Aims.
We aim to measure the Sloan
r
′, Sloan
i
′,
J
, and
Ks
magnitudes of Starlink’s STARLINK-1130 (Darksat) and STARLINK-1113 low Earth orbit (LEO) communication satellites and determine the ...effectiveness of the Darksat darkening treatment from the optical to the near-infrared (NIR).
Methods.
Four observations of Starlink’s LEO communication satellites, Darksat and STARLINK-1113, were conducted on two nights with two telescopes. The Chakana 0.6 m telescope at the Ckoirama observatory (Chile) observed both satellites on 5 Mar. 2020 (UTC) and 7 Mar. 2020 (UTC) using a Sloan
r
′ and Sloan
i
′ filter, respectively. The ESO VISTA 4.1 m telescope with the VIRCAM instrument observed both satellites on 5 Mar. 2020 (UTC) and 7 Mar. 2020 (UTC) in the NIR
J
-band and
Ks
-band, respectively.
Results.
The calibration, image processing, and analysis of the Darksat images give
r
≈ 5.6 mag,
i
≈ 5.0 mag,
J
≈ 4.2 mag, and
Ks
≈ 4.0 mag when scaled to a range of 550 km (airmass = 1) and corrected for the solar incidence and observer phase angles. In comparison, the STARLINK-1113 images give
r
≈ 4.9 mag,
i
≈ 4.4 mag,
J
≈ 3.8 mag, and
Ks
≈ 3.6 mag when corrected for range, solar incidence, and observer phase angles. The data and results presented in this work show that the special darkening coating used by Starlink for Darksat has darkened the Sloan
r
′ magnitude by 50%, Sloan
i
′ magnitude by 42%, NIR
J
magnitude by 32%, and NIR
Ks
magnitude by 28%.
Conclusions.
The results show that both satellites increase in reflective brightness with increasing wavelength and that the effectiveness of the darkening treatment is reduced at longer wavelengths. This shows that the mitigation strategies being developed by Starlink and other LEO satellite operators need to take into account other wavelengths, not just the optical. This work highlights the continued importance of obtaining multi-wavelength observations of many different LEO satellites in order to characterise their reflective properties and to aid the community in developing impact simulations and developing mitigation tools.
ABSTRACT Two cold gas giant planets orbiting a G-type main-sequence star in the galactic disk were previously discovered in the high-magnification microlensing event OGLE-2012-BLG-0026. Here, we ...present revised host star flux measurements and a refined model for the two-planet system using additional light curve data. We performed high angular resolution adaptive optics imaging with the Keck and Subaru telescopes at two epochs while the source star was still amplified. We detected the lens flux, H = 16.39 0.08. The lens, a disk star, is brighter than predicted from the modeling in the original study. We revisited the light curve modeling using additional photometric data from the B&C telescope in New Zealand and CTIO 1.3 m H-band light curve. We then include the Keck and Subaru adaptive optic observation constraints. The system is composed of a ∼4-9 Gyr lens star of Mlens = 1.06 0.05 M at a distance of Dlens = 4.0 0.3 kpc, orbited by two giant planets of 0.145 0.008 MJup and 0.86 0.06 MJup, with projected separations of 4.0 0.5 au and 4.8 0.7 au, respectively. Because the lens is brighter than the source star by 16 8% in H, with no other blend within one arcsec, it will be possible to estimate its metallicity using subsequent IR spectroscopy with 8-10 m class telescopes. By adding a constraint on the metallicity it will be possible to refine the age of the system.
Context. Microlensing is a unique method to probe low mass exoplanets beyond the snow line. However, the scientific potential of the new microlensing planet discovery is often unfulfilled due to lack ...of knowledge of the properties of the lens and source stars. The discovery light curve of the super Earth MOA-2007-BLG-192Lb suffers from significant degeneracies that limit what can be inferred about its physical properties. Aims. High resolution adaptive optics images allow us to solve this problem by resolving the microlensing target from all unrelated background stars, yielding the unique determination of magnified source and lens fluxes. This estimation permits the solution of our microlens model for the mass of the planet and its host and their physical projected separation. Methods. We observed the microlensing event MOA-2007-BLG-192 at high angular resolution in JHKs with the NACO adaptive optics system on the VLT while the object was still amplified by a factor 1.23 and then at baseline 18 months later. We analyzed and calibrated the NACO photometry in the standard 2MASS system in order to accurately constrain the source and the lens star fluxes. Results. We detect light from the host star of MOA-2007-BLG-192Lb, which significantly reduces the uncertainties in its characteristics as compared to earlier analyses. We find that MOA-2007-BLG-192L is most likely a very low mass late type M-dwarf (0.084-0.012+0.015 M⊙) at a distance of 660-70+100 pc orbited by a 3.2-1.8+5.2 M⊕ super-Earth at 0.66-0.22+0.51 AU. We then discuss the properties of this cold planetary system.
