The Origin of B-type Runaway Stars: Non-LTE Abundances as a Diagnostic

Journal Article · Sat Jun 10 04:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA745A· OSTI ID:22663521

McEvoy, Catherine M.; Dufton, Philip L.; Smoker, Jonathan V.; Keenan, Francis P. ^[1]; Lambert, David L. ^[2]; Schneider, Fabian R. N. ^[3]; De Wit, Willem-Jan ^[4]

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1. Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, Belfast BT7 1NN (United Kingdom)
2. The University of Texas at Austin, Department of Astronomy, RLM 16.316, Austin, TX 78712 (United States)
3. Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom)
4. European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Vitacura, Santiago 19 (Chile)

There are two accepted mechanisms to explain the origin of runaway OB-type stars: the binary supernova (SN) scenario and the cluster ejection scenario. In the former, an SN explosion within a close binary ejects the secondary star, while in the latter close multibody interactions in a dense cluster cause one or more of the stars to be ejected from the region at high velocity. Both mechanisms have the potential to affect the surface composition of the runaway star. tlusty non-LTE model atmosphere calculations have been used to determine the atmospheric parameters and the C, N, Mg, and Si abundances for a sample of B-type runaways. These same analytical tools were used by Hunter et al. for their analysis of 50 B-type open-cluster Galactic stars (i.e., nonrunaways). Effective temperatures were deduced using the Si-ionization balance technique, surface gravities from Balmer line profiles, and microturbulent velocities derived using the Si spectrum. The runaways show no obvious abundance anomalies when compared with stars in the open clusters. The runaways do show a spread in composition that almost certainly reflects the Galactic abundance gradient and a range in the birthplaces of the runaways in the Galactic disk. Since the observed Galactic abundance gradients of C, N, Mg, and Si are of a similar magnitude, the abundance ratios (e.g., N/Mg) are as obtained essentially uniform across the sample.

• OSTI ID: 22663521
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 842; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
ATMOSPHERES
BALMER LINES
COMPARATIVE EVALUATIONS
EXPLOSIONS
GALAXIES
GRAVITATION
INTERACTIONS
IONIZATION
ROTATION
SPECTRA
STARS
SURFACES
VELOCITY