Interferometric Visibility and Closure Phase of Microlensing Events with Finite Source Size

Interferometers from the ground and space will be able to resolve the two images in a microlensing event. This will at least partially lift the inherent degeneracy between physical parameters in microlensing events. To increase the signal-to-noise ratio, intrinsically bright events with large magnifications will be preferentially selected as targets. These events may be influenced by finite source size effects both photometrically and astrometrically. Using observed finite source size events as examples, we show that the fringe visibility can be affected by 5% - 10%, and the closure phase by a few degrees: readily detectable by ground and space interferometers. Such detections will offer unique information about the lens-source trajectory relative to the baseline of the interferometers. Combined with photometric finite source size effects, interferometry offers a way to measure the angular sizes of the source and the Einstein radius accurately. Limb-darkening changes the visibility by a small amount compared with a source with uniform surface brightness, marginally detectable with ground-based instruments. We discuss the implications of our results for the plans to make interferometric observations of future microlensing events.Comment: 18 pages, 9 figures, submitted to MNRA

A New Photometric Model of the Galactic Bar using Red Clump Giants

We present a study of the luminosity density distribution of the Galactic bar using number counts of red clump giants (RCGs) from the OGLE-III survey. The data were recently published by Nataf et al. (2013) for 9019 fields towards the bulge and have $2.94\times 10^6$ RC stars over a viewing area of $90.25 \,\textrm{deg}^2$. The data include the number counts, mean distance modulus ($\mu$), dispersion in $\mu$ and full error matrix, from which we fit the data with several tri-axial parametric models. We use the Markov Chain Monte Carlo (MCMC) method to explore the parameter space and find that the best-fit model is the $E_3$ model, with the distance to the GC is 8.13 kpc, the ratio of semi-major and semi-minor bar axis scale lengths in the Galactic plane $x_{0},y_{0}$, and vertical bar scale length $z_0$, is $x_0:y_0:z_0 \approx 1.00:0.43:0.40$ (close to being prolate). The scale length of the stellar density profile along the bar's major axis is $\sim$ 0.67 kpc and has an angle of $29.4^\circ$, slightly larger than the value obtained from a similar study based on OGLE-II data. The number of estimated RC stars within the field of view is $2.78 \times 10^6$, which is systematically lower than the observed value. We subtract the smooth parametric model from the observed counts and find that the residuals are consistent with the presence of an X-shaped structure in the Galactic centre, the excess to the estimated mass content is $\sim 5.8$. We estimate the total mass of the bar is $\sim 1.8 \times 10^{10} M_\odot$. Our results can be used as a key ingredient to construct new density models of the Milky Way and will have implications on the predictions of the optical depth to gravitational microlensing and the patterns of hydrodynamical gas flow in the Milky Way.Comment: 15 pages, 6 figures, 4 tables. MNRAS accepte

Faint-source-star planetary microlensing: the discovery of the cold gas-giant planet OGLE-2014-BLG-0676Lb

We report the discovery of a planet – OGLE-2014-BLG-0676Lb– via gravitational microlensing. Observations for the lensing event were made by the following groups: Microlensing Observations in Astrophysics; Optical Gravitational Lensing Experiment; Wise Observatory; RoboNET/Las Cumbres Observatory Global Telescope; Microlensing Network for the Detection of Small Terrestrial Exoplanets; and μ-FUN. All analyses of the light-curve data favour a lens system comprising a planetary mass orbiting a host star. The most-favoured binary lens model has a mass ratio between the two lens masses of (4.78 ± 0.13) × 10−3. Subject to some important assumptions, a Bayesian probability density analysis suggests the lens system comprises a 3.09^(+1.02)_(−1.12) MJ planet orbiting a 0.62^(+0.20)_(−0.22) M_⊙ host star at a deprojected orbital separation of 4.40^(+2.16)_(−1.46) au. The distance to the lens system is 2.22^(+0.96)_(−0.83) kpc. Planet OGLE-2014-BLG-0676Lb provides additional data to the growing number of cool planets discovered using gravitational microlensing against which planetary formation theories may be tested. Most of the light in the baseline of this event is expected to come from the lens and thus high-resolution imaging observations could confirm our planetary model interpretation

Planetary Microlensing at High Magnification

Simulations of planetary microlensing at high magnification that were carried out on a cluster computer are presented. It was found that the perturbations due to two-thirds of all planets occur in the time interval [-0.5t_FWHM, 0.5t_ FWHM] with respect to the peak of the microlensing light curve, where t_FWHM is typically about 14 hours. This implies that only this restricted portion of the light curve need be intensively monitored for planets, a very significant practical advantage. Nearly all planetary detections in high magnification events will not involve caustic crossings. We discuss the issues involved in determining the planetary parameters in high magnification microlensing events. Earth mass planets may be detected with 1-m class telescopes if their projected orbital radii lie within about 1.5 - 2.5 AU. Giant planets are detectable over a much larger region. For multi-planet systems the perturbations due to individual planets can be separated under certain conditions. The size of the source star needs to be determined independently, but the presence of spots on the source star is likely to be negligible, as is the effect of planetary motion during an event.Comment: 12 pages, 13 embedded figures, accepted for publication by MNRA

