centre code in bits33 - 35; for example MOD(sourceId / 4294967296, 8) can be used to distinguish between sources initialised via the Initial Gaia Source List by the Torino DPC (code = 0) and sources otherwise detected and assigned by Gaia observations (code>0) - a 25-bitplus 7 bit sequence number within the HEALPix pixel in bits 1-32 split into: - a 25 bitrunning number in bits 8-32; the running numbers are defined to be positive, i.e. never zero - a 7-bit component number in bits 1- 7 This means that the HEALpix index leel 12 of a given source is contained in the most significant bits. HEALpix index of 12 and lower levels can thus be retrieved as follows: - HEALpix level 12 = source_id / 34359738368 - HEALpix level 11 = source_id / 137438953472 - HEALpix level 10 = source_id / 549755813888 - HEALpix level n = source_id / 235*4(12-level) Additional details can be found in the Gaia DPAC public document _Source Identifiers - Assignment and Usage throughout DPAC_ (document code GAIA-C3-TN-ARI-BAS-020). Note (G3): A unique single numerical identifier of the source obtained from GaiaSource (for a detailed description see GaiaSource.sourceId). Note in particular that these identifiers are by convention negative for SSOs. Note (G4): Gaiacentric epoch TCB(Gaia) in JD corresponding to the time of crossing of the fiducial line of the CCD. This is the epoch to which the target coordinates and the position/velocity of Gaia are referred to. To avoid loss of precision the reference time J2010.0 is subtracted. Barycentric JD in TCB - 2455197.5. Note (G5): for single-mode pulsators classified as fundamental mode pulsators, this parameter is filled with the periodicity found in the time-series. For double-mode RR Lyrae this parameter is filled with the period corresponding to the longer periodicity. For double-mode DCEPs this parameter is filled with the period corresponding to the longer periodicity if the DCEP is classified as "F/1O" or "F/2O". For triple-mode DCEPs this parameter is filled with the period corresponding to the longer periodicity if the DCEP is classified as "F/1O/2O" This value is obtained by modelling the G band time series using the Levenberg-Marquardt non linear fitting algorithm (see Clementini et al., 2016A&A...595A.133C, Cat. I/337). Note (G6): This parameter is filled with the uncertainty of the period parameter. Its value is derived from Monte Carlo simulations that generate several (100) time series with the same time path as the data points but with magnitudes generated randomly around the corresponding data values. For each of these time series the period is computed. The mean of all the periods and its standard deviation are then derived, and the latter value is used to fill the periodError parameter. The value refers to the analysis performed on the G band time series. Note (G7): for single-mode pulsators classified as first-overtone pulsators, this parameter is filled with the periodicity found in the time-series. For double-mode RR Lyrae this parameter is filled with the period corresponding to the shortest periodicity. For double-mode DCEPs this parameter is filled with the period corresponding to the shortest periodicity if the DCEP is classified as "F/1O"; otherwise it is filled with the longest one if the classification is "1O/2O" or "1O/3O". For triple-mode DCEPs this parameter is filled with the period corresponding to the intermediate periodicity if the DCEP is classified as "F/1O/2O"; it is filled with the longest periodicity if the classification is "1O/2O/3O". This value is obtained by modelling the G time series using the Levenberg-Marquardt non linear fitting algorithm (see Clementini et al., 2016A&A...595A.133C, Cat. I/337) Note (G8): For single-mode DCEPs classified as second-overtone pulsators, this parameter is filled with the periodicity found in the time-series. For double-mode DCEPs this parameter is filled with the period corresponding to the shortest periodicity if the DCEP is classified as "1O/2O" of "F/2O"; otherwise it is filled with the longest periodicity if the classification is "2O/3O". For triple-mode DCEPs this parameter is filled with the period corresponding to the shortest periodicity if the DCEP is classified as "F/1O/2O"; it is filled with the intermediate periodicity if the classification is "1O/2O/3O". This value is obtained by modelling the G time series using the Levenberg-Marquardt non linear fitting algorithm (see Clementini et al., 2016A&A...595A.133C, Cat. I/337). Note (G9): for double-mode DCEPs this parameter is filled with the periodicity found in the time-series corresponding to the shortest periodicity if the DCEP is classified as "1O/3O" of "2O/3O". For triple-mode DCEPs this parameter is filled with the period corresponding to the shortest periodicity if the DCEP is classified as "1O/2O/3O". This value is obtained by modelling the G time series using the Levenberg-Marquardt non linear fitting algorithm (see Clementini et al., 2016A&A...595A.133C, Cat. I/337). Note (G10): Epoch of maximum light for the Gaia G band light curve. It corresponds to the Baricentric Julian day (BJD) of the maximum value of the light curve model which is closest to the BJD of the first observations -3 times the period of the source (first periodicity depending on the pulsation mode). The mentioned BJD is offset by JD 2455197.5 (= J2010.0) (Barycentric JD in TCB - 2455197.5 (day)). Note (G11): This parameter is filled with the uncertainty of the Average_magnitude parameter. Its value is derived from Monte Carlo simulations that generate several (100) time series with the same time path as the data points but with magnitudes generated randomly around the corresponding data values. For each of these time series the Average_magnitude is computed. The mean of all the magnitudes found and its standard deviation are then computed, and the latter value is kept to fill the AveragemagnitudeError parameter. Note (G12): This