The Oosterhoff Dichotomy in the Galactic Bulge

Zdeněk Prudil, Eva K. Grebel, István Dékány, Radosław Smolec and Marek Skarka

We explore the possibility that the Oosterhoff dichotomy in fundamental-mode RR Lyrae stars exists also in the Galactic bulge. We utilized data from the OGLE-IV survey together with a recently published list of non-modulated RR Lyraes in this region. The aforementioned stars form two hook patterns in the Fourier parameter space. These structures can be well separated by dividing them in the period–I band amplitude plane, which resembles the division of Oosterhoff groups known from other samples of RR Lyrae stars. In addition, we compare detected Oosterhoff groups in the Galactic bulge with the two Oosterhoff populations in the Sagittarius dwarf galaxy, LMC, SMC, and globular clusters.

Proceedings of the Polish Astronomical Society, vol. 6, 37-41 (2018)

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