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تسجيل مستخدم جديدThe First Neptune Analog or Super-Earth with Neptune-like Orbit: MOA-2013-BLG-605Lb
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We present the discovery of the first Neptune analog exoplanet or super-Earth with Neptune-like orbit, MOA-2013-BLG-605Lb. This planet has a mass similar to that of Neptune or a super-Earth and it orbits at $9sim 14$ times the expected position of the snow-line, $a_{rm snow}$, which is similar to Neptunes separation of $ 11,a_{rm snow}$ from the Sun. The planet/host-star mass ratio is $q=(3.6pm0.7)times 10^{-4}$ and the projected separation normalized by the Einstein radius is $s=2.39pm0.05$. There are three degenerate physical solutions and two of these are due to a new type of degeneracy in the microlensing parallax parameters, which we designate the wide degeneracy. The three models have (i) a Neptune-mass planet with a mass of $M_{rm p}=21_{-7}^{+6} M_{Earth}$ orbiting a low-mass M-dwarf with a mass of $M_{rm h}=0.19_{-0.06}^{+0.05} M_odot$, (ii) a mini-Neptune with $M_{rm p}= 7.9_{-1.2}^{+1.8} M_{Earth}$ orbiting a brown dwarf host with $M_{rm h}=0.068_{-0.011}^{+0.019} M_odot$ and (iii) a super-Earth with $M_{rm p}= 3.2_{-0.3}^{+0.5} M_{Earth}$ orbiting a low-mass brown dwarf host with $M_{rm h}=0.025_{-0.004}^{+0.005} M_odot$ which is slightly favored. The 3-D planet-host separations are 4.6$_{-1.2}^{+4.7}$ AU, 2.1$_{-0.2}^{+1.0}$ AU and 0.94$_{-0.02}^{+0.67}$ AU, which are $8.9_{-1.4}^{+10.5}$, $12_{-1}^{+7}$ or $14_{-1}^{+11}$ times larger than $a_{rm snow}$ for these models, respectively. The Keck AO observation confirm that the lens is faint. This discovery suggests that low-mass planets with Neptune-like orbit are common. So processes similar to the one that formed Neptune in our own Solar System or cold super-Earth may be common in other solar systems.
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