Resolved Kinematics of Runaway and Field OB Stars in the Small Magellanic Cloud
AuthorOey, M. S.
Jones, J. Dorigo
Januszewski, H. C.
Lennon, D. J.
AffiliationUniv Arizona, Steward Observ
galaxies: star clusters: general
stars: kinematics and dynamics
stars: massive; X-rays: binaries
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationM. S. Oey et al 2018 ApJL 867 L8
JournalASTROPHYSICAL JOURNAL LETTERS
Rights© 2018. The American Astronomical Society. All rights reserved.
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at email@example.com.
AbstractWe use Gaia Data Release 2 proper motions of field OB stars from the Runaways and Isolated O-Type Star Spectroscopic Survey of the Small Magellanic Cloud (SMC) to study the kinematics of runaway stars. The data reveal that the SMC Wing has a systemic peculiar motion relative to the SMC Bar of (v(alpha), v(delta)) = (62 +/- 7, -18 +/- 5) km s(-1) and relative radial velocity +4.5 +/- 5.0 km s(-1). This unambiguously demonstrates that these two regions are kinematically distinct: the Wing is moving away from the Bar, and towards the Large Magellanic Cloud with a 3D velocity of 64 +/- 10 km s(-1). This is consistent with models for a recent, direct collision between the Clouds. We present transverse velocity distributions for our field OB stars, confirming that unbound runaways comprise on the order of half our sample, possibly more. Using eclipsing binaries and double-lined spectroscopic binaries as tracers of dynamically ejected runaways, and high-mass X-ray binaries (HMXBs) as tracers of runaways accelerated by supernova kicks, we find significant contributions from both populations. The data suggest that HMXBs have lower velocity dispersion relative to dynamically ejected binaries, consistent with the former group corresponding to less energetic supernova kicks that failed to unbind the components. Evidence suggests that our fast runaways are dominated by dynamical, rather than supernova, ejections.
VersionFinal published version
SponsorsNational Science Foundation [AST-1514838]; University of Michigan; NASA's Einstein Postdoctoral Fellowship program [PF5-160139]; NASA ATP [17-ATP17-0070]; NSF CAREER award [AST-1455260]