43 research outputs found
Search for Sc-K line emission from RX J0852.0--4622 Supernova remnant with Suzaku
We searched for evidence of line emission around 4keV from the northwestern
rim of the supernova remnant RX J0852.0-4622 using Suzaku XIS data. Several
papers have reported the detection of an emission line around 4.1keV from this
region of the sky. This line would arise from K-band fluorescence by Sc, the
immediate decay product of 44Ti. We performed spectral analysis for the entire
portion of the NW rim of the remnant within the XIS field of view, as well as
various regions corresponding to regions of published claims of line emission.
We found no line emission around 4.1keV anywhere, and are able to set a
restrictive upper limit to the X-ray flux: 1.1x10^-6 s^-1 cm^-2 for the entire
field. For every region, our flux upper limit falls below that of the
previously claimed detection. Therefore, we conclude that, to date, no definite
X-ray line feature from Sc-K emission has been detected in the NW rim of RX
J0852.0-4622. Our negative-detection supports the recent claim that RX
J0852-4622 is neither young (1700--4000 yr) nor nearby(~750 pc).Comment: Published in PAS
Expansion Velocity of Ejecta in Tycho's Supernova Remnant Measured by Doppler Broadened X-ray Line Emission
We show that the expansion of ejecta in Tycho's supernova remnant (SNR) is
consistent with a spherically symmetric shell, based on Suzaku measurements of
the Doppler broadened X-ray emission lines. All the strong K_alpha line
emission show broader widths at the center than at the rim, while the centroid
energies are constant across the remnant (except for Ca). This is the pattern
expected for Doppler broadening due to expansion of the SNR ejecta in a
spherical shell. To determine the expansion velocities of the ejecta, we
applied a model for each emission line feature having two Gaussian components
separately representing red- and blue-shifted gas, and inferred the Doppler
velocity difference between these two components directly from the fitted
centroid energy difference. Taking into account the effect of projecting a
three-dimensional shell to the plane of the detector, we derived average
spherical expansion velocities independently for the K_alpha emission of Si, S,
Ar, and Fe, and K_beta of Si. We found that the expansion velocities of Si, S,
and Ar ejecta of 4700+/-100 km/s are distinctly higher than that obtained from
Fe K_alpha emission, 4000+/-300 km/s, which is consistent with segregation of
the Fe in the inner ejecta. Combining the observed ejecta velocities with the
ejecta proper-motion measurements by Chandra, we derived a distance to the
Tycho's SNR of 4+/-1 kpc.Comment: Accepted to Apj, 25 pages, 7 figures, 5 table
Measurements of the charge ratio and polarization of cosmic-ray muons with the Super-Kamiokande detector
We present the results of the charge ratio (R) and polarization (Pμ0) measurements using the decay electron events collected from 2008 September to 2022 June by the Super-Kamiokande detector. Because of its underground location and long operation, we performed high precision measurements by accumulating cosmic-ray muons. We measured the muon charge ratio to be R=1.32±0.02 (stat.+syst.) at EμcosθZenith=0.7+0.3−0.2 TeV, where Eμ is the muon energy and θZenith is the zenith angle of incoming cosmic-ray muons. This result is consistent with the Honda flux model while this suggests a tension with the πK model of 1.9σ. We also measured the muon polarization at the production location to be Pμ0=0.52±0.02 (stat.+syst.) at the muon momentum of 0.9+0.6−0.1 TeV/c at the surface of the mountain; this also suggests a tension with the Honda flux model of 1.5σ. This is the most precise measurement ever to experimentally determine the cosmic-ray muon polarization near 1 TeV/c. These measurement results are useful to improve the atmospheric neutrino simulations
Gamma-ray Diagnostics of r-process Nucleosynthesis in the Remnants of Galactic Binary Neutron-Star Mergers
We perform a full nuclear-network numerical calculation of the -process
nuclei in binary neutron-star mergers (NSMs), with the aim of estimating
-ray emissions from the remnants of Galactic NSMs up to years
old. The nucleosynthesis calculation of 4,070 nuclei is adopted to provide the
elemental composition ratios of nuclei with an electron fraction
between 0.10 and 0.45 . The decay processes of 3,237 unstable nuclei are
simulated to extract the -ray spectra. As a result, the NSMs have
different spectral color in -ray band from various other astronomical
objects at less than years old. In addition, we propose a new
line-diagnostic method for that uses the line ratios of either
Ba/K or Am/Co, which become larger
than unity for young and old -process sites, respectively, with a low
environment. From an estimation of the distance limit for
-ray observations as a function of the age, the high sensitivity in the
sub-MeV band, at approximately photons s cm or
erg s cm, is required to cover all the NSM remnants in
our Galaxy if we assume that the population of NSMs by
\citet{2019ApJ...880...23W}. A -ray survey with sensitivities of
-- photons s cm or -- erg
s cm in the 70--4000 keV band is expected to find emissions from
at least one NSM remnant under the assumption of NSM rate of 30 Myr. The
feasibility of -ray missions to observe Galactic NSMs are also studied.Comment: 17 pages in double column, 14 figures, 1 table, Accepted for
publication in Ap