I/350                 Gaia EDR3                       (Gaia Collaboration, 2020)

Gaia Early Data Release 3 (Gaia EDR3). Gaia collaboration <Astron. Astrophys., 649, A1 (2021)> =2020yCat.1350....0G =2020A&A...649A...1G =doi:10.5270/esa-1ugzkg7
ADC_Keywords: Surveys ; Stars, standard ; Positional data ; Proper motions ; Photometry, photographic ; Cross identifications ; Radial velocities ; Stars, variable ; Minor planets; Parallaxes, trigonometric Mission_Name: Gaia Keywords: catalogs - astrometry - parallaxes - proper motions - techniques: photometric - techniques: radial velocities Abstract: Gaia DR3 data (both Gaia EDR3 and the full Gaia DR3) are based on data collected between 25 July 2014 (10:30 UTC) and 28 May 2017 (08:44 UTC), spanning a period of 34 months. As a comparison, Gaia DR2 was based on 22 months of data and Gaia DR1 was based on observations collected during the first 14 months of Gaia's routine operational phase. Survey completeness: The Gaia EDR3 catalogue is essentially complete between G=12 and G=17. The source list for the release is incomplete at the bright end and has an ill-defined faint magnitude limit, which depends on celestial position. The combination of the Gaia scan law coverage and the filtering on data quality which will be done prior to the publication of Gaia EDR3, does lead to some regions of the sky displaying source density fluctuations that reflect the scan law pattern. In addition, small gaps exist in the source distribution, for instance close to bright stars. Astrometry: The parallax improvement is typically 20% with respect to Gaia DR2. The proper motions are typically a factor two better than in Gaia DR2. An overall reduction of systematics has been achieved. E.g., the parallax zero point deduced from the extragalactic sources is about -20µas. A tentative correction formula for the parallax zero point will be provided. Closer to the release date of Gaia Early Data Release 3, an update will be given on the astrometry. Photometry: The G-band photometric uncertainties are ∼0.25mmag for G<13, 1mmag at G=17, and 5mmag at G=20mag. The GBP-band photometric uncertainties are ∼1mmag for G<13, 10mmag at G=17, and 100mmag at G=20mag. The GRP-band photometric uncertainties are ∼1mmag for G<13, 5mmag at G=17, and 50mmag at G=20mag. Closer to the release date of Gaia Early Data Release 3, an update will be given on the photometry. Gaia EDR3 does not contain new radial velocities. The radial velocities of Gaia Data Release 2 have been added to Gaia EDR3 in order to ease the combination of spectrosopic and astrometric data. Radial velocities: Gaia EDR3 hence contains Gaia DR2 median radial velocities for about 7.21 million stars with a mean G magnitude between ∼4 and ∼13 and an effective temperature (Teff) in the range ∼3550 to 6900K. The overall precision of the radial velocities at the bright end is of the order of ∼200-300m/s while at the faint end, the overall precision is ∼1.2km/s for a Teff of 4750K and ∼3.5km/s for a Teff of 6500K. Before publication in Gaia EDR3, an additional filtering has been performed onto the Gaia DR2 radial velocities to remove some 4000 sources that had wrong radial velocities. Please be aware that the Gaia DR2 values are assigned to the Gaia EDR3 sources through an internal cross-match operation. In total, ∼10000 Gaia DR2 radial velocities could not be associated to a Gaia EDR3 source. Astrophysical parameters: Gaia EDR3 does not contain new astrophysical parameters. Astrophysical parameters have been published in Gaia DR2 and a new set is expected to be released with the full Gaia DR3 release. Variable stars: Gaia EDR3 does not contain newly classified variable stars. For the overview of the currently available variable stars from Gaia DR2, have a look here. Classifications for a larger set of variable stars are expected with the full Gaia DR3 release. Solar system objects: A large set of solar system objects with orbits will become available with the full Gaia DR3 release. Information on the currently available asteroids in Gaia DR2 can be found here. Documentation: Data release documentation is provided along with each data release in the form of a downloadable PDF and a webpage. The various chapters of the documentation have been indexed at ADS allowing them to be cited. Please visit the Gaia Archive (https://gea.esac.esa.int/archive) to access this documentation, and make sure to check out all relevant information given through the documentation overview page (https://www.cosmos.esa.int/web/gaia-users/archive). Description: Contents of Gaia EDR3: The five-parameter astrometric solution - positions on the sky (alpha,delta), parallaxes, and proper motions - for around 1.5 billion (1.5x109) sources, with a limiting magnitude of about G~=21 and a bright limit of about G~=3. The astrometric solution will be accompanied with some new quality indicators, like RUWE, and source image descriptors. In addition, two-parameters solutions - positions on the sky (alpha,delta) - for around 300 million additional sources. G magnitudes for around 1.8 billion sources. GBP and GRP magnitudes for around 1.5 billion sources. Please be aware that the photometric system for the G, GBP, and GRP bands in Gaia EDR3 is different from the photometric system as used in Gaia DR2 and Gaia DR1. Full passband definitions for G, GBP, and GRP. More information will become available here. About 1.5 million celestial reference frame (Gaia-CRF) sources. Cross-matches between Gaia EDR3 sources on the one hand and Hipparcos-2, Tycho-2 + TDSC merged, 2MASS PSC (merged with 2MASX), SDSS DR13, Pan-STARRS1 DR1, SkyMapper DR1, GSC 2.3, APASS DR9, RAVE DR5, allWISE, and URAT-1 data on the other hand. Additionally, a Gaia EDR3 to Gaia DR2 match will be provided. Simulated data from Gaia Object Generator (GOG) and Gaia Universe Model Snapshot (GUMS) will be provided. The commanded scan law covering the Gaia EDR3 data collection period will be provided. Also the major periods where data was not sent to the ground or could not be processed are identified. Gaia DR3 data (both Gaia EDR3 and the full Gaia DR3) are based on data collected between 25 July 2014 (10:30 UTC) and 28 May 2017 (08:44 UTC), spanning a period of 34 months. As a comparison, Gaia DR2 was based on 22 months of data and Gaia DR1 was based on observations collected during the first 14 months of Gaia's routine operational phase. The reference epoch for Gaia DR3 (both Gaia EDR3 and the full Gaia DR3) is 2016.0. Remember that the reference epoch is different for each Gaia data release (it was was J2015.5 for Gaia DR2 and J2015.0 for Gaia DR1). Positions and proper motions are referred to the ICRS, to which the optical reference frame defined by Gaia EDR3 is aligned. The time coordinate for Gaia EDR3 is the barycentric coordinate time (TCB). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file gaiaedr3.sam 1035 1000 GaiaSource EDR3 data agncrid.dat 88 1614173 AGN cross-identifications (AgnCrossId.csv) tyc2tdsc.dat 348 2561887 Tycho-2 merged with the TDSC catalog and TDSC supplement comscanl.dat 198 8967691 *Representation of the Gaia scanning law over the 34 month time period covered by the Gaia Data Release 3 framers.dat 42 429249 Sources used to compute the Gaia reference frame (FrameRotatorSource.csv)
