Name: Sebastian Ramirez

Institution: Pontificia Universidad Catolica de Chile

e-mail: sramirez(no-spam)astro.puc.cl

Partner Contry: CHI

Science Meeting: Yes

User Meeting: Yes

NGO Staff Meeting: No

Presentation: Yes

Format: Poster

Title: Millimagnitude Photometry for Transiting Extrasolar Planetary Candidates: The Puzzle of the Extremely Red OGLE-TR-82 Primary Solved

Co-authors' Institutions: Pontificia Universidad Cat?lica, Universidad de Chile, Universidad de Buenos Aires, Universidad de Concepci?n, Warsaw University Observatory, European Southern Observatory, Harvard CFA, INS Lyon, GEMINI-South Observatory.

Abstract:

We present precise new V , I, and K-band photometry for the planetary transit candidate star OGLE-TR-82. Good seeing V-band images allows us to measure V = 20.6 in spite of the presence of a brighter neighbour about 1" away. This faint magnitude answers the question why it has not been possible to measure radial velocities for this object. One transit of this star is well defined in the light curves in the i-band obtained at GEMINI-South. The measurement of the transit allows to verify that this is not a false positive, to confirm the transit amplitude measured by OGLE, and to improve the ephemeris. The near-infrared photometry obtained at the ESO NTT yields K = 12.2 ? 0.1,and V-K = 8.4?0.1, implying that this is a nearby M7V star, or a very reddened distant M-type red giant. Due to the extreme nature of this object, we have not yet been able to measure velocities for this star, but consider two different possible transit configurations. Based on the new data, the nearby M7V dwarf hypothesis yields a radius for the companion of Rp = 0.3 ? 0.1 RJ, i.e. the size of Neptune. The reddened giant hypothesis suggests a normal low mass main-sequence star for the companion. However, both scenarios are inconsistent with the transit length measured here, suggesting a more complicated system. Near-IR spectroscopy finally shows that OGLE-TR-82 is a distant, reddened giant of spectral type M0III. Therefore, we discard the planetary nature of the companion, which is most likely a late M dwarf star. As a case study, this new kind of system that can mimick a planetary transit is a lesson to learn for future transit surveys.

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