
            DATABASE FOR N.SANDULEAK'S LMC SUPERGIANTS.

                            M. Morel

	In the late 1960s N. Sanduleak compiled a catalogue of LMC members, based on examination of deep objective-prism spectra obtained at CTIO, Chile. His catalogue listed 1273 objects, of which the overwhelming majority are early-type supergiants. The region of sky surveyed extends from 4h45m to 6h00m in RA, and -65 to -72 Dec.
	Sanduleak's catalogue as published contained only coarse or approximate data for coordinates, photographic magnitudes and many of the spectral classifications. The catalogue served as a finding list for further studies of these objects. Subsequent papers by other astronomers have provided quality photometry and  spectral classifications. However, to my knowledge, no complete list of accurate positions has been published for the Sanduleak stars.  My aim here is to bring together the best data in one database. Published photometric and spectral data is combined with astrometric data from GSC and USNO-A2.0 catalogues (not always easy, as these modern catalogues provide uneven and
patchy coverage of the LMC region).

NASA-ADC VERSION OF SANDULEAK'S CATALOGUE. In April 1982 I learned that Sanduleak's catalogue had been put into computer- readable form by the Astronomical Data Center at Goddard Space Flight Center, Maryland, USA. Upon my request Dr Wayne H. Warren Jr sent me a hardcopy print of their version. In August 1982 he sent photocopies of the finder charts showing the positions of all the NS stars. These materials were the starting point, enabling reliable identifications to be made. Charts were essential, given the crowding in many LMC fields and the rough coordinates. By late 1998 when CD-ROM charting packages such as Guide etc were in wide use, I felt that a computer-readable database, containing accurate positions, would permit observers to identify the Sanduleak stars in the absence of the published finder charts.
THE DATABASE.	The aim of this database is therefore to:
1. provide accurate positions for all NS stars, to permit unambiguous identification, as far as possible. This meant correlating each NS star with entries in GSC or USNO-A2.0.
2. bring together reliable UBV photometry for all NS stars, as far as possible.
3. provide auxiliary information for identification purposes- GSC number, additional ids., and notes.
	My database originally consisted of eight files, named as follows:
NS-65LMC.
NS-66LMC.
NS-67LMC.
NS-68LMC.
NS-69LMC.
NS-70LMC.
NS-71LMC.
NS-72LMC.
       The positions, as compiled in 1999, were of ordinary precision, RA to nearest 0.1s, Declination to nearest arcsecond.
	These have now (May 2008) been combined into a single spreadsheet file -
Sanduleak_comb.xls.  In late 2007 I undertook to extract positions of higher precision, especially from UCAC2.  A number of positions have been taken from the catalogue of Philip Massey.  The sources are listed at the top of the table.

STRUCTURE OF DATABASE.
     The column headings are self-evident.  Additional remarks are added at the end of the main table.
   
NS number:  This number is reproduced from Sanduleak's cat. Some stars have a suffix (a, b or c) in lower case, as employed by Sanduleak, but some later astronomers have used upper case.
HD/HDE number: These numbers are given where existing. Where space permits I have also inserted the Westerlund and Smith (WS) number for some Wolf-Rayet stars. The complete list of WS stars with corresponding NS numbers is appended below.
Spectral Type: Generally taken from the catalogue of Rousseau et al (1978).
Photoelectric Data: The two main sources are Rousseau et al (1978) and Isserstedt (1979). Some gaps were filled with data from the GCPD (Mermilliod). A colon (":") indicates an uncertain value. Variable stars are flagged by "v". Names are given in notes.
Coordinates: The majority of stars were found in either GSC or USNO-A2.0, but superior coordinates have been inserted where possible.. A few NS stars could not be found in either catalogue, and the position was then estimated from the Guide8 display (providing there were suitable reference stars in the vicinity). In a very few cases I had to fall back on published paper charts, such as "LMC Selected Areas" (Morel 1990) or the Hodge & Wright atlas (1967). Sample  codes:   G = GSC; A2 = USNO-A2.0; B = J. Breysacher (1999); U = UCAC2
Bear in mind that Sanduleak's zones were based on B1975 equinox. My positions are for J2000, so one will occasionally find stars that have crossed into an adjoining zone, due to precession. eg NS-66 18 and NS-67 10 are now both slightly north of their respective zones.
GSC numbers: The numbers retrieved from the HST Guide Star Catalog, when the NS star could be found in the GSC.  
										
