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Title: Hypervelocity star candidates in the SEGUE G and K dwarf sample

We present 20 candidate hypervelocity stars from the Sloan Extension for Galactic Understanding and Exploration (SEGUE) G and K dwarf samples. Previous searches for hypervelocity stars have only focused on large radial velocities; in this study, we also use proper motions to select the candidates. We determine the hypervelocity likelihood of each candidate by means of Monte Carlo simulations, considering the significant errors often associated with high proper motion stars. We find that nearly half of the candidates exceed their escape velocities with at least 98% probability. Every candidate also has less than a 25% chance of being a high-velocity fluke within the SEGUE sample. Based on orbits calculated using the observed six-dimensional positions and velocities, few, if any, of these candidates originate from the Galactic center. If these candidates are truly hypervelocity stars, they were not ejected by interactions with the Milky Way's supermassive black hole. This calls for a more serious examination of alternative hypervelocity-star ejection scenarios.
Authors:
;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6]
  1. Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States)
  2. Research School of Astronomy and Astrophysics, The Australian National University, Weston, ACT 2611 (Australia)
  3. Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife (Spain)
  4. National Optical Astronomy Observatory, Tucson, AZ 85719 (United States)
  5. Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States)
  6. Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)
Publication Date:
OSTI Identifier:
22348040
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 780; 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; BLACK HOLES; COMPUTERIZED SIMULATION; DWARF STARS; ERRORS; EXPLORATION; INTERACTIONS; MILKY WAY; MONTE CARLO METHOD; ORBITS; PROBABILITY; PROPER MOTION; RADIAL VELOCITY