III/188 IUE Atlas of B-Type Stellar Spectra (Walborn+ 1995)
International Ultraviolet Explorer Atlas of B-type Spectra from 1200 to 1900 A Walborn N.R., Parker J.W., Nichols J.S. <NASA Reference Publication #1363 (1995)> =1995NASAR1363....0W
ADC_Keywords: Stars, B-type ; Spectra, ultraviolet ; Atlases Mission_Name: IUE Abstract: The IUE Atlas of B-type Stellar Spectra is an atlas of B-type spectra consisting of short-wavelength, high-resolution data from the International Ultraviolet Explorer archive, designed to complement the widely used O-star atlas from the same source (Walborn, Nichols-Bohlin, & Panek 1985, NASA Reference Publication 1155, catalog III/115). The atlas presented here completes the OB natural group, i.e., to spectral type B3 for the main sequence and giants, type B5 at class Ib, and B8 at Ia, which is also the most relevant domain for stellar-wind effects among normal B-type spectra. Introduction: A primary objective of the IUE Atlas of B-type Stellar Spectra is to chart in detail the gradual disappearance of the stellar-wind features in normal spectra as a function of spectral type and luminosity class. As in the O-star atlas, which first demonstrated the strong correlation between the optical spectral types and the UV wind behaviour in the majority of the stars, the principal selection criterion was the existence of high-weight optical spectral classifications, which are quoted here without any revisions based upon the UV data. Some peculiar categories also are presented including a number of hypergiants, stars of types BN/BC (and including three of type O9.7 acquired since the O Atlas), and stars with enhanced winds. 86 images have been selected from the IUE archive for the atlas. The processing and presentation is as similar as possible to the O-star atlas, with the SWP data (roughly 1200-1900 angstrom range) rectified and rebinned to a uniform resolution of 0.25 angstrom. The conclusions from the B Star Atlas are similar to those from the O Star Atlas, namely, that the UV stellar-wind features display strong systematic trends as a functions of spectral type and luminosity class, and a high degree of correlation with the optical classifications as the winds decline toward the later types. A somewhat higher rate of exceptions to these correlations can be recognized among the B spectra (11%) than the O (2%), but they remain a small fractions of the total sample and do not prevent clear delineation of the normal behaviour. Indeed, it is only as a result of the latter that the exceptions can be identified and described. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file stars.dat 100 86 Star IDs, Spectral Types, IUE image numbers, PI names, atlas plate numbers spectra.dat 80 68800 Fluxes and data quality flags splices.dat 74 1118 Splice points of spectra
See also: III/83 : IUE low-dispersion spectra of normal stars (Heck+, 1984) III/115 : IUE Atlas of O-Type Stellar Spectra (Walborn+ 1985) VI/99 : Merged Log of IUE Observations (1978Jan - 1992Dec) Byte-by-byte Description of file: stars.dat
Bytes Format Units Label Explanations
1- 10 A10 --- ID HD/HDE or Sanduleak (Sk) number of star 13- 26 A14 --- Name Name of star 29- 44 A16 --- Sp Optical spectral classification 47- 51 I5 --- SWP_num SWP camera image number of observation 52 A1 --- Aper [LS] IUE Large or Small Aperture 54- 69 A16 --- PI_name Name of the IUE principal investigator 72- 73 I2 --- Plate_1 *First atlas plate showing spectrogram 75- 76 I2 --- Plate_2 ?Second atlas plate showing spectrogram 78- 79 I2 --- Plate_3 ?Third atlas plate showing spectrogram 81- 82 I2 h RAh Right Ascension J2000 (hours) 84- 85 I2 min RAm Right Ascension J2000 (minutes) 87- 90 F4.1 s RAs Right Ascension J2000 (seconds) 92 A1 --- DE- Declination J2000 (sign) 93- 94 I2 deg DEd Declination J2000 (degrees) 96- 97 I2 arcmin DEm Declination J2000 (minutes) 99-100 I2 arcsec DEs ?Declination J2000 (seconds)
Note on Plate_1: Location of of the spectrogram in the printed atlas. Each plate covers two pages in the atlas (first page covers 1200-1500 A, and the second page covers 1500-1900 A). Some spectrograms appear on more than one plate.
Byte-by-byte Description of file: spectra.dat
Bytes Format Units Label Explanations
1- 10 A10 --- ID *HD/HDE or Sanduleak (Sk) number of star 13- 16 I4 0.1nm lambda *Wavelength of first flux/quality pair 18- 26 F9.5 --- flux_1 *Normalized flux at wavelength=lambda 29- 32 F4.2 --- qual_1 *Data quality flag associated with flux_1 34- 42 F9.5 --- flux_2 Normalized flux at wavelength=lambda+0.025 nm 45- 48 F4.2 --- qual_2 Data quality flag associated with flux_2 50- 58 F9.5 --- flux_3 Normalized flux at wavelength=lambda+0.050 nm 61- 64 F4.2 --- qual_3 Data quality flag associated with flux_3 66- 74 F9.5 --- flux_4 Normalized flux at wavelength lambda+0.075 nm 77- 80 F4.2 --- qual_4 Data quality flag associated with flux_4
Note on ID: There are 800 records for each star, and the ID appears at the beginning of each record for a given star. Note on lambda: The quoted wavelength value is the wavelength of the flux_1 and qual_1 data pair. The wavelengths for the subsequent flux/qual data pairs in the record are in increments of 0.025 nm. Note on flux_1: See Appendix A: "Data Preparation" for a brief description of how the normalized flux was calculated. Note on qual_1: See Appendix A: "Data Preparation" for a brief description of how this normalized quality factor was calculated.
