We report observations of a stellar occultation by the classical Kuiper Belt object (50000) Quaoar that occurred on 2019 June 28. A single-chord high-cadence (2 Hz) photometry data set was obtained ...with the Tomo-e Gozen CMOS camera mounted on the 1.05 m Schmidt telescope at Kiso Observatory. The obtained ingress and egress data do not show any indication of atmospheric refraction and allow new 1 and 3 upper limits of 6 and 16 nbar, respectively, to be set for the surface pressure of a pure methane atmosphere. These upper limits are lower than the saturation vapor pressure of methane at Quaoar's expected mean surface temperature (T ∼ 44 K) and imply the absence of a ∼10 nbar-level global atmosphere formed by methane ice on Quaoar's surface.
We present our optical follow-up observations to search for an electromagnetic counterpart of the first gravitational wave source GW150914 in the framework of the Japanese collaboration for ...Gravitational wave ElectroMagnetic follow-up (J-GEM), which is an observing group utilizing optical and radio telescopes in Japan, as well as in New Zealand, China, South Africa, Chile, and Hawaii. We carried out a wide-field imaging survey with the Kiso Wide Field Camera (KWFC) on the 1.05 m Kiso Schmidt telescope in Japan and a galaxy-targeted survey with Tripole5 on the B&C 61 cm telescope in New Zealand. Approximately 24 deg2 regions in total were surveyed in i-band with KWFC and 18 nearby galaxies were observed with Tripole5 in g-, r-, and i-bands 4–12 days after the gravitational wave detection. Median 5 σ depths are i ∼ 18.9 mag for the KWFC data and g ∼ 18.9 mag, r ∼ 18.7 mag, and i ∼ 18.3 mag for the Tripole5 data. The probability for a counterpart to be in the observed area is 1.2% in the initial skymap and 0.1% in the final skymap. We do not find any transient source associated to an external galaxy with spatial offset from its center, which is consistent with the local supernova rate.
Radar and optical simultaneous observations of meteors are important to understand the size distribution of the interplanetary dust. However, faint meteors detected by high power large aperture radar ...observations, which are typically as faint as 10 mag. In optical, have not been detected until recently in optical observations, mainly due to insufficient sensitivity of the optical observations. In this paper, two radar and optical simultaneous observations were organized. The first observation was carried out in 2009–2010 using Middle and Upper Atmosphere Radar (MU radar) and an image-intensified CCD camera. The second observation was carried out in 2018 using the MU radar and a mosaic CMOS camera, Tomo-e Gozen, mounted on the 1.05-m Kiso Schmidt Telescope. In total, 331 simultaneous meteors were detected. The relationship between radar cross sections and optical V-band magnitudes was well approximated by a linear function. A transformation function from the radar cross section to the V-band magnitude was derived for sporadic meteors. The transformation function was applied to about 150,000 meteors detected by the MU radar in 2009–2015, large part of which are sporadic, and a luminosity function was derived in the magnitude range of −1.5–9.5 mag. The luminosity function was well approximated by a single power-law function with the population index of r=3.52±0.12. The present observation indicates that the MU radar has capability to detect interplanetary dust of 10−5–100g in mass as meteors.
•In total, 331 meteors were detected simultaneously by radar and optically.•A correlation between the radar cross section and the optical magnitude is firmly confirmed.•The mass range of the meteor detected by MU radar is constrained to about 105−100 g.
We obtain a new construction of compact complex surfaces with trivial canonical bundle. In our construction we glue together two compact complex surfaces with an anticanonical divisor under suitable ...conditions. Then we show that the resulting compact manifold admits a complex structure with trivial canonical bundle by solving an elliptic partial differential equation. We generalize this result to cases where we have other than two components to glue together. With this generalization, we construct examples of complex tori, Kodaira surfaces and K3 surfaces. Lastly we deal with the smoothing problem of a normal crossing complex surface X with at most double curves. We prove that we still have a family of smoothings of X in a weak sense even when X is not Kählerian or H^{1}(X,\mathcal{O}_{X})\neq 0 , in which cases the smoothability result of Friedman Fr is not applicable.
We give a differential-geometric construction of Calabi–Yau fourfolds by the ‘doubling’ method, which was introduced in Doi and Yotsutani (N Y J Math 20:1203–1235,
2014
) to construct Calabi–Yau ...threefolds. We also give examples of Calabi–Yau fourfolds from toric Fano fourfolds. Ingredients in our construction are admissible pairs, which were first dealt with by Kovalev (J Reine Angew Math 565:125–160,
2003
). Here in this paper an admissible pair
(
X
¯
,
D
)
consists of a compact Kähler manifold
X
¯
and a smooth anticanonical divisor
D
on
X
¯
. If two admissible pairs
(
X
¯
1
,
D
1
)
and
(
X
¯
2
,
D
2
)
with
dim
C
X
¯
i
=
4
satisfy the gluing condition, we can glue
X
¯
1
\
D
1
and
X
¯
2
\
D
2
together to obtain a compact Riemannian 8-manifold (
M
,
g
) whose holonomy group
Hol
(
g
)
is contained in
Spin
(
7
)
. Furthermore, if the
A
^
-genus of
M
equals 2, then
M
is a Calabi–Yau fourfold, i.e., a compact Ricci-flat Kähler fourfold with holonomy
SU
(
4
)
. In particular, if
(
X
¯
1
,
D
1
)
and
(
X
¯
2
,
D
2
)
are identical to an admissible pair
(
X
¯
,
D
)
, then the gluing condition holds automatically, so that we obtain a compact Riemannian 8-manifold
M
with holonomy contained in
Spin
(
7
)
. Moreover, we show that if the admissible pair is obtained from any of the toric Fano fourfolds, then the resulting manifold
M
is a Calabi–Yau fourfold by computing
A
^
(
M
)
=
2
.
We present a new method for effectively selecting objects which may be low-mass active black holes (BHs) at galaxy centers using high-cadence optical imaging data, and our first spectroscopic ...identification of an active 2.7 × 106 M⊙ BH at z = 0.164. This active BH was originally selected due to its rapid optical variability, from a few hours to a day, based on Subaru Hyper Suprime-Cam g-band imaging data taken with a 1 hr cadence. Broad and narrow Hα lines and many other emission ones are detected in our optical spectra taken with Subaru FOCAS, and the BH mass is measured via the broad Hα emission line width (1880 km s−1) and luminosity (4.2 × 1040 erg s−1) after careful correction to the atmospheric absorption around 7580–7720 Å. We measure the Eddington ratio and find it to be as low as 0.05, considerably smaller than those in a previous SDSS sample with similar BH mass and redshift, which indicates one of the special potentials of our Subaru survey. The g − r color and morphology of the extended component indicate that the host galaxy is a star-forming galaxy. We also show the effectiveness of our variability selection for low-mass active BHs.
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