40 research outputs found
MOA-2020-BLG-135Lb: A New Neptune-class Planet for the Extended MOA-II Exoplanet Microlens Statistical Analysis
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 and separation
, the planet lies exactly at the break and likely peak of the
exoplanet mass-ratio function derived by the MOA collaboration (Suzuki et al.
2016). 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
and a host star of mass
, located at a distance
. With a prior that holds that planet
occurrence scales in proportion to the host star mass, the estimated lens
system properties are ,
, and . This planet qualifies for inclusion in the extended MOA-II
exoplanet microlens sample.Comment: 22 pages, 6 figures, 4 tables, submitted to the AAS Journal
KMT-2021-BLG-1077L: The fifth confirmed multiplanetary system detected by microlensing
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. We test various models in combination with several interpretations. 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 and , which correspond to and
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 a mass of , and it hosts
two gas giant planets with masses of and . The planets lie beyond
the snow line of the host with projected separations of and . The planetary system resides in the
Galactic bulge at a distance of . 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.Comment: 9 pages, 8 figure
KMT-2021-BLG-1150Lb: Microlensing planet detected through a densely covered planetary-caustic signal
Recently, there have been reports of various types of degeneracies in the
interpretation of planetary signals induced by planetary caustics. In this
work, we check whether such degeneracies persist in the case of well-covered
signals by analyzing the lensing event KMT-2021-BLG-1150, for which the light
curve exhibits a densely and continuously covered short-term anomaly. In order
to identify degenerate solutions, we thoroughly investigate the parameter space
by conducting dense grid searches for the lensing parameters. We then check the
severity of the degeneracy among the identified solutions. We identify a pair
of planetary solutions resulting from the well-known inner-outer degeneracy,
and find that interpreting the anomaly is not subject to any degeneracy other
than the inner-outer degeneracy. The measured parameters of the planet
separation (normalized to the Einstein radius) and mass ratio between the lens
components are for the inner
solution and for the outer
solution. According to a Bayesian estimation, the lens is a planetary system
consisting of a planet with a mass
and its host with a mass lying toward
the Galactic center at a distance ~kpc. By
conducting analyses using mock data sets prepared to mimic those obtained with
data gaps and under various observational cadences, it is found that gaps in
data can result in various degenerate solutions, while the observational
cadence does not pose a serious degeneracy problem as long as the anomaly
feature can be delineated.Comment: 9 pages, 8 figure
Mass Production of 2021 KMTNet Microlensing Planets III: Analysis of Three Giant Planets
We present the analysis of three more planets from the KMTNet 2021
microlensing season. KMT-2021-BLG-0119Lb is a planet
orbiting an early M-dwarf or a K-dwarf, KMT-2021-BLG-0192Lb is a planet orbiting an M-dwarf, and KMT-2021-BLG-0192Lb is a planet orbiting a very--low-mass M dwarf or a brown dwarf.
These by-eye planet detections provide an important comparison sample to the
sample selected with the AnomalyFinder algorithm, and in particular,
KMT-2021-BLG-2294, is a case of a planet detected by-eye but not by-algorithm.