The Take-Over and Reform of the Maritime Customs Against Native Customs： A Case Study of Fengyang Native Customs

海关对常关的接管和改革研究，长期以来主要集中于对二十世纪初海关接管通商口岸五十里内常关的研究。其中既有对这一波接管和改革总体性的研究，也有对典型个案进行剖析的案例研究。但对于发生于1929-1930年的海关接管和改革五十里外常关的研究至今则鲜有研究成果问世。仅笔者所见就只有何小敏对扬由关的个案研究曾较为深入地涉及到这一问题，但她也没有对扬由关被接管后的制度变革作出详细地研究。至于这一时期凤阳常关被海关接管和改革的研究，则一直付诸阙如。 本文运用海关接管和改革凤阳常关留存下来的档案和其它资料，对财政部派遣海关人员接管凤阳关的原因与总税务司的态度、改革所处的环境及其影响、改革的总体计划和简要过程...The research about that Maritime Customs controlled and reformed Native Customs mainly focused on Maritime Customs took over Native Customs in the trade ports within fifty miles in the early twentieth century.There are both the overall research and the typical case studies. But it is few research results about that Maritime Customs controlled and reformed Native Customs outside fifty miles away in...学位：历史学硕士院系专业：人文学院历史学系_中国近现代史学号：1032009115187

ExELS: an exoplanet legacy science proposal for the ESA Euclid mission. II. Hot exoplanets and sub-stellar systems

The Exoplanet Euclid Legacy Survey (ExELS) proposes to determine the frequency of cold exoplanets down to Earth mass from host separations of ~1 AU out to the free-floating regime by detecting microlensing events in Galactic Bulge. We show that ExELS can also detect large numbers of hot, transiting exoplanets in the same population. The combined microlensing+transit survey would allow the first self-consistent estimate of the relative frequencies of hot and cold sub-stellar companions, reducing biases in comparing "near-field" radial velocity and transiting exoplanets with "far-field" microlensing exoplanets. The age of the Bulge and its spread in metallicity further allows ExELS to better constrain both the variation of companion frequency with metallicity and statistically explore the strength of star-planet tides. We conservatively estimate that ExELS will detect ~4100 sub-stellar objects, with sensitivity typically reaching down to Neptune-mass planets. Of these, ~600 will be detectable in both Euclid's VIS (optical) channel and NISP H-band imager, with ~90% of detections being hot Jupiters. Likely scenarios predict a range of 2900-7000 for VIS and 400-1600 for H-band. Twice as many can be expected in VIS if the cadence can be increased to match the 20-minute H-band cadence. The separation of planets from brown dwarfs via Doppler boosting or ellipsoidal variability will be possible in a handful of cases. Radial velocity confirmation should be possible in some cases, using 30-metre-class telescopes. We expect secondary eclipses, and reflection and emission from planets to be detectable in up to ~100 systems in both VIS and NISP-H. Transits of ~500 planetary-radius companions will be characterised with two-colour photometry and ~40 with four-colour photometry (VIS,YJH), and the albedo of (and emission from) a large sample of hot Jupiters in the H-band can be explored statistically.Comment: 18 pages, 16 figures, accepted MNRA

ExELS: an exoplanet legacy science proposal for the ESA Euclid mission. II. Hot exoplanets and sub-stellar systems

The Exoplanet Euclid Legacy Survey (ExELS) proposes to determine the frequency of cold exoplanets down to Earth mass from host separations of ~1 AU out to the free-floating regime by detecting microlensing events in Galactic Bulge. We show that ExELS can also detect large numbers of hot, transiting exoplanets in the same population. The combined microlensing+transit survey would allow the first self-consistent estimate of the relative frequencies of hot and cold sub-stellar companions, reducing biases in comparing "near-field" radial velocity and transiting exoplanets with "far-field" microlensing exoplanets. The age of the Bulge and its spread in metallicity further allows ExELS to better constrain both the variation of companion frequency with metallicity and statistically explore the strength of star-planet tides. We conservatively estimate that ExELS will detect ~4100 sub-stellar objects, with sensitivity typically reaching down to Neptune-mass planets. Of these, ~600 will be detectable in both Euclid's VIS (optical) channel and NISP H-band imager, with ~90% of detections being hot Jupiters. Likely scenarios predict a range of 2900-7000 for VIS and 400-1600 for H-band. Twice as many can be expected in VIS if the cadence can be increased to match the 20-minute H-band cadence. The separation of planets from brown dwarfs via Doppler boosting or ellipsoidal variability will be possible in a handful of cases. Radial velocity confirmation should be possible in some cases, using 30-metre-class telescopes. We expect secondary eclipses, and reflection and emission from planets to be detectable in up to ~100 systems in both VIS and NISP-H. Transits of ~500 planetary-radius companions will be characterised with two-colour photometry and ~40 with four-colour photometry (VIS,YJH), and the albedo of (and emission from) a large sample of hot Jupiters in the H-band can be explored statistically.Comment: 18 pages, 16 figures, accepted MNRA