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            A Catalog of Spectroscopically Identified White Dwarfs

                            (McCook and Sion 1987)


                Documentation for the Computer-Readable Version


                              Wayne H. Warren Jr.
                                   July 1988


                        Doc. No. NSSDC/WDC-A-R&S 88-15



                  National Space Science Data Center (NSSDC)/
          World Data Center A for Rockets and Satellites (WDC-A-R&S)
                 National Aeronautics and Space Administration
                          Goddard Space Flight Center
                              Greenbelt, MD 20771




                                   Abstract

        The machine-readable version of the catalog, as it is currently
     being distributed from the Astronomical Data Center, is described.
     This catalog is a compilation of 1279 white dwarfs that been
     identified spectroscopically up to January 1987. It is the third
     edition of the Villanova Catalog of Spectroscopically Identified White
     Dwarfs and contains a large collection of basic photometric and
     spectroscopic data (with literature references), cross identifications
     to alternate designations, and computed absolute visual magnitudes
     based upon trigonometric parallaxes or the best available
     color-magnitude calibration.


1   Introduction


1.1   Description

   The present compilation is an expanded and updated successor to the first
(McCook and Sion 1977) and second (McCook and Sion 1984) editions of the
catalog. Due to the great increase in the number of newly identified spec-
troscopic degenerates and the publication of important surveys since the
previous editions, a new catalog was considered appropriate at this time.
Although the third edition does not incorporate a large number of newly
discovered stars, quite a few revisions, corrections, and some additions have
been made. New parallax and photometric data have been included, the de-
scriptions of the names entries expanded, and the notes section considerably
enlarged. As such, the new catalog provides a valuable addition to the large
number of machine-readable catalogs presently available to the astronomical
community.
   This document describes the machine-readable version of A Catalog of
Spectroscopically Identified White Dwarfs as it is currently being distributed
from the Astronomical Data Center (ADC). It is intended to enable users to read
and process the computerized catalog without problems and guesswork, and it
should be used only to supplement the information contained in the published
paper. Since there are several important formatting differences between the
published and machine-readable tables, users of the machine version are
encouraged to carefully study the data descriptions in the following sections
of this document before using and interpreting the data. A copy of this
document should be transmitted to any recipient of the machine-readable catalog
originating from the ADC.


1.2   Source Reference

McCook, G. P. and Sion, E. M. 1987, Astrophys. J. Suppl. 65, 603.


                                       1




2   Structure


2.1   File Summary

   The machine version of A Catalog of Spectroscopically Identified White
Dwarfs consists of five files. Table 1 gives the machine-independent file
attributes. All logical records are of fixed length, and if the catalog is
received on magnetic tape, it will contain blocks of fixed length (as noted
below) except that the last block of each file may be short. The second file
contains the basic data of the catalog, while succeeding ones contain textual
information to facilitate the use of the catalog data. The data file is in a
multiple-record format per object in order to allow all known observations of a
star to be reported. Although coordinates have been added to all records, those
other than the first for a given object may contain mostly blank fields except
for those that were needed to record particular multiple observations of the
object.

           ________________________________________________________
          | A Catalog of Spectroscopically Identified White Dwarfs |
          |                 (McCook and Sion 1987)                 |
          |________________________________________________________|
          |      |              | Record | Record |    Number of   |
          | File |   Contents   | Format | Length |     Records    |
          |______|______________|________|________|________________|
          |   1  | Introduction | Fixed  |   80   |       501      |
          |   2  | Data         | Fixed  |  188   |      2420      |
          |   3  | Notes        | Fixed  |   80   |       200      |
          |   4  | Names        | Fixed  |   30   |      2809      |
          |   5  | References   | Fixed  |   80   |       320      |
          |______|______________|________|________|________________|

                 Table 1: Summary Description of Catalog Files


   The information contained in the above table is sufficient for a user to
describe the indigenous characteristics of the machine-readable version of A
Catalog of Spectroscopically Identified White Dwarfs to a computer. Information
easily varied from installation to installation, such as block size (physical
record length), blocking factor (number of logical records per physical
record), total number of blocks, density, number of tracks and character coding
(ASCII, EBCDIC) for tapes, is not included, but should always accompany
secondary copies if any are supplied to other users or installations.