KMT-2021-BLG-2294Lb is part of a population of microlensing planets around
very-low-mass host stars that spans the full range of planet masses, in
contrast to the planet population at au, which shows a strong
preference for small planets.Comment: 17 pages, 12 figures, 7 tables. Accept for publication in The
Astronomical Journa
KMT-2022-BLG-0440Lb: A New Microlensing Planet with the Central-Resonant Caustic Degeneracy Broken
We present the observations and analysis of a high-magnification microlensing
planetary event, KMT-2022-BLG-0440, for which the weak and short-lived
planetary signal was covered by both the KMTNet survey and follow-up
observations. The binary-lens models with a central caustic provide the best
fits, with a planet/host mass ratio, -- at
. The binary-lens models with a resonant caustic and a brown-dwarf
mass ratio are both excluded by . The binary-source model
can fit the anomaly well but is rejected by the ``color argument'' on the
second source. From Bayesian analyses, it is estimated that the host star is
likely a K or M dwarf located in the Galactic disk, the planet probably has a
Neptune-mass, and the projected planet-host separation is
or au, subject to the close/wide degeneracy. This is the
third planet from a high-magnification planetary signal (). Together with another such planet, KMT-2021-BLG-0171Lb, the
ongoing follow-up program for the KMTNet high-magnification events has
demonstrated its ability in detecting high-magnification planetary signals for
planets, which are challenging for the current microlensing
surveys.Comment: MNRAS accepte
Systematic KMTNet Planetary Anomaly Search. V. Complete Sample of 2018 Prime-Field
We complete the analysis of all 2018 prime-field microlensing planets
identified by the KMTNet AnomalyFinder. Among the 10 previously unpublished
events with clear planetary solutions, 8 are either unambiguously planetary or
are very likely to be planetary in nature: OGLE-2018-BLG-1126,
KMT-2018-BLG-2004, OGLE-2018-BLG-1647, OGLE-2018-BLG-1367, OGLE-2018-BLG-1544,
OGLE-2018-BLG-0932, OGLE-2018-BLG-1212, and KMT-2018-BLG-2718. Combined with
the 4 previously published new AnomalyFinder events and 12 previously published
(or in preparation) planets that were discovered by eye, thismakes a total of
24 2018 prime-field planets discovered or recovered by AnomalyFinder. Together
with a paper in preparation on 2018 sub-prime planets, this work lays the basis
for the first statistical analysis of the planet mass-ratio function based on
planets identified in KMTNet data. By systematically applying the heuristic
analysis of Hwang et al. (2022) to each event, we identify the small
modification in their formalism that is needed to unify the so-called
close/wide and inner/outer degeneracies, as conjectured byComment: 22 pages, 14 tables, 15 figure
KMT-2023-BLG-1431Lb: A New Microlensing Planet from a Subtle Signature
The current studies of microlensing planets are limited by small number
statistics. Follow-up observations of high-magnification microlensing events
can efficiently form a statistical planetary sample. Since 2020, the Korea
Microlensing Telescope Network (KMTNet) and the Las Cumbres Observatory (LCO)
global network have been conducting a follow-up program for high-magnification
KMTNet events. Here, we report the detection and analysis of a microlensing
planetary event, KMT-2023-BLG-1431, for which the subtle (0.05 magnitude) and
short-lived (5 hours) planetary signature was characterized by the follow-up
from KMTNet and LCO. A binary-lens single-source (2L1S) analysis reveals a
planet/host mass ratio of , and the
single-lens binary-source (1L2S) model is excluded by . A
Bayesian analysis using a Galactic model yields estimates of the host star mass
of , the planetary mass of , and the lens distance of kpc. The projected planet-host separation of au or , subject to the
close/wide degeneracy. We also find that without the follow-up data, the
survey-only data cannot break the degeneracy of central/resonant caustics and
the degeneracy of 2L1S/1L2S models, showing the importance of follow-up
observations for current microlensing surveys.Comment: PASP submitted. arXiv admin note: text overlap with arXiv:2301.0677
MOA-2019-BLG-008Lb : a new microlensing detection of an object at the planet/brown dwarf boundary