The numerical kernel approach to difference imaging has been implemented and applied to gravitational microlensing events observed by the PLANET collaboration. The effect of an error in the ...source-star coordinates is explored and a new algorithm is presented for determining the precise coordinates of the microlens in blended events, essential for accurate photometry of difference images. It is shown how the photometric reference flux need not be measured directly from the reference image but can be obtained from measurements of the difference images combined with the knowledge of the statistical flux uncertainties. The improved performance of the new algorithm, relative to isis2, is demonstrated.
Aims. We report the discovery of a planet with a high planet-to-star mass ratio in the microlensing event MOA-2009-BLG-387, which exhibited pronounced deviations over a 12-day interval, one of the ...longest for any planetary event. The host is an M dwarf, with a mass in the range 0.07 M⊙ < Mhost < 0.49 M⊙ at 90% confidence. The planet-star mass ratio q = 0.0132 ± 0.003 has been measured extremely well, so at the best-estimated host mass, the planet mass is mp = 2.6 Jupiter masses for the median host mass, M = 0.19 M⊙. Methods. The host mass is determined from two “higher order” microlensing parameters. One of these, the angular Einstein radius θE = 0.31 ± 0.03 mas has been accurately measured, but the other (the microlens parallax πE, which is due to the Earth’s orbital motion) is highly degenerate with the orbital motion of the planet. We statistically resolve the degeneracy between Earth and planet orbital effects by imposing priors from a Galactic model that specifies the positions and velocities of lenses and sources and a Kepler model of orbits. Results. The 90% confidence intervals for the distance, semi-major axis, and period of the planet are 3.5 kpc < DL < 7.9 kpc, 1.1 AU < a < 2.7 AU, and 3.8 yr < P < 7.6 yr, respectively.
ABSTRACT We report the discovery of a microlensing planet OGLE-2012-BLG-0950Lb with a planet/host mass ratio of . A long term distortion detected in both MOA and OGLE light curve can be explained by ...the microlens parallax due to the Earth's orbital motion around the Sun. Although the finite source effect is not detected, we obtain the lens flux by the high resolution Keck AO observation. Combining the microlens parallax and the lens flux reveal the nature of the lens: a planet with mass of is orbiting around an M-dwarf with mass of with a planet-host projected separation of au located at kpc from us. This is the first mass measurement from only microlens parallax and the lens flux without the finite source effect. In the coming space observation-era with Spitzer, K2, Euclid, and WFIRST, we expect many such events for which we will not be able to measure any finite source effect. This work demonstrates an ability of mass measurements in such events.
General movement patterns for North Atlantic right whales are known, but quantitative season-specific estimates of individual movements and the resultant distributions do not exist. We use a Brownian ...Bridge movement model to estimate individual movement patterns and spatial probability distributions using time- and location-specific photo-identified right whales from 1978 through 2007 to produce monthly estimates of movement and distribution patterns for the population in the NW Atlantic, from Cape Cod northward. For comparative purposes we also estimate right whale transition probabilities among ocean regions to estimate rates of emigration and immigration, likely destinations, and monthly regionally specific population estimates. Areas were identified that right whales may frequent and that are potential locations of the regularly unaccounted proportion of the population. These areas, requiring additional survey effort, include the Gulf of St. Lawrence, Scotian Shelf, Columbia Ledges and western Jordan Basin. Our results show that along the northeast Atlantic coasts of Canada and the USA, right whales annually migrate in a general counter-clockwise pattern; north and east along the continental shelf in the spring and summer, and south and west along the coast during autumn and winter. The results also provide quantitative spatio-temporal estimates of right whales for all regions, including those that are rarely or never surveyed. The spatial probability distributions that we provide can be used in the future to quantitatively evaluate risks to right whales from human activities, particularly vessel traffic and commercial fishing, and thereby increase our ability to manage the risks and improve right whale conservation.
We analyze the photometric data obtained by PLANET and OGLE on the caustic-crossing binary-lens microlensing event OGLE-2002-BLG-069. Thanks to the excellent photometric and spectroscopic coverage of ...the event, we are able to constrain the lens model up to the known ambiguity between close and wide binary lenses. The detection of annual parallax in combination with measurements of extended-source effects allows us to determine the mass, distance and velocity of the lens components for the competing models. While the model involving a close binary lens leads to a Bulge-Disc lens scenario with a lens mass of $M=(0.51 \pm 0.15) ~M_\odot$ and distance of $D_{\rm{L}}=(2.9\pm 0.4) ~{\rm{kpc}}$, the wide binary lens solution requires a rather implausible binary black-hole lens ($M \gtrsim 126 ~M_\odot$). Furthermore we compare current state-of-the-art numerical and empirical models for the surface brightness profile of the source, a G5III Bulge giant. We find that a linear limb-darkening model for the atmosphere of the source star is consistent with the data whereas a PHOENIX atmosphere model assuming LTE and with no free parameter does not match our observations.
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