IUE Ultraviolet Spectral Atlas of Standard Stars


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Project Information : Observations
* "Normal" Stars * Star Spatial Distribution * Star Spectral Type Distribution *

* "Normal" Stars
The observations, assembled here, were done mostly by Wu and his collaborators. Only a small number of images were taken from the IUE calibration programs and the other Guest Observers.

All observations were made in the low dispersion mode, with a spectral resolution of about 6 Å. For stars with a spectral type of F2 or earlier, both the short wavelength (1150-1975 Å) and long wavelength (1975-3200 Å) spectral regions were observed, while the short wavelength spectrum was generally not obtained for stars later than F2. In order to maximize the signal-to-noise (S/N) ratio, essentially all the spectra were taken in trail or pseudo-trail mode. Additionally, many observations have a complementary spectrum taken in the small aperture, such that higher exposure levels can be achieved for the spectral regions that tend to be underexposed.

Wu and his collaborators selected the candidate stars according to the following criteria: no known variability or peculiarity; not a member of a multiple system that has a companion that can introduce non-negligible flux to the observed spectrum; reliable MK spectral types and UBV photometry are available; low (or lower) interstellar extinction; and bright enough to give good S/N ratio at reasonable exposure times (generally 30 minutes or less), yet faint enough to give reliable trail rates (about 10 arcsec/sec or less). To provide additional cross checking against peculiarity and variability in the candidate stars, many of the spectral type and luminosity class combinations have two or more stars.

The observations provide a reasonably comprehensive coverage of the HR diagram. Note that many F, G, K dwarfs and giants have an appreciable number of observed stars. This is intended to include a range of metallicity to facilitate the modelling of the important main sequence turn-off components in older stellar populations.

The observations for the pervious atlas (Wu et al. 1983, 1991, 1997) were made during the period from March 1980 to September 1994. And the data presented in the three installments were processed by different versions of the IUESIPS and reduced by the software which was available in the IUE Data Analysis Center at the time. Thus, the previous atlas is lacking in internal consistency. Also, the noise characteristics, instrument parameters, and calibration which directly relate to the accuracy of the reported stellar fluxes, are better known now. The IUE Project has developed the NEWSIPS pipeline processing system which incorporates these latest improvements in the treatment of the IUE data. The Project has essentially reprocessed all the data with the NEWSIPS pipeline, and created the IUE Final Archive. Therefore, the time is ripe for the production of a new atlas, based on the data from the Final Archive, which will have the uniformly processed data and significantly improved accuracy for the stellar fluxes. For a detailed discussion of the Final Archive and the recalibration of the IUE spectra, see Nichols & Linsky (1996). For the new atlas, selected high quality spectra of a star will be merged to increase the S/N, and to repair spectral regions contaminated by reseaux, cosmic ray hits and other blemishes. page_top

* Spatial Distribution (476 "Normal" Stars)

Observations : Spatial Distribution (476 "Normal" Stars)

  • O
  • B
  • A
  • F
  • G
  • K
  • M
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* Star Distribution in Spectral Types

Observations : Star Distribution in Spectral Types

* O * B * A * F * G * K * M *
O Star VI V IV III II Ib Iab Ia If In m
3   2                  
4   2                  
5   1   3              
6       2         1 1  
6.5               1      
7   1   2 2            
7.5       2 1     1      
8   2           2      
8.5   1         1        
9   1 1                
9.5   2   2   1 1 1      
9.7             1        
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B Star VI V IV III II Ib Iab Ia If In m
0   1   1 1 1          
0.5   1 1 3   1   1      
1   3   2 3 3 2 1      
1.5   2 2 3              
2   2 3 3 1 1   1      
2.5   4 1 2   1          
3   4 2 1 1   1 1      
4   3 2 3              
5   3 2 3 1 2   1      
6   3 2 2   1   1      
7   4   1              
7   1   2 2            
8   2   4 1            
9   2 2 1     2 1      
9.5   5   1              
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A Star VI V IV III II Ib Iab Ia If In m
0   4 1 2 1 1   1      
1   5 1         1     1
2               1      
3   6   2 1           1
4   1                  
5   2 1 1 1 1          
6     1         1      
7   1 4   1            
8   1       1          
9       1              
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F Star VI V IV III II Ib Iab Ia If In m
0   2 1 2   1          
1       2 2            
2   2 1 3   1   1      
3   2 1 2       2      
4   2 2 2              
5 1 6 2 2   2          
6   7 3 1   1          
7   7 2     2          
8   6 4     2 1 1      
9   7                  
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G Star VI V IV III II Ib Iab Ia If In m
0   10 4 2 1 2          
1   5 1   1 1          
2   8 1     2   1      
3   2     1 1          
4       2 1 1          
5   5 1 2 1 1          
6   2                  
7       2              
8   7 3 7 1 1          
9       3 1            
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K Star VI V IV III II Ib Iab Ia If In m
0   4 1 11   2          
1   3 3 2 1 1          
2   2 1 9 3 1          
3   2   4 2 1          
4       4   1          
5   1   3     1        
7   1   4   1          
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M Star VI V IV III II Ib Iab Ia If In m
0       4              
0.5   1   1              
1   2                  
2       4   1   1      
3   1   4 1            
3.5       1              
4         2            
4.5       2              
5       1              
6       1              
7       1              
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last updated: Jan. 2003/b>