Funding: R.A.S. and E.B. gratefully acknowledge support from NASA grant 80NSSC19K0291. Y.T. and J.W. acknowledge the support of DFG priority program SPP 1992 âExploring the Diversity of Extrasolar Planetsâ (WA 1047/11-1). K.H. acknowledges support from STFC grant ST/R000824/1. J.C.Y. acknowledges support from NSF grant No. AST-2108414. Work by C.H. was supported by the grants of the National Research Foundation of Korea (2019R1A2C2085965 and 2020R1A4A2002885). D.M.B. acknowledges the support of the NYU Abu Dhabi Research Enhancement Fund under grant RE124. This work was partly supported by the National Science Foundation of China (grant Nos. 11333003, 11390372, and 11761131004 to S.M.). The MOA project is supported by JSPS KAKENHI grant Nos. JSPS24253004, JSPS26247023, JSPS23340064, JSPS15H00781, JP16H06287, and JP17H02871.We report on the observations, analysis and interpretation of the microlensing event MOA-2019-BLG-008. The observed anomaly in the photometric light curve is best described through a binary lens model. In this model, the source did not cross caustics and no finite-source effects were observed. Therefore, the angular Einstein ring radius ΞE cannot be measured from the light curve alone. However, the large event duration, tE ⌠80 days, allows a precise measurement of the microlensing parallax ÏE. In addition to the constraints on the angular radius Ξ* and the apparent brightness Is of the source, we employ the Besançon and GalMod galactic models to estimate the physical properties of the lens. We find excellent agreement between the predictions of the two galactic models: the companion is likely a resident of the brown dwarf desert with a mass Mp ⌠30 MJup, and the host is a main-sequence dwarf star. The lens lies along the line of sight to the Galactic bulge, at a distance of â€4 kpc. We estimate that in about 10 yr the lens and source will be separated by âŒ55 mas, and it will be possible to confirm the exact nature of the lensing system by using high-resolution imaging from ground- or space-based observatories.Publisher PDFPeer reviewe
OGLE-2019-BLG-0825: Constraints on the Source System and Effect on Binary-lens Parameters arising from a Five Day Xallarap Effect in a Candidate Planetary Microlensing Event
We present an analysis of microlensing event OGLE-2019-BLG-0825. This event
was identified as a planetary candidate by preliminary modeling. We find that
significant residuals from the best-fit static binary-lens model exist and a
xallarap effect can fit the residuals very well and significantly improves
values. On the other hand, by including the xallarap effect in our
models, we find that binary-lens parameters like mass-ratio, , and
separation, , cannot be constrained well. However, we also find that the
parameters for the source system like the orbital period and semi major axis
are consistent between all the models we analyzed. We therefore constrain the
properties of the source system better than the properties of the lens system.
The source system comprises a G-type main-sequence star orbited by a brown
dwarf with a period of days. This analysis is the first to demonstrate
that the xallarap effect does affect binary-lens parameters in planetary
events. It would not be common for the presence or absence of the xallarap
effect to affect lens parameters in events with long orbital periods of the
source system or events with transits to caustics, but in other cases, such as
this event, the xallarap effect can affect binary-lens parameters.Comment: 19 pages, 7 figures, 6 tables. Accepted by A
OGLE-2014-BLG-0319 : a sub-Jupiter-mass planetary event encountered degeneracy with different mass ratios and lens-source relative proper motions
We report the discovery of a sub-Jovian-mass planet, OGLE-2014-BLG-0319Lb. The characteristics of this planet will be added into a future extended statistical analysis of the Microlensing Observations in Astrophysics (MOA) collaboration. The planetary anomaly of the light curve is characterized by MOA and OGLE survey observations and results in three degenerate models with different planetary-mass ratios of q = (10.3, 6.6, 4.5) Ă 10â4. We find that the last two models require unreasonably small lens-source relative proper motions of ÎŒrel ⌠1 mas yrâ1. Considering Galactic prior probabilities, we rule out these two models from the final result. We conduct a Bayesian analysis to estimate physical properties of the lens system using a Galactic model and find that the lens system is composed of a sub-Jovian planet orbiting a M dwarf near the Galactic Bulge. This analysis demonstrates that Galactic priors are useful to resolve this type of model degeneracy. This is important for estimating the mass-ratio function statistically. However, this method would be unlikely successful in shorter timescale events, which are mostly due to low-mass objects, like brown dwarfs or free-floating planets. Therefore, careful treatment is needed for estimating the mass-ratio function of the companions around such low-mass hosts, which only the microlensing can probe