Microlens OGLE-2005-BLG-169 Implies That Cool Neptune-like Planets Are Common

By A. Gould, A. Udalski, D. An, D. Bennett, A. Zhou, S. Dong, N. Rattenbury, B. Gaudi, P. Yock, I. Bond and 26 more. 2006

172 citations recorded by the source corpus.

We detect a Neptune mass ratio (q ≃ 8 × 10-5) planetary companion to the lens star in the extremely high magnification (A ~ 800) microlensing event OGLE-2005-BLG-169. If the parent is a main-sequence star, it has mass M ~ 0.5 M☉, implying a planet mass of ~13 M⊕ and projected separation of ~2.7 AU. When intensely monitored over their peak, high-magnification events similar to OGLE-2005-BLG-169 have nearly complete sensitivity to Neptune mass ratio planets with projected separations of 0.6-1.6 Einstein radii, corresponding to 1.6-4.3 AU in the present case. Only two other such events were monitored well enough to detect Neptunes, and so this detection by itself suggests that Neptune mass ratio planets are common. Moreover, another Neptune was recently discovered at a similar distance from its parent star in a low-magnification event, which are more common but are individually much less sensitive to planets. Combining the two detections yields 90% upper and lower frequency limits f = 0.38 over just 0.4 decades of planet-star separation. In particular, f > 16% at 90% confidence. The parent star hosts no Jupiter-mass companions with projected separations within a factor 5 of that of the detected planet. The lens-source relative proper motion is μ ~ 7-10 mas yr-1, implying that if the lens is sufficiently bright, I ≲ 23.8, it will be detectable by the Hubble Space Telescope by 3 years after peak. This would permit a more precise estimate of the lens mass and distance and, so, the mass and projected separation of the planet. Analogs of OGLE-2005-BLG-169Lb orbiting nearby stars would be difficult to detect by other methods of planet detection, including radial velocities, transits, and astrometry.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/a5c45f07e84df14c2a5a4dbd05bf00be216be6c7

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In Astronomy and Astrophysics

1. Nuno C. Santos
2. S. Udry
3. M. Mayor
4. Sara Seager
5. J. Southworth
6. F. Bouchy
7. C. Lovis
8. F. Pepe

In Instrumentation

1. Nuno C. Santos
2. S. Udry
3. J. Southworth
4. Sara Seager
5. M. Mayor
6. F. Pepe
7. C. Lovis
8. F. Bouchy

Citations in the corpus

• Mass-Radius Relationships for Solid Exoplanets (2007, background): “In one planetary system, the Neptune-mass planet is the most massive planet in the system (Gould et al. 2006).”
• The HARPS search for southern extra-solar planets - XXXI. The M-dwarf sample (2011, background): “The microlensing technique probes a mass-separation domain complementary to the RV and transit techniques and has shown evidences that, at large separations, low-mass planets outnumber giant planets (Gould et al. 2006).”
• A Low-Mass Planet with a Possible Sub-Stellar-Mass Host in Microlensing Event MOA-2007-BLG-192 (2008, background): “Our discovery adds strength to the claim that low-mass planets are substantially more common at these separations around stars of less than a Solar mass (Gould et al. 2006).”
• A COLD NEPTUNE-MASS PLANET OGLE-2007-BLG-368Lb: Cold neptunes are common (2009, methodology): “So far 8 planetary systems with 9 planets have been found by this technique (Udalski et al. 2005; Beaulieu et al. 2006; Gould et al. 2006; Gaudi et al. 2008; Bennett et al. 2008; Dong et al. 2009b; Janczak et al. 2010), which have very distinct properties from those detected by other techniques.”