                                       2




2.2   Introduction (File 1 of 5)

   This file is composed of straight text and contains the introduction to the
published catalog. Column descriptions of catalog data are given here and are
therefore only briefly repeated in this document. A detailed byte-by-byte
description of the data format is not included in this introduction, however,
and is therefore given in the following section of this document.


2.3   Catalog (File 2 of 5)

   This file contains the compilation of basic data for the degenerate stars
included in the catalog. General data descriptions and remarks about the data
sources, etc. are given in the introductory file.
   As mentioned in Section 2.1, the data file may contain more than one logical
record per object if multiple values of reported data exist. This means that
any data field, except for the WD number and coordinates, may be blank. Since
the "names" field contains two subfields, there is space for two alternate
designations before a second record is needed. The inclusion of more than a
single value of any other datum requires that a second or succeeding record be
present. Thus, for example, the object WD0000+171 (the first degenerate in the
catalog) has only a single record, whereas WD0000-170 (the second object) has
four records because four values of the proper motion are included in the
catalog. All of the other fields are not blank, however, because three
alternate identifiers, two UBV values, and two multichannel spectrophotometric
data are included.
   Table 2 gives a byte-by-byte description of the contents of the data file. A
suggested Fortran format specification for reading each data field is included
and can be modified depending upon individual programming and processing
requirements (Fortran 77 character string-type formats are used); however,
caution is advised when substituting format specifications, since many data
fields contain character data and others are blank when data are absent.
Particular care is required for the photometric data (color indices), proper
motions, and trigonometric parallax, where valid zero values can exist, but
where fields are blank for nonexistent data, and where precision may vary
within the same field. It is safest to buffer in records in an unformatted mode
or read them with character (A) formats and test for blank data fields before
processing with numerical formats for calculations and/or searching purposes.
For such fields, primary numerical format specifications are given to indicate
decimal-point locations, while alternate A-type formats are specified in
parentheses. Default (null) values are always blanks in data fields for which
primary suggested formats are given as A.


WD number                    Stars having identical catalog numbers, whether
                             binary or not, are distinguished by using the
                             designations .1 and .2 in bytes 9-10.

Coordinate accuracy flag     Specifies the accuracy (and in some cases


                                       3




 _____________________________________________________________________________
|         |        |   Suggested   | Default |                                |
|  Bytes  | Units  |     Format    |  Value  |               Data             |
|_________|________|_______________|_________|________________________________|
|   1-10  |  ---   | A10 (I4,F6.1) |   ---   | WD number                      |
|  11-13  | hours  |      I3       |   ---   | Right ascension                |
|  14-16  |  min   |      I3       |   ---   | RA                             |
|  17-19  |  sec   |      I3       |   ---   | RA                             |
|    20   |  ---   |      I1       |   ---   | Coordinate accuracy flag       |
|  21-23  |  deg   |      I3       |   ---   | Declination                    |
|  24-28  | arcmin |      F5.1     |   ---   | Dec                            |
|    29   |  ---   |      1X       |   ---   | Blank                          |
|  30-35  |  ---   |      A6       |   ---   | Spectral type                  |
|  36-39  |  ---   |      A4       |   ---   | Spectral-type reference        |
|    40   |  ---   |      1X       |   ---   | Blank                          |
|  41-65  |  ---   |      A25      |   ---   | Names                          |
|  66-71  |  mag   |   F6.2 (A6)   |  blank  | Visual or photographic mag.    |
|    72   |  ---   |      A1       |   ---   | Magnitude uncertainty flag (:) |
|  73-74  |  ---   |      A2       |   ---   | Photographic mag. designation  |
|  75-79  |  mag   |   F5.2 (A5)   |  blank  | B-V color                      |
|    80   |  ---   |      A1       |   ---   | B-V uncertainty flag (:)       |
|  81-83  |  ---   |      A3       |   ---   | Color class                    |
|  84-88  |  mag   |   F5.2 (A5)   |  blank  | U-B color                      |
|    89   |  ---   |      A1       |   ---   | U-B uncertainty flag (:)       |
|  90-93  |  ---   |      A4       |   ---   | Wide-band photometry reference |
|  94-95  |  ---   |      2X       |   ---   | Blank                          |
|  96-100 |  mag   |   F5.2 (A5)   |  blank  | Multichannel V magnitude       |
|   101   |  ---   |      A1       |   ---   | Magnitude uncertainty flag (:) |
| 102-107 |  mag   |   F6.2 (A6)   |  blank  | Multichannel g-r color         |
| 108-111 |  ---   |      A4       |   ---   | Spectrophotometric reference   |
| 112-118 |  mag   |   F7.3 (A7)   |  blank  | V(y) magnitude                 |
| 119-124 |  mag   |   F6.3 (A6)   |  blank  | b-y color                      |
| 125-131 |  mag   |   F7.3 (A7)   |  blank  | u-b color                      |
| 132-135 |  ---   |      A4       |   ---   | uvby reference                 |
| 136-137 |  ---   |      2X       |   ---   | Blank                          |
| 138-142 |  [1]   | F5.2 (A5)     |  blank  | Absolute visual magnitude      |
|   143   |  ---   |      A1       |   ---   | Absolute visual magnitude code |
| 144-146 |        |      A3       |   ---   | Absolute visual magnitude ref. |
|_________|________|_______________|_________|________________________________|
|            [1] Units are magnitudes or kelvins (see MV explanation)         |
|_____________________________________________________________________________|

