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.
Over the past 3 years, Auckland University of Technology has established the first radio astronomical observatory in New Zealand, which, because of its remote geographic location, has quickly become ...a member of a number of international VLBI networks, in particular the IVS and the LBA. Not only has this added significantly to the observational power in the Pacific and Oceania, but by utilising new fibre connections within New Zealand, and across the Pacific and the Tasman Sea, the New Zealand radio telescopes have now been linked to many in Australia, Asia and the Pacific. Recent astronomical results are presented and plans for widening New Zealand participation in Australasian, Asia-Pacific and global VLBI research and development are outlined. Real-time e-VLBI is a vital part of New Zealand's capability development towards the SKA. The rapid and challenging establishment of New Zealand radio astronomy can serve as a model for the engagement in mega-Science and e-Science by resource-limited institutions and nations. Perspectives for collaboration between New Zealand and Thailand in the field of radio astronomy are included.
This report summarizes the geodetic VLBI activities in New Zealand in 2010. It provides geographical and technical details of WARK12M - the new IVS network station operated by the Institute for Radio ...Astronomy and Space Research (IRASR) of Auckland University of Technology (AUT). The details of the VLBI system installed in the station are outlined along with those of the collocated GNSS station. We report on the status of broadband connectivity and on the results of testing data transfer protocols; we investigate UDP protocols such as 'tsunami' and UDT and demonstrate that the UDT protocol is more efficient than 'tsunami' and 'ftp'. In general, the WARK12M IVS network station is fully equipped, connected and tested to start participating in regular IVS observational sessions from the beginning of 2011.
Using data from the Complete Nearby (\(z_{host}<0.02\)) sample of Type Ia Supernovae (CNIa0.02), we discover a linear relation between two parameters derived from the \(B-V\) color curves of Type Ia ...supernovae: the "color stretch" \(s_{BV}\) and the rising color slope \(s_0^*(B-V)\) after the peak, and this relation applies to the full range of \(s_{BV}\). The \(s_{BV}\) parameter is known to be tightly correlated with the peak luminosity, and especially for "fast decliners" (dim Type Ia supernovae), and the luminosity correlation with \(s_{BV}\) is markedly better than with the classic light-curve width parameters such as \(\Delta{m_{15}(B)}\). Thus our new linear relation can be used to infer peak luminosity from \(s_0^*\). Unlike \(s_{BV}\) (or \(\Delta{m_{15}}\)), the measurement of \(s_0^*(B-V)\) does not rely on the well-determined time of light-curve peak or color maximum, making it less demanding on the light-curve coverage than past approaches.
It has recently been discovered that some, if not all, classical novae emit GeV gamma rays during outburst, but the mechanisms involved in the production of the gamma rays are still not well ...understood. We present here a comprehensive multi-wavelength dataset---from radio to X-rays---for the most gamma-ray luminous classical nova to-date, V1324 Sco. Using this dataset, we show that V1324 Sco is a canonical dusty Fe-II type nova, with a maximum ejecta velocity of 2600 km s\(^{-1}\) and an ejecta mass of few \(\times 10^{-5}\) M\(_{\odot}\). There is also evidence for complex shock interactions, including a double-peaked radio light curve which shows high brightness temperatures at early times. To explore why V1324~Sco was so gamma-ray luminous, we present a model of the nova ejecta featuring strong internal shocks, and find that higher gamma-ray luminosities result from higher ejecta velocities and/or mass-loss rates. Comparison of V1324~Sco with other gamma-ray detected novae does not show clear signatures of either, and we conclude that a larger sample of similarly well-observed novae is needed to understand the origin and variation of gamma rays in novae.
