RR Lyrae Stars in Stellar Streams with Gaia: The Escapers

AbstractCosmological models predict that large galaxies like the Milky Way formed from the accretion of smaller stellar systems. The most spectacular of these merger events are stellar tidal streams, rivers of stars and dark matter that envelop the discs of spiral galaxies. We present a research project for a collaboration with amateur astronomers in the study of the formation process of our Galaxy. The main objective is the search for RR Lyrae variable stars in the known stellar streams (Sagitarius, Monoceros, Orphan, etc) a project that can be carried out using small telescopes. The catalogue of candidate variable stars were selected from SDSS data based in colour criteria and it will be sent to interested amateur astronomers who wish to participate in scientific research in one of the most active and competitive topics in Galactic astronomy.

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Reflex motion in the Milky Way stellar halo resulting from the Large Magellanic Cloud infall

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slaa029 ◽

2020 ◽

Vol 494 (1) ◽

pp. L11-L16 ◽

Cited By ~ 9

Author(s):

Michael S Petersen ◽

Jorge Peñarrubia

Keyword(s):

Milky Way ◽

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Centre Of Mass ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Disc Centre ◽

Stellar Streams ◽

Stellar Halo ◽

Lyrae Stars

ABSTRACT We present the results of N-body models of the Milky Way and Large Magellanic Cloud system and study the kinematic reflex motion in the stellar halo owing to the barycentre displacement of the disc. In agreement with previous studies, we find that the Milky Way disc may be moving at 40 $\, {\rm km~s^{-1}}$ relative to the barycentre prior to the Large Magellanic Cloud infall. The resulting reflex motion is visible in tangential velocities of the stellar halo as a simple dipole. The signal is strongest for stars with long dynamical times, identifiable in position-velocity data as stars with large apocentres, whose dynamical memory is still well represented by the unperturbed Milky Way potential. The signal varies across the sky depending on the stellar tracer and may be up to the same magnitude as the velocity of the disc centre of mass, making reflex motion a source of bias for Milky Way potential determinations based on the modelling of stellar streams and/or smooth halo tracers such as blue horizontal branch or RR Lyrae stars.

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The Unusual Period Distribution of the RR Lyrae Variables in NGC 5897

International Astronomical Union Colloquium ◽

10.1017/s0252921100011957 ◽

1989 ◽

Vol 111 ◽

pp. 287-287

Author(s):

Amelia Wehlau

Keyword(s):

Light Curves ◽

Instability Strip ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Period Distribution ◽

Unusual Distribution ◽

Photoelectric Observations ◽

Lyrae Stars ◽

Branch Star ◽

Central Concentration

AbstractAttention is called to the rather unusual distribution of the periods of the RR Lyrae variables in NGC 5897, a metal-poor halo globular cluster with a very low central concentration. Of the seven RR Lyrae stars known in the cluster, three have periods between 0.797 and 0.856 day and two have periods of 0.45 and 0.42 day. The other two have periods of 0.34 and 0.35 day with much lower amplitudes of variation. Due to the lack of crowding in this cluster photoelectric observations and Fourier decompositions of the resulting light curves should be possible for at least six of the RR Lyrae variables. In addition, the cluster appears to contain a non-variable horizontal branch star, SK 120, lying within the instability strip. As this is the only well documented case of such a star, photoelectric observations of this star would also be desirable.

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General Properties of the Two Groups of Globular Clusters and Their Variable Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900010743 ◽

1975 ◽

Vol 67 ◽

pp. 541-543

Author(s):

A. V. Mironov ◽

N. N. Samus'

Keyword(s):

Chemical Composition ◽

Globular Clusters ◽

Variable Stars ◽

Rr Lyrae Stars ◽

General Properties ◽

Rr Lyrae ◽

Lyrae Stars

The dependences of the numbers of variable stars in globular clusters on the chemical composition are studied. For given metallicity the numbers of RR Lyrae stars reduced to some definite total number of stars in the cluster are different for the two groups of globular clusters introduced by Mironov.

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