Note on comscanl.dat: (from 2014-07-25 10:31:26 to 2017-05-28 08:46:29) (CommandedScanLaw.csv)
See also: II/328 : AllWISE Data Release (Cutri+ 2013) II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016) II/358 : SkyMapper Southern Sky Survey. DR1.1 (Wolf+, 2018) I/329 : URAT1 Catalog (Zacharias+ 2015) https://www.cosmos.esa.int/web/gaia/earlydr3 : Gaia EDR3 Home Page Byte-by-byte Description of file: gaiaedr3.sam
Bytes Format Units Label Explanations
1- 29 A29 --- EDR3Name Unique source designation (unique across all Data Releases) (designation) (1) 31- 45 F15.11 deg RAdeg Barycentric right ascension of the source (ICRS) at Ep=2016.0 (ra) 47- 61 F15.11 deg DEdeg Barycentric declination of the source (ICRS) at Ep=2016.0 (dec) 63- 81 I19 --- Source Unique source identifier (unique within a particular Data Release) (source_id) (2) 83-101 I19 --- SolID Solution Identifier (solution_id) (3) 103-112 I10 --- RandomI Random index used to select subsets (random_index) (4) 114-119 F6.1 yr Epoch Reference epoch (ref_epoch) (5) 121-127 F7.4 mas e_RAdeg Standard error eRA=eRA*cosDE of the right ascension of the source in ICRS at Ep=2016.0 (ra_error) 129-135 F7.4 mas e_DEdeg Standard error of the declination of the source in ICRS at at Ep=2016.0 (dec_error) 137-146 F10.4 mas Plx ? Absolute stellar parallax of the source at the Ep=2016.0 (parallax) 148-153 F6.4 mas e_Plx ? Standard error of the stellar parallax at Ep=2016.0 (parallax_error) 155-164 F10.4 --- RPlx ? Parallax divided by its standard error (parallaxovererror) 166-174 F9.3 mas/yr PM ? Total proper motion (pm) (6) 176-184 F9.3 mas/yr pmRA ? Proper motion in right ascension pmRA*cosDE of the source in ICRS at Ep=2016.0 (pmra) (7) 186-190 F5.3 mas/yr e_pmRA ? Standard error of proper motion in right ascension direction (pmra_error) (8) 192-200 F9.3 mas/yr pmDE ? Proper motion in declination direction (pmdec) (9) 202-206 F5.3 mas/yr e_pmDE ? Standard error of proper motion in declination direction (pmdec_error) (10) 208-214 F7.4 --- RADEcor [-1/1] Correlation between right ascension and declination (radeccorr) 216-222 F7.4 --- RAPlxcor [-1/1]? Correlation between right ascension and parallax (raparallaxcorr) 224-230 F7.4 --- RApmRAcor [-1/1]? Correlation between right ascension and proper motion in right ascension (rapmracorr) 232-238 F7.4 --- RApmDEcor [-1/1]? Correlation between right ascension and proper motion in declination (rapmdeccorr) 240-246 F7.4 --- DEPlxcor [-1/1]? Correlation between declination and parallax (decparallaxcorr) 248-254 F7.4 --- DEpmRAcor [-1/1]? Correlation between declination and proper motion in right ascension (decpmracorr) 256-262 F7.4 --- DEpmDEcor [-1/1]? Correlation between declination and proper motion in declination (decpmdeccorr) 264-270 F7.4 --- PlxpmRAcor [-1/1]? Correlation between parallax and proper motion in right ascension (parallaxpmracorr) 272-278 F7.4 --- PlxpmDEcor [-1/1]? Correlation between parallax and proper motion in declination (parallaxpmdeccorr) 280-286 F7.4 --- pmRApmDEcor [-1/1]? Correlation between proper motion in right ascension and proper motion in declination (pmrapmdeccorr) 288-291 I4 --- NAL Total number of observations AL (astrometricnobs_al) (11) 293-296 I4 --- NAC Total number of observations AC (astrometricnobs_ac) (12) 298-301 I4 --- NgAL Number of good observations AL (astrometricngoodobsal) (13) 303-305 I3 --- NbAL Number of bad observations AL (astrometricnbadobsal) (14) 307-315 F9.4 --- gofAL Goodness of fit statistic of model wrt along-scan observations (astrometricgofal) 317-329 F13.2 --- chi2AL AL chi-square value (astrometricchi2al) (15) 331-338 F8.3 mas epsi Excess noise of the source (astrometricexcessnoise) (16) 340-349 E10.3 --- sepsi Significance of excess noise (astrometricexcessnoise_sig) (17) 351-352 I2 --- Solved Which parameters have been solved for? (astrometricparamssolved) (18) 354 I1 --- APF Primary or secondary (astrometricprimaryflag) (19) 356-361 F6.3 um-1 nueff ? Effective wavenumber of the source used in the astrometric solution (nueffusedinastrometry) (20) 363-369 F7.4 um pscol ? Astrometrically estimated pseudocolour of the source (pseudocolour) (21) 371-377 F7.4 um e_pscol ? Standard error of the pseudocolour of the source (pseudocolour_error) (22) 379-384 F6.3 --- RApscolCorr [-1/1]? Correlation between right ascension and pseudocolour (rapseudocolourcorr) 386-391 F6.3 --- DEpscolCorr [-1/1]? Correlation between declination and pseudocolour (decpseudocolourcorr) 393-398 F6.3 --- PlxpscolCorr [-1/1]? Correlation between parallax and pseudocolour (parallaxpseudocolourcorr) 400-405 F6.3 --- pmRApscolCorr [-1/1]? Correlation between proper motion in right ascension and pseudocolour (pmrapseudocolourcorr) 407-412 F6.3 --- pmDEpscolCorr [-1/1]? Correlation between proper motion in declination and pseudocolour (pmdecpseudocolourcorr) 414-416 I3 --- MatchObsA Matched FOV transits used in the AGIS solution (astrometricmatchedtransits) (23) 418-419 I2 --- Nper Number of visibility periods used in Astrometric solution (visibilityperiodsused) 421-432 E12.6 mas amax The longest semi-major axis of the -5--10 error ellipsoid (astrometricsigma5dmax) (24) 434-436 I3 --- MatchObs The total number of field-of-view transits matched to this source (matched_transits) 438-440 I3 --- NewMatchObs The number of transits newly incorporated into an existing source in the current cycle (newmatchedtransits) (25) 442-444 I3 --- MatchObsrm The number of transits removed from an existing source in the current cycle (matchedtransitsremoved) (26) 446-454 E9.3 --- IPDgofha Amplitude of the IPD GoF versus position angle of scan (ipdgofharmonic_amplitude) (27) 456-464 E9.3 deg IPDgofhp Phase of the IPD GoF versus position angle of scan (ipdgofharmonic_phase) (28) 466-468 I3 --- IPDfmp Percent of successful-IPD windows with more than one peak (ipdfracmulti_peak) (29) 470-472 I3 --- IPDfow Percent of transits with truncated windows or multiple gate (ipdfracodd_win) (30) 474-481 F8.3 --- RUWE ? Renormalised unit weight error (ruwe) 483-491 E9.3 --- SDSk1 ? Degree of concentration of scan directions across the source (scandirectionstrength_k1) (31) 493-501 E9.3 --- SDSk2 ? Degree of concentration of scan directions across the source (scandirectionstrength_k2) (31) 503-511 E9.3 --- SDSk3 ? Degree of concentration of scan directions across the source (scandirectionstrength_k3) (31) 513-521 E9.3 --- SDSk4 ? Degree of concentration of scan directions across the source (scandirectionstrength_k4) (31) 523-530 F8.3 deg SDMk1 ? Mean position angle of scan directions across the source (scandirectionmean_k1) (32) 532-539 F8.3 deg SDMk2 ? Mean position angle of scan directions across the source (scandirectionmean_k2) (32) 541-548 F8.3 deg SDMk3 ? Mean position angle of scan directions across the source (scandirectionmean_k3) (32) 550-557 F8.3 deg SDMk4 ? Mean position angle of scan directions across the source (scandirectionmean_k4) (32) 559 I1 --- Dup Source with multiple source identifiers (duplicated_source) (33) 561-564 I4 --- o_Gmag Number of observations (CCD transits) that contributed to the G mean flux and mean flux error (photgn_obs) 566-576 E11.5 e-/s FG ? Mean flux in the G-band (photgmean_flux) 578-588 E11.5 e-/s e_FG ? Standard deviation of the G-band fluxes divided by sqrt(photGNObs) (photgmeanfluxerror) 590-598 F9.3 --- RFG ? Mean flux in the G-band divided by its error (photgmeanfluxover_error) 600-608 F9.6 mag Gmag ? G-band mean magnitude (Vega) (photgmean_mag) (34) 610-612 I3 --- o_BPmag ? Number of observations contributing to BP photometry (photbpn_obs) (35) 614-624 E11.5 e-/s FBP ? Mean flux in the integrated BP band (photbpmean_flux) 626-636 E11.5 e-/s e_FBP ? Error on the integrated BP mean flux (photbpmeanfluxerror) (36) 638-646 F9.3 --- RFBP ? Integrated BP mean flux divided by its error (photbpmeanfluxover_error) (37) 648-656 F9.6 mag BPmag ? Integrated BP mean magnitude (Vega) (photbpmean_mag) (38) 658-660 I3 --- o_RPmag Number of observations (CCD transits) that contributed to the integrated RP mean flux and mean flux error (photrpn_obs) 662-672 E11.5 e-/s FRP ? Mean flux in the integrated RP band (photrpmean_flux) 674-684 E11.5 e-/s e_FRP ? Error on the integrated RP mean flux (photrpmeanfluxerror) (39) 686-694 F9.3 --- RFRP ? Integrated RP mean flux divided by its error (photrpmeanfluxover_error) (40) 696-704 F9.6 mag RPmag ? Integrated RP mean magnitude (Vega) (photrpmean_mag) (41) 706-708 I3 --- NBPcont ? Number of BP contaminated transits (photbpncontaminatedtransits) (42) 710-712 I3 --- NBPblend ? Number of BP blended transits (photbpnblendedtransits) (43) 714-716 I3 --- NRPcont ? Number of RP contaminated transits (photrpncontaminatedtransits) (44) 718-720 I3 --- NRPblend ? Number of RP blended transits (photrpnblendedtransits) (45) 722 I1 --- Mode Photometry processing mode (photprocmode) 724-729 F6.3 --- E(BP/RP) ? BP/RP excess factor (photbprpexcessfactor) 731-739 F9.6 mag BP-RP ? BP-RP colour (photBpMeanMag - photRpMeanMag) (bp_rp) 741-749 F9.6 mag BP-G ? BP-G colour (photBpMeanMag - photGMeanMag) (bp_g) 751-759 F9.6 mag G-RP ? G-RP colour (photGMeanMag - photRpMeanMag) (g_rp) 761-767 F7.2 km/s RVDR2 ? Radial velocity from Gaia DR2 (dr2radialvelocity) (46) 769-773 F5.2 km/s e_RVDR2 ? Radial velocity error from Gaia DR2 (dr2radialvelocity_error) (47) 775-777 I3 --- o_RVDR2 Number of transits used to compute radial velocity in Gaia DR2 (dr2rvnb_transits) (48) 779-784 F6.1 K Tefftemp ? Teff of the template used to compute radial velocity in Gaia DR2 (dr2rvtemplate_teff) (49) 786-789 F4.1 [cm/s2] loggtemp ? logg of the template used to compute radial velocity in Gaia DR2 (dr2rvtemplate_logg) (50) 791-795 F5.2 [-] [Fe/H]temp ? [Fe/H] of the template used to compute radial velocity in Gaia DR2 (dr2rvtemplatefeh) (51) 797-810 F14.10 deg GLON Galactic longitude (l) (52) 812-825 F14.10 deg GLAT Galactic latitude (b) (53) 827-840 F14.10 deg ELON Ecliptic longitude (ecl_lon) 842-855 F14.10 deg ELAT Ecliptic latitude (ecl_lat) (54) 857-874 I18 --- PS1 ? Pan-STARRS1 cross-id name (panstarrs1) (55) 876-894 I19 --- SDSSDR13 ? SDSS DR13 cross-id name (sdssdr13) (55) 896-904 I9 --- SkyMapper2 ? SkyMapper2 cross-id name (skymapper2) (55) 906-914 I9 --- URAT1 ? URAT1 cross-id name (urat1) (55) 916-923 F8.6 mag e_Gmag ? Standard error of G-band mean magnitude (Vega) (added by CDS) (photgmeanmagerror) (G1) 925-932 F8.6 mag e_BPmag ? Standard error of BP mean magnitude (Vega) (added by CDS) (photbpmeanmagerror) (G1) 934-941 F8.6 mag e_RPmag ? Standard error of RP mean magnitude (Vega) (added by CDS) (photrpmeanmagerror) (G1) 943-951 F9.6 mag GmagCorr ? Calibration corrected G magnitude (added by CDS) (photgmeanmagcorrected) (G2) 953-960 F8.6 mag e_GmagCorr ? Standard error of calibration corrected G magnitude (added by CDS) (photgmeanmagerror_corrected) (G2) 962-972 E11.5 mag FGCorr ? Calibration corrected G-band mean flux (added by CDS) (photgmeanfluxcorrected) (G2) 974-979 F6.3 --- E(BP/RP)Corr ? Calibration corrected BP/RP excess factor (added by CDS) (photbprpexcessfactor_corrected) (G2) 981-995 F15.11 deg RAJ2000 Barycentric right ascension (ICRS) at Ep=2000.0 (added by CDS) (ra_epoch2000) 997-1011 F15.11 deg DEJ2000 Barycentric declination (ICRS) at Ep=2000.0 (added by CDS) (dec_epoch2000) 1013-1019 F7.4 mas e_RAJ2000 Standard error of right ascension (e_RA*cosDE) (added by CDS) (raepoch2000error) 1021-1027 F7.4 mas e_DEJ2000 Standard error of declination (added by CDS) (decepoch2000error) 1029-1035 F7.4 --- RADEcorJ2000 [-1/1] Correlation between right ascension and declination at epoch 2000 (added by CDS) (radecepoch2000_corr)
