Abstract
We present the first measurement of the mass function of free-floating planets (FFPs), or very wide orbit planets down to an Earth mass, from the MOA-II microlensing survey in 2006–2014. Six ...events are likely to be due to planets with Einstein radius crossing times
t
E
< 0.5 days, and the shortest has
t
E
= 0.057 ± 0.016 days and an angular Einstein radius of
θ
E
= 0.90 ± 0.14
μ
as. We measure the detection efficiency depending on both
t
E
and
θ
E
with image-level simulations for the first time. These short events are well modeled by a power-law mass function,
dN
4
/
d
log
M
=
(
2.18
−
1.40
+
0.52
)
×
(
M
/
8
M
⊕
)
−
α
4
dex
−1
star
−1
with
α
4
=
0.96
−
0.27
+
0.47
for
M
/
M
⊙
< 0.02. This implies a total of
f
=
21
−
13
+
23
FFPs or very wide orbit planets of mass 0.33 <
M
/
M
⊕
< 6660 per star, with a total mass of
80
−
47
+
73
M
⊕
star
−1
. The number of FFPs is
19
−
13
+
23
times the number of planets in wide orbits (beyond the snow line), while the total masses are of the same order. This suggests that the FFPs have been ejected from bound planetary systems that may have had an initial mass function with a power-law index of
α
∼ 0.9, which would imply a total mass of
171
−
52
+
80
M
⊕
star
−1
. This model predicts that Roman Space Telescope will detect
988
−
566
+
1848
FFPs with masses down to that of Mars (including
575
−
424
+
1733
with 0.1 ≤
M
/
M
⊕
≤ 1). The Sumi et al. large Jupiter-mass FFP population is excluded.
Abstract
We report the discoveries of low-mass free-floating planet (FFP) candidates from the analysis of 2006–2014 MOA-II Galactic bulge survey data. In this data set, we found 6111 microlensing ...candidates and identified a statistical sample consisting of 3535 high-quality single-lens events with Einstein radius crossing times in the range 0.057 <
t
E
/days < 757, including 13 events that show clear finite-source effects with angular Einstein radii of 0.90 <
θ
E
/
μ
as < 332.54. Two of the 12 events with
t
E
< 1 day have significant finite-source effects, and one event, MOA-9y-5919, with
t
E
= 0.057 ± 0.016 days and
θ
E
= 0.90 ± 0.14
μ
as, is the second terrestrial-mass FFP candidate to date. A Bayesian analysis indicates a lens mass of
0.75
−
0.46
+
1.23
M
⊕
for this event. The low detection efficiency for short-duration events implies a large population of low-mass FFPs. The microlensing detection efficiency for low-mass planet events depends on both the Einstein radius crossing times and the angular Einstein radii, so we have used image-level simulations to determine the detection efficiency dependence on both
t
E
and
θ
E
. This allows us to use a Galactic model to simulate the
t
E
and
θ
E
distribution of events produced by the known stellar populations and models of the FFP distribution that are fit to the data. Methods like this will be needed for the more precise FFP demographics determinations from Nancy Grace Roman Space Telescope data.
Abstract The Transiting Exoplanet Survey Satellite (TESS) mission measured light from stars in ∼85% of the sky throughout its 2 yr primary mission, resulting in millions of TESS 30-minute-cadence ...light curves to analyze in the search for transiting exoplanets. To search this vast data set, we aim to provide an approach that is computationally efficient, produces accurate predictions, and minimizes the required human search effort. We present a convolutional neural network that we train to identify short-period variables. To make a prediction for a given light curve, our network requires no prior target parameters identified using other methods. Our network performs inference on a TESS 30-minute-cadence light curve in ∼5 ms on a single GPU, enabling large-scale archival searches. We present a collection of 14,156 short-period variables identified by our network. The majority of our identified variables fall into two prominent populations, one of close-orbit main-sequence binaries and another of δ Scuti stars. Our neural network model and related code are additionally provided as open-source code for public use and extension.
