We present a catalogue of 285 RR Lyrae stars (RRLs) in the Draco dwarf spheroidal (dSph) galaxy, obtained by combining data from a number of different surveys including the Data Release 2 (DR2) of the European Space Agency cornerstone mission Gaia. We have determined individual distances to the RRLs in our sample using for the first time a Gaia G-band luminosity–metallicity relation (MG-- [Fe/H]) and study the structure of the Draco dSph as traced by its RRL population. We find that the RRLs located in the western/south-western region of Draco appear to be closer to us, which may be a clue of interaction between Draco and the Milky Way. The average distance modulus of Draco measured with the RRLs is μ =19.53± 0.07 mag, corresponding to a distance of 80.5± 2.6 kpc, in good agreement with previous determinations in the literature. Based on the pulsation properties of the RRLs, we confirm the Oosterhoff-intermediate nature of Draco. We present an additional sample of 41 candidate RRLs in Draco, which we selected from the Gaia DR2 catalogue based on the uncertainty of their G-band magnitudes. Additional epoch data that will become available in the Gaia Data Release 3 will help to confirm whether these candidates are bona fide Draco RRLs.
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Muraveva et al. (2020) studied this question.
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