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

Abstract

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 ofmore » 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.« less

Authors:
; ; ;  [1];  [2];  [3];  [4]
  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)
Publication Date:
OSTI Identifier:
22663521
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 842; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; ATMOSPHERES; BALMER LINES; COMPARATIVE EVALUATIONS; EXPLOSIONS; GALAXIES; GRAVITATION; INTERACTIONS; IONIZATION; ROTATION; SPECTRA; STARS; SURFACES; VELOCITY

Citation Formats

McEvoy, Catherine M., Dufton, Philip L., Smoker, Jonathan V., Keenan, Francis P., Lambert, David L., Schneider, Fabian R. N., and De Wit, Willem-Jan. The Origin of B-type Runaway Stars: Non-LTE Abundances as a Diagnostic. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA745A.
McEvoy, Catherine M., Dufton, Philip L., Smoker, Jonathan V., Keenan, Francis P., Lambert, David L., Schneider, Fabian R. N., & De Wit, Willem-Jan. The Origin of B-type Runaway Stars: Non-LTE Abundances as a Diagnostic. United States. doi:10.3847/1538-4357/AA745A.
McEvoy, Catherine M., Dufton, Philip L., Smoker, Jonathan V., Keenan, Francis P., Lambert, David L., Schneider, Fabian R. N., and De Wit, Willem-Jan. Sat . "The Origin of B-type Runaway Stars: Non-LTE Abundances as a Diagnostic". United States. doi:10.3847/1538-4357/AA745A.
@article{osti_22663521,
title = {The Origin of B-type Runaway Stars: Non-LTE Abundances as a Diagnostic},
author = {McEvoy, Catherine M. and Dufton, Philip L. and Smoker, Jonathan V. and Keenan, Francis P. and Lambert, David L. and Schneider, Fabian R. N. and De Wit, Willem-Jan},
abstractNote = {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.},
doi = {10.3847/1538-4357/AA745A},
journal = {Astrophysical Journal},
number = 1,
volume = 842,
place = {United States},
year = {Sat Jun 10 00:00:00 EDT 2017},
month = {Sat Jun 10 00:00:00 EDT 2017}
}
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