Other
Scientific paper
May 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009rmxac..35r.287m&link_type=abstract
XII Latin American IAU Regional Meeting (Eds. G. Magris, G. Bruzual, & L. Carigi) Revista Mexicana de Astronomía y Astrofísica (
Other
Scientific paper
We present precise new V, I, and K-band photometry for the planetary transit candidate star OGLE-TR-82. Good seeing V-band images acquired with the VIMOS instrument at ESO Very Large Telescope (VLT) allowed us to measure V = 20.6+/-0.03 mag star 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 has been observed with the GMOS-S instrument of GEMINI-South telescope in the i and g-bands. The measurement of the transit allows us to verify that this is not a false positive, to confirm the transit amplitude measured by OGLE, and to improve the ephemeris. The transit is well defined in the i-band light curve, with a depth of A_i=0.034 mag. It is less well defined, but deeper (A_g=0.1 mag) in the g-band, in which the star is significantly fainter. The near-infrared photometry obtained with the SOFI array at the ESO New Technology Telescope (NTT) yields K = 12.2+/-0.1, and V - K = 8.4+/-0.1, so red that it is unlike any other transit candidate studied before. Due to the extreme nature of this object, we have not yet been able to measure velocities for this star, but based on the new data we consider two different possible configurations: (1) a nearby M7V star, or (2) a blend with a very reddened distant red giant. The nearby M7V dwarf hypothesis would give a radius for the companion of R_p = 0.3+/-0.1 R_J, i.e. the size of Neptune. Near-IR spectroscopy finally shows that OGLE-TR-82 is a distant, reddened giant of spectral type K3III, with A_V=6. Therefore, we discard the planetary nature of the companion. We conclude that this system is a main-sequence binary blended with a background red giant.
Ivanov Valentin Dimitrov
Miranda S. H.
Pietrzynski Grzegorz
Ramirez Solange S.
~Minniti Dante
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