GENERAL. The data, especially the photometry, is presented "as is". Small range variability has been found in scores of LMC stars through p.e. photometry. The 4th ed. of the GCVS presents a new naming system for LMC variables. Well known variables from the early decades of the 20th century have been given new designations, as well as recent discoveries. All NS stars with variable star names are recorded in the notes, with ranges. The Wolf-Rayet stars present a special problem for photometrists as these stars concentrate much of their radiation into a number of emission lines, and consequently conventional photometry can result in inconsistent results.  The recent catalogue by Breysacher et al (1999) lists v magnitudes for all 134 LMC W-R stars, some
narrow band in  Smith's 1968 system,  others corrected Johnson V mags. There are often significant differences (of the order of 0.5-1.0 mag.) when compared with Johnson V mags, and I choose not to insert this new data in my database, at this stage.

REFERENCES.
1. Rousseau, J., Martin, N., Prevot, L., Rebeirot, E., Robin, A.
and Brunet, J.P.: 1978, Astron. Astrophys. Suppl. 31,243-260.
2. Isserstedt, J.: 1979, Astron. Astrophys. Suppl. 38,239-243.
3. Westerlund, B.E., Smith, L.F.: 1964, Mon. Not. R. Astron. Soc. 128, 311.     [WS numbers for 58 LMC Wolf-Rayet stars]. 
4. Sanduleak, N.: 1970, Contr. Cerro Tololo Int. Am. Obs 89
[NASA-ADC version (1986): ADC Cat. III-3113. "A Deep Objective-
Prism Survey for Large Magellanic Cloud Members"]
5. GUIDE STAR CATALOG. 1989, Space Telescope Science Institute.
6. USNO-A2.0 CATALOGUE. 1998, D.G. Monet, US Naval Observatory.
7. Morel, M. 1990. "LMC Selected Areas", published by Morel
Astrographics, 6 Blakewell Road, Thornton NSW 2322
8. Hodge, P. and Wright F.W. 1967. "The Large Magellanic Cloud",
The Smithsonian Institution, Washington.
9. General Catalogue of Variable Stars, 4th ed., Vol. 5, 1995.
N.N. Samus, Editor-in-Chief, Moscow, Kosmosinform.
10. Breysacher, J., Azzopardi, M. and Testor, G.: 1999, Astron. Astrophys. Suppl. 137,117-145 [The fourth catalogue of Population I Wolf-Rayet stars in the Large Magellanic Cloud]. 


TABLE 1. Correspondences between NS and WS numbers.
---------------------------------------------------
WS        NS         WS        NS         WS        NS
1     -66 3          19    -71 21         37   -67 218
2     -67 20         20    -65 57         38   -69 209a
3     -66 21         21    -71 26         39   -69 222
4     -69 42         22    -68 77         40   -69 223
5     -66 28         23    -67 104        41   -69 231
6     -68 15         24    -68 80         42   -69 234
7     -67 32         25    -69 133        43   -69 235
8     -66 51         26    -68 82         44   -69 241
9     -70 54         27    -69 141        45   -69 245
10    -68 57         28    -70 92         46   -69 246
11    -67 63         29    -68 102        47   -69 248
12    -69 79         30    -68 104        48   -69 251
13    -69 81         31    -67 144        49   -69 255
14    -69 86         32    -71 38         50   -69 258
15    -69 95         33    -67 160        51   -67 259
16    -69 106        34    -67 161        52   -67 263
17    -65 45         35    -69 191        53   -67 268
18    -65 55         36    -69 207
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The WS paper (1964) provides good finder charts for all stars, which may facilitate identification of stars in crowded regions.
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Acknowledgement.
I am indebted to Dave Monet, US Naval Observatory, Flagstaff, AZ, for providing the USNO-A2.0 catalogue on CD-ROM. It greatly assisted in visualizing many LMC star fields, and identifying many Sanduleak stars which are not in the GSC.
  
(c) 1999 M. Morel. (Updated 2008 May 8).

POSTSCRIPT.
Since 1999 a number of communications have taken place between Brian Skiff and myself, concerning the identification of the Sanduleak stars. It was probably inevitable that Brian would tackle this dataset himself, employing the high-precision catalogues which have been released after 1999, namely 2MASS and UCAC2, plus other professional materials.  His catalogue of precise positions for the Sanduleak stars was released in February 2008.  It is available from
ftp://ftp.lowell.edu/pub/bas/starcats/sanduleak.lmc   and also from CDS Strasbourg.
    A comparison of our two datasets in late 2007 turned up few fundamental disagreements.    
    The user of my database is strongly urged to refer to Brian Skiff's work, for remarks concerning precise identifications, and alternative ids. etc.

MM. 2008 May 8.