449 research outputs found
Vortices in atomic-molecular Bose-Einstein condensates
The structure and stability of vortices in hybrid atomic-molecular
Bose-Einstein condensates is analyzed in the framework of a two-component
Gross-Pitaevskii-type model that describes the stimulated Raman-induced
photoassociation process. New types of topological vortex states are predicted
to exist in the coherently coupled two-component condensates even without a
trap, and their nontrivial dynamics in the presence of losses is demonstrated.Comment: 7 pages, 6 figure
Optical Properties of (162173) 1999 JU3: In Preparation for the JAXA Hayabusa 2 Sample Return Mission
We investigated the magnitude-phase relation of (162173) 1999 JU3, a target
asteroid for the JAXA Hayabusa 2 sample return mission. We initially employed
the international Astronomical Union's H-G formalism but found that it fits
less well using a single set of parameters. To improve the inadequate fit, we
employed two photometric functions, the Shevchenko and Hapke functions. With
the Shevchenko function, we found that the magnitude-phase relation exhibits
linear behavior in a wide phase angle range (alpha = 5-75 deg) and shows weak
nonlinear opposition brightening at alpha< 5 deg, providing a more reliable
absolute magnitude of Hv = 19.25 +- 0.03. The phase slope (0.039 +- 0.001
mag/deg) and opposition effect amplitude (parameterized by the ratio of
intensity at alpha=0.3 deg to that at alpha=5 deg, I(0.3)/I(5)=1.31+-0.05) are
consistent with those of typical C-type asteroids. We also attempted to
determine the parameters for the Hapke model, which are applicable for
constructing the surface reflectance map with the Hayabusa 2 onboard cameras.
Although we could not constrain the full set of Hapke parameters, we obtained
possible values, w=0.041, g=-0.38, B0=1.43, and h=0.050, assuming a surface
roughness parameter theta=20 deg. By combining our photometric study with a
thermal model of the asteroid (Mueller et al. in preparation), we obtained a
geometric albedo of pv = 0.047 +- 0.003, phase integral q = 0.32 +- 0.03, and
Bond albedo AB = 0.014 +- 0.002, which are commensurate with the values for
common C-type asteroids.Comment: 27 pages, 4 figure, accepted for publication in the Astrophysical
Journa
Subaru Hyper Suprime-Cam Survey for An Optical Counterpart of GW170817
We perform a -band survey for an optical counterpart of a binary neutron
star coalescence GW170817 with Subaru/Hyper Suprime-Cam. Our untargeted
transient search covers deg corresponding to the credible
region of GW170817 and reaches the completeness magnitude of mag
on average. As a result, we find 60 candidates of extragalactic transients,
including J-GEM17btc (a.k.a. SSS17a/DLT17ck). While J-GEM17btc is associated
with NGC 4993 that is firmly located inside the 3D skymap of GW170817, the
other 59 candidates do not have distance information in the GLADE v2 catalog or
NASA/IPAC Extragalactic Database (NED). Among 59 candidates, 58 are located at
the center of extended objects in the Pan-STARRS1 catalog, while one candidate
has an offset. We present location, -band apparent magnitude, and time
variability of the candidates and evaluate the probabilities that they are
located inside of the 3D skymap of GW170817. The probability for J-GEM17btc is
being much higher than those for the other 59 candidates
(). Furthermore, the possibility, that at
least one of the other 59 candidates is located within the 3D skymap, is only
. Therefore, we conclude that J-GEM17btc is the most-likely and
distinguished candidate as the optical counterpart of GW170817.Comment: 14 pages, 9 figures. Accepted for publication in PASJ (Publications
of the Astronomical Society of Japan
A Planetary Microlensing Event with an Unusually Red Source Star: MOA-2011-BLG-291
We present the analysis of planetary microlensing event MOA-2011-BLG-291,
which has a mass ratio of and a source star that
is redder (or brighter) than the bulge main sequence. This event is located at
a low Galactic latitude in the survey area that is currently planned for NASA's
WFIRST exoplanet microlensing survey. This unusual color for a microlensed
source star implies that we cannot assume that the source star is in the
Galactic bulge. The favored interpretation is that the source star is a lower
main sequence star at a distance of kpc in the Galactic disk.