Simultaneous broadband spectral and temporal studies of blazars are an important tool for investigating active galactic nuclei (AGN) jet physics. We study the spectral evolution between quiescent and ...flaring periods of 22 radio-loud AGN through multi-epoch, quasi-simultaneous broadband spectra. For many of these sources these are the first broadband studies. We use a Bayesian block analysis of \Fermi/LAT light curves in order to determine time ranges of constant flux for constructing quasi-simultaneous SEDs. The shapes of the resulting 81 SEDs are described by two logarithmic parabolas and a blackbody spectrum where needed. For low states the peak frequencies and luminosities agree well with the blazar sequence, higher luminosity implying lower peak frequencies. This is not true for sources in a high state. The \(\gamma\)-ray photon index in Fermi/LAT correlates with the synchrotron peak frequency in low and intermediate states. No correlation is present in high states. The black hole mass cannot be determined from the SEDs. Surprisingly, the thermal excess often found in FSRQs at optical/UV wavelengths can be described by blackbody emission and not an accretion disk spectrum. The "harder-when-brighter" trend, typically seen in X-ray spectra of flaring blazars, is visible in the blazar sequence. Our results for low and intermediate states, as well as the Compton dominance, are in agreement with previous results. Black hole mass estimates using the parameters from Bonchi (2013) are in agreement with some of the more direct measurements. For two sources, estimates disagree by more than four orders of magnitude, possibly due to boosting effects. The shapes of the thermal excess seen predominantly in flat spectrum radio quasars are inconsistent with a direct accretion disk origin.
The kinematics of isolated brown dwarfs in the Galaxy, beyond the solar neighborhood, is virtually unknown. Microlensing has the potential to probe this hidden population, as it can measure both the ...mass and five of the six phase-space coordinates (all except the radial velocity) even of a dark isolated lens. However, the measurements of both the microlens parallax and finite-source effects are needed in order to recover the full information. Here, we combine \(Spitzer\) satellite parallax measurement with the ground-based light curve, which exhibits strong finite-source effects, of event OGLE-2017-BLG-0896. We find two degenerate solutions for the lens (due to the known satellite-parallax degeneracy), which are consistent with each other except for their proper motion. The lens is an isolated brown dwarf with a mass of either \(18\pm1M_J\) or \(20\pm1M_J\). This is the lowest isolated-object mass measurement to date, only \(\sim\)45\% more massive than the theoretical deuterium-fusion boundary at solar metallicity, which is the common definition of a free-floating planet. The brown dwarf is located at either \(3.9\pm0.1\) kpc or \(4.1\pm0.1\) kpc toward the Galactic bulge, but with proper motion in the opposite direction of disk stars, with one solution suggesting it is moving within the Galactic plane. While it is possibly a halo brown dwarf, it might also represent a different, unknown population.
We report the results of a successful 7 hour 1.4 GHz VLBI experiment using two new stations, ASKAP-29 located in Western Australia and WARK12M located on the North Island of New Zealand. This was the ...first geodetic VLBI observing session with the participation of these new stations. We have determined the positions of ASKAP-29 and WARK12M. Random errors on position estimates are 150-200 mm for the vertical component and 40-50 mm for the horizontal component. Systematic errors caused by the unmodeled ionosphere path delay may reach 1.3 m for the vertical component.
It has recently been discovered that some, if not all, classical novae emit GeV gamma-rays during outburst, but the mechanisms involved in the production ofgamma-rays are still not well understood. ...We present here a comprehensive multiwavelength data set-from radio to X-rays-for the most gamma-ray-luminous classical nova to date, V1324 Sco. Using this data set, we show that V1324 Sco is a canonical dusty Fe II-type nova, with a maximum ejecta velocity of 2600 km s(-1) and an ejecta mass of a few x 10(-5) M-circle dot. There is also evidence for complex shock interactions, including a double-peaked radio light curve which shows high brightness temperatures at early times. To explore why V1324. Sco was so gamma-ray luminous, we present a model of the nova ejecta featuring strong internal shocks and find that higher gamma-ray luminosities result from higher ejecta velocities and/or mass-loss rates. Comparison of V1324. Sco with other gamma-ray-detected novae does not show clear signatures of either, and we conclude that a larger sample of similarly well-observed novae is needed to understand the origin and variation of gamma-rays in novae.
