Journal article
Are the Double-mode Bulge RR Lyrae Stars with Identical Period Ratios the Relic of a Disrupted Stellar System?
Astrophysical journal. Letters, Vol.877(2), p.L17
06/01/2019
DOI: 10.3847/2041-8213/ab1fe4
Abstract
Radial velocities of 15 double-mode bulge RR Lyrae (RR01) stars are presented, 6 of which belong to a compact group of RRO1 stars in pulsation space, with the ratio of first-overtone period to fundamental mode period, P-fo/P-f similar to 0.74, and P-f similar to 0.44. It has been suggested that these pulsationally clumped RR01 stars are a relic of a disrupted dwarf galaxy or stellar cluster, as they also appear to be spatially coherent in a vertical strip across the bulge. However, the radial velocities of the stars presented here, along with proper motions from Gaia DR2, show a large range of radial velocities, proper motions, and distances for the bulge RR01 stars in the pulsation clump, much larger than the RR01 stars in the Sagittarius dwarf galaxy (Sgr). Therefore, in contrast to the kinematics of the RRL stars belonging to Sgr, and those in and surrounding the bulge globular cluster NGC 6441, there is no obvious kinematic signature within the pulsationally clumped RR01 stars. If the pulsationally clumped RR01 stars belonged to the same system in the past and were accreted, their accretion in the inner Galaxy was not recent, as the kinematic signature of this group has been lost (i.e., these stars are now well-mixed within the inner Galaxy). We show that the apparent spatial coherence reported for these stars could have been caused by small number statistics. The orbits of the RR01 stars in the inner Galaxy suggest that they are confined to the innermost similar to 4 kpc of the Milky Way.
Details
- Title: Subtitle
- Are the Double-mode Bulge RR Lyrae Stars with Identical Period Ratios the Relic of a Disrupted Stellar System?
- Creators
- Andrea Kunder - Saint Martin's UniversityAlex Tilton - Saint Martin's UniversityDylon Maertens - Saint Martin's UniversityJonathan Ogata - Saint Martin's UniversityDavid Nataf - Johns Hopkins UniversityR. Michael Rich - University of California, Los AngelesChristian I. Johnson - Center for Astrophysics Harvard & SmithsonianChristina Gilligan - Dartmouth CollegeBrian Chaboyer - Dartmouth College
- Resource Type
- Journal article
- Publication Details
- Astrophysical journal. Letters, Vol.877(2), p.L17
- Publisher
- IOP Publishing Ltd
- DOI
- 10.3847/2041-8213/ab1fe4
- ISSN
- 2041-8205
- eISSN
- 2041-8213
- Number of pages
- 7
- Grant note
- NS-2017321 / M. J. Mudrock Charitable Trust Australian Astronomical Observatory
- Language
- English
- Date published
- 06/01/2019
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984701731302771
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