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): 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 bits 33 - 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-bit plus 7 bit sequence number within the HEALPix pixel in bits 1 - 32 split into: - a 25 bit running 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 at level 12 of a given source is contained in the most significant bits. HEALpix index of level 12 and lower can thus be retrieved as follows: - HEALpix index at level 12 = source_id / 34359738368 - HEALpix index at level 11 = source_id / 137438953472 - HEALpix index level 10 = source_id / 549755813888 - HEALpix index at level n = source_id / (235x4(12-n)) = source_id/2(59-2n) 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) available from https://www.cosmos.esa.int/web/gaia/public-dpac-documents Note (3): 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 (4): 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 sources in the table. 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 (5): Reference epoch to which the astrometric source parameters are referred, expressed as a Julian Year in TCB. Note (6): The total proper motion calculated as the magnitude of the resultant vector of the proper motion component vectors pmra and pmdec, i.e. pm2 = pmRA2 + pmDE2. Note (7): This is the local tangent plane projection of the proper motion vector in the direction of increasing right ascension. Note (8): Standard error e_pmRA*cosDE of the local tangent plane projection of the proper motion vector in the direction of increasing right ascension at the reference epoch refEpoch Note (9): Proper motion in declination of the source at the reference epoch refEpoch. This is the projection of the proper motion vector in the direction of increasing declination. Note (10): Standard error of the proper motion component in declination at the reference epoch refEpoch Note (11): 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 (12): 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). 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 (13): 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 (14): 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 (15): Astrometric goodness-of-fit (chi2) in the AL direction. chi2 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 (16): 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. The excess source noise is further explained in Sects. 3.6 and 5.1.2 Note (17): A dimensionless measure (D) of the significance of the calculated astrometricExcessNoise (εi). A value D>2 indicates that the given i 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. The excess noise significance is further explained in Sect. 5.1.2. Note (18): The seven bits of astrometricParamsSolved indicate which parameters have been estimated in AGIS for this source. A set bit means the parameter was updated, an unset bit means the parameter was not updated. The least-significant bit corresponds to ra. The table below shows the values of astrometricParamsSolved for relevant combinations of the parameters. The radial proper motion (µr) is formally considered to be one of the astrometric parameters of a source, and the sixth bit is therefore reserved for it. It is also in principle updatable in AGIS, but in practice it will always be computed from a spectroscopic radial velocity and the estimated parallax, in which case the bit is not set. C is the pseudocolour of the source, i.e. the astrometrically estimated effective wavenumber. astrometricParamsSolved ra dec parallax pmra pmdec µr C ------------------------- ---- ----- ---------- ------ ------- ---- --- 0000011 = 3 0000111 = 7 0011011 = 27 0011111 = 31 0111111 = 63 1011111 = 95 In practice all the sources in DR3 have only values of 3, 31 or 95 for the astrometricParamsSolved, corresponding to two-parameter (position), five-parameter (position, parallax, and proper motion) and six-parameter (position, parallax, proper motion and astrometrically estimated effective wavenumber) solutions. Note (19): 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 (20): Effective wavenumber of the source, νeff, in µm-1. This νeff is the value used in the image parameter determination and in the astrometric calibration if reliable mean BP and RP photometry were available. It is the photon-flux weighted inverse wavelength, as estimated from the BP and RP bands. The field is provided for astrometric solutions with five parameters but is empty for those with two or six parameters. Due to cyclic processing of the astrometry and the photometry, this effective wavenumber might be different from the one computed using the latest available photometry. Moreover, if no reliable photometry was available at the time of the astrometric processing, this field is empty and an astrometrically estimated value of the effective wavenumber may instead be given in the pseudocolour field. Note (21): The pseudocolour is the astrometrically estimated effective wavenumber of the photon flux distribution in the astrometric (G) band, measured in µm-1. The value in this field was estimated from the chromatic displacements of image centroids, calibrated by means of the photometrically determined effective wavenumbers (νeff) of primary sources. The field is empty when chromaticity was instead taken into account using the photometrically determined νeff given in the field nuEffUsedInAstrometry. Note (22): Standard error σ_pseudocolour of the astrometrically determined pseudocolour of the source. Note (23): The number of field-of-view 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 matchedTransits, the difference being the FOV transits that were not used in the astrometric solution because of bad data or excluded time intervals. Note (24): 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, sin ζ, T/2, T/2), ζ = 45° is the solar aspect angle in the nominal scanning law, and T the time coverage of the data used in the solution. astrometricSigma5dMax is given for all the solutions, as its size is one of the criteria for accepting or rejecting the 5 or 6-parameter solution. In case of a 2- parameter solution (astrometricParamsSolved = 3) it gives the value for the rejected 5 or 6-parameter solution, and can then be arbitrarily large. Note (25): Individual field-of-view transits are crossmatched into unique sources at the start of each reprocessing cycle taking the source list from the previous cycle as a starting point. During that process a combination of appending, merging and splitting operations is performed to create a more complete and reliable map of unique sources given the available information. Existing individual sources may accrete further transits, may be merged into fewer unique sources, or may split into two or more new, unique sources as more measurements are accumulated. Field newMatchedTransits logs the number of transits newly appended to an existing source during the most recent cyclic reprocessing crossmatch. It refers exclusively to the sourceId. Note (26): Individual field-of-view transits are crossmatched into unique sources at the start of each reprocessing cycle taking the source list from the previous cycle as a starting point. During that process a combination of appending, merging and splitting operations is performed to create a more complete and reliable map of unique sources