212 research outputs found
Early phase observations of extremely luminous Type Ia Supernova 2009dc
We present early phase observations in optical and near-infrared wavelengths
for the extremely luminous Type Ia supernova (SN Ia) 2009dc. The decline rate
of the light curve is , which is one of the
slowest among SNe Ia. The peak -band absolute magnitude is mag even if the host extinction is mag. It reaches
mag for the host extinction of mag as
inferred from the observed Na {\sc i} D line absorption in the host. Our
-band photometry shows that the SN is one of the most luminous SNe Ia
also in near-infrared wavelengths. These results indicate that SN 2009dc
belongs to the most luminous class of SNe Ia, like SN 2003fg and SN 2006gz. We
estimate the ejected Ni mass of \Msun for no host
extinction case (or 1.6 0.4 M for the host extinction of
mag). The C {\sc ii} 6580 absorption line keeps visible
until a week after maximum, which diminished in SN 2006gz before its maximum
brightness. The line velocity of Si {\sc ii} 6355 is about 8000 km
s around the maximum, being considerably slower than that of SN 2006gz,
while comparable to that of SN 2003fg. The velocity of the C {\sc ii} line is
almost comparable to that of the Si {\sc ii}. The presence of the carbon line
suggests that thick unburned C+O layers remain after the explosion. SN 2009dc
is a plausible candidate of the super-Chandrasekhar mass SNe Ia
Collectivity of neutron-rich Ti isotopes
The structure of the neutron-rich nucleus 58Ti was investigated via proton inelastic scattering in inverse kinematics at a mean energy of 42.0 MeV/nucleon. By measuring the deexcitation γ rays, three transitions with the energies of 1046(11) keV, 1376(18) keV, and 1835(27) keV were identified. The angle-integrated cross section for the 1046-keV excitation, which corresponds to the decay from the first 2+ state, was determined to be 13(7) mb. The deformation length δp,p′ was extracted from the cross section to be 0.83−0.30+0.22 fm. The energy of the first 2+ state and the δp,p′ value are comparable to the ones of 56Ti, which indicates that the collectivity of the Ti isotopes does not increase significantly with neutron number until N=36. This fact indicates that 58Ti is outside of the region of the deformation known in the neutron-rich nuclei around N=40
The Hyper Suprime-Cam SSP Survey: Overview and Survey Design
Hyper Suprime-Cam (HSC) is a wide-field imaging camera on the prime focus of
the 8.2m Subaru telescope on the summit of Maunakea in Hawaii. A team of
scientists from Japan, Taiwan and Princeton University is using HSC to carry
out a 300-night multi-band imaging survey of the high-latitude sky. The survey
includes three layers: the Wide layer will cover 1400 deg in five broad
bands (), with a point-source depth of . The
Deep layer covers a total of 26~deg in four fields, going roughly a
magnitude fainter, while the UltraDeep layer goes almost a magnitude fainter
still in two pointings of HSC (a total of 3.5 deg). Here we describe the
instrument, the science goals of the survey, and the survey strategy and data
processing. This paper serves as an introduction to a special issue of the
Publications of the Astronomical Society of Japan, which includes a large
number of technical and scientific papers describing results from the early
phases of this survey.Comment: 14 pages, 7 figures, 5 tables. Corrected for a typo in the
coordinates of HSC-Wide spring equatorial field in Table
A galaxy populations study of a radio-selected protocluster at z~3.1
We present a population study of several types of galaxies within the
protocluster surrounding the radio galaxy MRC0316-257 at z~3.1. In addition to
the known population of Ly_alpha emitters (LAEs) and [OIII] emitters, we use
colour selection techniques to identify protocluster candidates that are Lyman
break galaxies (LBG) and Balmer break galaxies (BBGs). The radio galaxy field
contains an excess of LBG candidates, with a surface density 1.6\pm0.3 times
larger than found for comparable blank fields. This surface overdensity
corresponds to an LBG volume overdensity of ~8\pm4. The BBG photometric
redshift distribution peaks at the protocluster's redshift, but we detect no
significant surface overdensity of BBG. This is not surprising because a volume
overdensity similar to the LBGs would have resulted in a surface density of
~1.2 that found in the blank field. This could not have been detected in our
sample. Masses and star formation rates of the candidate protocluster galaxies
are determined using SED fitting. These properties are not significantly
different from those of field galaxies. The galaxies with the highest masses
and star formation rates are located near the radio galaxy, indicating that the
protocluster environment influences galaxy evolution at z~3. We conclude that
