OGLE-2008-BLG-513L b

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OGLE-2008-BLG-513L b

Post by Sirius_Alpha on 22nd June 2011, 2:24 am

OGLE-2008-BLG-513Lb: The Orbital Solution for a Microlensing Planet
http://arxiv.org/abs/1106.4013v1

The dominant features of the microlensing event OGLE-2008-BLG-513 arise from a 2-body lens with a mass ratio q=0.027+/-0.001. The light curve cannot be adequately described by a static, 2-body lens model, which forces us to consider the orbital motion of the lens system. Including orbital motion improves the fit by Delta chi^2>1000. We model the orbital motion as a Keplerian orbit, and with the additional information from microlens parallax, we are able to place constraints on all eight parameters of the orbit. If our model is correct, this gives us the most complete orbital information of any microlensing planet. We find that the host star is 0.18<M_L/M_Sun<0.34, and the planet is 5.0<m_p/M_Jup<9.6 with semimajor axis a ~3.0 AU. Although this model fully explains the shape of the light curve, it has the unusual requirement that if the lens system is bound, the source is at a distance of 1.2<D_S/kpc<1.8 rather than the typical distance of 8 kpc. This event is also unusual because the position of the source in the VIH color-color diagram, which is determined independent of the light curve model, is strange compared to the stars in the field and cannot be easily explained. A nearby source may help explain why the colors of the source are so peculiar, although this explanation is not completely satisfactory. This peculiarity provides us with a means to confirm or refute our microlensing model by obtaining a spectrum of the source, which we predict will show a metal-poor, late-K/early-M dwarf. If our model is confirmed by such a spectrum, this massive planet close to its M dwarf host likely presents a challenge to both core accretion and gravitational instability planet formation theories.


Last edited by Sirius_Alpha on 11th July 2011, 9:09 pm; edited 3 times in total (Reason for editing : Edited link to direct it to the relevant version of the arXiv paper, and corrected paper title)

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Re: OGLE-2008-BLG-513L b

Post by Sirius_Alpha on 11th July 2011, 9:07 pm

Nevermind.

http://arxiv.org/abs/1106.4013v2
A static binary star solution for OGLE-2008-BLG-513 has been found. The mass ratio and separation for this solution are q~0.28, s~0.86. This model has a chi^2 comparable to the chi^2 of the model with a planetary mass ratio and orbital motion that was presented in this paper. Because the model with a static, binary star lens is simpler than the model originally presented in this paper, Occam's Razor says it is likely to be the correct solution. Consequently, this paper has been withdrawn from ApJ.

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Re: OGLE-2008-BLG-513L b

Post by tommi59 on 18th July 2011, 12:37 pm

Now unconfirmed. A static binary star solution for OGLE-2008-BLG-513 has been found. The mass ratio and separation for this solution are q~0.28, s~0.86. This model has a chi^2 comparable to the chi^2 of the model with a planetary mass ratio and orbital motion that was presented in this paper. Because the model with a static, binary star lens is simpler than the model originally presented in this paper, Occam's Razor says it is likely to be the correct solution. Consequently, this paper has been withdrawn from ApJ." (Yee et al. 2011 - http://arxiv.org/abs/1106.4013).


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