given the available information. Existing individual sources may accrete further transits, may be merged into fewer unique sources, or may split into two or more new, unique sources as more measurements are accumulated. Field matchedTransitsRemoved logs the number of transits removed during the most recent cyclic reprocessing crossmatch from those allocated to an existing source during all previous cycles. It refers exclusively to the sourceId. Note (27): This statistic measures the amplitude of the variation of the IPD GoF (reduced chi-square) as function of the position angle of the scan direction. A large amplitude indicates that the source is double, in which case the phase indicates the position angle of the pair modulo 180 degrees. The quantity was computed using only transits used in the astrometric solution, for example those without the EPSL and without outliers. Let ψ be the position angle of the scan direction. The following expression is fitted to the IPD GoF for all the AF observations of the source: ln(GoF) = c0 + c2cos(2ψ) + s2sin(2ψ) The amplitude and phase of the variation are calculated as ipdGofHarmonicAmplitude = sqrt{c22+s22} ipdGofHarmonicPhase = 1/2atan2(s2,c2) (+180°) where atan2 returns the angle in degrees, and 180 is added for negative values. Note (28): This statistic measures the phase of the variation of the IPD GoF (reduced chi-square) as function of the position angle of the scan direction. The quantity was computed using only transits used in the astrometric solution, for example those without the EPSL and without outliers. See the description of parameter ipdGofHarmonicAmplitude for further details. Note (29): This field provides information on the raw windows used for the astrometric processing of this source coming from the Image Parameters Determination (IPD) module in the core processing. It provides the fraction of windows (having a successful IPD result), as percentage (from 0 to 100), for which the IPD algorithm has identified a double peak, meaning that the detection may be a visually resolved double star (either just visual double or real binary). The quantity was computed using all transits where the IPD was successful. Note (30): This field is calculated during AGIS and provides information on the raw windows used for the astrometric processing of this source. It provides the fraction (as a percentage, from 0 to 100) of transits having either truncation or multiple gates flagged in one or more windows. Such a situation invariably means that the on-board VPU detected some nearby source (which may be just a spurious detection, but typically could be some real nearby source - having another distinct transit and most probably assigned to a different source). So in general a non-zero fraction indicates that this source may be contaminated by another nearby source. The quantity was computed using all transits where the IPD was successful. Note (31): The scanDirectionStrengthK1...4 and scanDirectionMeanK1...4 quantify the distribution of AL scan directions across the source. scanDirectionStrengthK1 (and similarly 2,3,4) are the absolute value of the trigonometric moments mk = exp(ikθ) for k = 1, 2, 3, 4 where θ is the position angle of the scan and the mean value is taken over the astrometricNGoodObsAl observations contributing to the astrometric parameters of the source. θ is defined in the usual astronomical sense: θ = 0 when the FoV is moving towards local North, and θ = 90° towards local East. N.B. When astrometricNObsAc >0 the scan direction attributes are not provided at Gaia EDR3. Hence for all sources brighter than G≃13, and for a tiny fraction of fainter sources (∼1%), these 8 scan direction fields will be NULL. The scanDirectionStrengthK1...4 are numbers between 0 and 1, where 0 means that the scan directions are well spread out in different directions, while 1 means that they are concentrated in a single direction (given by the corresponding scanDirectionMeanK1...4). The different orders k are statistics of the scan directions modulo 360°/k. For example, at first order (k=1), θ=10° and θ=190° count as different directions, but at second order (k=2) they are the same. Thus, scanDirectionStrengthK1 is the degree of concentration when the sense of direction is taken into account, while scanDirectionStrengthK2 is the degree of concentration without regard to the sense of direction. A large value of scanDirectionStrengthK4 indicates that the scans are concentrated in two nearly orthogonal directions. Note (32): The scanDirectionStrengthK1...4 and scanDirectionMeanK1...4 attributes quantify the distribution of AL scan directions across the source. scanDirectionMeanK1 (and similarly for k = 2, 3, 4) is 1/k times the argument of the trigonometric moments mk = exp(ikθ), where θ is the position angle of the scan and the mean value is taken over the astrometricNGoodObsAl observations contributing to the astrometric parameters of the source. θ is defined in the usual astronomical sense: θ=0 when the FoV is moving towards local North, and θ=90° towards local East. N.B. When astrometricNObsAc>0 the scan direction attributes are not provided at Gaia EDR3. Hence for all sources brighter than G∼13, and for a tiny fraction of fainter sources (∼1%), these 8 scan direction fields will be NULL. scanDirectionMeanK1 (and similarly for k = 2, 3, 4) is an angle between -180°/k and +180°/k, giving the mean position angle of the scans at order k. The different orders k are statistics of the scan directions modulo 360°/k. For example, at first order (k=1), θ=10° and θ=190° count as different directions, but at second order (k=2) they are the same. Thus, scanDirectionMeanK1 is the mean direction when the sense of direction is taken into account, while scanDirectionMeanK2 is the mean direction without regard to the sense of the direction. For example, scanDirectionMeanK1 = 0 means that the scans preferentially go towards North, while scanDirectionMeanK2 = 0 means that they preferentially go in the North-South direction, and scanDirectionMeanK4 = 0 that they preferentially go either in the North-South or in the East-West direction. Note (33): 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. The duplicity criterion used for Gaia DR3 is an angular distance of 0.18 arcsec, while a limit of 0.4 arcsec was used for Gaia DR2. Note (34): Mean magnitude in the G band. 