I/239/epophot Tycho/Hipparcos Epoch Photometry Data ================================================================================ Description: The Hipparcos and Tycho Catalogues (ESA 1997) are accessible as Catalog ( at ftp://cdsarc.u-strasbg.fr/pub/cats/I/239), or can directly be queried by VizieR from http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=I/239 or mirrors http://vizier.nao.ac.jp/viz-bin/VizieR?-source=I/239 http://vizier.hia.nrc.ca/viz-bin/VizieR?-source=I/239 http://vizier.cfa.harvard.edu/viz-bin/VizieR?-source=I/239 http://urania.iucaa.ernet.in/viz-bin/VizieR?-source=I/239 http://archive.ast.cam.ac.uk/viz-bin/VizieR?-source=I/239 http://www.inasan.rssi.ru/viz-bin/VizieR?-source=I/239 http://www.bao.ac.cn/viz-bin/VizieR?-source=I/239 Transit data related to Tycho Catalogue objects considered to be of greatest astrophysical value constitute the Tycho Epoch Photometry Annex A, and is included in the CD-ROMs version of the Hiparcos catalogue; it concerns 34446 objects. Epoch photometry for 481553 objects originally constitutes the Tycho Epoch Photometry Annex B; however the data related to some of the zones could not be recovered, but the majority of the lost data could be reconstructed and are marked as 'b' in the status of Tycho Epoch Photometry. The results of the individual transits stored in a 2-level directory tree, the first level being made of the 2 leftmost digits of the TYC1 number (the leftmost of the 3 numbers making up the TYC designation). The Epoch Photometry data for all stars sharing the same TYC1 number are stored in a file, with a blank line is inserted between two objects; these files have been compressed with the gzip utility, but the starting byte of each individual file is reported in index files. Each object contained in the Epoch Photometry Annex consists in a 1-line header, followed by the individual transit records. The record structure is described in section 2.6 of the first volume of the Hipparcos catalogue (pp. 229-235), and summarized below in the "Header Records" section and "Individual transit records" section. It should be noted that the mean magnitudes reported in the header records (and also in the Tycho catalogue) have been computed with de-censoring methods -- i.e. absence of detections have been taken into account. The result is that the mean magnitudes are generally fainter than what can be derived from an arithmetic mean of the individual magnitudes. Transit data related to Hipparcos objects are stored in the hip_epo.dat file of the CD-ROM version of the Hipparcos catalogue, and described in section 2.5 (pages 217-225) of volume 1. The transit data are stored also as a header records described in the "Hipparcos Header Records" section below, followed by transit records described in the "Hipparcos Transit Records" section. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- README 80 . This file tyc_epo.dat 14 524423 The status of Tycho Epoch Photometry -------------------------------------------------------------------------------- See also: I/239 : The Hipparcos and Tycho Catalogues (ESA 1997) Byte-by-byte Description of file: tyc_epo.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 12 A12 --- TYC Tycho star name 14 A1 --- morePhoto *[ABbc-] Availability of Tycho Epoch Photometry -------------------------------------------------------------------------------- Note on morePhoto: the statuses are: A : Best part of Tycho Epoch Photometry B : Less reliable Tycho Epoch Photometry b : indicates a class 'B' which was reconstructed in 2001 for some missing stars; the reconstruction did not give exactly the same result. c : star announced without Epoch Photometry, but a photometry could be derived in 2001. - : indicates a class 'B' for which the Epoch Photometry could not be reconstructed -------------------------------------------------------------------------------- Header Records: -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- TYC1 TYC1-3 number 6- 10 I5 --- TYC2 TYC1-3 12 I1 --- TYC3 TYC1-3 14- 16 I3 --- Ntr Number of transit records 18- 20 I3 --- Nb Number of transits measured in the B_T_ band 22- 27 F6.3 mag BTmag ? Mean BT magnitude (median or de-censored mean) 29- 33 F5.3 mag e_BTmag ? Mean error on BTmag 35- 40 F6.3 mag BTmax ? BTmag at maximum (15th percentile) 42- 47 F6.3 mag BTmin ? BTmag at minimum (85th percentile) 49- 51 I3 --- Nv Number of transits measured in the V_T_ band 53- 58 F6.3 mag VTmag ? Mean VT magnitude (median or de-censored mean) 60- 64 F5.3 mag e_VTmag ? Mean error on VTmag 66- 71 F6.3 mag VTmax ? VTmag at maximum (15th percentile) 73- 78 F6.3 mag VTmin ? VTmag at minimum (85th percentile) 80- 81 I2 --- Flag1 [0,63]? Duplicity/variability flag (1) 83- 84 I2 --- Flag2 [0,7] Status (2) ------------------------------------------------------------------------------- Note (1): Flag made of 6 bits: 0 = approximate magnitude (from Tycho field T36) 1 = Variable or suspected from GCVS or NSV catalogues (from Tycho field T47) 2 = Variable or suspected from Tycho analysis (from Tycho field T48) 3 = close pair, known from Hipparcos or Tycho (from Tycho field T2) 4 = double or suspected, unresolved by Tycho (from Tycho field T49) 5 = Variable or suspected from Hipparcos analysis (from Hipparcos field H6) Note (2): Flag made of 3 bits: 0 = standard star for photometric calibration in normal processing 1 = standard star for photometric calibration in reprocessing 2 = photometric reduction used instrument parameters from reprocessing The value of this flag is set to 3 (bits 0 and 1 set) for reconstructed photometry (stars having the 'b' or 'c' status in the morePhoto column of the tyc_epo.dat file). In this case, the values of Flag1, and of the magnitudes, are blank. ------------------------------------------------------------------------------- Individual transit records: -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 F10.5 d JD-2440000 *Observation epoch (barycentric Julian date) (TT1) 12- 17 F6.3 mag BTmag ? Transit calibrated magnitude for B_T_ (TT2) 19- 23 F5.3 mag e_BTmag ? Standard error on BTmag (TT3) 25- 30 F6.2 ct BTbg Background counts per sample (1/600s) (TT4) 32- 37 F6.3 mag VTmag ? Transit calibrated magnitude for V_T_ (TT5) 39- 43 F5.3 mag e_VTmag ? Standard error on VTmag (TT6) 45- 50 F6.2 ct VTbg Background counts per sample (1/600s) (TT7) 52- 58 F7.1 arcsec z *Position at which the star transitted (TT8) 60- 64 F5.1 deg PAz *Position angle of the slit normal (TT9) 66- 70 I5 mas Du ? Astrometric residual of the transit (TT10) 72- 75 I4 mas e_Du ? Expected standard error on Du (TT11) 77- 81 F5.1 --- F2 *? Goodness of fit (TT12) 83- 84 I2 --- Tflg *[0,31] Transit flags (TT13) -------------------------------------------------------------------------------- Note on JD-2440000: for reconstructed transits (stars having the 'b' or 'c' status in the morePhoto column of the tyc_epo.dat file), 4 decimals only are supplied; 5 decimals are supplied for the other transit times. Note on z, PAz: location of the transit on the star mapper slits. The position angle of the slit normal is reckoned positive in the direction of motion of the star in the field of view. Note on F2: values exceeding +2.5 to +3 indicate a bad fit to the data. Note on Tflg: the transit flag is made of 5 fits: 0 = magnitude not measured in B_T_ 1 = magnitude not measured in V_T_ 2 = transit rejected in astrometry and de-censoring 3 = transit on the vertical(0)/inclined(1) slit 4 = transit in following(0)/preceding(1) field Therefore, transits having the rightmost bit set (i.e. Tflg&1 != 0) have blank BTmag and e_BTmag columns; similarly, transits having (Tflg&2 != 0) have blank VTmag and e_BTmag. -------------------------------------------------------------------------------- Hipparcos Header Records: -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 6 I6 --- HIP Hipparcos number 8 A1 --- m_HIP Component flag, similar to column H48 (1) 10- 15 F6.3 mag V-I Color index used for photometric reductions 17- 19 I3 --- Ntr Number of total transits 21- 23 I3 --- Nh Number of photometrically accepted transits 29- 35 F7.4 mag Hpmag Median Hipparcos magnitude 37- 42 F6.4 mag e_Hpmag Standard error on Hpmag 44- 48 F5.2 mag Hpmax 5th percentile (max) Hipparcos magnitude 50- 54 F5.2 mag Hpmin 95th percentile (min) Hipparcos magnitude 57- 67 F11.7 d Per ? Variability period 69- 77 F9.4 d T0 ? Reference epoch (BJD-2440000) 79 A1 --- VType Variability type, from Hipparcos H52 field (2) 81 A1 --- Flg1 Variability Annex flag (from H53) 83 A1 --- Flg2 [ABC] Existing Light curve (from H54) -------------------------------------------------------------------------------- Note (1): indicates the component to which the photometry refers: A to Z : the letter indicates the specified component measured * : combined Hpmag of a double system, corrected for attenuation - : combined Hpmag of a multiple system, not corrected for attenuation Note (2): the type is defined as: C : no variability detected ("constant") D : duplicity-induced variability M : possibly micro-variable (amplitude < 0.03mag) P : periodic variable R : V-I colour index was revised due to variability analysis U : unsolved variable which does not fall in the other categories -------------------------------------------------------------------------------- Hipparcos Transit Records: -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 F10.5 d JD-2440000 Observation epoch (barycentric Julian date) (HT1) 12- 18 F7.4 mag Hpmag Transit calibrated Hp magnitude (HT2) 20- 24 F5.3 mag e_Hpmag Standard error on Hpmag (HT3) 26- 28 I3 --- Tflg *[0,511] Quality flag (HT4) -------------------------------------------------------------------------------- Note on Tflg: the transit flag is made of 9 fits: 0 = NDAC only 1 = FAST only 2 = (not used) 3 = Very high background estimate (threshold 70 Hz) 4 = Possible interfering object in either field of view 5 = FAST quality flag set 6 = Perturbed for other identified reasons 7 = Observation during Sun-pointing mode 8 = Significant difference between FAST and NDAC data -------------------------------------------------------------------------------- ================================================================================ (End) Francois Ochsenbein [CDS] 2002-May-09