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J/A+A/275/549     Interstellar extinction curves    (Jenniskens+ 1993)
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Environment dependence of interstellar extinction curves
     Jenniskens P., Greenberg J.M.
    <Astron. Astrophys. 275, 549 (1993)>
    =1993A&A...275..549J
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ADC_Keywords: Extinction ; Photometry, ultraviolet
Keywords: ISM: dust, extinction - ISM: HII regions -
          ISM: reflection nebulae - Ultraviolet: interstellar

Abstract:
  The data are a decomposition of the extinction curves published by
  Aiello S., Barsella B., Chlewicki G., Greenberg J.M., Patriarchi P.,
  and Perinotto M. (1988A&AS...73..195A) in the parameter scheme of
  Fitzpatrick E.L. and Massa D. (1988ApJ...328..734F). Each extinction
  curve k(x) = (A(lambda)-A(V))/(A(B)-A(V)) is given by:
     k(x) = c1 + c2*x + c3* D(x,x0,y) + c4*F(x)

  Where x = 1/wavelength (in inverse micron), D is a Drude profile:
     D(x,x0,y) = x^2^/((x^2^-x0^2^)^2^ + y^2^x^2^)
  and F is a polynomial of order 3:
     F(x) = 0.05392(x-5.9)^2^ + 0.0564(x-5.9)^3^   for 5.9<x<8.0
     F(x) = 0                                      for     x<5.9
  In this scheme the parameters have the following meaning:
  c1: related directly to c2 because of normalisation k(x)
  c2: slope of the linear rise ( mag/E(B-V) )
  y:  width of the bump  (inverse micron)
  c3:  c3/y^2^ is bump height, pi*c3/(2.*y) is bump area
  x0: position of the bump (inverse micron)
  c4: amount of FUV non-linear rise contribution:
      at 8 mu^-1^: 2.9c4 (mag/E(B-V))

      |                                                       *  ^
      |                                                     *    2.9c4
      |                    ^        *                    *
  k(x)|                 c3/y^2    *   *               *       .. v
      |                         *<  y  >*        *..
      |                    v  *       ..  * *
      |                    *..  c2
   1  |               *
   0  |            *
      |^        *
      |Rv   *
      |v____________________________|_____________________________
                   V  B             x0           5.9         8.0
                                         x=1/wavelength  (1/micron)


  Values of Rv, the ratio of total to selective extinction, can be found in
  Aiello et al. (1988A&AS...73..195A).


File Summary:
--------------------------------------------------------------------------------
 FileName    Lrecl    Records    Explanations
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ReadMe          80          .    This file
table           68        115    Extinction coefficients
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Byte-by-byte Description of file: table
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   Bytes Format  Units   Label    Explanations
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   1- 11  A11    ---     starname Designation of star.
  13- 16  F4.2   ---     k(U)     ? Extinction in U band
  19- 23  F5.2   ---     c1       Coefficient (see text)
  24- 28  F5.2   um      c2       Coefficient (see text)
  29- 33  F5.2   ---     c3       Coefficient (see text)
  34- 38  F5.2   ---     c4       Coefficient (see text)
  40- 43  F4.2   um-1    y        Width of the bump
  45- 49  F5.3   um-1    x0       Position of the bump
  52- 56  F5.3   ---     chisq    Indication of the deviation between fitted
                                    curve and actual data
      59  I1     ---     Q        Quality indication of the data (1)
      61  I1     ---     IPSC     [0/2] IRAS point source classification (2)
  66- 68  A3     ---     TYPE     Environment characterisation from IRAS Skyflux
                                   maps (3)
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Note (1): The quality are:
   Q=1 gives a bad fit to the U band extinction, due to saturation at long
       wavelength, and spectra marked
   Q=2 show signs of underexposure in the bump.
Note (2): IPSC classification as (for IPSC>0):
   IPSC=1 is point source with 12 micron flux smaller than 25,
   IPSC=2 is point source with 25 micron flux smaller than 12.
Note (3): the characterisation takes the following values:
     CS: circumstellar
     DIF: diffuse medium line of sight (no aparent heating)
     BUB: bubble, extended region of increased 60/100 around OB association
     HII: HII region, compact regions of highly increased 60/100
     REF: reflection nebulae, small compact regions of highly increased 60/100
          associated with B type stars.
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(End)                                    Patricia Bauer      [CDS]   10-Sep-1993