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 (35): Number of observations (CCD transits) that contributed to the integrated BP mean flux and mean flux error. Note (36): Error on the mean flux in the integrated BP band (errors are computed from the dispersion about the weighted mean of input calibrated photometry). A handful of sources have error equal to zero. Note (37): Integrated BP mean flux divided by its error. A handful of sources have error equal to zero, meaning that the ratio is NULL. Note (38): 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 (39): Error on the mean flux in the integrated RP band (errors are computed from the dispersion about the weighted mean of input calibrated photometry). A handful of sources have error equal to zero. Note (40): Integrated RP mean flux divided by its error. A handful of sources have error equal to zero, meaning that the ratio is NULL. Note (41): 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 (42): Number of BP transits that contributed to the mean photometry and were considered to be contaminated by one or more nearby sources. The contaminating sources may come from the other field of view. Note (43): Number of BP transits that contributed to the mean photometry and were flagged to be blends of more than one source (i.e. more than one source is present in the observing window). The blended sources may come from different fields of view. Note (44): Number of RP transits that contributed to the mean photometry and were considered to be contaminated by one or more nearby sources. The contaminating sources may come from the other field of view. Note (45): Number of RP transits that contributed to the mean photometry and were flagged to be blends of more than one source (i.e. more than one source is present in the observing window). The blended sources may come from different fields of view. Note (46): Spectroscopic radial velocity in the solar barycentric reference frame. The radial velocity provided is the median value of the radial velocity measurements at all epochs. At Gaia EDR3 this value is simply that copied in from Gaia DR2. The Gaia DR2 values are assigned to the Gaia EDR3 sources through an internal cross-match operation and about 11000 sources could not be matched. In addition about 4000 identified spurious radial velocities are not copied. For further details see Section [ssec:cu6spe_nonewdata] in the online documentation for the release. Note (47): The dr2RadialVelocityError 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. At Gaia EDR3 this column is simply that copied in from Gaia DR2. The Gaia DR2 radial velocities and associated quantities are assigned to the Gaia EDR3 sources through an internal cross-match operation and about 11000 sources could not be matched. In addition about 4000 identified spurious radial velocities, along with their associated values, are not copied. For further details see Section [ssec:cu6spe_nonewdata] in the online documentation for the release. In detail, dr2RadialVelocityError = sqrt(sigma2Vrad + 0.112) where sigmaVrad is the error on the median: sigmaVrad = sqrt(pi/2).(sigma(Vradt)/sqrt(dr2RvNbTransits)) where sigma(Vradt) is the standard deviation of the epoch radial velocities and dr2RvNbTransits the number of transits for which a Vradt has been obtained. Note (48): The number of transits (epochs) used to compute dr2RadialVelocity. At Gaia EDR3 this value is simply that copied in from Gaia DR2. The Gaia DR2 radial velocities and associated quantities are assigned to the Gaia EDR3 sources through an internal cross-match operation and about 11000 sources could not be matched. In addition about 4000 identified spurious radial velocities, along with their associated values, are not copied. For further details see Section [ssec:cu6spe_nonewdata] in the online documentation for the release. Note (49): Effective temperature of the synthetic spectrum template used to determine dr2RadialVelocity. N.B. the purpose of this parameter is to provide information on the synthetic template spectrum used to determine dr2RadialVelocity, and not to provide an estimate of the stellar effective temperature of this source. At Gaia EDR3 this value is simply that copied in from Gaia DR2. The Gaia DR2 radial velocities and associated quantities are assigned to the Gaia EDR3 sources through an internal cross-match operation and about 11000 sources could not be matched. In addition about 4000 identified spurious radial velocities, along with their associated values, are not copied. For further details see Section [ssec:cu6spe_nonewdata] in the online documentation for the release. Note (50): log of the synthetic spectrum template used to determine dr2RadialVelocity. N.B. the purpose of this parameter is to provide information on the synthetic template spectrum used to determine dr2RadialVelocity, and not to provide an estimate of the logg of this source. At Gaia EDR3 this value is simply that copied in from Gaia DR2. The Gaia DR2 radial velocities and associated quantities are assigned to the Gaia EDR3 sources through an internal cross-match operation and about 11000 sources could not be matched. In addition about 4000 identified spurious radial velocities, along with their associated values, are not copied. For further details see Section [ssec:cu6spe_nonewdata] in the online documentation for the release. Note (51): Fe/H of the synthetic spectrum template used to determine dr2RadialVelocity. N.B. the purpose of this parameter is to provide information on the synthetic template spectrum used to determine dr2RadialVelocity, and not to provide an estimate of the stellar atmospheric Fe/H of this source. At Gaia EDR3 this value is simply that copied in from Gaia DR2. The Gaia DR2 radial velocities and associated quantities are assigned to the Gaia EDR3 sources through an internal cross-match operation and about 11000 sources could not be matched. In addition about 4000 identified spurious radial velocities, along with their associated values, are not copied. For further details see Section [ssec:cu6spe_nonewdata] in the online documentation for the release. Note (52): Galactic Longitude of the object at reference epoch refEpoch, see Section [ssec:cu3astintrogalactic] of the release documentation for conversion details. Note (53): Galactic Latitude of the object at reference epoch refEpoch, see Section [ssec:cu3astintrogalactic] of the release documentation for conversion details. Note (54): Ecliptic Latitude of the object at reference epoch refEpoch. For further details see the description for attribute eclLon. Note (55): Cross-identifications from Gaia EDR3 "best neighbour" tables, panstarrs1bestneighbour, sdssr13bestneighbour, skymapperdr2bestneighbour and urat1bestneighbour.
