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

Andrea Kunder; R Rich; K Hawkins; R Poleski; J Storm; C Johnson; J Shen; Z-Y Li; M Cordero; D Nataf

doi:10.1088/2041-8205/808/1/L12

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

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

Andrea Kunder, R Rich, K Hawkins, R Poleski, J Storm, C Johnson, J Shen, Z-Y Li, M Cordero and D Nataf

Astrophysical journal. Letters, Vol.808(1), pp.1-6

07/20/2015

DOI: 10.1088/2041-8205/808/1/L12

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Abstract

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 super(-1) and true space velocity of -482 22 km s super(-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.

Clumps

Galactic bulge

Galactic halos

Galaxies

Metallicity

Radial velocity

Stars

Variable stars

Details

Title: Subtitle: A HIGH-VELOCITY BULGE RR LYRAE VARIABLE ON A HALO-LIKE ORBIT
Creators: Andrea Kunder - Leibniz Institute for Astrophysics Potsdam
R Rich
K Hawkins - University of Cambridge
R Poleski - University of Warsaw
J Storm - Leibniz Institute for Astrophysics Potsdam
C Johnson - Center for Astrophysics Harvard & Smithsonian
J Shen - Shanghai Astronomical Observatory
Z-Y Li - Shanghai Astronomical Observatory
M Cordero - Max Planck Institute for Astronomy
D Nataf - Australian National University
Resource Type: Journal article
Publication Details: Astrophysical journal. Letters, Vol.808(1), pp.1-6
DOI: 10.1088/2041-8205/808/1/L12
ISSN: 2041-8205
eISSN: 2041-8213
Number of pages: 6
Language: English
Date published: 07/20/2015
Academic Unit: Physics and Astronomy
Record Identifier: 9984701832102771

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