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J/A+A/610/A30       B stars in 4 open clusters              (Aidelman+, 2018)

Open clusters: III. Fundamental parameters of B stars in NGC 6087, NGC 6250, NGC 6383, and NGC 6530. B-type stars with circumstellar envelopes. Aidelman Y., Cidale L.S., Zorec J., Panei J.A. <Astron. Astrophys. 610, A30 (2018)> =2018A&A...610A..30A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, B-type ; Spectrophotometry ; Observatory log Keywords: open clusters and associations: individual: NGC 6087 - open clusters and associations: individual: NGC 6250 - open clusters and associations: individual: NGC 6383 - open clusters and associations: individual: NGC 6530 - stars: fundamental parameters - stars: emission-line Abstract: Stellar physical properties of star clusters are poorly known and the cluster parameters are often very uncertain. Our goals are to perform a spectrophotometric study of the B star population in open clusters to derive accurate stellar parameters, search for the presence of circumstellar envelopes, and discuss the characteristics of these stars. The BCD spectrophotometric system is a powerful method to obtain stellar fundamental parameters from direct measurements of the Balmer discontinuity. To this end, we wrote the interactive code MIDE3700. The BCD parameters can also be used to infer the main properties of open clusters: distance modulus, color excess, and age. Furthermore, we inspected the Balmer discontinuity to provide evidence for the presence of circumstellar disks and identify Be star candidates. We used an additional set of high-resolution spectra in the Hα region to confirm the Be nature of these stars. We provide Teff, logg, Mv, Mbol, and spectral types for a sample of 68 stars in the field of the open clusters NGC6087, NGC6250, NGC6383, and NGC6530, as well as the cluster distances, ages, and reddening. Then, based on a sample of 230 B stars in the direction of the 11 open clusters studied along this series of three papers, we report 6 new Be stars, 4 blue straggler candidates, and 15 B-type stars (called Bdd) with a double Balmer discontinuity, which indicates the presence of circumstellar envelopes. We discuss the distribution of the fraction of B, Be, and Bdd star cluster members per spectral subtype. The majority of the Be stars are dwarfs and present a maximum at the spectral type B2-B4 in young and intermediate-age open clusters (<40Myr). Another maximum of Be stars is observed at the spectral type B6-B8 in open clusters older than 40Myr, where the population of Bdd stars also becomes relevant. The Bdd stars seem to be in a passive emission phase. Our results support previous statements that the Be phenomenon is present along the whole main sequence band and occurs in very different evolutionary states.We find clear evidence of an increase of stars with circumstellar envelopes with cluster age. The Be phenomenon reaches its maximum in clusters of intermediate age (10-40Myr) and the number of B stars with circumstellar envelopes (Be plus Bdd stars) is also high for the older clusters (40-100Myr). Description: Tables 1 and 2: Log of observations of low and high-resolution spectra taken with the Boller & Chivens and REOSC DC spectrographs, respectively. The coordinates α and δ correspond to the ICRS system (ep=2000 and eq=J2000). Tables 9, 11, 13 and 15: Stellar fundamental parameters from the BCD system. Tables 10, 12, 14 and 16: Physical parameters and distance to the stars. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 110 68 Log of observations of low-resolution spectra table2.dat 110 63 Log of observations of high-resolution spectra table9.dat 120 18 Stellar fundamental parameters for NGC 6087 table10.dat 95 18 Physical parameters and distance for NGC 6087 table11.dat 120 15 Stellar fundamental parameters for NGC 6250 table12.dat 95 15 Physical parameters and distance for NGC 6250 table13.dat 120 12 Stellar fundamental parameters for NGC 6383 table14.dat 95 12 Physical parameters and distance for NGC 6383 table15.dat 120 23 Stellar fundamental parameters for NGC 6530 table16.dat 95 23 Physical parameters and distance for NGC 6530
