Follow-up observations of high-magnification gravitational microlensing events can fully exploit their intrinsic sensitivity to detect extrasolar planets, especially those with small mass ratios. To ...make followup more uniform and efficient, we develop a system, HighMagFinder, based on the real-time data from the Korean Microlensing Telescope Network (KMTNet) to automatically alert possible ongoing high-magnification events. We started a new phase of follow-up observations with the help of HighMagFinder in 2021. Here we report the discovery of two planets in high-magnification microlensing events, KMT-2021-BLG-0171 and KMT-2021-BLG-1689, which were identified by the HighMagFinder. We find that both events suffer the ``central-resonant'' caustic degeneracy. The planet-host mass-ratio is \(q\sim4.7\times10^{-5}\) or \(q\sim 2.2\times10^{-5}\) for KMT-2021-BLG-0171, and \(q\sim2.5\times10^{-4}\) or \(q\sim 1.8\times10^{-4}\) for KMT-2021-BLG-1689. Together with two events reported by Ryu et al. (2022), four cases that suffer such degeneracy have been discovered in the 2021 season alone, indicating that the degenerate solutions may have been missed in some previous studies. We also propose a new factor for weighting the probability of each solution from the phase-space. The resonant interpretations for the two events are disfavored under this consideration. This factor can be included in future statistical studies to weight degenerate solutions.
PKS B1322-110 is a radio quasar that is located only 8.5' in angular separation from the bright B star Spica. It exhibits intra-day variability in its flux density at GHz frequencies attributed to ...scintillations from plasma inhomogeneities. We have tracked the rate of scintillation of this source for over a year with the Australia Telescope Compact Array, recording a strong annual cycle that includes a near-standstill in August and another in December. The cycle is consistent with scattering by highly anisotropic plasma microstructure, and we fit our data to that model in order to determine the kinematic parameters of the plasma. Because of the low ecliptic latitude of PKS B1322-110, the orientation of the plasma microstructure is poorly constrained. Nonetheless at each possible orientation our data single out a narrow range of the corresponding velocity component, leading to a one-dimensional constraint in a two-dimensional parameter space. The constrained region is consistent with a published model in which the scattering material is associated with Spica and consists of filaments that are radially oriented around the star. This result has a 1% probability of arising by chance.
With the establishment of the AUT University 12m radio telescope at Warkworth, New Zealand has now become a part of the international Very Long Baseline Interferometry (VLBI) community. A major ...product of VLBI observations are images in the radio domain of astronomical objects such as Active Galactic Nuclei (AGN). Using large geographical separations between radio antennas, very high angular resolution can be achieved. Detailed images can be created using the technique of VLBI Earth Rotation Aperture Synthesis. We review the current process of VLBI radio imaging. In addition we model VLBI configurations using the Warkworth telescope, AuScope (a new array of three 12m antennas in Australia) and the Australian Square Kilometre Array Pathfinder (ASKAP) array currently under construction in Western Australia, and discuss how the configuration of these arrays affects the quality of images. Recent imaging results that demonstrate the modeled improvements from inclusion of the AUT and first ASKAP telescope in the Australian Long Baseline Array (LBA) are presented.
We report the analysis of OGLE-2019-BLG-0960, which contains the smallest mass-ratio microlensing planet found to date (q = 1.2--1.6 x 10^{-5} at 1-sigma). Although there is substantial uncertainty ...in the satellite parallax measured by Spitzer, the measurement of the annual parallax effect combined with the finite source effect allows us to determine the mass of the host star (M_L = 0.3--0.6 M_Sun), the mass of its planet (m_p = 1.4--3.1 M_Earth), the projected separation between the host and planet (a_perp = 1.2--2.3 au), and the distance to the lens system (D_L = 0.6--1.2 kpc). The lens is plausibly the blend, which could be checked with adaptive optics observations. As the smallest planet clearly below the break in the mass-ratio function (Suzuki et al. 2016; Jung et al. 2019), it demonstrates that current experiments are powerful enough to robustly measure the slope of the mass-ratio function below that break. We find that the cross-section for detecting small planets is maximized for planets with separations just outside of the boundary for resonant caustics and that sensitivity to such planets can be maximized by intensively monitoring events whenever they are magnified by a factor A > 5. Finally, an empirical investigation demonstrates that most planets showing a degeneracy between (s > 1) and (s < 1) solutions are not in the regime (|log s| >> 0) for which the "close"/"wide" degeneracy was derived. This investigation suggests a link between the "close"/"wide" and "inner/outer" degeneracies and also that the symmetry in the lens equation goes much deeper than symmetries uncovered for the limiting cases.
