A HIGH-VELOCITY BULGE RR LYRAE VARIABLE ON A HALO-LIKE ORBIT

Journal Article · Mon Jul 20 00:00:00 EDT 2015 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/808/1/L12· OSTI ID:22518931

Kunder, Andrea; Storm, J. ^[1]; Rich, R. M. ^[2]; Hawkins, K. ^[3]; Poleski, R. ^[4]; Johnson, C. I. ^[5]; Shen, J.; Li, Z. -Y. ^[6]; Cordero, M. J. ^[7]; Nataf, D. M. ^[8]; Bono, G. ^[9]; Walker, A. R. ^[10]; Koch, A. ^[11]; De Propris, R. ^[12]; Udalski, A.; Szymanski, M. K.; Soszynski, I.; Pietrzynski, G.; Ulaczyk, K.; Wyrzykowski, Ł. ^[13] ; others, and

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1. Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany)
2. Department of Physics and Astronomy, University of California at Los Angeles, Los Angeles, CA 90095-1562 (United States)
3. Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom)
4. Department of Astronomy, Ohio State University, 140 W. 18th Avenue, Columbus, OH 43210 (United States)
5. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
6. Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)
7. Astronomisches Rechen-Institut: Zentrum für Astronomie, Mönchhofstr. 12-14, D-69120 Heidelberg (Germany)
8. Research School of Astronomy and Astrophysics, The Australian National University, Canberra, ACT 2611 (Australia)
9. Dipartimento di Fisica, Universita di Roma Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Roma (Italy)
10. Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, Casilla 603, La Serena (Chile)
11. Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, D-69117 Heidelberg (Germany)
12. Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Turku (Finland)
13. Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland)

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{sup −1} and true space velocity of −482 ± 22 km s{sup −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.

• OSTI ID: 22518931
• Journal Information: Astrophysical Journal Letters, Vol. 808, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
GALAXIES
MILKY WAY
ORBITS
RADIAL VELOCITY
RED GIANT STARS
SPACE
VARIABLE STARS