III/115 IUE Atlas of O-Type Stellar Spectra (Walborn+ 1985)
International Ultraviolet Explorer Atlas of O-type Spectra from 1200 to 1900 A Walborn N.R., Nichols-Bohlin J., Panek R.J. <NASA Reference Publication #1155 (1985)> =1985NASAR1155....0W
ADC_Keywords: Stars, O ; Spectroscopy ; Spectra, ultraviolet ; Atlases Mission_Name: IUE Abstract: The International Ultraviolet Explorer Atlas of O-Type Spectra From 1200 to 1900 A (Walborn et el. 1985) lists normalized fluxes and flux quality factors, splice points, and identifying information (star name/number, spectral type, SWP number, and name of the principal investigator) on 101 spectrograms of 98 O-type stars. The primary purpose of this work is to investigate the existence of systematic trends in the ultraviolet line spectra of the O stars, including the prominent stellar wind features, and the degree to which they correlate with the optical spectral classifications. A subsidiary objective is to identify ultraviolet features which may themselves prove useful as classifications criteria. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file stars.dat 100 100 Star IDs, Spectral Types, IUE image numbers, PI names, atlas page numbers spectra.dat 80 80800 Fluxes and data quality flags splices.dat 74 1313 Splice points of spectra
See also: III/188 : IUE Atlas of B-Type Stellar Spectra (Walborn+ 1995) III/83 : IUE low-dispersion spectra of normal stars (Heck+, 1984) VI/99 : Merged Log of IUE Observations (NASA-ESA, 1999) 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 Approximately 200 O stars have short-wavelength, high-resolution data in the IUE archive. 120 of these were examined for possible inclusion in the atlas. The primary selection criterion was the availability of homogeneous optical spectral classifications by Walborn (1972 AJ 77, 312; 1973 AJ 78, 1067). In general, known interacting binaries and very rapid rotators were avoided, but a number of peculiar objects and categories which have been well described optically were specifically included. A.2 Processing The IUE Spectral Image Processing System (IUESIPS) data were retrieved from the IUE data archive. Each gross spectrum included samples of the observed signal along each echelle order, integrated along a pseudo-slit; and a corresponding sample of the interorder background. Sample wavelength and a data quality indicator were also included. 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. Overlap among adjacent orders [was] discarded beyond the wavelengths at which which the sensitivities [were] equal. These points of overlap are listed in the second file. The spectrum was then resampled to 0.25 A resolution: Each original sample was considered an estimate of the flux averaged over a bin whose width was equal to the spacing between the adjacent points. Each new sample was computed as a weighted average of the original samples; the weight of each original sample is equal to the fraction of its bin which falls within the 0.25 A window centered on the new wavelength point. However, the weight is zero for any original point for which the IUESIPS quality factor indicated contamination by a camera reseau, saturation of the vidicon camera, or a particle radiation hit. The new sample points were spaced evenly at 0.25 A intervals from 1150 A to 1950 A. For each new sample point, a quality factor was computed as the sum of the weights for the original samples contributing to the new point. This quality factor ranges from about 6 at 1200 A (where there is no effect of a reseau, etc.) to about 4 at 1800 A for IUESIPS processing at GSFC before November 1981. With the newer version of IUESIPS, this factor is roughly doubled due to the finer wavelength sampling of the spectrum. 3. The resampled spectrum was then rescaled in order to locate the stellar continuum at an approximately uniform level: This ... was performed interactively ... by identifying about a dozen "continuum" points spaced along the interval 1150-1950 A. Then, the flux was divided by a cubic spline interpolated through these points. The intention here was not to precisely define a stellar continuum; it was simply to place the spectrum onto a convenient scale for plotting over the full spectral range. The renormalization function usually showed a broad hump between 1400 and 1600 A. It is unclear whether this represents a rise in the instrument sensitivity near 1500 A or an effect of blended spectral absorption features near 1400 and 1600 A. Similarly, the data quality factor was normalized to remove the effect of the decreasing spectral dispersion toward longer wavelengths, which causes the number of original samples within a 0.25 A window to decrease. Narrow positive spikes in the flux data due to particle radiation hits and the geocoronal Lyman alpha emission were eliminated manually. In addition, the catalog authors note the following: Small deviations from unity in the data quality factor occur where a few of the original sample points in the 0.25 A resample window were contaminated by a reseau. Large deviations from unity occur where most or all of the points were affected by a reseau. In many cases, no effect of the reseau is apparent in the stellar spectrum; this occurs when the reseau falls close to but not precisely onto the stellar spectrum, and the interorder background is weak. 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 [GSFC/Code 680] 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|