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OGLE-2017-BLG-1434Lb: Eighth q<1×10-4 Mass-Ratio Microlens Planet Confirms Turnover in Planet Mass-Ratio Function

Udalski A., Ryu Y.-H., Sajadian S., Gould A., Mróz P., Poleski R., Szymański M. K., Skowron J., Soszyński I., Kozłowski S., Pietrukowicz P., Ulaczyk K., Pawlak M., Rybicki K., Iwanek P., Albrow M. D., Chung S. -J., Han C., Hwang K.-H., Jung Y. K., Shin I.-G., Shvartzvald Y., Yee J. C., Zang W., Zhu W., Cha S.-M., Kim D.-J., Kim H.-W., Kim S.-L., Lee C.-U., Lee D.-J, Lee Y., Park B.-G., Pogge R. W., Bozza W., Dominik M., Helling C., Hundertmark M., Jørgensen U. G., Longa-Peña P., Lowry S., Burgdorf M., Campbell-White J., Ciceri S., Evans D., Jaimes R. F., Fujii Y. I., Haikala L. K., Henning T., Hinse T. C., Mancini L., Peixinho N., Rahvar S., Rabus M., Skottfelt J., Snodgrass C., Southworth J., von Essen C.

Acta Astronomica

2018

Vol. 68, No. 1

1--42

We report the discovery of a cold Super-Earth planet (mp=4.4±0.5 M⊕) orbiting a low-mass (M=0.23±0.03 M⊙) M dwarf at projected separation a⊥=1.18±0.10 a.u., i.e., about 1.9 times the distance the snow line. The system is quite nearby for a microlensing planet, DL=0.86±0.09 kpc. Indeed, it was the large lens-source relative parallax πrel=1.0 mas (combined with the low mass M) that gave rise to the large, and thus well-measured, "microlens parallax" πE∝(πrel/M)1/2 that enabled these precise measurements. OGLE-2017-BLG-1434Lb is the eighth microlensing planet with planet-host mass ratio q<1×10-4. We apply a new planet-detection sensitivity method, which is a variant of "V/Vmax", to seven of these eight planets to derive the mass-ratio function in this regime. We find dN/d lnq ∝ qp, with p=1.05+0.78 -0.68, which confirms the "turnover" in the mass function found by Suzuki et al. relative to the power law of opposite sign n=-0.93±0.13 at higher mass ratios q≳2×10-4. We combine our result with that of Suzuki et al. to obtain p=0.73+0.42 -0.34.

OGLE-2017-BLG-0373Lb: A Jovian Mass-Ratio Planet Exposes A New Accidental Microlensing Degeneracy

Skowron J., Ryu Y.-H., Hwang K.-H., Udalski A., Mróz P., Kozłowski S., Soszyński I., Pietrukowicz P., Szymański M. K., Poleski R., Ulaczyk K., Pawlak M., Rybicki K., Iwanek P., Albrow M. D., Chung S.-J., Gould A., Han C., Jung Y. K., Shin I.-G., Shvartzvald Y., Yee J. C., Zang W., Zhu W., Cha S.-M., Kim D.-J., Kim H.-W., Kim S.-L., Lee C.-U., Lee D.-J, Lee Y., Park B.-G., Pogge R. W.

Acta Astronomica

2018

Vol. 68, No. 1

43--61

We report the discovery of microlensing planet OGLE-2017-BLG-0373Lb. We show that while the planet-host system has an unambiguous microlens topology, there are two geometries within this topology that fit the data equally well, which leads to a factor 2.5 difference in planet-host mass ratio, i.e., q=1.5×10-3 vs. q=0.6×10-3. We show that this is an "accidental degeneracy" in the sense that it is due to a gap in the data. We dub it "the caustic-chirality degeneracy". We trace the mathematical origins of this degeneracy, which should enable similar degenerate solutions to be easily located in the future. A Bayesian estimate, based on a Galactic model, yields a host mass M=0.25+0.30 -0.15 M⊙ at a distance DL=5.9+1.3 -1.95 kpc. The lens-source relative proper motion is relatively fast, μ=9 mas/yr, which implies that the host mass and distance can be determined by high-resolution imaging after about 10 years. The same observations could in principle resolve the discrete degeneracy in q, but this will be more challenging.

Characterization of Cu and Ni Nano-Fluids Synthesized by Pulsed Wire Evaporation Method

Kim H.-S., Yilmaz F., Dharmaiah P., Lee D.-J, Lee T.-H., Hong S.-J.

Archives of Metallurgy and Materials

2017

Vol. 62, iss. 2B

999--1004

In the present work, Cu and Ni nanofluids were synthesized using the pulsed wire evaporation (PWE) method in the different aqueous medias, namely (ethanol and ethylene glycol), and the effects of the aqueous media on the dispersion state, stability, and particle size of nanoparticles were studied. The size and morphology of synthesized nano-particles were investigated by transmission electron microscopy (TEM). Also, the dispersion stability of the nanofluids was evaluated by turbiscan analysis. The TEM results showed that the nano-particles were spherical in shape, and the average particle size was below 100 nm. The average particle size of the Cu nano-particles was smaller than that of Ni, which was attributed to a difference in the specific sublimation energy of the elements. Moreover, ethylene glycol (EG) exhibited higher suspension stability than ethanol. Finally, the dispersion stability of Cu@EG displayed the highest value due to lower particle size and greater viscosity.