J/ApJ/753/13          OI equivalent widths in Be stars          (Mathew+, 2012)
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A study of the role of Ly{beta} fluorescence on O I line strengths in Be stars.
    Mathew B., Banerjee D.P.K., Subramaniam A., Ashok N.M.
   <Astrophys. J., 753, 13 (2012)>
   =2012ApJ...753...13M
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ADC_Keywords: Equivalent widths ; Stars, Be ; Spectroscopy ; Spectral types
Keywords: atomic processes; circumstellar matter; infrared: stars ;
          line: formation; stars: emission-line, Be; techniques: spectroscopic

Abstract:
    The possibility of the Ly{beta} fluorescence mechanism being
    operational in classical Be (CBe) stars and thereby contributing to
    the strength of the OI{lambda}8446 line has been recognized for long.
    However, this supposition needs to be quantified by comparing observed
    and predicted OI line ratios. In the present work, optical and
    near-infrared spectra of CBe stars are presented. We analyze the
    observed strengths of the OI{lambda}7774, {lambda}8446, {lambda}11287,
    and {lambda}13165 lines, which have been theoretically proposed as
    diagnostics for identifying the excitation mechanism. We have
    considered and examined the effects of Ly{beta} fluorescence,
    collisional excitation, recombination, and continuum fluorescence on
    these O I line strengths. From our analysis it appears that the
    Ly{beta} fluorescence process is indeed operative in Be stars.

Description:
    Our optical sample of classical Be (CBe) stars is drawn from the study
    of Mathew et al. (2008MNRAS.388.1879M) who performed a survey to
    identify CBe stars in 207 open clusters using slitless spectroscopy.
    The spectroscopy of 150 CBe stars in 39 open clusters in the
    wavelength range 3800-9000{AA} is presented in Mathew & Subramaniam
    (2011, Cat. J/other/BASI/39.517) - the optical spectra analyzed here
    are from this study. Briefly, these spectroscopic observations were
    obtained in 2005-2007 using the HFOSC (Himalayan Faint Object
    Spectrograph Camera) imager-spectrograph instrument available on the
    2.0m Himalayan Chandra Telescope, located at Hanle, India.

File Summary:
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 FileName   Lrecl  Records   Explanations
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ReadMe         80        .   This file
table1.dat     74       77   List of classical Be stars which show OI(7774)
                             and OI(8446) in emission, with equivalent width
                             and line flux ratio estimates
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See also:
  J/other/BASI/39.517 : Spectroscopy of classical Be stars (Mathew+, 2011)
  J/ApJ/700/1216 : Spectroscopy of Be stars in open clusters (McSwain+, 2009)
  J/A+A/451/1053 : Fundamental parameters of Be stars (Fremat+, 2006)
  J/ApJ/653/657  : Spectroscopic obs. of Herbig Ae/Be stars (Manoj+, 2006)
  J/AJ/129/856   : Herbig Ae/Be stars in nearby OB assoc. (Hernandez+, 2005)
  J/MNRAS/358/66 : uvby{beta} photometry of NGC 663 (Fabregat+, 2005)
  J/ApJS/161/118 : byH{alpha} photometry in open clusters (McSwain+, 2005)
  J/A+A/384/473  : O, B and Be stars equivalent widths (Lenorzer+, 2002)

Byte-by-byte Description of file: table1.dat
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  Bytes Format Units   Label   Explanations
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  1- 12  A12   ---     Cluster Cluster name
 14- 16  A3    ---     Star    Star designation within the cluster, as in
                               Mathew & Subramaniam 2011 (J/other/BASI/39.517)
 18- 22  A5    ---     SpT     MK spectral type
 24- 34  A11  "Y/M/D"  Date    Observation date
 36- 40  F5.2  0.1nm   W7774   OI(7774) observed equivalent width in {AA}
 42- 46  F5.2  0.1nm   W8446   OI(8446) observed equivalent width in {AA}
 48- 52  F5.2  0.1nm   W7774c  OI(7774) equivalent width, corrected for
                               underlying stellar absorption component
 54- 58  F5.2  0.1nm   W8446c  OI(8446) equivalent width, corrected for
                               underlying stellar absorption component
 60- 64  F5.2  ---     Irat    [0.7/10.6] Line flux ratio I(8446/7774)
 66- 69  F4.2  mag     E(B-V)  [0.1/2] Extinction E(B-V)
 71- 74  F4.2  ---     Ic      [0.4/6.6] Extinction-corrected line flux
                                         ratio of I(8446/7774)
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History:
    From electronic version of the journal

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(End)                                     Emmanuelle Perret [CDS]    07-Feb-2014