scholarly journals Chemical Abundances of OB Stars in Five OB Associations

2001 ◽  
Vol 552 (1) ◽  
pp. 309-320 ◽  
Author(s):  
Simone Daflon ◽  
Katia Cunha ◽  
Sylvia R. Becker ◽  
Verne V. Smith
Keyword(s):  
Chemical Abundances ◽  
Ob Stars ◽  
Ob Associations

scholarly journals Chemical Abundances of OB Stars with High Projected Rotational Velocities

2001 ◽  
Vol 563 (1) ◽  
pp. 325-333 ◽  
Author(s):  
Simone Daflon ◽  
Katia Cunha ◽  
Keith Butler ◽  
Verne V. Smith
Keyword(s):  
Chemical Abundances ◽  
Ob Stars

Chemical Abundances of OB Stars in the Cepheus OB2 Association

1999 ◽  
Vol 522 (2) ◽  
pp. 950-959 ◽  
Author(s):  
Simone Daflon ◽  
Katia Cunha ◽  
Sylvia R. Becker
Keyword(s):  
Chemical Abundances ◽  
Ob Stars

Chemical Abundances for a Sample of Southern OB Stars. II. The Outer Disk

2004 ◽  
Vol 606 (1) ◽  
pp. 514-519 ◽  
Author(s):  
Simone Daflon ◽  
Katia Cunha ◽  
Keith Butler
Keyword(s):  
Chemical Abundances ◽  
Ob Stars ◽  
Outer Disk

Variability Survey of Massive Stars in OB-Associations: Preliminary Results on the Cygnus Region

2012 ◽  
Vol 21 (4) ◽  
Author(s):  
J. Laur ◽  
T. Tuvikene ◽  
T. Eenmäe ◽  
I. Kolka ◽  
L. Leedjärv
Keyword(s):  
Massive Stars ◽  
Light Curves ◽  
Ob Stars ◽  
Preliminary Results ◽  
Red Supergiants ◽  
Ob Associations

AbstractWe present V - and I-passband photometry of massive stars in the Cyg OB1 and Cyg OB2 associations, based on about 80 observing nights spanning 300 days in the 2011 season. The variability of 22 supergiants and 48 OB-stars with luminosity classes III-V is analyzed. We report two new variable OB stars and 15 variable supergiants of which four are new discoveries. The light variations of Schulte 12 are interpreted as microvariability. We also present light curves of the red supergiants BC Cyg and BI Cyg which exhibit brightness drop of more than 0.4 mag during the season.

scholarly journals Chemical abundances of fast-rotating OB stars

2014 ◽  
Vol 9 (S307) ◽  
pp. 94-95
Author(s):  
Constantin Cazorla ◽  
Thierry Morel ◽  
Yaël Nazé ◽  
Gregor Rauw
Keyword(s):  
Massive Stars ◽  
Evolutionary Models ◽  
Rotating Stars ◽  
Chemical Abundances ◽  
Single Star ◽  
Ob Stars ◽  
Detailed Surface ◽  
Normal Nitrogen ◽  
First Time ◽  
Fast Rotating

AbstractFast rotation in massive stars is predicted to induce mixing in their interior, but a population of fast-rotating stars with normal nitrogen abundances at their surface has recently been revealed (Hunter et al.2009; Brott et al.2011, but see Maeder et al.2014). However, as the binary fraction of these stars is unknown, no definitive statements about the ability of single-star evolutionary models including rotation to reproduce these observations can be made. Our work combines for the first time a detailed surface abundance analysis with a radial-velocity monitoring for a sample of bright, fast-rotating Galactic OB stars to put strong constraints on stellar evolutionary and interior models.

scholarly journals OB stars on the outermost borders of M31

1970 ◽  
Vol 38 ◽  
pp. 69-71
Author(s):  
F. Börngen ◽  
G. Friedrich ◽  
G. Lenk ◽  
L. Richter ◽  
N. Richter
Keyword(s):  
Stellar System ◽  
Test Field ◽  
Special Test ◽  
Stellar Objects ◽  
Ob Stars ◽  
Mean Error ◽  
M 31 ◽  
The Mean ◽  
Ob Associations