                   Table 2: Data File Record Format



                                       4




 _____________________________________________________________________________
|         |        |   Suggested   | Default |                                |
|  Bytes  | Units  |     Format    |  Value  |               Data             |
|_________|________|_______________|_________|________________________________|
| 147-153 | arcsec |   F7.4 (A7)   |  blank  | Annual proper motion (PM)      |
|   154   |  ---   |      A1       |   ---   | PM code                        |
| 155-159 |  deg   |   F5.1 (A5)   |  blank  | PM position angle              |
| 160-163 |  ---   |      A4       |   ---   | PM reference                   |
| 164-168 |  km/s  |      I5       |  blank  | Radial velocity                |
| 169-170 |  ---   |      2X       |   ---   | Blank                          |
| 171-174 |  ---   |      A4       |   ---   | Radial-velocity reference      |
| 175-181 | arcsec |   F7.4 (A7)   |  blank  | Trigonometric parallax (TP)    |
|   182   |  ---   |      A1       |   ---   | TP code                        |
| 183-184 | 0.001" |      I2       |  blank  | TP mean error                  |
| 185-188 |        |      A4       |   ---   | To reference                   |
|_________|________|_______________|_________|________________________________|

             Table 3: Data File Record Format (continued)



                             precision) to which the equatorial coordinates
                             are given:

                               1  Right ascension given in hours, minutes and
                                  seconds; Declination reported in degrees,
                                  arcminutes and tenths.

                               2  RA originally given in hours, minutes and
                                  tenths, in which case a conversion to seconds
                                  has been effected in order to make the format
                                  uniform. In some cases, RA may be given to
                                  hours and minutes only (bytes 18-19 blank).
                                  Dec is generally given in degrees and whole
                                  minutes only (byte 28 blank).

Equatorial coordinates       Equinox 1950.

Spectral type                Classification according to the new system
                             described by Sion et al. (1983). A full
                             description of the notation is given in the
                             introductory file.

Spectral-type reference      Coded reference given in the references file (5).
                             In many cases, the primary classification
                             reference is not given, but may be found in the
                             secondary reference listed.


                                       5




Names                        Cross identifiers to the various designations by
                             which each star is commonly known. A key to the
                             names is given in the introductory file and an
                             extensive table of cross identifications, ordered
                             alphabetically, is provided in the NAMES file (4).

Visual or photographic magnitude   A V magnitude on the UBV sytem is given
                             where available. If the star has not been observed
                             on the UBV system, a photographic magnitude may be
                             reported. Precision varies from whole magnitudes
                             to hundredths for V; it is to tenths only for ptg.

Magnitude uncertainty flag   A colon (:) denotes an uncertain value.

Photographic magnitude designation   The characters "pg" are present if the
                             magnitude is photographic.

B-V color                    This field may be blank for succeeding records of
                             the same object (as can any fields except for the
                             WD identifier and coordinates) or if a photo-
                             graphic magnitude is reported in bytes 67-71 and a
                             color class is coded in bytes 81-83.

B-V uncertainty flag         A colon (:) denotes an uncertain value.

Color class                  A color class from either the Lowell or Luyten
                             proper-motion surveys is given if only a
                             photographic magnitude is available.

U-B color                    U-B on the Johnson and Morgan UBV system.

U-B uncertainty flag         A colon (:) denotes an uncertain value.