However, the source could also be a turn-off star on the far side of the bulge
or a sub-giant in the far side of the Galactic disk if it experiences
significantly more reddening than the bulge red clump stars. However, these
possibilities have only a small effect on our mass estimates for the host star
and planet. We find host star and planet masses of and from a Bayesian
analysis with a standard Galactic model under the assumption that the planet
hosting probability does not depend on the host mass or distance. However, if
we attempt to measure the host and planet masses with host star brightness
measurements from high angular resolution follow-up imaging, the implied masses
will be sensitive to the host star distance. The WFIRST exoplanet microlensing
survey is expected to use this method to determine the masses for many of the
planetary systems that it discovers, so this issue has important design
implications for the WFIRST exoplanet microlensing survey
Spectroscopic Mass and Host-star Metallicity Measurements for Newly Discovered Microlensing Planet OGLE-2018-BLG-0740Lb
We report the discovery of the microlensing planet OGLE-2018-BLG-0740Lb. The
planet is detected with a very strong signal of , but
the interpretation of the signal suffers from two types of degeneracies. One
type is caused by the previously known close/wide degeneracy, and the other is
caused by an ambiguity between two solutions, in which one solution requires to
incorporate finite-source effects, while the other solution is consistent with
a point-source interpretation. Although difficult to be firmly resolved based
on only the photometric data, the degeneracy is resolved in strong favor of the
point-source solution with the additional external information obtained from
astrometric and spectroscopic observations. The small astrometric offset
between the source and baseline object supports that the blend is the lens and
this interpretation is further secured by the consistency of the spectroscopic
distance estimate of the blend with the lensing parameters of the point-source
solution. The estimated mass of the host is and the mass
of the planet is (close solution) or (wide solution) and the lens is located at a distance of ~kpc.
The bright nature of the lens, with (), combined with
its dominance of the observed flux suggest that radial-velocity (RV) follow-up
observations of the lens can be done using high-resolution spectrometers
mounted on large telescopes, e.g., VLT/ESPRESSO, and this can potentially not
only measure the period and eccentricity of the planet but also probe for
close-in planets. We estimate that the expected RV amplitude would be .Comment: 12 pages, 11 figures, 4 table
Candidate Brown-dwarf Microlensing Events with Very Short Timescales and Small Angular Einstein Radii
Short-timescale microlensing events are likely to be produced by substellar brown dwarfs (BDs), but it is difficult to securely identify BD lenses based on only event timescales t_E because short-timescale events can also be produced by stellar lenses with high relative lens-source proper motions. In this paper, we report three strong candidate BD-lens events found from the search for lensing events not only with short timescales (t_E ≲ 6 days) but also with very small angular Einstein radii (θ_E ≲ 0.05 mas) among the events that have been found in the 2016–2019 observing seasons. These events include MOA-2017-BLG-147, MOA-2017-BLG-241, and MOA-2019-BLG-256, in which the first two events are produced by single lenses and the last event is produced by a binary lens. From the Monte Carlo simulations of Galactic events conducted with the combined t_E and θ_E constraint, it is estimated that the lens masses of the individual events are
0.051^(+0.100)_(−0.027) M⊙, 0.044^(+0.090)_(−0.023) M⊙, and 0.046^(+0.067)_(−0.023) M⊙/0.038^(+0.056)_(−0.019) M⊙ and the probability of the lens mass smaller than the lower limit of stars is ~80% for all events. We point out that routine lens mass measurements of short-timescale lensing events require survey-mode space-based observations
OGLE-2018-BLG-0022: First Prediction of an Astrometric Microlensing Signal from a Photometric Microlensing Event
In this work, we present the analysis of the binary microlensing event
OGLE-2018-BLG-0022 that is detected toward the Galactic bulge field. The dense
and continuous coverage with the high-quality photometry data from ground-based
observations combined with the space-based {\it Spitzer} observations of this
long time-scale event enables us to uniquely determine the masses and of the individual lens components.
Because the lens-source relative parallax and the vector lens-source relative
proper motion are unambiguously determined, we can likewise unambiguously
predict the astrometric offset between the light centroid of the magnified
images (as observed by the {\it Gaia} satellite) and the true position of the
source. This prediction can be tested when the individual-epoch {\it Gaia}
astrometric measurements are released.Comment: 10 pages, 10 figures, 4 table
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