See also: B/ocl : Optically visible open clusters and Candidates (Dias+ 2002-2015) Byte-by-byte Description of file: table1.dat table2.dat
Bytes Format Units Label Explanations
1- 13 A13 --- Cl Open cluster name 15- 17 I3 --- ID ?=0 Nomenclature (G1) 19- 33 A15 --- Obj Other designation 35- 36 I2 h RAh Right ascension (Eq=J2000 (Ep=2000) 38- 39 I2 min RAm Right ascension (Eq=J2000 (Ep=2000) 41- 45 F5.2 s RAs Right ascension (Eq=J2000 (Ep=2000) 47 A1 --- DE- Declination sign (Eq=J2000, Ep=2000) 48- 49 I2 deg DEd Declination (Eq=J2000, Ep=2000) 51- 52 I2 arcmin DEm Declination (Eq=J2000, Ep=2000) 54- 58 F5.2 arcsec DEs Declination (Eq=J2000, Ep=2000) 60- 63 F4.2 --- AM1 Air mass of first observation 65- 69 F5.2 --- AM2 ?=99.99 Air mass of second observation 71- 75 F5.2 --- AM3 ?=99.99 Air mass of third observation 77- 86 A10 "date" Date1 Date of first observation 88- 97 A10 "date" Date2 Date of second observation 99-108 A10 "date" Date3 Date of third observation 110 I1 --- N Number of observations
Byte-by-byte Description of file: table9.dat table11.dat table13.dat table15.dat
Bytes Format Units Label Explanations
1- 3 I3 --- ID ?=0 Nomenclature of star (G1) 5- 19 A15 --- Obj Other designation 21- 22 A2 --- n_Obj [dd ] Second Balmer Discontinuity (2) 24- 27 F4.2 --- D Photospheric component of the Balmer discontinuity 29- 30 I2 0.1nm lambda1 ? Mean spectral position of the Balmer discontinuity 32- 35 F4.2 um Phib Observed color gradient 37- 44 A8 --- SpType Spectral type 46- 58 A13 --- n_SpType Other object types (3) 60- 64 I5 K Teff Effective Temperature 65- 66 A2 --- n_Teff [man: ] Extrapolated values flag for Teff (4) 68- 71 I4 K e_Teff Error in Effective Temperature 73- 76 F4.2 [cm/s2] logg Stellar surface gravity 77- 78 A2 --- n_logg [man: ] Extrapolated values flag for logg (4) 80- 83 F4.2 [cm/s2] e_logg Error in logg 85- 89 F5.2 mag VMAG Absolute Magnitude in V filter 90- 91 A2 --- n_VMAG [man: ] Extrapolated values flag for VMAG (4) 93- 96 F4.2 mag e_VMAG Error in Absolute Magnitude 98-102 F5.2 mag Mbol Bolometric Magnitude 103-104 A2 --- n_Mbol [man: ] Extrapolated values flag for Mbol (4) 106-109 F4.2 mag e_Mbol Error in Bolometric Magnitude 111-114 F4.2 um Phi0 Intrinsic color gradient 115 A1 --- n_Phi0 [man: ] Extrapolated values flag fro Phi0 (4) 117-120 F4.2 um e_Phi0 Error in Intrinsic color gradient
Note (2): Flag as follows: dd = Star with a Second Balmer Discontinuity Note (3): Object types as follows: mk = Spectral types derived using the MK-system so = Spectral types derived using The Galactic O-Star Spectroscopic Survey Sota et al. (2011ApJS..193...24S, Cat. III/274) BE = Spectroscopic binary BE2 = Double line spectroscopic binary BEc = Eclipsing binary Be = Known Be star BS = Blue straggler star CP2 = Chemically peculiar star Em = Emission-line star Halpha = Star with emission in Hα He = Helium star IR = Star with infrared excess MA = Magnetic Ap star p = Chemically peculiar star ST = Triple system V = Variable star VB = Reported as visual binary star Vr = Radial velocity variable Vv = Probable variable like Vega star Note (4): Extrapolated values flags as follows: a = Values interpolated from Cox & Pilachowski (2000PhT....53j..77C) m = Value calculated in this work, using a relation between Phi0b and (B-V)0 given by Moujtahid et al. (1998, Cat. J/A+AS/129/289) n = Stellar parameter given by Martins et al. (2005A&A...436.1049M) The symbol : is used to indicate extrapolated values.