Wide-band photometry reference   Coded reference given in the references
                             file (5).

Multichannel V magnitude     V magnitude determined from multichannel
                             spectrophotometric observations. Precision
                             varies (tenths or hundredths).

Magnitude uncertainty flag   A colon (:) denotes an uncertain value.

Multichannel g-r color       Color determined from multichannel spectrophoto-
                             metric observations.

V(y) magnitude               V as determined from four-color (uvby) photo-
                             electric observations. In general, this should
                             agree well with the V magnitude from wide-band
                             photometry. Most values are reported to
                             hundredths, but a few to thousandths are included.


                                       6




b-y color                    Values are generally reported to thousandths, but
                             precision varies.

u-b color                    As determined from four-color observations. The
                             u-b index is computed from the nominal uvby
                             colors c1 and m1 by:

                                    (u - b) = c1 + 2[m1 + (b - y)]

uvby reference               Coded reference given in the references file (1).

Absolute visual magnitude MV   MV computed from either a trigonometric parallax
                             or from measured colors according to the following
                             priority:

                               (1)   trig. par. > 0.1 arcsec

                               (2)   Multichannel spectrophotometric colors

                               (3)   uvby colors

                               (4)   UBV photometry

                             Exceptions to this priority system are denoted by
                             the codes (0), (5) and (6) and are described in
                             the introductory file. A notable exception is
                             present in the machine version for reference code
                             (5) [see byte 143 explanation].

MV code                      In most cases, data are given in units of
                             magnitudes. However, for the DO and DOZ white
                             dwarfs, the compilers have replaced MV values with
                             directly derivable effective temperatures. These
                             are given in bytes 138-142 in units of 1.E5 K in
                             the machine version and are denoted by the
                             presence of an "E" in byte 143. See the intro-
                             ductory file or the published paper for additional
                             information. A colon for uncertainty in MV can
                             occur here also.

MV reference                 Coded reference given in the references file (5).

Proper Motion                The annual proper motion is given in seconds of
                             arc and the precision varies. Estimated proper
                             motions (EPM) are also reported with a code in
                             byte 154 (see ex- planation below).


                                       7




PM code                      In cases where only an EPM is reported in the
                             Lowell proper-motion surveys, bytes 148-153 are
                             blank and a corresponding code is given in byte
                             154. These codes are defined in Giclas et al.
                             (1967, 1970) and are the following:

                               0  Stars of blue color whose motions are too
                                  small to definitely verify on all plates.

                               1  EPM <= 0.1 arcsec.

                               2  EPM 0.1 arcsec <= PM < 0.2 arcsec.

                               3  EPM 0.2 arcsec <= PM < 0.26 arcsec.

PM position angle            Position angles are given to varying precision,
                             but there is always a decimal point in byte 158 in
                             the machine version.

PM reference                 Coded reference given in the references file (5).

Radial velocity              Observed radial velocity uncorrected for solar
                             motion and for gravitational redshift.

Radial-velocity reference    Coded reference given in the references file (5).

Trigonometric parallax (TP)  Published values of observed TP.

TP code                      A colon (:) denotes an uncertain value.

TP mean error                Reported mean errors associated with measured
                             parallaxes.

TP reference                 Coded reference given in the references file (5).



2.4   Notes (File 3 of 5)


This file contains the notes for stars flagged by an asterisk in byte 35 of the
data file.


WD number   Number of the star in the main data file.

Notes       Notes in free text (upper case only) form.  When bytes 5-16 are
            blank, this record continues the remarks for the previous star.



                                       8



                        _______________________________
                       | Bytes |  Format   |    Data   |
                       |_______|___________|___________|
                       |  1-4  |   4X      | Blank     |
                       |  5-16 |   A12     | WD number |
                       | 17-18 |   2X      | Blank     |
                       | 19-80 |   A62     | Notes     |
                       |_______|___________|___________|

                       Table 4: Notes File Record Format


2.5   Names (File 4 of 5)

   This file contains an extensive cross-identification table from commonly
used white-dwarf designations to the WD numbers employed in the catalog. The
file is ordered alphabetically and is reasonably uniform within each designa-
tion type, i.e., it can be sorted and resorted by name and the records will
emerge in order by both name and numerical designation. This uniformity was
achieved by allocating the first part of the names field to the alphabetic part
of each designation and the second part to the corresponding number. Component
designations for multiple systems follow the numerical part of a name in a
uniform format.