the protocluster around MRC0316-257 is still in the early stages of formation.Comment: 19 pages, 20 figures, accepted for publication in MNRA
"Dark" GRB 080325 in a Dusty Massive Galaxy at z ~ 2
We present optical and near infrared observations of GRB 080325 classified as
a "Dark GRB". Near-infrared observations with Subaru/MOIRCS provided a clear
detection of afterglow in Ks band, although no optical counterpart was
reported. The flux ratio of rest-wavelength optical to X-ray bands of the
afterglow indicates that the dust extinction along the line of sight to the
afterglow is Av = 2.7 - 10 mag. This large extinction is probably the major
reason for optical faintness of GRB 080325. The J - Ks color of the host
galaxy, (J - Ks = 1.3 in AB magnitude), is significantly redder than those for
typical GRB hosts previously identified. In addition to J and Ks bands, optical
images in B, Rc, i', and z' bands with Subaru/Suprime-Cam were obtained at
about one year after the burst, and a photometric redshift of the host is
estimated to be z_{photo} = 1.9. The host luminosity is comparable to L^{*} at
z \sim 2 in contrast to the sub-L^{*} property of typical GRB hosts at lower
redshifts. The best-fit stellar population synthesis model for the host shows
that a large dust extinction (Av = 0.8 mag) attributes to the red nature of the
host and that the host galaxy is massive (M_{*} = 7.0 \times 10^{10} Msun)
which is one of the most massive GRB hosts previously identified. By assuming
that the mass-metallicity relation for star-forming galaxies at z \sim 2 is
applicable for the GRB host, this large stellar mass suggests the high
metallicity environment around GRB 080325, consistent with inferred large
extinction.Comment: 22 pages, 10 figures, accepted for publication in The Astrophysical
Journa
Measurement and comparison of individual external doses of high-school students living in Japan, France, Poland and Belarus -- the "D-shuttle" project --
Twelve high schools in Japan (of which six are in Fukushima Prefecture), four
in France, eight in Poland and two in Belarus cooperated in the measurement and
comparison of individual external doses in 2014. In total 216 high-school
students and teachers participated in the study. Each participant wore an
electronic personal dosimeter "D-shuttle" for two weeks, and kept a journal of
his/her whereabouts and activities. The distributions of annual external doses
estimated for each region overlap with each other, demonstrating that the
personal external individual doses in locations where residence is currently
allowed in Fukushima Prefecture and in Belarus are well within the range of
estimated annual doses due to the background radiation level of other
regions/countries
An Improved Measurement of Mixing-induced CP Violation in the Neutral B Meson System
We present an improved measurement of the standard model CP violation
parameter sin2phi_1 (also known as sin2beta) based on a sample of 85 times 10^6
B Bbar pairs collected at the Upsilon(4S) resonance with the Belle detector at
the KEKB asymmetric-energy e+e- collider. One neutral B meson is reconstructed
in a J/psi K_S, psi(2S) K_S, chi_{c1} K_S, eta_c K_S, J/psi K^{*0}, or J/psi
K_L CP-eigenstate decay channel and the flavor of accompanying B meson is
identified from itsdecay products. From the asymmetry in the distribution of
the time intervals between the two B meson decay points, we obtain sin2phi_1 =
0.719 +/- 0.074(stat) +/- 0.035(syst). We also report measurements of CP
violation parameters for the related B^0 -> J/psi pi^0 decay mode and the
penguin-dominated processes B^0 -> eta' K_S, phi K_S and K^+K^- K_S.Comment: 11 pages, 4 figures, 4 tables, contributed to ICHEP200
Determination of |Vcb| using the semileptonic decay \bar{B}^0 --> D^{*+}e^-\bar{\nu}
We present a measurement of the Cabibbo-Kobayashi-Maskawa (CKM) matrix
element |Vcb| using a 10.2 fb^{-1} data sample recorded at the \Upsilon(4S)
resonance with the Belle detector at the KEKB asymmetric e^+e^- storage ring.
By extrapolating the differential decay width of the \bar{B}^0 -->
D^{*+}e^-\bar{\nu} decay to the kinematic limit at which the D^{*+} is at rest
with respect to the \bar{B}^0, we extract the product of |Vcb| with the
normalization of the decay form factor F(1), |Vcb |F(1)=
(3.54+/-0.19+/-0.18)x10^{-2}, where the first error is statistical and the
second is systematic. A value of |Vcb| = (3.88+/-0.21+/-0.20+/-0.19)x10^{-2} is
obtained using a theoretical calculation of F(1), where the third error is due
to the theoretical uncertainty in the value of F(1). The branching fraction
B(\bar{B}^0 --> D^{*+}e^-\bar{\nu}) is measured to be
(4.59+/-0.23+/-0.40)x10^{-2}.Comment: 20 pages, 6 figures, elsart.cls, submitted to PL
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