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Register a new userTwo Jupiter-Mass Planets Discovered by the KMTNet Survey in 2017
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We report two microlensing events, KMT-2017-BLG-1038 and KMT-2017-BLG-1146 that are caused by planetary systems. These events were discovered by KMTNet survey observations from the $2017$ bulge season. The discovered systems consist of a planet and host star with mass ratios, $5.3_{-0.4}^{+0.2} times 10^{-3}$ and $2.0_{-0.1}^{+0.6} times 10^{-3}$, respectively. Based on a Bayesian analysis assuming a Galactic model without stellar remnant hosts, we find that the planet, KMT-2017-BLG-1038Lb, is a super Jupiter-mass planet ($M_{rm p}= 2.04_{-1.15}^{+2.02},M_{rm J}$) orbiting a mid-M dwarf host ($M_{rm h}= 0.37_{-0.20}^{+0.36}, M_{odot}$) that is located at $6.01_{-1.72}^{+1.27}$ kpc toward the Galactic bulge. The other planet, KMT-2017-BLG-1146Lb, is a sub Jupiter-mass planet ($M_{rm p}= 0.71_{-0.42}^{+0.80},M_{rm J}$) orbiting a mid-M dwarf host ($M_{rm h}= 0.33_{-0.20}^{+0.36},M_{odot}$) at a distance toward the Galactic bulge of $6.50_{-2.00}^{+1.38}$ kpc. Both are potentially gaseous planets that are beyond their hosts snow lines. These typical microlensing planets will be routinely discovered by second-generation microlensing surveys, rapidly increasing the number of detections.
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We report two microlensing planet candidates discovered by the KMTNet survey in $2017$. However, both events have the 2L1S/1L2S degeneracy, which is an obstacle to claiming the discovery of the planets with certainty unless the degeneracy can be resolved. For KMT-2017-BLG-0962, the degeneracy cannot be resolved. If the 2L1S solution is correct, KMT-2017-BLG-0962 might be produced by a super Jupiter-mass planet orbiting a mid-M dwarf host star. For KMT-2017-BLG-1119, the light curve modeling favors the 2L1S solution but higher-resolution observations of the baseline object tend to support the 1L2S interpretation rather than the planetary interpretation. This degeneracy might be resolved by a future measurement of the lens-source relative proper motion. This study shows the problem of resolving 2L1S/1L2S degeneracy exists over a much wider range of conditions than those considered by the theoretical study of Gaudi (1998).
Type-II migration of giant planets has a speed proportional to the discs viscosity for values of the alpha viscosity parameter larger than 1.e-4 . At lower viscosities previous studies, based on 2D simulations have shown that migration can be very chaotic and often characterized by phases of fast migration. The reason is that in low-viscosity discs vortices appear due to the Rossby-wave instability at the edges of the gap opened by the planet. Migration is then determined by vortex-planet interactions. Our aim is to study migration in low viscosity 3D discs. We performed numerical simulations using 2D (including self-gravity) and 3D codes. After selecting disc masses for which self-gravity is not important, 3D simulations without self-gravity can be safely used. In our nominal simulation only numerical viscosity is present. We then performed simulations with prescribed viscosity to assess the threshold below which the new migration processes appear. We show that for alpha viscosity <= 1.e-5 two migration modes are possible which differ from classical Type-II migration, in the sense that they are not proportional to the discs viscosity. The first occurs when the gap opened by the planet is not very deep. This occurs in 3D simulations and/or when a big vortex forms at the outer edge of the planetary gap, diffusing material into the gap. We call this type of migration vortex-driven migration. This migration is very slow and cannot continue indefinitely, because eventually the vortex dissolves. The second migration mode occurs when the gap is deep so that the planets eccentricity grows to a value ~0.2 due to inefficient eccentricity damping by corotation resonances. This second, faster migration mode appears to be typical of 2D models in discs with slower damping of temperatures perturbations.
We present the discovery of two transiting exoplanets. HAT-P-28b orbits a V=13.03 G3 dwarf star with a period P = 3.2572 d and has a mass of 0.63 +- 0.04 MJ and a radius of 1.21 + 0.11 -0.08 RJ yielding a mean density of 0.44 +- 0.09 g cm-3. HAT-P-29b orbits a V=11.90 F8 dwarf star with a period P = 5.7232 d and has a mass of 0.78 +0.08 -0.04 MJ and a radius of 1.11 +0.14 -0.08 RJ yielding a mean density of 0.71 +- 0.18 g cm-3. We discuss the properties of these planets in the context of other known transiting planets.
In the core-accretion model the nominal runaway gas-accretion phase brings most planets to multiple Jupiter masses. However, known giant planets are predominantly Jupiter-mass bodies. Obtaining longer timescales for gas accretion may require using realistic equations of states, or accounting for the dynamics of the circumplanetary disk (CPD) in low-viscosity regime, or both. Here we explore the second way using global, three-dimensional isothermal hydrodynamical simulations with 8 levels of nested grids around the planet. In our simulations the vertical inflow from the circumstellar disk (CSD) to the CPD determines the shape of the CPD and its accretion rate. Even without prescribed viscosity Jupiters mass-doubling time is $sim 10^4$ years, assuming the planet at 5.2 AU and a Minimum Mass Solar Nebula. However, we show that this high accretion rate is due to resolution-dependent numerical viscosity. Furthermore, we consider the scenario of a layered CSD, viscous only in its surface layer, and an inviscid CPD. We identify two planet-accretion mechanisms that are independent of the viscosity in the CPD: (i) the polar inflow -- defined as a part of the vertical inflow with a centrifugal radius smaller than 2 Jupiter-radii and (ii) the torque exerted by the star on the CPD. In the limit of zero effective viscosity, these two mechanisms would produce an accretion rate 40 times smaller than in the simulation.
In this paper, we present the results of timing observations of PSRs J1949+3106 and J1950+2414, two binary millisecond pulsars discovered in data from the Arecibo ALFA pulsar survey (PALFA). The timing parameters include precise measurements of the proper motions of both pulsars, which show that PSR J1949+3106 has a transversal motion very similar to that of an object in the local standard of rest. The timing also includes measurements of the Shapiro delay and the rate of advance of periastron for both systems. Assuming general relativity, these allow estimates of the masses of the components of the two systems; for PSR J1949+3106, the pulsar mass is $M_p , = , 1.34^{+0.17}_{-0.15} , M_{odot}$ and the companion mass $M_c , = , 0.81^{+0.06}_{-0.05}, M_{odot}$; for PSR J1950+2414 $M_p , = , 1.496 , pm , 0.023, M_{odot}$ and $M_c , = , 0.280^{+0.005}_{-0.004}, M_{odot}$ (all values 68.3 % confidence limits). We use these masses and proper motions to investigate the evolutionary history of both systems: PSR J1949+3106 is likely the product of a low-kick supernova; PSR J1950+2414 is a member of a new class of eccentric millisecond pulsar binaries with an unknown formation mechanism. We discuss the proposed hypotheses for the formations of these systems in light of our new mass measurements.
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