This directory contains some stars with unusual spectra (i.e., those with spectra not on the OBAFGKM sequence, or with emission lines).
Not all stars with spectral peculiarities are expected to have unusual polarization, so HPOL has not observed stars with all possible spectral peculiarities.

The plots here may show somewhat different wavelength ranges than the standards plots in order to show the spectral peculiarities better.
The plot header will give the star name or names, maybe information about spectral type and the catalog in which it appears, and date of observation.
Variations in extinction during a night can cause the red and blue observation flux levels to not match.

  Catalog abbreviations:
  AMMT   Abt Meinel Morgan Tapscott An Atlas of Low Dispersion Grating Stellar Spectra
  C+J       Cowley & Jaschek AJ 74, 375 1969
  GGv69   Gray & Garrison ApJSup 69, 301
  GGv70   Gray & Garrison ApJSup 70, 626
  KM       Keenan & McNeil An Atlas of Spectra of the Cooler Stars
  KM2        Keenan & McNeil ApJSup 71, 245 1989
  KY        Keenan & Yorka BICDS 29, 25 1985
  L           Lesh ApJSupp 17, 371
  MAT     Morgan Abt Tapscott Revised MK Spectral Atlas for Stars Earlier than the Sun
  W         Walborn ApJSupp 23, 257
  Y          Yamashita, Nariai, Norimoto An Atlas of Representative Stellar Spectra


  P Cyg      redblue    The prototype P Cygni star; MAT has a spectrum. The term "P Cygni profile" refers to an emission line with an absorption line on its shortward wing. The HPOL spectrum resolution is not good enough to see the absorptions well; they are obvious on the MAT spectrm.
  P Cyg       redblue   Same observation as above, different vertical scale to show weaker emission lines better.
  R Cor Bor redblue;    The prototype R CorBor star
  Chi Oph    redblue    B2Vne   Obvious emission at Halpha and Hbeta, higher hydrogen Balmer lines may be partly filled in; also emission in the Paschen lines in the nearIR spectrum.
  Alpha2 CVn;   an Ap star. Two nights plotted on the same graph, with the second night plot shifted downward. This magnetic star has a period of some five days; differences between the two spectra are not solely noise.

  3 Wolf-Rayet stars:
  HD191765:  redblue    WN6
  HD192641:  redblue    WC7
  EZ CMa:     redblue    WN5

  Composite Spectra:

  HR6497:  redblue    A pair of about A0V in a 3 day orbit with a G giant in a 1000+ day orbit. At the short wavelength end of the blue spectrum the A stars dominate, at longer wavelengths features in the G star spectrum appear, and it dominates in the red spectrum.

  HD25498:  redblue     About K0III + A3V. In this case the K star is a lot brighter relative to the A star than above. The short end of the blue spectrum is noisy (star is faint and reddened), but the hydrogen lines are stronger than would be expected for a K star; the K star dominates the red spectrum.
Though hard to see here because of the noisy blue spectrum, the higher hydrogen lines are easily seen on a spectrum plate.
Spectroscopic binary data for this system is in Astron & Astrophys 473, 829 2007.
This star has several spectral types, from G0V to G0Ia, given in research papers in which spectral type was estimated from photometry - which does not work for systems with comparable brightness stars of greatly different temperatures.

Nova Cas 1995
Spectra taken over several months showing the evolution of the spectrum of this slow nova.
The first HPOL observation was made about 1 week after the discovery announcement; the discovery came about 3 weeks after the initial explosion.
See IAU Circular 6283 for discussion of some of these spectral changes by Space Astronomy Lab staff members.

CI Aql = Nova Aql 2000 = Nova Aql 1917
This is a recurrent nova; a white dwarf with a K star companion in a .6 day orbit.
Observations were made 4 and 6 days after the outburst was discovered, which in turn must have been several days after the outburst occurred.
  000502#1 000502#2 000502#3 000502#4
The P Cygni absorption in the hydrogen Balmer lines is stronger two days later:
  000504#1 000504#2 000504#3 000504#4