parameter is filled with the peak-to-peak amplitude value of the band light curve. The peak-to-peak amplitude is calculated as the (maximum)-(minimum) of the modelled folded light curve in the band. The light curve of the target star is modelled with a truncated Fourier series (mag(tj)=zp+{SIGMA}[Aisin(ix2πνmaxtj+φi)]). Zero-point (zp), period (1/νmax), number of harmonics (i), amplitudes (Ai), and phases (φi) of the harmonics, for the band light curve are determined using the Levenberg-Marquardt non linear fitting algorithm. Note (G13): This parameter is filled with the uncertainty value of the Amplitude parameter. Its value is derived from Monte Carlo simulations that generate several (100) time series with the same time path as the data points but with magnitudes generated randomly around the corresponding data values. For each of these time series the peakToPeakG is computed. The mean of all the amplitudes found and its standard deviation are then computed, and the latter value is kept to fill the Amplitude_Error parameter. Note (G14): this parameter is filled with the [Fe/H] metallicity derived for the source from the Fourier parameters of the G-band light curve. Note (G15): this parameter is filled with the Fourier decomposition parameter R21=A2/A1 (R31=A3/A_1), where A2 is the amplitude of the 2nd harmonic, A3 is the amplitude of the 3rd harmonic and A1 is the amplitude of the fundamental harmonic of the truncated Fourier series defined as (mag(tj)=zp+{SIGMA}[Aisin(ix2Πνmaxtj+φi)]) used to model the G-band light curve. Zero-point (zp), period (1/νmax), number of harmonics (i), amplitudes (Ai), and phases (φi) of the harmonics, are determined using the Levenberg-Marquardt non linear fitting algorithm. Note (G16): this parameter is filled with the uncertainty value on the r21G/r31G parameter. Its value is derived from Monte Carlo simulations that generate several (100) time series with the same time path as the data points but with magnitudes generated randomly around the corresponding data values. For each of these time series the r21G/r31G is computed. The mean of all the r21G/r31G values found and its standard deviation are then computed, and the latter value is kept to fill the r21G/r31GError parameter. Note (G17): this parameter is filled with the Fourier decomposition parameter φ21=φ2-2φ1 (φ31=φ3-3φ1): where φ2 is the phase of the 2nd harmonic, φ3 is the phase of the 3rd harmonic and φ1 is the phase of the fundamental harmonic of the truncated Fourier series defined as (mag(tj)=zp+{SIGMA}[Aisin(ix2πνmaxtj+φi)]) used to model the G-band light curve. Zero-point (zp), period (1/νmax), number of harmonics (i), amplitudes (Ai), and phases (φi) of the harmonics, are determined using the Levenberg-Marquardt non linear fitting algorithm. Note (G18): this parameter is filled with the uncertainty of the phi21G (phi31G) parameter. Its value is derived from Monte Carlo simulations that generate several (100) time series with the same time path as the data points but with magnitudes generated randomly around the corresponding data values. For each of these time series the phi21G (phi31G) is computed. The mean of all the phi21G ((phi31G) values is found and its standard deviation are then computed, and the latter value is kept to fill the phi21G((phi31G)Error parameter.
History: From Gaia team Acknowledgements: For radial velocity catalog: Caroline Soubiran, caroline.soubiran(at)u-bordeaux.fr, [Lab. d'Astrophys. Bordeaux] For all other catalogs: Gaia team References: Gaia Data Release 2: Summary of the contents and survey properties, Gaia Collaboration, Brown, A.G.A., et al. (2018A&A..in.prep...) Gaia Data Release 2: The astrometric solution, Lindegren, L., et al. (2018A&A..in.prep...) Gaia Data Release 2: Calibration and mitigation of electronic offset effects in Gaia data, Hambly, N., et al. (2018A&A..in.prep...) Gaia Data Release 2: Processing of the photometric data, Riello, M., et al. (2018A&A..in.prep...) Gaia Data Release 2: The photometric content and validation, Evans, D.W., et al. (2018A&A..in.prep...) Gaia Data Release 2: The Gaia Radial Velocity Spectrometer, Cropper, M., et al. (2018A&A..in.prep...) Gaia Data Release 2: The catalogue of radial velocity standard stars Soubiran, C., et al. (2018A&A..in.prep...) Gaia Data Release 2: Processing, validation and performance of the spectroscopic data, Sartoretti, P., et al. (2018A&A..in.prep...) Gaia Data Release 2: Properties and validation of the radial velocities, Katz, D., et al. (2018A&A..in.prep...) Gaia Data Release 2: Summary of variability processing and analysis results, Holl, B., et al. (2018A&A..in.prep...) Gaia Data Release 2: First stellar parameters from Apsis, Andrae, R., et al. (2018A&A..in.prep...) Gaia Data Release 2: Catalogue validation, Arenou, F., et al. (2018A&A..in.prep...) Gaia Data Release 2: Cross-match with external catalogues: algorithm and statistics, Marrese, P.M., et al. (2018A&A..in.prep...) Gaia Data Release 2: On the use of Gaia parallaxes, Luri, X., et al. (2018A&A..in.prep...) Gaia Data Release 2: The celestial reference frame (Gaia-CRF2), Gaia Collaboration, Mignard, F., et al. (2018A&A..in.prep...) Gaia Data Release 2: Observational Hertzsprung-Russell diagrams, Gaia Collaboration, Babusiaux, C., et al. (2018A&A..in.prep...) Gaia Data Release 2: Observations of Solar System objects, Gaia Collaboration, Spoto, F., et al. (2018A&A..in.prep...) Gaia Data Release 2: Mapping the Milky Way disk kinematics, Gaia Collaboration, Katz, D., et al. (2018A&A..in.prep...) Gaia Data Release 2: The kinematics of globular clusters and dwarf galaxies around the Milky Way, Gaia Collaboration, Helmi, A., et al. (2018A&A..in.prep...) Gaia Data Release 2: Variable stars in the Colour-Magnitude Diagram, Gaia Collaboration, Eyer, L., et al. (2018A&A..in.prep...)
(End) Arnaud Siebert, Thomas Boch, Patricia Vannier [CDS] 25-Apr-2018
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