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.
Aims.
We inspect the microlensing data of the KMTNet survey collected during the 2018-2020 seasons in order to find lensing events produced by binaries with brown dwarf (BD) companions.
Methods.
In ...order to pick out binary-lens events with candidate BD lens companions, we conducted systematic analyses of all anomalous lensing events observed during the seasons from 2018 to 2020. By applying a selection criterion of mass ratio between the lens components of 0.03 ≲
q
≲ 0.1, we identify four binary-lens events with candidate BD companions, namely KMT-2018-BLG-0321, KMT-2018-BLG-0885, KMT-2019-BLG-0297, and KMT-2019-BLG-0335. For the individual events, we present interpretations of the lens systems and measure the observables that can be used to constrain the physical lens parameters.
Results.
The masses of the lens companions estimated from the Bayesian analyses based on the measured observables indicate high probabilities that the lens companions are in the BD mass regime; that is, 59%, 68%, 66%, and 66% for the four respective events.
The Microlensing Observations in Astrophysics (MOA-II) survey has performed high cadence, wide field observations of the Galactic Bulge from New Zealand since 2005. The hourly cadence of the survey ...during eight months of the year, across nearly 50 deg2 of sky, provides an opportunity to sample asteroid lightcurves in the broad MOA-R filter. We perform photometry of a subset of bright asteroids numbered observed by the survey. We obtain 26 asteroid rotation periods, including for two asteroids where no prior data exist, and present evidence for the possible non-principal axis rotation of (2011) Veteraniya. This archival search could be extended to several thousands of asteroids brighter than 22nd magnitude.
Recent heavy-ion collision experiments reported a surprisingly short lifetime for the hypertriton, which has been recognized as the hypertriton lifetime puzzle. Our J-PARC E73 experiment contributes ...to solve this puzzle with an independent experimental method by employing
3
He(
K
−
,
π
0
)
3
Λ
H reaction. In this contribution, we will demonstrate our capability to provide
3
Λ
H binding energy information by deriving the production cross section ratio,
σ
3
Λ
H
/
σ
4
Λ
H
. The production cross section data for
3
Λ
H and
4
Λ
H are already available as the pilot run of E73 experiment and data analysis is in progress.
We present the analysis of five black hole candidates identified from gravitational microlensing surveys. Hubble Space Telescope astrometric data and densely sampled light curves from ground-based ...microlensing surveys are fit with a single-source, single-lens microlensing model in order to measure the mass and luminosity of each lens and determine if it is a black hole. One of the five targets (OGLE-2011-BLG-0462/MOA-2011-BLG-191 or OB110462 for short) shows a significant >1 mas coherent astrometric shift, little to no lens flux, and has an inferred lens mass of 1.6–4.4 M⨀. This makes OB110462 the first definitive discovery of a compact object through astrometric microlensing and it is most likely either a neutron star or a low-mass black hole. This compact-object lens is relatively nearby (0.70–1.92 kpc) and has a slow transverse motion of <30 kms-1. OB110462 shows significant tension between models well fit to photometry versus astrometry, making it currently difficult to distinguish between a neutron star and a black hole. Additional observations and modeling with more complex system geometries, such as binary sources, are needed to resolve the puzzling nature of this object. For the remaining four candidates, the lens masses are <2M⨀, and they are unlikely to be black holes; two of the four are likely white dwarfs or neutron stars. We compare the full sample of five candidates to theoretical expectations on the number of black holes in the Milky Way (∼108 ) and find reasonable agreement given the small sample size.
We complete the analysis of all 2018 prime-field microlensing planets identified by the Korea Microlensing Telescope Network (KMTNet) Anomaly Finder. Among the ten previously unpublished events with ...clear planetary solutions, eight 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 four previously published new Anomaly Finder events and 12 previously published (or in preparation) planets that were discovered by eye, this makes a total of 24 2018 prime-field planets discovered or recovered by Anomaly Finder. Together with a paper in preparation on 2018 subprime 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 to each event, we identified the small modification in their formalism that is needed to unify the so-called close-wide and inner-outer degeneracies.
Development of an 1-m long prototype TOF-RPC for the J-PARC π20 beam line Tomida, Natsuki; Hayashi, Futaba; Chang, Wen-Chen ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
November 2023, Letnik:
1056
Journal Article
Recenzirano
We have developed a prototype multi-gap Resistive Plate Chamber (RPC) for a time-of-flight (TOF) detector at the J-PARC π20 beam line. It is a double stack RPC with five 0.26-mm gas gaps in each ...stack. Its readout strips are 25 mm wide and 940 mm long. We have also developed an amplifier board which can be used for TOF-RPCs in general and carried out a beam test to evaluate the performance of the RPC and this new board. Timing measurements and a time-walk correction using a time-over-threshold (TOT) method were found to work well without stretching signals. We obtained time resolutions of 60-70 ps when the test particle’s position was determined using 5 mm × 10 mm trigger detectors and 65-80 ps without this position determination.
We are developing time-of-flight (TOF) multi-gap Resistive Plate Chambers (MRPCs) which perform both timing and hit position measurements, the TOF-tracker MRPC, for muon detection to measure ...exclusive Drell–Yan reaction (π−p→γ∗n→μ+μ−n) at J-PARC’s hadron hall. Here we report on the development of a prototype TOF-tracker MRPC with a sensitive area of 500×1000mm2 and its performance in an electron-positron particle beam at the SPring-8 synchrotron in Japan.
•Development of the muon detector for both timing and hit position measurements.•Beam test for examination of the basic performance the muon detector.•Achievement of a time resolution of 100 ps.
