14.4.9 urat1_original_valid
URAT-1 Catalogue
Reference paper:
The first U.S. Naval Observatory Astrometric Robotic Telescope Catalog (URAT1), Zacharias et al. (2015).
Original catalogue:
CDS
urat1_oid : Unique Numeric Identifier (long)
Incremental unique numeric identifier (increasing with declination).
This is the only field which was not in the original URAT1 catalogue, but was added for cross-match purposes.
urat1_identifier : source Id in original catalog (string)
Official URAT1 star ID numbers consist of 2 parts, the 3-digit zone
number (zzz) and the 6-digit running record number (nnnnnn) along a
zone.
Thus a URAT1 star number is given by:
URAT1-zzznnnnnn
The main catalog data are arranged in declination zones of 0.2 degree
width. Zones are numbered from 1 starting at the South Pole and
increasing toward north. The first zone with data in URAT1 is 326
for -25.0 to -24.8 deg Dec. There is a separate file for each zone
up to zone 900 near the north celestial pole.
ra : RA, ICRS at mean epoch (double, Angle[deg])
Positions are on the International Celestial Reference System (ICRS) as represented by the UCAC4 catalog.
Mean observed positions are given at mean epoch of URAT observations (epoch). Thus the epoch is slightly different from star to star, but it is always in the range between 2012.311 and 2014.679.
dec : DEC, ICRS at mean epoch (double, Angle[deg])
Positions are on the International Celestial Reference System (ICRS) as represented by the UCAC4 catalog.
Mean observed positions are given at mean epoch of URAT observations (epoch). Thus the epoch is slightly different from star to star, but it is always in the range between 2012.311 and 2014.679.
ra_error : Position error from model (double, Angle[arcsec])
ra_error = posError
posError gives an estimate of the error of the mean position components (ra and dec).
A mean was taken over RA and DEC component errors because they are very similar for most stars.
Here a model is used which include image profile fit (x,y data) errors, atmospheric turbulence, and astrometric reduction error propagations. A systematic error floor of 5 mas was added RMS. The model error is likely a better estimate of the true positional errors than the scatter error, at least for small numbers of observations.
dec_error : Position error from model (double, Angle[arcsec])
dec_error = posError
posError gives an estimate of the error of the mean position components (ra and dec).
A mean was taken over RA and DEC component errors because they are very similar for most stars.
Here a model is used which include image profile fit (x,y data) errors, atmospheric turbulence, and astrometric reduction error propagations. A systematic error floor of 5 mas was added RMS. The model error is likely a better estimate of the true positional errors than the scatter error, at least for small numbers of observations.
epoch : Epoch for mean URAT1 observation (double, Time[Julian Years])
epoch = mean epoch of URAT observations.
f_mag : mean observerd magnitude in URAT bandpass (double, Magnitude[mag])
This is the mean, observed magnitude in the 680-762 nm URAT bandpass, calibrated by APASS photometry. This bandpass is between R and I, thus further into the red than UCAC. Observations in non-photometric nights *are* included thus the URAT magnitudes need to be taken with caution. Unknown or unrealistic magnitudes are set to NULL. The faintest maybe real celestial object magnitude is about 19.0, while the URAT1 catalog should be complete to about magnitude 18.0.
f_mag_error : URAT photometry error (double, Magnitude[mag])
The photometric error of URAT bandpass observations is derived from the scatter of individual observations. A systematic error floor of 0.01 mag has been RMS added. Unknown errors are
indicated by NULL.
b_mag : APASS B magnitude (double, Magnitude[mag])
APASS B magnitude.
A custom set of APASS (The AAVSO Photometric All-Sky Survey) data was kindly provided to us by Arne Henden to include the DR8 data plus single photometric observations.
For a total of 71614 stars with no DR8 data the DR6 data was used.
v_mag : APASS V magnitude (double, Magnitude[mag])
APASS V magnitude.
A custom set of APASS (The AAVSO Photometric All-Sky Survey) data was kindly provided to us by Arne Henden to include the DR8 data plus single photometric observations.
For a total of 71614 stars with no DR8 data the DR6 data was used.
g_mag : APASS g magnitude (double, Magnitude[mag])
APASS g magnitude.
A custom set of APASS (The AAVSO Photometric All-Sky Survey) data was kindly provided to us by Arne Henden to include the DR8 data plus single photometric observations.
For a total of 71614 stars with no DR8 data the DR6 data was used.
r_mag : APASS r magnitude (double, Magnitude[mag])
APASS r magnitude.
A custom set of APASS (The AAVSO Photometric All-Sky Survey) data was kindly provided to us by Arne Henden to include the DR8 data plus single photometric observations.
For a total of 71614 stars with no DR8 data the DR6 data was used.
i_mag : APASS i magnitude (double, Magnitude[mag])
APASS i magnitude.
A custom set of APASS (The AAVSO Photometric All-Sky Survey) data was kindly provided to us by Arne Henden to include the DR8 data plus single photometric observations.
For a total of 71614 stars with no DR8 data the DR6 data was used.
b_mag_error : Error on APASS B magnitude (double, Magnitude[mag])
Error on APASS B magnitude.
v_mag_error : Error on APASS V magnitude (double, Magnitude[mag])
Error on APASS V magnitude.
g_mag_error : Error on APASS g magnitude (double, Magnitude[mag])
Error on APASS g magnitude.
r_mag_error : Error on APASS r magnitude (double, Magnitude[mag])
Error on APASS r magnitude.
i_mag_error : Error on APASS i magnitude (double, Magnitude[mag])
Error on APASS i magnitude.