CDROM/APJS/V107/P281 Atlas of Hot, Luminous Stars at 2 Microns (Hanson+ 1996) ================================================================================ A Spectral Atlas of Hot, Luminous Stars at 2 microns M. M. Hanson, P. S. Conti, and M. J. Rieke <1996, ApJS, 107, 281> =1996ApJS..107..281H ================================================================================ Abstract: We present 2 um (K band) spectra of 180 well-studied, optically visible, luminous stars. Most of the stars are of OB spectral type, but we have also included a number of Oe and Be stars, OBN and OBC stars, cool hypergiant stars, and high-mass X-ray binary stars. Our aim in studying normal OB stars is to develop an empirical relationship between 2 um spectral features of these massive stars and their stellar temperature and luminosity. We find the system of lines between 2.0 and 2.2 um is particulary good for differentiating the early- and mid-O type stars. In the late-O and early-B stars, differentiation becomes more difficult, as the features show only moderate changes. We have developed a spectral classification system for the K band to be used to estimate effective temperatures of O and early-B stars. We demonstrate that K-band spectroscopy is superior in estimating the temperature of hot, luminous stars than the traditional methods of using infrared or even optical photometric colors alone. The only requirements are that adequate resolution (R > 1000) and signal-to-noise (S/N ~ 70) be achieved. With our classification system, stars behind large amounts of visible extinction, such as young, heavily reddened H II regions throughout our Galaxy, may be identified and studied for the first time through 2 um spectroscopy. Emission lines are commonly seen in the K-band spectra of supergiant stars, however, the OBN supergiants, which have a higher ratio of some processed materials at their surface, may be more likely to show line emission, especially the He I singlet transition at 2.058 um. This has led us to propose an evolutionary scenario for some of the Galactic center He I emission-line stars, which evokes rotational mixing (Maeder 1987; Langer 1992) to explain both the strong line emission and high luminosity of these mysterious sources. We have compared our spectroscopic database with the most recent stellar atmosphere models. We are encouraged by the good match between the model line profiles at 2 um of Schaerer et al. (1996b) and those observed in OB stars. Finally, we include a thorough discussion of the observational and reduction methods employed to obtain the spectra shown in this atlas for the benefit of those wishing to obtain similar, classification-quality, near-infrared spectra. Keywords: atlases -- infrared: stars -- stars: early-type -- stars: fundamental parameters Description: The data for the 2 micron spectra appear in two subdirectories: 'fits' contains FITS spectral images; 'ascii' contains ASCII spectra. Table 1 (described below) contains a column called 'File' which lists the eight-character file name for the data in these two directories. To derive the complete file name, take the value of the 'File' field in table1.dat and append the string '.dat' for the ASCII file and '.fit' for the FITS file. For example, the value for the first star in Table 1 is 'hd108 '. The FITS file corresponding to this file is in 'fits/hd108.fit' and the ASCII file is in 'ascii/hd108.dat'. File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table1.dat 98 187 Stars in 2 micron spectral atlas table1.tex 97 216 AASTeX version of table1.dat ascii/* 27 --- Directory of ASCII spectra fits/* 2880 --- Directory of FITS spectra -------------------------------------------------------------------------------- Byte-per-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1-11 A11 --- Star *Star number 12-13 2X --- --- Blank 14-21 A8 --- File *Eight-character name for data files 22-23 2X --- --- Blank 24-39 A16 --- Sp_opt Optical spectral type 40 A1 --- u_Sp_opt [:] A colon indicates Sp is uncertain 41 1X --- --- Blank 42-44 A3 --- r_Sp_opt *Reference to optical spectral type 45-46 2X --- --- Blank 47-52 A6 --- Detector *Detector used for the observation 53-54 2X --- --- Blank 55-58 I4 --- SpRes Spectral resolution, Lambda / dLambda 59-60 2X --- --- Blank 61-67 A7 --- DateObs Date of observation 68-69 2X --- --- Blank 70-81 A12 --- Sp_K K-band spectral type 82-83 2X --- --- Blank 84-98 A15 --- Notes Notes, mostly alternate identifications -------------------------------------------------------------------------------- Notes for file: table1.dat -------------------------------------------------------------------------------- Star: Star name. If this field is blank it indicates that this is a second observation of the star in the previous record. In this case the fields Sp_opt, u_Sp_opt and r_Sp_opt are also blank. Note that HD 47129 is also known as Plaskett's Star. Bagnuolo, Gies & Wiggs (1992) show it to be a pair of supergiants. File: This is the eight-character file name used for the ASCII and FITS data files mentioned in the Description above. r_Sp_opt: Reference to the optical spectral type. Please refer to the printed paper for complete references. W72 Walborn (1972) W73 Walborn (1973) MT Massey & Thompson (1991) C74 Conti (1974) Mth Mathys (1988) C71 Conti & Alschuler (1971) W76 Walborn (1976) M55 Morgan, Code, & Whitford (1955) WF Walborn & Fitzpatrick (1990) L Lennon, Dufton, & Fitzsimmons (1992) BS Bright Star Catalogue, Hoffleit (1982) S SIMBAD database J93 Jones et al. (1993) GS Garmany & Stencil (1992) vP van Paradijs (1993) HP Howarth & Prinja (1989) G77 Garrison, Hiltner, & Schild (1977) Detector: CRSP KPNO Cryogenic Infrared Spectrometer FSPEC Steward Observatory Infrared Spectrometer IRS CTIO Infrared Spectrometer OSIRIS Ohio State Infrared Imaging Spectrometer -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 09-Oct-96