Van den Bergh (1964) has selected and mapped OB associations in M 31 on the basis of plates taken with the Tautenburg 52 inch Schmidt camera. The selection was done by the blinking method. The task of the present investigation is to find if there exist OB stars (single or in association) on the outermost borders of this stellar system. For this purpose we measured the brightness of all stellar objects in UBV down to the magnitude 20m.0 (B) on Tautenburg plates in a special test field (Figure 1). It includes 0.26 square degrees and its centre has a distance of 104′ = 22 kpc from the centre of M 31. This test field includes too Baade's field IV with the photoelectric standards in UBV observed by Arp (Baade and Swope, 1963) and the OB associations OB 184, OB 185 and OB 186 of Van den Bergh. The total number of stars brighter than 20m.0 (B) was 996. The stars within the associations OB 184 and OB 185 are not included in these statistics. From this number, 704 objects could be measured in all 3 colours. We found among them 23 blue objects with U–B ≤ U− ≤ −0m.25. The mean error of the brightness on the basis of 4 plates in each colour does not exceed ±0m.0.7 for stars of 19m.0 (B).

scholarly journals Projected Rotational Velocities in Galactic OB Stars of Different OB Associations

2004 ◽  
Vol 215 ◽  
pp. 43-44
Author(s):  
L. J. Corral ◽  
A. Herrero ◽  
M. R. Villamariz
Keyword(s):  
Massive Stars ◽  
Rotational Velocity ◽  
Ob Stars ◽  
Ob Associations

As a first step to study the influence that rotation has in the evolution of the most massive stars, we obtained the projected rotational velocity (v sin i) of a sample of OB stars from clusters and associations. We found that most of our stars present v sin i lower than 200 km/s.

scholarly journals Internal motions in OB associations with Gaia DR2

2020 ◽  
Vol 493 (2) ◽  
pp. 2339-2351 ◽  
Author(s):  
A M Melnik ◽  
A K Dambis
Keyword(s):  
Expansion Velocity ◽  
Giant Molecular Clouds ◽  
Proper Motions ◽  
Ob Stars ◽  
Internal Motions ◽  
Ob Associations ◽  
Stellar Masses ◽  
Formation Efficiency ◽  
First Time ◽  
Gaia Dr2

ABSTRACT We study the motions inside 28 OB associations with the use of Gaia DR2 proper motions. The average velocity dispersion calculated for 28 OB associations including more than 20 stars with Gaia DR2 proper motion is σv = 4.5 km s−1. The median virial and stellar masses of OB associations are Mvir = 8.9 × 105 and Mst = 8.1 × 103 M⊙, respectively. The median star-formation efficiency in parent giant molecular clouds appears to be ϵ = 1.2 per cent. Gaia DR2 proper motions confirm the expansion in the Per OB1, Car OB1, and Sgr OB1 associations found earlier with Gaia DR1 data. We also detect the expansion in Gem OB1, Ori OB1, and Sco OB1 associations, which became possible for the first time now when analysed with Gaia DR2 proper motions. The analysis of the distribution of OB stars in the Per OB1 association shows the presence of a shell-like structure with the radius of 40 pc. Probably, the expansion of the Per OB1 association started with the velocity greater than the present-day expansion velocity equal to 5.0 ± 1.7 km s−1.

scholarly journals Formation of cold filaments from colliding superbubbles

2013 ◽  
Vol 9 (S296) ◽  
pp. 282-286
Author(s):  
Evangelia Ntormousi ◽  
Katharina Fierlinger ◽  
Andreas Burkert ◽  
Fabian Heitsch
Keyword(s):  
Star Formation ◽  
Numerical Simulations ◽  
Large Scale ◽  
Ob Stars ◽  
Ob Associations

AbstractWe present results from numerical simulations of expanding and colliding supershells. These large-scale spherical shocks, created by the combined feedback from several OB stars, are unstable to a number of hydrodynamical instabilities, so they quickly fragment into cold and highly structured clumps. A collision between two large shells can organize these small clumps into very filamentary structures, of tens of parsecs length and less than a parsec thick. In simulations where the flow of stellar material is followed with a tracer quantity, cold structures practically do not contain any enriched material from the OB associations at the time of their creation. In this context then, the clumps are created almost exclusively out of diffuse ISM material, containing almost no wind or supernova matter. Although the mechanism presented here is possibly not the only route for filament creation, this predicted property may help identify regions of sequential star formation.

Chemical Abundances for a Sample of Southern OB Stars

2004 ◽  
Vol 604 (1) ◽  
pp. 362-371 ◽  
Author(s):  
Simone Daflon ◽  
Katia Cunha ◽  
Keith Butler
Keyword(s):  
Chemical Abundances ◽  
Ob Stars
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