                  ___________________________________________
                 |       | Suggested |                       |
                 | Bytes |  Format   |         Data          |
                 |_______|___________|_______________________|
                 |  1-16 |   A16     | Name                  |
                 | 17    |   A1      | Component designation |
                 | 18    |   1X      | Blank                 |
                 | 19-30 |   A12     | WD number             |
                 |_______|___________|_______________________|

                       Table 5: Names File Record Format


Name                    The commonly used name for the degenerate.

Component designation   Identification of the component for a multiple-star
                        system.

WD number               The WD designation used in the catalog.



2.6   References (File 5 of 5)

   This file contains the bibliographical references ordered by the codes used
in the data file.



                                       9



                     ____________________________________
                    |       | Suggested |                |
                    | Bytes |  Format   |     Data       |
                    |_______|___________|________________|
                    | 1-2   |    A2     | Reference code |
                    | 3     |    1X     | Blank          |
                    | 4-80  |    A77    | Reference      |
                    |_______|___________|________________|

                    Table 6: References File Record Format



Reference code  A two-character code used in the data file to cite a reference.

Reference       Reference in free text (upper case only) form.  Bytes 1-9 of a
                record are blank if it is a continuation of a reference.



3   History


3.1   Remarks and Modifications

   The machine-readable data files of A Catalog of Spectroscopically Identified
White Dwarfs were received on floppy disks from Dr. George P. McCook of
Villanova University on January 20, 1988. The individual files of the catalog
were uploaded to the IBM 3081K computer of the NASA Space and Earth Sciences
Computing Center at Goddard Space Flight Center, where the data were examined
for uniformity, structure, and ease of machine processing. Based upon this
analysis, the following modifications to the data files were made with the
collaboration of the compilers:


  1. Individual corrections were made to the data file based upon the presence
     of certain superfluous characters, data misalignment, and a few erroneous
     values.

  2. The data file was reformatted in order to isolate photographic magnitude
     designations, color classes, Teffcodes in the MV field, and EPM codes from
     their corresponding numerical fields, thus allowing all data to be read
     and searched with a uniform format. Color-index data, which can have zero
     values, must clearly still be read with a character format and tested for
     blanks before data searches can be run, but the present uniformity in
     format and coding allows for simplified processing and sorting, etc.

  3. The original data file had positional data only in the first record of a
     group. Right ascension values were also given in different formats
     ("mm ss" and "mm.m"). All data were therefore converted to the "mm ss"
     format and the coordinate accuracy flags were added between the RA and Dec


                                      10




     fields. A program was then written to transcribe the coordinates from the
     first record of each degenerate to all other records for the same object,
     thus simplifying the searching and sorting of the data by position.

  4. Certain data, such as declination, magnitudes, and position angles of
     proper motions, were present as both integer and real numbers. Decimal
     points were added to all of these, even if there are no fractional units,
     so that all data can be processed with a single format specification.

  5. The names file was structured in a multicolumn format as in the published
     catalog. The entire file was reformatted to produce a single record per
     object and the name field was expanded to allow for a reasonably uniform
     format to be designed and implemented. Names were also converted from all
     upper to mixed case, depending upon how they are used in the literature
     and in the original sources.



3.2   Acknowledgments

   Appreciation is expressed to Drs. George P. McCook and Edward M. Sion for
supplying the machine-readable catalog, for collaborating to make the changes
described above, and for reviewing this documentation before its final release.
Dr. Sion's prompt responses by telephone and electronic mail helped greatly to
speed up the completion of the work and thus to make the data available to the
astronomical community sooner.



3.3   References



Giclas, H. L., Burnham, R. Jr., and Thomas, N. G. 1967, Lowell Obs. Bull.
      No. 141.

Giclas, H. L., Burnham, R. Jr., and Thomas, N. G. 1970, Lowell Obs. Bull.
      No. 153.

McCook, G. P. and Sion, E. M. 1977, A Catalog of Spectroscopically Identified
      White Dwarfs, 1st edition, Villanova Univ. Obs. Contrib. No. 2.

McCook, G. P. and Sion, E. M. 1984, A Catalog of Spectroscopically Identi-
      fied White Dwarfs, 2nd edition, Villanova Univ. Obs. Contrib. No. 3.



                                      11


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