We report the results of a successful 24 hour 6.7 GHz VLBI experiment using the 30 meter radio telescope WARK30M near Warkworth, New Zealand, recently converted from a radio telecommunications ...antenna, and two radio telescopes located in Australia: Hobart 26-m and Ceduna 30-m. The geocentric position of WARK30M is determined with a 100 mm uncertainty for the vertical component and 10 mm for the horizontal components. We report correlated flux densities at 6.7 GHz of 175 radio sources associated with Fermi gamma-ray sources. A parsec scale emission from the radio source 1031-837 is detected, and its association with the gamma-ray object 2FGL J1032.9-8401 is established with a high likelihood ratio. We conclude that the new Pacific area radio telescope WARK30M is ready to operate for scientific projects.
We describe our approach to the conversion of a former 100-foot (30-m) telecommunication antenna in New Zealand into a radio telescope. We provide the specifications of the Earth Station and identify ...the priorities for the conversion. We describe implementation of this plan with regards to mechanical and electrical components, as well as design of the telescope control system, telescope networking for VLBI, and telescope maintenance. Plans for RF, front-end and back-end developments based on radio astronomical priorities are outlined.
The Warkworth 12-m Radio Telescope is operated by the Institute for Radio Astronomy and Space Research (IRASR) at AUT University, Auckland, New Zealand. This report briefly reviews the ...characteristics of the 12-m VLBI station. We report on a number of activities and technical developments.
Kiwi Advanced Research and Education Network (KAREN) has been used to transfer large volumes of radio astronomical data between the AUT Radio Astronomical Observatory at Warkworth, New Zealand and ...the international organisations with which we are collaborating and conducting observations. Here we report on the current status of connectivity and on the results of testing different data transfer protocols. We investigate new UDP protocols such as "tsunami" and UDT and demonstrate that the UDT protocol is more efficient than "tsunami" and ftp. We report on our initial steps towards real-time eVLBI and the attempt to directly stream data from the radio telescope receiving system to the correlation centre without intermediate buffering/recording.
We report the discovery and analysis of the planetary microlensing event OGLE-2017-BLG-0406, which was observed both from the ground and by the \({\it Spitzer}\) satellite in a solar orbit. At high ...magnification, the anomaly in the light curve was densely observed by ground-based-survey and follow-up groups, and it was found to be explained by a planetary lens with a planet/host mass ratio of \(q=7.0 \times 10^{-4}\) from the light-curve modeling. The ground-only and \({\it Spitzer}\)-"only" data each provide very strong one-dimensional (1-D) constraints on the 2-D microlens parallax vector \(\bf{\pi_{\rm E}}\). When combined, these yield a precise measurement of \(\bf{\pi_{\rm E}}\), and so of the masses of the host \(M_{\rm host}=0.56\pm0.07\,M_\odot\) and planet \(M_{\rm planet} = 0.41 \pm 0.05\,M_{\rm Jup}\). The system lies at a distance \(D_{\rm L}=5.2 \pm 0.5 \ {\rm kpc}\) from the Sun toward the Galactic bulge, and the host is more likely to be a disk population star according to the kinematics of the lens. The projected separation of the planet from the host is \(a_{\perp} = 3.5 \pm 0.3 \ {\rm au}\), i.e., just over twice the snow line. The Galactic-disk kinematics are established in part from a precise measurement of the source proper motion based on OGLE-IV data. By contrast, the \({\it Gaia}\) proper-motion measurement of the source suffers from a catastrophic \(10\,\sigma\) error.
We report the mass and distance measurements of two single-lens events from the 2017 Spitzer microlensing campaign. The ground-based observations yield the detection of finite-source effects, and the ...microlens parallaxes are derived from the joint analysis of ground-based observations and Spitzer observations. We find that the lens of OGLE-2017-BLG-1254 is a \(0.60 \pm 0.03 M_{\odot}\) star with \(D_{\rm LS} = 0.53 \pm 0.11~\text{kpc}\), where \(D_{\rm LS}\) is the distance between the lens and the source. The second event, OGLE-2017-BLG-1161, is subject to the known satellite parallax degeneracy, and thus is either a \(0.51^{+0.12}_{-0.10} M_{\odot}\) star with \(D_{\rm LS} = 0.40 \pm 0.12~\text{kpc}\) or a \(0.38^{+0.13}_{-0.12} M_{\odot}\) star with \(D_{\rm LS} = 0.53 \pm 0.19~\text{kpc}\). Both of the lenses are therefore isolated stars in the Galactic bulge. By comparing the mass and distance distributions of the eight published Spitzer finite-source events with the expectations from a Galactic model, we find that the Spitzer sample is in agreement with the probability of finite-source effects occurrence in single lens events.
