期刊
ASTROPHYSICAL JOURNAL LETTERS
卷 808, 期 1, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/2041-8205/808/1/L12
关键词
Galaxy: bulge; Galaxy: formation; Galaxy: halo; Galaxy: kinematics and dynamics; stars: Population II; stars: variables: RR Lyrae
资金
- National Science Foundation [NSF PHY11-25915, AST-1413755]
- German Research Foundation (DFG) [Sonderforschungsbereich SFB 881]
- Polish Ministry of Science and Higher Education through the program Ideas Plus [IdP2012 000162]
- Clay Fellowship
- 973 Program of China [2014CB845700]
- National Natural Science Foundation of China [11333003, 11322326, 11403072]
- Strategic Priority Research Program The Emergence of Cosmological Structures of the Chinese Academy of Sciences [XDB09000000]
- Shanghai Sailing Program [14YF1407700]
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1413755] Funding Source: National Science Foundation
We report on the RR Lyrae variable star, MACHO 176.18833.411, located toward the Galactic bulge and observed within the data from the ongoing Bulge RR Lyrae Radial Velocity Assay, which has the unusual radial velocity of -372 +/- 8 km s(-1) and true space velocity of -482 +/- 22 km s(-1) relative to the Galactic rest frame. Located less than 1 kpc from the Galactic center and toward a field at (l, b) = (3, -2.5), this pulsating star has properties suggesting it belongs to the bulge RR Lyrae star population, yet a velocity indicating it is abnormal, at least with respect to bulge giants and red clump stars. We show that this star is most likely a halo interloper and therefore suggest that halo contamination is not insignificant when studying metal-poor stars found within the bulge area, even for stars within 1 kpc of the Galactic center. We discuss the possibility that MACHO 176.18833.411 is on the extreme edge of the bulge RR Lyrae radial velocity distribution, and also consider a more exotic scenario in which it is a runaway star moving through the Galaxy.
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