Byte-by-byte Description of file: table1[0246].dat
Bytes Format Units Label Explanations
1- 3 I3 --- ID ?=0 Nomenclature of star (G1) 5- 19 A15 --- Obj Other designation 21- 22 A2 --- n_Obj [dd ] Second Balmer Discontinuity (2) 24- 28 F5.2 mag Vmag Visual magnitude in V filter (3) 30- 34 F5.2 mag E(B-V) ?=99.99 Color excess (4) 36- 40 F5.2 mag e_E(B-V) ?=99.99 Error in color excess 42- 45 F4.1 mag MOD True distance modulus 47- 49 F3.1 mag e_MOD Error in true distance modulus 51- 53 A3 --- Member Membership to the cluster (5) 55- 60 F6.2 arcmin AD Angular distance to the cluster center 62- 66 F5.1 % Pmemb Membership probability 68- 70 F3.1 [Lsun] logL ? Luminosity 72- 74 F3.1 [Lsun] e_logL ? Error in luminosity 76- 80 F5.1 Msun Mass ? Stellar mass 82- 85 F4.1 Msun e_Mass ? Error in stellar mass 87- 89 I3 Ma Age ? Age of the star 91- 95 F5.1 Ma e_Age ? Error in age of the star
Note (2): Flag as follows: dd = Star with a Second Balmer Discontinuity Note (3): Vmag values obtained from SIMBAD database Note (4): The distances of the stars with negative color gradients were determined using the distance modulus assigned to the cluster Note (5): Membership to the cluster codes as follows: m = Member stars pm = Probable member stars pnm = Probable non-member stars nm = Non-member stars
Global notes: Note (G1): Nomenclatures: for Collinder 223 correspond to Claria & Lapasset (1991PASP..103..998C), Cl* Collinder 223 CL NNN in Simbad for Hogg 16 to Vazquez & Feinstein (1991A&AS...90..317V), Cl* Hogg 16 VF NN in Simbad for NGC 2645 to Forbes & Short (1994AJ....108..594F), Cl Pismis 6 NN in Simbad for NGC 3114 to Lynga (1962ArA.....3...65L), Cl* NGC 3114 L NNN in Simbad for NGC 3766 to Ahmed (1962PROE....3...60A) for NGC 4755 to WEBDA, for NGC 6025 to Feinstein (1971, Cat. J/PASP/83/800) and Kilambi (1975PASP...87..975K), NGC 6025 NNN in Simbad for NGC 6087 to Fernie (1961ApJ...133...64F) and Breger (1966PASP...78..293B), Cl* NGC 6087 F NNN in Simbad for NGC 6250 to Moffat & Vogt (1975A&AS...20..155M) and Herbst (1977AJ.....82..902H), NGC 6250 NN in Simbad for NGC 6383 to Eggen (1961RGOB...27...61E), The (1965CoBos..32....0T) and Lloyd Evans (1978MNRAS.184..661L), NGC 6383 NNN in Simbad for NGC 6530 to Walker (1957ApJ...125..636W) and Kilambi (1977MNRAS.178..423K), NGC 6530 NNN in Simbad
Acknowledgements: Yael Judith Aidelman, aidelman(at) References: Aidelman et al., Paper I 2012A&A...544A..64A Aidelman et al., Paper II 2015A&A...577A..45A
(End) Yael Judith Aidelman [UNLP, CONICET], Patricia Vannier [CDS] 06-Nov-2017
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