ABSTRACT We present the discovery of the first Neptune analog exoplanet or super-Earth with a Neptune-like orbit, MOA-2013-BLG-605Lb. This planet has a mass similar to that of Neptune or a ...super-Earth and it orbits at 9 ∼ 14 times the expected position of the snow line, asnow, which is similar to Neptune's separation of 11 asnow from the Sun. The planet/host-star mass ratio is q = (3.6 0.7) × 10−4 and the projected separation normalized by the Einstein radius is s = 2.39 0.05. There are three degenerate physical solutions and two of these are due to a new type of degeneracy in the microlensing parallax parameters, which we designate "the wide degeneracy." The three models have (i) a Neptune-mass planet with a mass of orbiting a low-mass M-dwarf with a mass of , (ii) a mini-Neptune with orbiting a brown dwarf host with , and (iii) a super-Earth with orbiting a low-mass brown dwarf host with , which is slightly favored. The 3D planet-host separations are au, au, and au, which are , , or times larger than asnow for these models, respectively. Keck adaptive optics observations confirm that the lens is faint. This discovery suggests that low-mass planets with Neptune-like orbits are common. Therefore processes similar to the one that formed Neptune in our own solar system or cold super-Earths may be common in other solar systems.
ABSTRACT In this paper, we demonstrate the severity of the degeneracy between the microlens-parallax and lens-orbital effects by presenting the analysis of the gravitational binary-lens event ...OGLE-2015-BLG-0768. Despite the obvious deviation from the model based on the linear observer motion and the static binary, it is found that the residual can be almost equally well explained by either the parallactic motion of the Earth or the rotation of the binary-lens axis, resulting in the severe degeneracy between the two effects. We show that the degeneracy can be readily resolved with the additional data provided by space-based microlens parallax observations. By enabling us to distinguish between the two higher-order effects, space-based microlens parallax observations will not only make it possible to accurately determine the physical lens parameters but also to further constrain the orbital parameters of binary lenses.
Gaia Data Release 3 Wyrzykowski, Ł.; Kruszyńska, K.; Rybicki, K. A. ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
674
Journal Article
Recenzirano
Odprti dostop
Context.
One of the rarest types of variability is the phenomenon of gravitational microlensing, a transient brightening of a background star due to an intervening lensing object. Microlensing is a ...powerful tool for studying the invisible or otherwise undetectable populations in the Milky Way, including planets and black holes.
Aims.
We describe the first
Gaia
catalogue of candidate microlensing events, give an overview of its content, and discuss its validation.
Methods.
The catalogue of
Gaia
microlensing events was composed by analysing the light curves of around 2 billion sources of
Gaia
DR3 from all over the sky covering 34 months, between 2014 and 2017.
Results.
We present 363
Gaia
microlensing events and discuss their properties. Of these, 90 have never been reported before and have not been discovered by other surveys. The contamination of the catalogue is assessed to 0.6%–1.7%.
We present a study of the detectability of transient events associated with galaxies for the Gaia European Space Agency astrometric mission. We simulated the on-board detections, and on-ground ...processing for a mock galaxy catalogue to establish the properties required for the discovery of transient events by Gaia, specifically tidal disruption events (TDEs) and supernovae (SNe). Transients may either be discovered by the on-board detection of a new source or by the brightening of a previously known source. We show that Gaia transients can be identified as new detections on-board for offsets from the host galaxy nucleus of 0.1-0.5 arcsec, depending on magnitude and scanning angle. The Gaia detection system shows no significant loss of SNe at close radial distances to the nucleus. We used the detection efficiencies to predict the number of transients events discovered by Gaia. For a limiting magnitude of 19, we expect around 1300 SNe per year: 65 per cent SN Ia, 28 per cent SN II and 7 per cent SN Ibc, and ~20 TDEs per year.
We used Optical Gravitational Lensing Experiment (OGLE-IV) deep (stacked) images (V 23 mag, I 23 mag at 3 ) of the Magellanic System, encompassing an area of ∼670 deg2, to perform a search for high-z ...quasar candidates. We combined the optical OGLE data with the mid-IR Wide-field Infrared Survey Explorer 3.4/4.6/12 m data, and devised a multicolor selection procedure. We identified 33 promising candidates and then spectroscopically observed the two most variable sources. We report the discovery of two high-z quasars, OGLE J015531−752807 at a redshift z = 5.09 and OGLE J005907−645016 at a redshift of z = 4.98. The variability amplitude of both quasars at the rest-frame wavelength ∼1300 is much larger (∼0.4 mag) than other quasars (∼0.15 mag) at the same rest-frame wavelength but lower redshifts (2 < z < 5). A larger sample of such sources with at least decade-long light curves would be necessary to determine whether increased variability is typical in the population of high-z quasars, or whether we are finding extreme outliers. The Large Synoptic Survey Telescope will provide such light curves for sources 3-4 mag fainter than OGLE.