Byte-by-byte Description of file: agncrid.dat
Bytes Format Units Label Explanations
1- 25 A25 --- Name Source name in the external catalog (sourcenamein_catalogue) 27- 45 I19 --- Source Gaia source ID (source_id) 47- 88 A42 --- Cat Catalog name (catalogue_name) (1)
Note (1): Catalog names as follows: 2WHSP (Changet al. 2017) = 2WHSP catalog, Chang et al., 2017A&A...598A..17C, Cat. J/A+A/598/A17 ALMA calibrators (Bonato et al. 2019) = ALMA Calibrator Catalogue, Bonato et al., 2019MNRAS.485.1188B, Cat. J/MNRAS/485/1188 AllWISE (Secrestet al. 2015) = AllWISE Data Release, Cat. II/328 Secrest et al., 2015ApJS..221...12S, Cat. J/ApJ/221/12 Gaia-unWISE (Shuet al. 2019) = Gaia-unWISE catalog of AGN, Shu et al., 2019MNRAS.489.4741S ICRF3K ICRF3S/X ICRF3X/Ka LAMOST phase1 DR1-5 = LAMOST DR1-DR5 Luo et al., 2015RAA....15.1095L, DR5 Cat, V/164 LQAC5 (Souchay et al.2019) = Astrometric Catalogue 5, LQAC-5, Souchay et al., 2019A&A...624A.145S, Cat. J/A+A/624/A145 LQRF(Andrei et al. 2009) = LQRF: Large Quasar Reference Frame, Andrei et al., 2009A&A...505..385A, Cat. I/313 Milliquas v6.5 update (Flesch 2019) = Million Quasars (Milliquas) catalog, Flesch et al., 2015PASA...32...10F, Cat. VII/283 (v6.3) OCARS (Malkin 2018) = OCARS catalog, Malkin, 2016ARep...60..996M, http://www.gaoran.ru/english/as/ac_vlbi/ocars.txt R90 (Assefet al. 2018) = WISE AGN catalog, Assef et al;, 2018ApJS..234...23A, Cat. J/ApJS/234/23 Roma-BZCAT release 5 (Massaro et al.2015) = Roma BZCAT - 5th edition, Massaro et al., 2015Ap&SS.357...75M, Cat. VII/274 SDSS DR14Q (Pariset al. 2018) = SDSS quasar catalog, fourteenth data release, Paris et al., 2018A&A...613A..51P, Cat. VII/286
Byte-by-byte Description of file: tyc2tdsc.dat
Bytes Format Units Label Explanations
1- 14 A14 --- IDTyc2 Tycho-2 identifier (TYC1-TYC2-TYC3) (id) 16- 21 I6 --- HIP ? Hipparcos number (hip) 23- 28 I6 --- TYC1 TYC1 component from TYC or GSC (tyc1) 30- 36 I7 --- TYC2 TYC2 component from TYC or GSC (tyc2) 38- 40 I3 --- TYC3 TYC2 component from TYC or GSC (tyc3) 42- 51 I10 --- TYC Numeric Tycho-2 identifier ((tyc1*1000000)+(tyc2*10)+(tyc3)) (id_tycho) 53- 55 A3 --- IDTyc1 Tycho-1 star (tyc) 57- 68 E12.8 deg RATdeg Observed Tycho-2 Right Ascension (ICRS) at epoch 1990+EpRA1990 (ra) 70- 81 E12.8 deg DETdeg Observed Tycho-2 Declination (ICRS) at epoch 1990+EpDE1990 (dec) 83- 94 E12.8 --- --- --- 96-107 E12.8 --- --- --- 109-120 E12.8 deg RAmdeg ? Mean Right Ascension (ICRS) at Ep=J2000 (ra_mdeg) 122-133 E12.8 deg DEmdeg ? Mean Declination (ICRS) at Ep=J2000 (de_mdeg) 135-141 F7.1 mas/yr pmRA ? Proper motion in right ascension, pmRA*cos(DE) (pm_ra) 143-149 F7.1 mas/yr pmDE ? Proper motion in Declination (pm_de) 151-154 F4.2 yr EpRA1990 Epoch-1990 of RAdeg (ep_ra1990) 156-159 F4.2 yr EpDE1990 Epoch-1990 of DEdeg (ep_de1990) 161-167 F7.2 yr EpRAmdeg ? Mean epoch of RAmdeg (epram) 169-175 F7.2 yr EpDEmdeg ? Mean epoch of DEmdeg (epdem) 177-178 I2 --- Num ? Number of positions used for forming mean data (num) 180-184 F5.1 mas e_RATdeg Uncertainty RA*cos(dec), of observed Tycho-2 RA (eradeg) 186-190 F5.1 mas e_DETdeg Uncertainty of observed Tycho-2 Dec (ededeg) 192-195 F4.1 --- Corr ? Correlation (RAdeg,DEdeg) (corr) 197-201 F5.1 mas e_RAmdeg ? Uncertainty RA*cos(dec),at mean epoch (eramdeg) 203-207 F5.1 mas e_DEmdeg ? Uncertainty of Dec at mean epoch (edemdeg) 209-212 F4.1 mas/yr e_pmRA ? Uncertainty proper motion in RA*cos(dec) (epmra) 214-217 F4.1 mas/yr e_pmDE ? Uncertainty of proper motion in Dec (epmde) 219-221 F3.1 --- q_RAmdeg ? Goodness of fit for mean RA (qramdeg) 223-225 F3.1 --- q_DEmdeg ? Goodness of fit for mean DE (qdemdeg) 227-229 F3.1 --- q_pmDE ? Goodness of fit for pmDe (qpmde) 231-233 F3.1 --- q_pmRA ? Goodness of fit for pmRa (qpmra) 235-237 A3 --- pflag Mean position flag (pflag) 239-241 A3 --- posflg Type of Tycho-2 solution (posflg) 243-246 A4 --- CCDM CCDM component identifier for HIP stars (ccdm) 248-250 I3 --- prox ? Proximity indicator (prox) 252-257 F6.3 mag BTmag ? Tycho-2 BT magnitude (bt_mag) 259-264 F6.3 mag VTmag ? Tycho-2 VT magnitude (vt_mag) 266-270 F5.3 mag e_BTmag ? Uncertainty of BTmag (ebtmag) 272-276 F5.3 mag e_VTmag ? Uncertainty of VTmag (evtmag) 278-282 I5 --- TDSC ? TDSC identifier for the system (sys_no) 284-287 A4 --- cmp Component designation (cmp) 289-290 I2 --- Nmain ? Number of components in TDSC main catalogue (n_main) 292 I1 --- Nsup ? Number of components in the TDSC supplement (n_sup) 294 A1 --- magflg TDSC photometry flag (magflg) 296-307 A12 --- WDS WDS identifier for the system (wds) 309 A1 --- Note TDSC notes (note) 311-316 I6 --- HD ? HD identifier for TDSC entries (hd) 318-321 A4 --- rcmp Reference component for position angle and separation (rcmp) 323-327 F5.1 deg PA ? Position angle of the present component (cmp) with respect to the reference component (rcmp) (pa) 329-335 F7.2 arcsec Sep ? Separation of the present component (cmp) with respect to the reference component (rcmp) (sep) 337-340 F4.1 deg e_PA ? Uncertainty of the position angle (e_pa) 342-344 I3 --- e_PA.Sep ? Uncertainty of the position angle * separation (epasep) 346-348 I3 mas e_Sep ? Uncertainty of the separation (e_sep)
Byte-by-byte Description of file: comscanl.dat
Bytes Format Units Label Explanations
1- 18 F18.13 d JD [1666.42/2704.38] Julian date in TCB at Gaia (JD-2455197.5) (jd_time) (1) 20- 37 F18.13 d BJD-FOV1 [1666.42/2704.38] Observation time for FOV1 Barycentric JD (in TCB) (BJD-2455197.5) (bjd_fov1) (2) 39- 56 F18.13 d BJD-FOV2 [1666.42/2704.38] Observation time for FOV2 Barycentric JD (in TCB) (BJD-2455197.5) (bjd_fov2) (3) 58- 75 I18 --- OBMT Observation time at Gaia converted to OBMT using the HATT (High Accuracy Time Transformation) (obmt_time) 77- 88 E12.10 deg RA1deg FOV1 barycentric right ascension in ICRS at given time BJD-FOV1 (ra_fov1) 90-103 E14.10 deg DE1deg FOV1 barycentric declination in ICRS at given time BJD-FOV1 (dec_fov1) 105-113 I9 --- HP1 [0/201326589] FOV1 HEALPix level 12 (healpixfov1) (4) 115-127 E13.10 --- SA1 [-180/180] FOV1 Scan position angle (scananglefov1) 129-140 E12.10 deg RA2deg FOV2 barycentric right ascension in ICRS at given time BJD-FOV2 (ra_fov2) 142-154 E13.10 deg DE2deg FOV1 barycentric declination in ICRS at given time BJD-FOV2 (dec_fov2) 156-164 I9 --- HP2 [56/201326571] FOV2 HEALPix level 12 (healpixfov2) (4) 166-178 E13.10 --- SA2 [-180/180] FOV2 Scan position angle (scananglefov2) 180-198 I19 --- SolID Solution ID (solution_id) (5)
Note (1): The time at which the scan angles and FoV angles are evaluated in TCB (Temps Coordonnee Barycentrique) with 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. Note (2): 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 corresponding to an infinitely distant source at (raFov1, decFov1), 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. Note (3): 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 corresponding to an infinitely distant source at (raFov2, decFov2), 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. Note (4): Level 12 nested scheme HEALPix containing the Field of View (preceding) right ascension and declination. This field can be used in conjunction with sourceId, whose most significant bits contain HEALPix information. Note (5): 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.
