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HDEC - Henry Draper Extension Charts Catalog. |
HEASARC Archive |
The HDEC catalog contains information on 86,933 stars, comprising accurate (0.5 arcseconds error) positions, (for more than 96 per cent of them) proper motions with a typical accuracy of 5.5 milliarcseconds (mas) per year, and the original spectral classifications. The current database contains the main portion of the catalog. An additional set of information, primarily comprising HD entries with cross-identifications with known or suspected variable stars, was included in the A.J. Cannon Memorial Volume (Cannon and Mayall 1949). This list was extended by Nesterov et al. (1991) to more than 500 identifications with variable stars. This latter expanded list, together with a list of entries which have uncertain identifications, is not included in the HEASARC version of this catalog but is available at the legacy anonymous ftp site (legacy.gsfc.nasa.gov) in the directory heasarc/dbase/misc_files/hdec as the file hdec.remarks. If the parameter `Remarks' is set to 'R' for an entry in the HDEC database, this means that there is a remark about that particular star in the above file.
Name
The name of the star, constructed by concatenating the prefix `HD' ,
the HD number, and the component identification (if any). Notice that the
IAU Dictionary of Astronomical Nomenclature recommends the prefix HD rather
than HDE for stars in the HDEC.
HD
The HD number of the star: notice that stars in the
HDEC have HD numbers in the range [272151/359083] inclusive.
RA
The right ascension of the star. For those stars for which proper motions
were known, the epoch of the position is J2000.0. If the star was identified
with either an AC or a GSC star (i.e., there is no known proper motion), the
position is given at the corresponding epoch of observation (specified by
the parameter observing_epoch). The modern-epoch positions have a typical
accuracy of 0.45 arcseconds.
Dec
The declination of the star. For those stars for which proper motions
were known, the epoch of the position is J2000.0. If the star was identified
with either an AC or a GSC star (i.e., there is no known proper motion), the
position is given at the corresponding epoch of observation (specified by
the parameter observing_epoch). The modern-epoch positions have a typical
accuracy of 0.45 arcseconds.
LII
The galactic longitude of the star.
BII
The galactic latitude of the star.
Component
The component identification for multiple systems using the
usual notation A, B, C, D, E, F. Notice that stars in multiple systems are
given the same HD number.
Remarks
A parameter that is set to 'R' if there is an individual remark
for this star given in the 'remarks' file. This latter file is not part of
the current database but can be obtained from the legacy anonymous ftp site
(legacy.gsfc.nasa.gov); it is in the directory heasarc/dbase/misc_files/hdec
as the file hdec.remarks.
Spect_Type
The HD spectral class of the star.
App_Mag
The apparent magnitude of the star: this is the photographic
B-magnitude taken from the Astrographic Catalog (AC) (for those entries
having the parameter position_source = "P", "A" or "C"), or the Guide Star
Catalog J or V magnitude (for those entries having the parameter
position_source = "G"). The typical accuracy of these magnitudes is 0.3 mag.
Position_Source
A flag referring to the catalog from which the star
position was obtained: "P" = the PPM Star Catalog, "C" = the Guide Star and
Astrographic Catalogs (GSC-AC), "A" = the Astrographic Catalog (AC), "G" =
the Guide Star Catalog (GSC), "M" means that no identification with any of
teh above-listed catalogs was possible, and that the position given is a reduced
measured one, and "V" means that the position was taken from either the
General Catalog of Variable Stars (GCVS) or the Catalog of Suspected Variable
Stars (CSVS).
Proper_Motion_Flag
A flag that is set to "T" if proper motions are given,
but set to "F" if only a position at a single epoch is known.
Proper_Motion_RA
The annual proper motion in RA, in units of arcseconds per
year. The typical rms error of the total proper motion is 5.5 mas per year.
Proper_Motion_Dec
The annual proper motion in Dec, in units of arcseconds per
year. The typical rms error of the total proper motion is 5.5 mas per year.
Observing_Epoch
For those stars for which only a single observation is
available, this parameter contains the observation epoch in Julian years.
Class
The browse classification of the star, derived from its listed
spectral type.