ABSTRACT We report the discovery of a microlensing exoplanet OGLE-2012-BLG-0563Lb with the planet-star mass ratio of . Intensive photometric observations of a high-magnification microlensing event ...allow us to detect a clear signal of the planet. Although no parallax signal is detected in the light curve, we instead succeed at detecting the flux from the host star in high-resolution JHK′-band images obtained by the Subaru/AO188 and Infrared Camera and Spectrograph instruments, allowing us to constrain the absolute physical parameters of the planetary system. With the help of spectroscopic information about the source star obtained during the high-magnification state by Bensby et al., we find that the lens system is located at 1.3 kpc from us, and consists of an M dwarf (0.34 M ) orbited by a Saturn-mass planet (0.39 MJup) at the projected separation of 0.74 AU (close model) or 4.3 AU (wide model). The probability of contamination in the host star's flux, which would reduce the masses by a factor of up to three, is estimated to be 17%. This possibility can be tested by future high-resolution imaging. We also estimate the and colors of the host star, which are marginally consistent with a low metallicity mid-to-early M dwarf, although further observations are required for the metallicity to be conclusive. This is the fifth sub-Jupiter-mass ( ) microlensing planet around an M dwarf with the mass well constrained. The relatively rich harvest of sub-Jupiters around M dwarfs is contrasted with a possible paucity of ∼1-2 Jupiter-mass planets around the same type of star, which can be explained by the planetary formation process in the core-accretion scheme.
Global 'second-generation' microlensing surveys aim to discover and characterize extrasolar planets and their frequency, by means of round-the-clock high-cadence monitoring of a large area of the ...Galactic bulge, in a controlled experiment. We report the discovery of a giant planet in microlensing event MOA-2011-BLG-322. This moderate-magnification event, which displays a clear anomaly induced by a second lensing mass, was inside the footprint of our second-generation microlensing survey, involving MOA, OGLE and the Wise Observatory. The event was observed by the survey groups, without prompting alerts that could have led to dedicated follow-up observations. Fitting a microlensing model to the data, we find that the time-scale of the event was t
E = 23.2 ± 0.8 d, and the mass ratio between the lens star and its companion is q = 0.028 ± 0.001. Finite-source effects are marginally detected, and upper limits on them help break some of the degeneracy in the system parameters. Using a Bayesian analysis that incorporates a Galactic structure model, we estimate the mass of the lens at
, at a distance of 7.56 ± 0.91 kpc. Thus, the companion is likely a planet of mass
, at a projected separation of
au, rather far beyond the snow line. This is the first pure-survey planet reported from a second-generation microlensing survey, and shows that survey data alone can be sufficient to characterize a planetary model. With the detection of additional survey-only planets, we will be able to constrain the frequency of extrasolar planets near their systems' snow lines.
ABSTRACT We report the first mass and distance measurements of a caustic-crossing binary system OGLE-2014-BLG-1050 L using the space-based microlens parallax method. Spitzer captured the second ...caustic crossing of the event, which occurred ∼10 days before that seen from Earth. Due to the coincidence that the source-lens relative motion was almost parallel to the direction of the binary-lens axis, the fourfold degeneracy, which was known before only to occur in single-lens events, persists in this case, leading to either a lower-mass (0.2 and 0.07 ) binary at ∼1.1 kpc or a higher-mass (0.9 and 0.35 ) binary at ∼3.5 kpc. However, the latter solution is strongly preferred for reasons including blending and lensing probability. OGLE-2014-BLG-1050 L demonstrates the power of microlens parallax in probing stellar and substellar binaries.
ABSTRACT We report the discovery of an extrasolar planet detected from the combined data of a microlensing event OGLE-2015-BLG-0051/KMT-2015-BLG-0048 acquired by two microlensing surveys. Despite the ...fact that the short planetary signal occurred in the very early Bulge season during which the lensing event could be seen for just about an hour, the signal was continuously and densely covered. From the Bayesian analysis using models of the mass function, and matter and velocity distributions, combined with information on the angular Einstein radius, it is found that the host of the planet is located in the Galactic bulge. The planet has a mass and it is orbiting a low-mass M-dwarf host with a projected separation . The discovery of the planet demonstrates the capability of the current high-cadence microlensing lensing surveys in detecting and characterizing planets.
We present an analysis of the gravitational microlensing event OGLE-2013-BLG-0102. The light curve of the event is characterized by a strong short-term anomaly superposed on a smoothly varying ...lensing curve with a moderate magnification A sub(max) ~ 1.5. It is found that the event was produced by a binary lens with a mass ratio between the components of q = 0.13 and the anomaly was caused by the passage of the source trajectory over a caustic located away from the barycenter of the binary. Based on the analysis of the effects on the light curve due to the finite size of the source and the parallactic motion of the Earth, we determine the physical parameters of the lens system. The measured masses of the lens components are M sub(1) = 0.096 + or - 0.013 M sub(middot in circle) and M sub(2) = 0.012 + or - 0.002 M sub(middot in circle), which correspond to near the hydrogen-burning and deuterium-burning mass limits, respectively. The distance to the lens is 3.04 + or - 0.31 kpc and the projected separation between the lens components is 0.80 + or - 0.08 AU.
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