We report the light-curve analysis for the event MOA-2020-BLG-135, which leads to the discovery of a new Neptune-class planet, MOA-2020-BLG-135Lb. With a derived mass ratio of q=1.52+0.39-0.31x10-4 ...and separation s ≈ 1, the planet lies exactly at the break and likely peak of the exoplanet mass-ratio function derived by the Microlensing Observations in Astrophysics (MOA) Collaboration. We estimate the properties of the lens system based on a Galactic model and considering two different Bayesian priors: one assuming that all stars have an equal planet-hosting probability and the other that planets are more likely to orbit more-massive stars. With a uniform host mass prior, we predict that the lens system is likely to be a planet of mass mplanet= 11.3 +19.2 -6.9M⨁ and a host star of mass Mhost=0.23+0.39-0.14M⨀, located at a distance 𝐃𝐋=7.9+1.0-1.0 kpc. With a prior that holds that planet occurrence scales in proportion to the host-star mass, the estimated lens system properties are mplanet=25+22 -15 M⨁, M Mhost=0.53+0.42 -0,32 M⨀, and DL=8.3+0.9-1.0.This planet qualifies for inclusion in the extended MOA-II exoplanet microlens sample.
Abstract We present high angular resolution imaging that detects the MOA-2008-BLG-379L exoplanet host star using Keck adaptive optics and the Hubble Space Telescope. These observations reveal host ...star and planet masses of M host = 0.434 ± 0.065 M ⊙ and m p = 2.44 ± 0.49 M Jupiter . They are located at a distance of D L = 3.44 ± 0.53 kpc, with a projected separation of 2.70 ± 0.42 au. These results contribute to our determination of exoplanet host star masses for the Suzuki et al. statistical sample, which will determine the dependence of the planet occurrence rate on the mass and distance of the host stars. We also present a detailed discussion of the image-constrained modeling version of the eesunhong light-curve modeling code that applies high angular resolution image constraints to the light-curve modeling process. This code increases modeling efficiency by a large factor by excluding models that are inconsistent with the high angular resolution images. The analysis of this and other events from the Suzuki et al. statistical sample reveals the importance of including higher-order effects, such as microlensing parallax and planetary orbital motion, even when these features are not required to fit the light-curve data. The inclusion of these effects may be needed to obtain accurate estimates of the uncertainty of other microlensing parameters that affect the inferred properties of exoplanet microlens systems. This will be important for the exoplanet microlensing survey of the Roman Space Telescope, which will use both light-curve photometry and high angular resolution imaging to characterize planetary microlens systems.
Aims.
The high-magnification microlensing event KMT-2021-BLG-1077 exhibits a subtle and complex anomaly pattern in the region around the peak. We analyze the lensing light curve of the event with the ...aim of revealing the nature of the anomaly.
Methods.
We test various models in combination with several interpretations: that the lens is a binary (2L1S), the source is a binary (1L2S), both the lens and source are binaries (2L2S), or the lens is a triple system (3L1S). We search for the best-fit models under the individual interpretations of the lens and source systems.
Results.
We find that the anomaly cannot be explained by the usual three-body (2L1S and 1L2S) models. The 2L2S model improves the fit compared to the three-body models, but it still leaves noticeable residuals. On the other hand, the 3L1S interpretation yields a model explaining all the major anomalous features in the lensing light curve. According to the 3L1S interpretation, the estimated mass ratios of the lens companions to the primary are ~1.56 × 10
−3
and ~1.75 × 10
−3
, which correspond to ~1.6 and ~1.8 times the Jupiter/Sun mass ratio, respectively, and therefore the lens is a multiplanetary system containing two giant planets. With the constraints of the event time-scale and angular Einstein radius, it is found that the host of the lens system is a low-mass star of mid-to-late M spectral type with amass of
M
h
= 0.14
−0.07
+0.19
M
Θ
, and it hosts two gas giant planets with masses of
M
p1
= 0.22
−0.12
+0.31
M
J
and
M
p2
= 0.25
−0.13
+0.35
. The planets lie beyond the snow line of the host with projected separations of
a
⊥,p1
= 1.26
−1.08
+1.41
AU and
a
⊥,p2
= 0.93
−0.80
+1.05
AU. The planetary system resides in the Galactic bulge at a distance of
D
L
= 8.24
−1.16
+1.02
kpc. The lens of the event is the fifth confirmed multiplanetary system detected by microlensing following OGLE-2006-BLG-109L, OGLE-2012-BLG-0026L, OGLE-2018-BLG-1011L, and OGLE-2019-BLG-0468L.
