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. =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 3800-9000{AA}. We re-estimated the extinction parameter (A_V_) for our sample stars using the newly available data from Gaia DR2 and suggest that it is important to consider A_V_ while measuring the Balmer decrement (i.e. D_34_ and D_54_) 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 D_34_>=2.7, implying that their circumstellar disc are generally optically thick in nature. One program star, HD 60855 shows H{alpha} in absorption - indicative of disc-less phase. From our analysis, we found that in classical Be stars, H{alpha} emission equivalent width values are mostly lower than 40{AA}, which agrees with that present in literature. Moreover, we noticed that a threshold value of ~10{AA} of H{alpha} emission equivalent width is necessary for Fe II emission to become visible. We also observed that emission line equivalent widths of H{alpha}, P14, Fe II 5169, and O I 8446{AA} 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, Cat. III/67). These stars were selected based on the observation visibility of HCT. The spectral coverage is from 3800 to 9000{AA}. The spectrum in the 'blue region' is taken with Grism 7 (3800-5500{AA}), which in combination with 167l slit provides an effective resolution of 10{AA} at H{beta}. The red region spectrum is taken with Grism 8 (5500-9000{AA}) and 167l slit, providing an effective resolution of 7{AA} at H{alpha}. 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: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- 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 A_V_ values table3.dat 18 35 List of 35 of our program stars for which A_V_ values are adopted from the literature table4.dat 66 115 Estimated Balmer decrements, D_34_ and D_54_ for our program stars -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- 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) -------------------------------------------------------------------------------- Note (1): Reference as follows: a = Zhang, Chen & Yang (2005NewA...10..325Z, Cat. J/other/NewA/10.325) b = Stevens, Stassun & Gaudi (2017AJ....154..259S, Cat. J/AJ/154/259) c = Gontcharov (2012AstL...38...87G, Cat. J/PAZh/38/108) d = Chen, Liu & Shan (2016MNRAS.463.1162C, Cat. J/MNRAS/463/1162) e = Varga et al. (2018A&A...617A..83V, Cat. J/A+A/617/A83) f = Swihart et al. (2017AJ....153...16S, Cat. J/AJ/153/16) -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 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) -------------------------------------------------------------------------------- Note (1): Flag as follows: * = Zhang et al. (2005NewA...10..325Z, Cat. J/other/NewA/10.325) obtained A_V_>1.0 for four stars flagged here Note (2): Reference as follows: a = Swihart et al. (2017AJ....153...16S, Cat. J/AJ/153/16) b = Chen et al. (2016MNRAS.463.1162C, Cat. J/MNRAS/463/1162) c = Zhang et al. (2005NewA...10..325Z, Cat. J/other/NewA/10.325) d = Gontcharov (2012AstL...38...87G, Cat. J/PAZh/38/108) -------------------------------------------------------------------------------- Byte-by-byte Description of file: table4.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 A10 --- Name Star name 12 A1 --- f_Name Flag on Name (1) 14- 18 F5.1 0.1nm EWHa Equivalent width of H{alpha} 20- 24 F5.2 0.1nm EWHb ? Equivalent width of H{beta} 26- 30 F5.2 0.1nm EWHg ? Equivalent width of H{gamma} 32- 36 F5.1 0.1nm EWcHa ? Absorption corrected equivalent width of H{alpha} 38- 42 F5.1 0.1nm EWcHb ? Absorption corrected equivalent width of H{beta} 44- 48 F5.1 0.1nm EWcHg ? Absorption corrected equivalent width of H{gamma} 50- 52 F3.1 --- D34c ? Estimated Balmer decrement (D_34_)c (2) 54- 57 F4.2 --- e_D34c ? Error on D34c 59- 61 F3.1 --- D54c ? Estimated Balmer decrement (D_54_)c (2) 63- 66 F4.2 --- e_D54c ? Error on D54c -------------------------------------------------------------------------------- Note (1): Flag as follows: * = For five other stars flagged with * we could not confirm the spectral types from the literature a = H{beta}, H{gamma} 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 H{alpha} in absorption after correcting for underlying stellar absorption Note (2): See section 3.4.1 of the article for details on the calculation of (D_34_)c and (D_54_)c -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Ana Fiallos [CDS] 05-Oct-2023