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arXiv · 1510.08457

No Evidence for Classical Cepheids and a New Dwarf Galaxy Behind the Galactic Disk

P. Pietrukowicz·A. Udalski·M. K. Szymanski·I. Soszynski·G. Pietrzynski·L. Wyrzykowski·R. Poleski·K. Ulaczyk·J. Skowron·P. Mroz·M. Pawlak·S. Kozlowski
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Abstract

Based on data from the ongoing OGLE Galaxy Variability Survey (OGLE GVS) we have verified observed properties of stars detected by the near-infrared VVV survey in a direction near the Galactic plane at longitude l~-27 deg and recently tentatively classified as classical Cepheids belonging to a, hence claimed, dwarf galaxy at a distance of about 90 kpc from the Galactic Center. Three of four stars are detected in the OGLE GVS I-band images. We show that two of the objects are not variable at all and the third one with a period of 5.695 d and a nearly sinusoidal light curve of an amplitude of 0.5 mag cannot be a classical Cepheid and is very likely a spotted object. These results together with a very unusual shape of the Ks-band light curve of the fourth star indicate that very likely none of them is a Cepheid and, thus, there is no evidence for a background dwarf galaxy. Our observations show that a great care must be taken when classifying objects by their low-amplitude close-to-sinusoidal near-infrared light curves, especially with a small number of measurements. We also provide a sample of high-amplitude spotted stars with periods of a few days that can mimick pulsations and even eclipses.

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P. Pietrukowicz, A. Udalski, M. K. Szymanski, I. Soszynski, G. Pietrzynski, L. Wyrzykowski, R. Poleski, K. Ulaczyk, J. Skowron, P. Mroz, M. Pawlak, S. Kozlowski. 2015-10-28. No Evidence for Classical Cepheids and a New Dwarf Galaxy Behind the Galactic Disk. https://doi.org/10.1088/2041-8205%2F813%2F2%2Fl40

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