Abstract We present the analysis of the microlensing event OGLE-2014-BLG-0221, a planetary candidate event discovered in 2014. The photometric light curve is best described by a binary-lens ...single-source model. Our light-curve modeling finds two degenerate models, with event timescales of t E ∼ 70 days and ∼110 days. These timescales are relatively long, indicating that the discovered system would possess a substantial mass. The two models are similar in their planetary parameters with a Jupiter mass ratio of q ∼ 10 −3 and a separation of s ∼ 1.1. Bayesian inference is used to estimate the physical parameters of the lens, revealing that the shorter timescale model predicts 65% and 25% probabilities of a late-type star and white dwarf host, respectively, while the longer timescale model favors a black hole host with a probability ranging from 60% to 95%, under the assumption that stars and stellar remnants have equal probabilities of hosting companions with planetary mass ratios. If the lens is a remnant, this would be the second planet found by microlensing around a stellar remnant. The current separation between the source and lens stars is 41–139 mas depending on the models. This indicates the event is now ready for high-angular-resolution follow-up observations to rule out either of the models. If precise astrometric measurements are conducted in multiple bands, the centroid shift due to the color difference between the source and lens would be detected in the luminous lens scenario.
Characterizing a planet detected by microlensing is hard if the planetary signal is weak or the lens-source relative trajectory is far from caustics. However, statistical analyses of planet ...demography must include those planets to accurately determine occurrence rates. As part of a systematic modelling effort in the context of a >10-yr retrospective analysis of MOA’s survey observations to build an extended MOA statistical sample, we analyse the light curve of the planetary microlensing event MOA-2014-BLG-472. This event provides weak constraints on the physical parameters of the lens, as a result of a planetary anomaly occurring at low magnification in the light curve. We use a Bayesian analysis to estimate the properties of the planet, based on a refined Galactic model and the assumption that all Milky Way’s stars have an equal planet-hosting probability. We find that a lens consisting of a 1.9(+2.2,−1.2)M(J) giant planet orbiting a 0.31(+0.36,−0.19)Mꙩ host at a projected separation of 0.75±0.24au is consistent with the observations and is most likely, based on the Galactic priors. The lens most probably lies in the Galactic bulge, at 7.2(+0.6,−1.7)kpc from Earth. The accurate measurement of the measured planet-to-host star mass ratio will be included in the next statistical analysis of cold planet demography detected by microlensing.
In this work, we generalize semi-supervised generative adversarial networks (GANs) from classification problems to regression problems. In the last few years, the importance of improving the training ...of neural networks using semi-supervised training has been demonstrated for classification problems. We present a novel loss function, called feature contrasting, resulting in a discriminator which can distinguish between fake and real data based on feature statistics. This method avoids potential biases and limitations of alternative approaches. The generalization of semi-supervised GANs to the regime of regression problems of opens their use to countless applications as well as providing an avenue for a deeper understanding of how GANs function. We first demonstrate the capabilities of semi-supervised regression GANs on a toy dataset which allows for a detailed understanding of how they operate in various circumstances. This toy dataset is used to provide a theoretical basis of the semi-supervised regression GAN. We then apply the semi-supervised regression GANs to a number of real-world computer vision applications: age estimation, driving steering angle prediction, and crowd counting from single images. We perform extensive tests of what accuracy can be achieved with significantly reduced annotated data. Through the combination of the theoretical example and real-world scenarios, we demonstrate how semi-supervised GANs can be generalized to regression problems.
This paper describes the interface and testing of an indoor navigation app - ASSIST - that guides blind & visually impaired (BVI) individuals through an indoor environment with high accuracy while ...augmenting their understanding of the surrounding environment. ASSIST features personalized interfaces by considering the unique experiences that BVI individuals have in indoor wayfinding and offers multiple levels of multimodal feedback. After an overview of the technical approach and implementation of the first prototype of the ASSIST system, the results of two pilot studies performed with BVI individuals are presented - a performance study to collect data on mobility (walking speed, collisions, and navigation errors) while using the app, and a usability study to collect user evaluation data on the perceived helpfulness, safety, ease-of-use, and overall experience while using the app. Our studies show that ASSIST is useful in providing users with navigational guidance, improving their efficiency and (more significantly) their safety and accuracy in wayfinding indoors. Findings and user feedback from the studies confirm some of the previous results, while also providing some new insights into the creation of such an app, including the use of customized user interfaces and expanding the types of information provided.
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