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J/ApJ/700/1216     Spectroscopy of Be stars in open clusters    (McSwain+, 2009)

Variability of Be stars in southern open clusters. McSwain M.V., Huang W., Gies D.R. <Astrophys. J., 700, 1216-1232 (2009)> =2009ApJ...700.1216M
ADC_Keywords: Clusters, open ; Stars, Be ; Stars, B-type ; Spectra, red ; Rotational velocities ; Effective temperatures ; Stars, masses Keywords: open clusters and associations: individual (NGC 3293, NGC 3766, NGC 4755, NGC 6231) - stars: emission-line, Be Abstract: We recently discovered a large number of highly active Be stars in the open cluster NGC 3766, making it an excellent location to study the formation mechanism of Be star disks. To explore whether similar disk appearances and/or disappearances are common among the Be stars in other open clusters, we present here multiple epochs of Hα spectroscopy for 296 stars in eight open clusters. We identify 12 new transient Be stars and confirm 17 additional Be stars with relatively stable disks. By comparing the Hα equivalent widths to the photometric y-Hα colors, we present a method to estimate the strength of the Hα emission when spectroscopy is not available. For a subset of 128 stars in four open clusters, we also use blue optical spectroscopy and available Stromgren photometry to measure their projected rotational velocities, effective temperatures, and polar surface gravities. We combine our Be star detections from these four clusters to investigate physical differences between the transient Be stars, stable Be stars, and normal B-type stars with no line emission. Both types of Be stars are faster rotating populations than normal B-type stars, and we find no significant physical differences between the transient and stable Be stars in our sample. Description: We obtained red optical spectra of 296 Be and B-type stars in eight open clusters during observing runs in 2005 February, 2006 May, and 2007 May using the Cerro Tolo Inter-American Observatory (CTIO) Blanco 4-m telescope with the Hydra multi-fiber spectrograph. For a subset of four open clusters, we also obtained blue optical spectra during the 2006 and 2007 runs. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 55 296 Hα equivalent widths table5.dat 115 128 Physical parameters of cluster members
See also: J/MNRAS/386/447 : RV catalogue of O-type stars in NGC 6231 (Sana+, 2008) J/A+A/457/265 : The VLT-FLAMES Survey of Massive Stars (Dufton+, 2006) J/ApJS/161/118 : byHα photometry in open clusters (McSwain+, 2005) J/ApJ/622/1052 : byHα photometry of NGC 3766 (McSwain+, 2005) J/A+A/402/549 : UBVRIHalpha photometry of NGC 3293 (Baume+, 2003) J/A+A/395/823 : CCD Δa-photometry of 5 open clusters (Paunzen+, 2002) J/A+A/369/511 : Open star clusters. III. NGC 4103, 5281, 4755 (Sanner+, 2001) J/AJ/115/734 : NGC 6231 UBVRI and Hα photometry (Sung+ 1998) J/A+A/315/384 : Binarity among B-stars in NGC 6231 (Raboud, 1996) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 13 A13 --- Cl Cluster identification (1) 15- 17 I3 --- MG Star identification in cluster 19- 24 F6.2 0.1nm WHa05 ? Halpha equivalent width in 2005 Feb (2) 26- 31 F6.2 0.1nm WHa06 ? Halpha equivalent width in 2006 May (2) 33- 38 F6.2 0.1nm WHa07 ? Halpha equivalent width in 2007 May (2) 40- 42 A3 --- Em2 Be stars and candidates found in our photometry (Paper II, Cat. J/ApJS/161/118) 44- 55 A12 --- Em Be star status based upon our red spectroscopic observations only; in this work
Note (1): W may be contaminated by nebular emission in NGC 3293 and IC 2581. Note (2): HJD(t-2450000) for the different clusters as follows: -------------------------------------------- Cluster 2005 Feb 2006 May 2007 May -------------------------------------------- Collinder 272 3404.832 3870.178 4225.757 Hogg 16 3404.832 3870.178 4225.757 IC 2581 3404.708 --- 4225.5494 NGC 3293 3404.772 3870.506 4223.321 NGC 3766 3403.790 3870.224 4225.662 NGC 4755 3403.863 --- 4223.717 NGC 6231 --- 3869.828 4223.813 NGC 6664 --- 3870.933 4223.930 --------------------------------------------
Byte-by-byte Description of file: table5.dat
Bytes Format Units Label Explanations
1- 2 A2 --- sp [Be ] Spectral class: B or Be star 4- 11 A8 --- Cl Cluster identification (<NGC NNNN> in Simbad) 13- 15 I3 --- MG Star identification in cluster 17- 19 I3 km/s vsini ? Rotational velocity 21- 22 I2 km/s e_vsini ? vsini uncertainty 24- 28 I5 K Teff ? Effective temperature 30- 33 I4 K e_Teff ? Teff uncertainty 35- 38 F4.2 [cm/s2] logg ? Surface gravity 40- 43 F4.2 [cm/s2] e_logg ? logg uncertainty 45- 48 F4.2 [cm/s2] loggP ? Polar surface gravity 50- 53 F4.1 Msun Mass ? Mass (M*) 55- 57 F3.1 Msun e_Mass ? Mass uncertainty 59- 62 F4.1 Rsun Rad ? Radius (R*) 64- 66 F3.1 Rsun e_Rad ? Rad uncertainty 68- 70 I3 km/s Vc ? Critical velocity (1) 72- 75 A4 --- SB? Binarity comment 77- 95 A19 --- Aut Author's name for SB? remark 97-115 A19 --- BibCode Bibcode for SB? remark
Note (1): The critical velocity is given in equation (5): Vcrit=(GM*/Re)0.5 where the equatorial radius Re=1.5Rp. For simplicity, we assume the polar radius of the star, Rp, is equal to R* (Rad). See section 4.2 for further details.
Nomenclature note: Stars are <Cl* {Cl} MG NNN> for Simbad. History: From electronic version of the journal 23-Sep-2011: Insert into VizieR 27-Sep-2011: Table 2 modified according to PDF version to include NGC 3766 which is missing in HTML version. References: McSwain & Gies. Paper I. 2005ApJ...622.1052M Cat. J/ApJ/622/1052 McSwain & Gies. Paper II. 2005ApJS..161..118M Cat. J/ApJS/161/118 McSwain et al. Paper III. 2008ApJ...672..590M
(End) Emmanuelle Perret [CDS] 27-Jul-2011
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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