Byte-by-byte Description of file: framers.dat
Bytes Format Units Label Explanations
1- 19 I19 --- Source Gaia source ID (source_id) 21- 25 A5 --- CRFO [False/True ] True if the source was a considered source for the reference frame orientation, false otherwise (consideredforreferenceframeorientation) 27- 31 A5 --- URFO [False/True ] True if the source was effectively used for the reference frame orientation, false otherwise (usedforreferenceframeorientation) 33- 36 A4 --- CRFF [False/True ] True if the source was a considered source for the reference frame spin determination, false otherwise (consideredforreferenceframespin) 38- 42 A5 --- URFF [False/True ] True if the source was effectively used for the reference frame spin determination, false otherwise (usedforreferenceframespin)
Global notes: Note (G1): Note on magnitude errors: They are obtained with a simple propagation of errors with the formulas e_Gmag = sqrt((-2.5/ln(10)*e_FG/FG)**2 + sigmaG_0**2) e_GBPmag = sqrt((-2.5/ln(10)*e_FGBP/FGBP)**2 + sigmaGBP_0**2)) e_GRPmag = sqrt((-2.5/ln(10)*e_FGRP/FGRP)**2 + sigmaGRP_0**2)) with the G, G_BP, G_RP zero point uncertainties sigmaG_0 = 0.0027553202 sigmaGBP_0 = 0.0027901700 sigmaGRP_0 = 0.0037793818 See https://www.cosmos.esa.int/web/gaia/edr3-passbands for more details Note (G2): Note on Calibration corrected values. G-band magnitude correction for sources with 6-parameter astrometric solutions. The paper Gaia Early Data Release 3: Photometric content and validation by Riello et al. (2020) explains that for sources with 6-parameter astrometric solutions the G-band magnitude should be corrected and a formula to do so is provided. The corresponding Python code to do this is presented in Gaia Early Data Release 3: Summary of the contents and survey properties (Gaia Collaboration et al., 2020). The source code can be found as a Jupyter notebook in this repository: https://github.com/agabrown/gaiaedr3-6p-gband-correction Corrected flux excess factor. The paper Gaia Early Data Release 3: Photometric content and validation by Riello et al. (2020) presents a corrected version of the photometric flux excess factor as published in the Gaia EDR3 catalogue. The corrected version acounts for the average variation of the flux excess for 'normal' sources. A formula for calculating the corrected excess factor is provided. The corresponding Python code to do this is presented in Gaia Early Data Release 3: Summary of the contents and survey properties (Gaia Collaboration et al., 2020). The source code can be found as a Jupyter notebook in this repository: https://github.com/agabrown/gaiaedr3-flux-excess-correction See also: https://www.cosmos.esa.int/web/gaia/edr3-code
History: From Gaia team Acknowledgements: Gaia team References: Gaia Early Data Release 3: Summary of the contents and survey properties Brown, A.G.A., et al., 2020A&A...649A...1G Gaia Early Data Release 3: The astrometric solution Lindegren, L., et al., 2020A&A...649A...2L Gaia Early Data Release 3: Photometric content and validation Riello, M., et al., 2020A+&...649A...3R, Cat. J/A+A/649/A3 Gaia Early Data Release 3: Parallax bias versus magnitude, colour and position Lindegren, L., et al., 2020A&A...649A...4L Gaia Early Data Release 3: Catalogue Validation Fabricius, C., et al., 2020A&A...649A...5F Gaia Early Data Release 3: The Gaia catalogue of nearby stars Gaia Collaboration, Smart, R.L., et al., 2020A&A...649A...6G, Cat. J/A+A/649/A6 Gaia Early Data Release 3: Structure and properties of the Magellanic Clouds Gaia Collaboration, Luri et al, 2020A&A...649A...7G Gaia Early Data Release 3: The Galactic anticentre Gaia Collaboration, Antoja, T., et al., 2020A&A...649A...8G Gaia Early Data Release 3: Acceleration of the solar system from Gaia astrometry Gaia Collaboration, Klioner, S.A., et al., 2020A&A...649A...9G Gaia Early Data Release 3: Building the Gaia DR3 source list - Cross-match of Gaia observations Torra, F., et al., 2020A&A...649A..10T Gaia Early Data Release 3: Modelling and calibration of Gaia's point and line spread functions Rowell, N., et al., 2020A&A...649A..11R Gaia Early Data Release 3: The celestial reference frame (GAIA-CRF3) Gaia Collaboration, et al. Gaia Early Data Release 3: Updated radial velocities from Gaia DR2 Seabroke, G.M., et al. Gaia Early Data Release 3: Cross-match with external catalogues - Algorithm and results Marrese, P., et al.
(End) Giacomo Monari, Thomas Boch, Patricia Vannier [CDS] 03-Dec-2020
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