Publications of the Astronomical Society of the Pacific 107: 846-852, 1995 September
An Extension of the Case-Hamburg OB-Star Surveys
John S. Drilling1 Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 Electronic mail: [email protected] Louis E. Bergeron Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218 Electronic mail: [email protected] Received 1995 March 27; accepted 1995 May 31
ABSTRACT. We have extended the Case-Hamburg OB-star surveys to £ = ±30° for / = ±60° using the Curtis Schmidt telescope and 4° objective prism at the Cerro Tololo Inter-American Observatory. A catalog of 234 OB stars and other objects with peculiar spectra is presented along with finding charts for those objects too faint to be included on the BD or CD charts. 1. INTRODUCTION 2. OBSERVATIONS AND RESULTS The Case-Hamburg OB-star surveys were completed One hundred ninety-four Kodak IIa-0 plates, covering the with the publication of Luminous Stars in the Southern Milky area of the sky shown in Fig. 1, were taken with the Curtis Way (LSS) by Stephenson and Sanduleak (1971). This cata- Schmidt telescope and 4° objective prism at the Cerro Tololo log lists 5132 OB stars or supergiants identified on Kodak Inter-American Observatory. Each of these plates covers a IIa-0 photographic plates taken with the Curtis Schmidt 5.2X5.2 degree area of the sky. The spectra have a dispersion of 280 Â/mm at Hy, which is more than twice as high as that Telescope and UV-transmitting objective prism at the Cerro of the LSS survey described above. However, because of the Tololo Inter-American Observatory. This instrumental setup increased exposure times (25 min as compared to 11 min for yields a dispersion of 580 A/mm at Η γ, which allows rough the LSS survey) and the decreased crowding of the spectra at MK types to be assigned to supergiants of spectral types the higher galactic latitudes, OB stars could be detected B6-G2. The OB stars (those which show nearly continuous down to photographic magnitude 12, as was the case for the spectra on these plates) were classified as OB+, OB, or OB", LSS survey. Due to the superior figure of the Curtis Schmidt in the order of increasing Balmer absorption-line strength. correcting plate and the superior seeing at Cerro Tololo, the The six earlier catalogs, which were published under the title limiting magnitude of this survey is also comparable to that Luminous Stars in the Northern Milky Way, were based on of the high-latitude extension of LSIV. + similar objective-prism plates taken with the large Schmidt An attempt was made to calibrate the OB , OB, and OB" subclasses by frequent inspection of a plate centered at telescopes at the Hamburg Observatory (Hardrop et al. o 1959—LSI; Hardrop et al. 1964—LSIII; Hardrop et al. /=304° and ¿?=0 , on which 141 OB stars contained in the LSS catalog could be identified. During the course of visual 1965—LSV) and the Warner and Swasey Observatory (Stock inspection of the plates, a number of other peculiar spectra et al. 1960—LSII; Nassau and Stephenson 1963—LSIV; were noted, which have also been included in the catalog. Nassau et al. 1965—LSVI). Together, these surveys cover These include spectra showing emission lines, suspected he- the entire Milky Way down to photographic magnitude 12 lium stars, suspected metal-poor stars (H and Κ absorption (galactic latitudes ±10° except in the case of LSIV, where stronger than normal relative to other absorption lines), and the coverage in galactic latitude was extended to ±30°). When the LSS catalog was published, one of us (J.S.D.) 40 began a program to obtain MK spectral types for all stars classified as OB+ in the surveys described above. As ex- pected, most of these stars turned out to be O-type stars and 20 early-B-type supergiants. However, unusually large numbers of extreme helium stars and very hot O-type subdwarfs were 0 also discovered as a result of this work (Drilling 1987). Be- cause the incidence of these rare and astrophysically inter- esting stars was highest for the high-latitude extension of -20 LSIV, we decided to extend the Case-Hamburg OB-star sur- veys to b= — 30° for / = ±60°. The results of this survey (LSE) are described below. -40 -50 50 Visiting Astronomer, Cerro Tololo Inter-American Observatory, which is operated by the Associated Universities for Research in Astronomy, Inc., Fig. 1—Area covered by the LSE survey and all identified survey objects. under contract with the National Science Foundation. LSS, LSIV, and LSII are earlier surveys mentioned in the text.
845 © 1995. Astronomical Society of the Pacific
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These rough coordinates and Β magnitudes were The results are given in Table 1, and finding charts for the then used to identify the stars in the NST Guide Star Catalog, stars are given in Fig. 2. Details of the emission line objects and it is the magnitudes and coordinates from this catalog are given in Table 2. The finding charts are IS'XIS', and which are given in Table 1 (except for star No. 229, which is were reproduced from the Palomar and ESO sky surveys for not included in the GSC). stars not included on the BD or CD charts. Equatorial coor- A program oí UBV photometry and follow-up spectros- dinates good to about 0.3 min of arc and rough Β magnitudes copy at higher resolution is underway, which should deter- mine, for example, whether any of the stars listed in Table 1 Table 2 Emission-Line Objects are previously unknown extreme helium stars or very hot O-type subdwarfs. A number of the results have already been LSE Comments published, and are referred to in the footnotes to Table 1. 108 strong H+K, Hß em. and faint cont. 140 strong H+K, Balmer em., other lines and ft. cont. 204, 260 Ce means carbon star with Ηβ,γ em. The authors would like to thank Sandra Cooper and Scott 207 Ηγ,δ em. and faint cont. 208 Η and faint cont. Dahm for their work on this survey. This research has made 216 Ηγ,δ and H+K em. and strong 4226(CaI) abs. (LPV?) 217 Ge means GO with Ηγ,δ em. use of the Simbad database, operated at CDS, Strasbourg, 229 Η + 4686 em. with faint cont. 230 Η + line near Balmer limit in emission (OB+) France. Astrometry obtained using the Guide Stars Selection 239 Peel Gal strong, other lines weak 261 many emission lines System Astrometric Support Program developed at the Space Telescope Science Institute (STScI is operated by the Asso- © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 852 DRILLING AND BERGERON ciation of Universities for Research in Astronomy, Inc. for Hardrop, J., Theile, I., and Voigt, Η. Η. 1964, Luminous Stars in the NASA). This work was supported in part by NSF Grant No. Northern Milky Way ΠΙ (Hamburg, Bergedorf) AST-8514574. Hardrop, J., Theile, I., and Voigt, Η. Η. 1965, Luminous Stars in the Northern Milky Way V (Hamburg, Bergedorf) Nassau, J., and Stephenson, C. B. 1963, Luminous Stars in the Northern Milky Way IV (Hamburg, Bergedorf) Nassau, J., Stephenson, C. B., and MacConnell, D. J. 1965, Lumi- REFERENCES nous Stars in the Northern Milky Way VI (Hamburg, Bergedorf) Drilling, J. S. 1987, in Second Conference on Faint Blue Stars, IAU Stephenson, C. B., and Sanduleak, N. 1971, Luminous Stars in the Colloquium No. 95, p. 489 Southern Milky Way, Publ. of the Warner and Swasey Obs., 1, 1 Hardrop, J., Rohlfs, K., Slettebak, Α., and Stock, J. 1959, Luminous Stock, J., Nassau, J., and Stephenson, C. B. 1960, Luminous Stars Stars in the Northern Milky Way I (Hamburg, Bergedorf) in the Northern Milky Way II (Hamburg, Bergedorf) © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System