Aims.
We analyze the microlensing event KMT-2019-BLG-0797. The light curve of the event exhibits two anomalous features from a single-lens single-source model, and we aim to reveal the nature of the ...anomaly.
Methods.
It is found that a model with two lenses plus a single source (2L1S model) can explain one feature of the anomaly, but the other feature cannot be explained. We test various models and find that both anomalous features can be explained by introducing an extra source to a 2L1S model (2L2S model), making the event the third confirmed case of a 2L2S event, following MOA-2010-BLG-117 and OGLE-2016-BLG-1003. It is estimated that the extra source comprises ∼4% of the
I
-band flux from the primary source.
Results.
Interpreting the event is subject to a close–wide degeneracy. According to the close solution, the lens is a binary consisting of two brown dwarfs with masses (
M
1
,
M
2
) ∼ (0.034, 0.021)
M
⊙
, and it is located at a distance of
D
L
∼ 8.2 kpc. According to the wide solution, on the other hand, the lens is composed of an object at the star–brown dwarf boundary and an M dwarf with masses (
M
1
,
M
2
) ∼ (0.06, 0.33)
M
⊙
located at
D
L
∼ 7.7 kpc. The source is composed of a late G dwarf to early K dwarf primary and an early-to-mid M dwarf companion.
We report the discovery of a low-mass-ratio planet (q = 1.3 × 10−4), i.e., 2.5 times higher than the Neptune/Sun ratio. The planetary system was discovered from the analysis of the KMT-2017-BLG-0165 ...microlensing event, which has an obvious short-term deviation from the underlying light curve produced by the host of the planet. Although the fit improvement with the microlens parallax effect is relatively low, one component of the parallax vector is strongly constrained from the light curve, making it possible to narrow down the uncertainties of the lens physical properties. A Bayesian analysis yields that the planet has a super-Neptune mass orbiting a Sun-like star located at 4.5 kpc. The blended light is consistent with these host properties. The projected planet-host separation is , implying that the planet is located outside the snow line of the host, i.e., asl ∼ 2.1 au. KMT-2017-BLG-0165Lb is the sixteenth microlensing planet with mass ratio q < 3 × 10−4. Using the fifteen of these planets with unambiguous mass-ratio measurements, we apply a likelihood analysis to investigate the form of the mass-ratio function in this regime. If we adopt a broken power law for the form of this function, then the break is at qbr 0.55 × 10−4, which is much lower than previously estimated. Moreover, the change of the power-law slope, ζ > 3.3, is quite severe. Alternatively, the distribution is also suggestive of a pileup of planets at Neptune-like mass ratios, below which there is a dramatic drop in frequency.
We show that microlensing event KMT-2016-BLG-1107 displays a new type of degeneracy between wide-binary and close-binary Hollywood events in which a giant-star source envelops the planetary caustic. ...The planetary anomaly takes the form of a smooth, two-day "bump" far out on the falling wing of the light curve, which can be interpreted either as the source completely enveloping a minor-image caustic due to a close companion with mass ratio q = 0.036, or partially enveloping a major-image caustic due to a wide companion with q = 0.004. The best estimates of the companion masses are both in the planetary regime ( and ) but differ by an even larger factor than the mass ratios due to different inferred host masses. We show that the two solutions can be distinguished by high-resolution imaging at first light on next-generation ("30 m") telescopes. We provide analytic guidance to understand the conditions under which this new type of degeneracy can appear.
We measure the relation between galaxy luminosity and disk circular velocity (the Tully-Fisher TF relation), in the g, r, i, and z bands, for a broadly selected sample of galaxies from the Sloan ...Digital Sky Survey, with the goal of providing well-defined observational constraints for theoretical models of galaxy formation. The input sample of 234 galaxies has a roughly flat distribution of absolute magnitudes in the range -18.5 > Mr > -22, and our only morphological selection is an isophotal axis ratio cut b/a < 0.6 to allow accurate inclination corrections. Long-slit spectroscopy from the Calar Alto and MDM observatories yields usable Ha rotation curves for 162 galaxies (69%), with a representative color and morphology distribution. We define circular velocities V80 by evaluating the rotation curve at the radius containing 80% of the i-band light. Observational errors, including estimated distance errors due to peculiar velocities, are small compared to the intrinsic scatter of the TF relation. The slope of the forward TF relation steepens from -5.5 ± 0.2 mag (log10 km s-1)-1 in the g band to -6.6 ± 0.2 mag (log10 km s-1)-1 in the z band. The intrinsic scatter is s 0.4 mag in all bands, and residuals from either the forward or inverse relations have an approximately Gaussian distribution. We discuss how Malmquist-type biases may affect the observed slope, intercept, and scatter. The scatter is not dominated by rare outliers or by any particular class of galaxies, although it drops slightly, to s 0.36 mag, if we restrict the sample to nearly bulgeless systems. Correlations of TF residuals with other galaxy properties are weak: bluer galaxies are significantly brighter than average in the g-band TF relation but only marginally brighter in the i band; more concentrated (earlier type) galaxies are slightly fainter than average, and the TF residual is virtually independent of half-light radius, contrary to the trend expected for gravitationally dominant disks. The observed residual correlations do not account for most of the intrinsic scatter, implying that this scatter is instead driven largely by variations in the ratio of dark to luminous matter within the disk galaxy population.