Byte-by-byte Description of file: splices.dat
Bytes Format Units Label Explanations
1- 10 A10 --- ID *HD/HDE or Sanduleak (Sk) number of star 11- 18 F8.1 0.1nm splice1 *First splice point 19- 26 F8.1 0.1nm splice2 ?Second splice point 27- 34 F8.1 0.1nm splice3 ?Third splice point 35- 42 F8.1 0.1nm splice4 ?Fourth splice point 43- 50 F8.1 0.1nm splice5 ?Fifth splice point 51- 58 F8.1 0.1nm splice6 ?Sixth splice point 59- 66 F8.1 0.1nm splice7 ?Seventh splice point 67- 74 F8.1 0.1nm splice8 ?Eighth splice point
Note on ID: There are 13 records for each star, and the ID appears at the beginning of each record for a given star. Note on splice1: Splice points are the wavelength values where overlap of successive orders of the IUE spectrum have been spliced together. These values come in four pairs per record, where for each pair: The first wavelength the beginning of the next (higher) order, and The second wavelength of the end of the previous (lower) order.
Appendix A: Data Preparation. This section briefly describes the steps involved in selecting and processing the data comprising this atlas. The following description was extracted from an edited version of Walborn et al. (1995). A.1 Selection As in the O Atlas, the principal selection criterion was the existence of high-weight optical spectral classifications, which are quoted here without any revisions based upon the UV data. A.2 Processing The processing of the spectral data presented in this Atlas is substantially similar to that used for the O Atlas. The high-resolution SWP data were retrieved from the National Space Science Data Center in their original IUESIPS processed form. Sample wavelength and a data quality indicator were also included. The spectral data were then further reduced at the IUE Data Analysis Center. Processing then proceeded through the following steps: 1. The background was smoothed and subtracted from the on-order signal to yield the net spectrum. 2. A "ripple" correction was applied to adjust for systematic variation along each order caused by the varying sensitivity of the echelle grating. The orders were then spliced at the points where sensitivities of adjacent orders are equal. These points of overlap are listed in the second file. The spectrum was then resampled to 0.25 A resolution: The complete concatenated spectrogram was rebinned to a uniform resolution of 0.25 A. The resampled points were computed from a weighted average of the original points, the weight being based on the fraction of the original bin that falls within the 0.25 A window centered at the new wavelength point. A weight of zero was assigned to any original point possessing an IUESIPS quality flag indicating reseau contamination, saturation, or a particle hit event. The new sample points are spaced evenly at 0.25 A intervals from 1150 to 1950 A. A new quality flag was derived for each rebinned point, computed as the sum of the weights for the original samples contributing to the new point. A minor error in this resampling algorithm was detected after preparation of the O Atlas in 1985. The end points of each bin overlapped by one extracted point, so that these end points were included in two bins. The error was subsequently corrected and it does not affect the data in the present Atlas. 3. The resampled spectrum was then rescaled in order to locate the stellar continuum at an approximately uniform level: Each rebinned spectrogram was normalized by dividing by a "continuum spectrum" created from a highly smoothed version of itself. In a few cases in which the resulting normalization was unsatisfactory, with remaining large-scale structure in the continuum, the normalization was redone manually. Similarly, the data-quality flags were normalized to remove the effect of the decreasing spectral dispersion at longer wavelengths, which results in a smaller number of original samples within each 0.25 A bin. Large geocoronal Lyman-alpha and particle-hit spikes were manually removed from the data, and in a few cases of low signal at the shorter wavelengths, noise spikes were truncated at the borders of the frame [normalized flux values of 0 and 2.5] to avoid overwriting the adjacent spectrograms. [This truncation also exists for the archived electronic version of these data, so many spectra will have chopped spikes, particularly in the region around Lyman-alpha.] The data-quality flags are coded as numbers between 0 and roughly 1: small downward spikes are produced when a few of the points in the bin are contaminated with a reseau mark, and large downward spikes are produced when all of the points in the bin have reseau or other contamination. Extracted spectral data points are flagged as contaminated by a reseau mark if the mark falls near or on the spectral order. It is possible for one or more rebinned points to have a near zero quality flag but the spectral data are unaffected by the reseau mark. Additional Note (December 2000): The Aperture column ("L" or "S" in column "Aper" of the "stars.dat" file) has been added at CDS, as well as the star positions.
(End) Joel W. Parker [Code 680/GSFC] 07-Aug-1995
|The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line|