J/MNRAS/500/3926 Optical spectroscopy of classical Be stars (Banerjee+, 2021)
Optical spectroscopy of Galactic field classical Be stars.
Banerjee G., Mathew B., Paul K.T., Subramaniam A., Bhattacharyya S.,
Anusha R.
<Mon. Not. R. Astron. Soc., 500, 3926-3943 (2021)>
=2021MNRAS.500.3926B 2021MNRAS.500.3926B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, Be ; Stars, emission ; Spectral types ; Extinction ;
Equivalent widths ; Spectra, optical
Keywords: techniques: spectroscopic - stars: emission-line, Be -
circumstellar matter
Abstract:
In this study, we analyse the emission lines of different species
present in 118 Galactic field classical Be stars in the wavelength
range of 3800-9000Å. We re-estimated the extinction parameter
(AV) for our sample stars using the newly available data from Gaia
DR2 and suggest that it is important to consider AV while measuring
the Balmer decrement (i.e. D34 and D54) values in classical Be
stars. Subsequently, we estimated the Balmer decrement values for 105
program stars and found that ∼20 per cent of them show D34≥2.7,
implying that their circumstellar disc are generally optically thick
in nature. One program star, HD 60855 shows Hα in absorption -
indicative of disc-less phase. From our analysis, we found that in
classical Be stars, Hα emission equivalent width values are
mostly lower than 40Å, which agrees with that present in
literature. Moreover, we noticed that a threshold value of ∼10Å of
Hα emission equivalent width is necessary for Fe II emission to
become visible. We also observed that emission line equivalent widths
of Hα, P14, Fe II 5169, and O I 8446Å for our program stars
tend to be more intense in earlier spectral types, peaking mostly near
B1-B2. Furthermore, we explored various formation regions of Ca II
emission lines around the circumstellar disc of classical Be stars. We
suggest the possibility that Ca II triplet emission can originate
either in the circumbinary disc or from the cooler outer regions of
the disc, which might not be isothermal in nature.
Description:
The spectroscopic observations of the CBe stars were carried out with
the HFOSC instrument mounted on the 2.1-m Himalayan Chandra Telescope
(HCT) located at Hanle, Ladakh, India. During 2007 December to 2009
January we observed 118 CBe stars selected from the catalogue of
Jaschek & Egret (1982IAUS...98..261J 1982IAUS...98..261J, Cat. III/67). These stars were
selected based on the observation visibility of HCT. The spectral
coverage is from 3800 to 9000Å. The spectrum in the 'blue region'
is taken with Grism 7 (3800-5500Å), which in combination with 167l
slit provides an effective resolution of 10Å at Hβ. The red
region spectrum is taken with Grism 8 (5500-9000Å) and 167l slit,
providing an effective resolution of 7Å at Hα. Dome flats
taken with halogen lamps were used for flat fielding the images. Bias
subtraction, flat-field correction, and spectral extraction were
performed with standard IRAF tasks. FeNe and FeAr lamp spectra were
taken with the object spectra for wavelength calibration. All the
extracted raw spectra were wavelength calibrated and continuum
normalized with IRAF tasks.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 59 138 List of our program CBe stars and the log of
observations
table2.dat 38 83 Our adopted distance for 83 of our sample stars
whose parallax values are available in Gaia DR2
and their re-estimated AV values
table3.dat 18 35 List of 35 of our program stars for which AV
values are adopted from the literature
table4.dat 66 115 Estimated Balmer decrements, D34 and D54
for our program stars
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See also:
III/67 : Catalogue of Be stars (Jaschek+, 1982)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Star name
12- 23 A12 --- OName Alternative name
25- 28 F4.1 mag Vmag V-band magnitude
30- 42 A13 --- SpType Spectral type
44- 53 I10 "Y:M:D" Date Observation date
55- 59 F5.1 s ExpTime Exposure time
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Star name
12- 15 I4 pc Dist Star distance
17- 19 I3 pc E_Dist Upper error on Dist
21- 23 I3 pc e_Dist Lower error on Dist
25- 27 F3.1 mag Av Re-estimated extinction
29- 32 F4.2 mag e_Av Error on Av
34- 36 F3.1 mag Avlit Extinction from literature
38 A1 --- r_Avlit Reference for Avlit (1)
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Note (1): Reference as follows:
a = Zhang, Chen & Yang (2005NewA...10..325Z 2005NewA...10..325Z, Cat. J/other/NewA/10.325)
b = Stevens, Stassun & Gaudi (2017AJ....154..259S 2017AJ....154..259S, Cat. J/AJ/154/259)
c = Gontcharov (2012AstL...38...87G 2012AstL...38...87G, Cat. J/PAZh/38/108)
d = Chen, Liu & Shan (2016MNRAS.463.1162C 2016MNRAS.463.1162C, Cat. J/MNRAS/463/1162)
e = Varga et al. (2018A&A...617A..83V 2018A&A...617A..83V, Cat. J/A+A/617/A83)
f = Swihart et al. (2017AJ....153...16S 2017AJ....153...16S, Cat. J/AJ/153/16)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Star name
11 A1 --- f_Name [*] Flag on Name (1)
13- 16 F4.2 mag Av Extinction from literature
18 A1 --- r_Av Reference for Av (2)
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Note (1): Flag as follows:
* = Zhang et al. (2005NewA...10..325Z 2005NewA...10..325Z, Cat. J/other/NewA/10.325) obtained
AV>1.0 for four stars flagged here
Note (2): Reference as follows:
a = Swihart et al. (2017AJ....153...16S 2017AJ....153...16S, Cat. J/AJ/153/16)
b = Chen et al. (2016MNRAS.463.1162C 2016MNRAS.463.1162C, Cat. J/MNRAS/463/1162)
c = Zhang et al. (2005NewA...10..325Z 2005NewA...10..325Z, Cat. J/other/NewA/10.325)
d = Gontcharov (2012AstL...38...87G 2012AstL...38...87G, Cat. J/PAZh/38/108)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Star name
12 A1 --- f_Name Flag on Name (1)
14- 18 F5.1 0.1nm EWHa Equivalent width of Hα
20- 24 F5.2 0.1nm EWHb ? Equivalent width of Hβ
26- 30 F5.2 0.1nm EWHg ? Equivalent width of Hγ
32- 36 F5.1 0.1nm EWcHa ? Absorption corrected equivalent width of
Hα
38- 42 F5.1 0.1nm EWcHb ? Absorption corrected equivalent width of
Hβ
44- 48 F5.1 0.1nm EWcHg ? Absorption corrected equivalent width of
Hγ
50- 52 F3.1 --- D34c ? Estimated Balmer decrement (D34)c (2)
54- 57 F4.2 --- e_D34c ? Error on D34c
59- 61 F3.1 --- D54c ? Estimated Balmer decrement (D54)c (2)
63- 66 F4.2 --- e_D54c ? Error on D54c
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Note (1): Flag as follows:
* = For five other stars flagged with * we could not confirm the spectral
types from the literature
a = Hβ, Hγ lines are not visible in case of HD 45726 and HD 58343
since Grism 7 spectra is not available for them
b = The star HD 60855, shows Hα in absorption after correcting for
underlying stellar absorption
Note (2): See section 3.4.1 of the article for details on the calculation of
(D34)c and (D54)c
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 05-Oct-2023