Abstract
We show that because the conditions for producing terrestrial microlens parallax (TPRX; i.e., a nearby disk lens) will also tend to produce a large lens-source relative proper motion (
μ
rel
...), source proper motion (
μ
S
) measurements in general provide a strong test of TPRX signals, which Gould & Yee (2013) showed were an important probe of free-floating planet (FFP) candidates. As a case study, we report a single-lens/single-source microlensing event designated as OGLE-2019-BLG-1058. For this event, the short timescale (∼2.5 days) and very fast
μ
rel
(∼17.6 mas yr
−1
) suggest that this isolated lens is an FFP candidate located in the disk of our Galaxy. For this event, we find a TPRX signal consistent with a disk FFP, but at low significance. A direct measurement of the
μ
S
shows that the large
μ
rel
is due to an extreme
μ
S
, and thus, the lens is consistent with being a very-low-mass star in the bulge and the TPRX measurement is likely spurious. By contrast, we show how a precise measurement of
μ
S
with the mean properties of the bulge proper motion distribution would have given the opposite result; i.e., provided supporting evidence for an FFP in the disk and the TPRX measurement.
We report the discovery of KMT-2018-BLG-1990Lb, a Jovian planet orbiting a late M dwarf at a distance of , and projected at 2.6 0.6 times the snow line distance, i.e., . This is the second Jovian ...planet discovered by the Korea Microlensing Telescope Network (KMTNet) in its low-cadence (0.4 hr−1) fields, demonstrating that this population can be probed based on relatively low-cadence survey-only microlensing data. However, while many Jovian-planet microlensing events will not have caustic crossings (e.g., the previous case, KMT-2016-BLG-1397) and some that do will be well characterized by low-cadence survey observations (e.g., the current case), in general higher-cadence follow-up observations of the caustic crossings are preferable. Such follow-up observations require microlensing alerts, which KMTNet now provides.
We present the analyses of two short-timescale microlensing events, KMT-2016-BLG-1820 and KMT-2016-BLG-2142. In both light curves, the brief anomalies were clearly captured and densely covered by the ...Korea Microlensing Telescope Network survey. From these analyses, we find that both events have small Einstein radii of , suggesting that the binary-lens systems are composed of very-low-mass components and/or are located much closer to the lensed stars than to Earth. From Bayesian analyses, we find that these binaries have total system masses of and , implying that they are well within the very-low-mass regime. The estimated lens-component masses indicate that the binary lenses consist of a giant-planet/brown-dwarf pair (KMT-2016-BLG-1820) and a dark/faint object pair (KMT-2016-BLG-2140) that are located near the deuterium-burning and hydrogen-burning mass limits, respectively. Both lens systems are likely to be in the Galactic disk with estimated distances of about 6 and 7 kpc. The projected lens-components separations are 1.1 and 0.8 au, and the mass ratios are 0.11 and 0.20. These prove that the microlensing method is effective to identify these closely separated very-low-mass binaries having low mass-ratios.
We have undertaken a new ground-based monitoring campaign to improve the estimates of the mass of the central black hole in NGC 4151. We measure the lag time of the broad Hb line response compared to ...the optical continuum at 5100 AA and find a lag of 6.6 super(+1.1-0.8) days. We combine our data with the recent reanalysis of UV emission lines by Metzroth and coworkers to calculate a weighted mean of the black hole mass, M sub(BH) = (4.57 super(+0.57-0.47)) x 10 super(7) M sub( ). The absolute calibration of the black hole mass is based on normalization of the AGN black hole mass-stellar velocity dispersion (M sub(BH)-s sub(*)) relationship to that of quiescent galaxies by Onken and coworkers. The scatter in the M sub(BH)-s sub(*) relationship suggests that reverberation-mapping-based mass measurements are typically uncertain by a factor of 3-4.
We report the discovery of a giant planet in the KMT-2016-BLG-1397 microlensing event, which was found by The Korea Microlensing Telescope Network alone. The timescale of this event is tE = 40.0 0.5 ...days, and the mass ratio between the lens star and its companion is q = 0.016 0.002. The planetary perturbation in the light curve is a smooth bump, resulting in the classical binary-lens/binary-source (2L1S/1L2S) degeneracy. We measure the V − I color of the (putative) two sources in the 1L2S model, and then effectively rule out the binary-source solution. The finite-source effect is marginally detected. Combined with the limits on the blend flux and the probability distribution of the source size normalized by the Einstein radius , a Bayesian analysis yields the lens mass , at distance of kpc. Thus, the companion is a super-Jupiter of a mass , at a projected separation au, indicating that the planet is well beyond the snow line of the host star.
We report the discovery of KMT-2018-BLG-1292Lb, a super-Jovian Mplanet = 5.0 1.2 MJ planet orbiting an F or G dwarf Mhost = 1.2 0.3 M , which lies physically within of the Galactic plane. The source ...star is a heavily extincted AI ∼ 5.2 luminous giant that has the lowest Galactic latitude, b = −0 28, of any planetary microlensing event. The relatively blue blended light is almost certainly either the host or its binary companion, with the first explanation being substantially more likely. This blend dominates the light at the I band and completely dominates at the R and V bands. Hence, the lens system can be probed by follow-up observations immediately, i.e., long before the lens system and the source separate due to their relative proper motion. The system is well characterized despite the low cadence, Γ = 0.15-0.20 hr−1, of observations and short viewing windows near the end of the bulge season. This suggests that optical microlensing planet searches can be extended to the Galactic plane at relatively modest cost.
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