J/ApJ/753/13 OI equivalent widths in Be stars (Mathew+, 2012)
A study of the role of Lyβ 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 2012ApJ...753...13M
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 Lyβ fluorescence mechanism being
operational in classical Be (CBe) stars and thereby contributing to
the strength of the OIλ8446 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 OIλ7774, λ8446, λ11287,
and λ13165 lines, which have been theoretically proposed as
diagnostics for identifying the excitation mechanism. We have
considered and examined the effects of Lyβ fluorescence,
collisional excitation, recombination, and continuum fluorescence on
these O I line strengths. From our analysis it appears that the
Lyβ 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 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 3800-9000Å 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 : uvbyβ photometry of NGC 663 (Fabregat+, 2005)
J/ApJS/161/118 : byHα 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 Å
42- 46 F5.2 0.1nm W8446 OI(8446) observed equivalent width in Å
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
(End) Emmanuelle Perret [CDS] 07-Feb-2014