163 research outputs found
Confirmation of dust scattering echo around MAXI J1421-613 by Swift observation
MAXI J1421-613 is an X-ray burster discovered by Monitor of All-sky X-ray
Image (MAXI) on 9 January 2014 and is considered to be a low-mass X-ray binary.
A previous study analyzing follow-up observation data obtained by Suzaku on 31
January to 3 February 2014 reported that an annular emission of ~3'-9' radius
was found around the transient source. The most plausible origin of the annular
emission is a dust scattering echo by the outburst of MAXI J1421-613. In this
paper, we confirm the annular emission by analyzing the data of the Swift
follow-up observation which was conducted by the photon counting mode on 18
January 2014. In a radial profile, we found an annular emission at ~2'.5-4'.5.
Its spectrum was well explained by an absorbed power law, and the photon index
was higher than that of MAXI J1421-613 itself by delta Gamma~2. The flux and
radius of the annular emission observed by Swift are explained by dust
scattering of the same outburst as is responsible for the annular emission
observed by Suzaku. Assuming that the dust layer causing the annular emission
found by Swift is located at the same position as the CO cloud in front of MAXI
J1421-613, the distance to the transient source was estimated to be ~3 kpc,
which is consistent with the value estimated by the previous study of Suzaku.Comment: 7 pages, 3 figures, accepted for publication in Advances in Space
Researc
Spectrum of Relativistic and Subrelativistic Cosmic Rays in the 100 pc Central Region
From the rate of hydrogen ionization and the gamma ray flux, we derived the
spectrum of relativistic and subrelativistic cosmic rays (CRs) nearby and
inside the molecular cloud Sgr B2 near the Galactic Center (GC). We studied two
cases of CR propagation in molecular clouds: free propagation and scattering of
particles by magnetic fluctuations excited by the neutral gas turbulence. We
showed that in the latter case CR propagation inside the cloud can be described
as diffusion with the coefficient cm s. For
the case of hydrogen ionization by subrelativistic protons, we showed that
their spectrum outside the cloud is quite hard with the spectral index
. The energy density of subrelativistic protons ( eV cm)
is one order of magnitude higher than that of relativistic CRs. These protons
generate the 6.4 keV emission from Sgr B2, which was about 30\% of the flux
observed by Suzaku in 2013. Future observations for the period after 2013 may
discover the background flux generated by subrelativistic CRs in Sgr B2.
Alternatively hydrogen ionization of the molecular gas in Sgr B2 may be caused
by high energy electrons. We showed that the spectrum of electron
bremsstrahlung is harder than the observed continuum from Sgr B2, and in
principle this X-ray component provided by electrons could be seen from the
INTEGRAL data as a stationary high energy excess above the observed spectrum
.Comment: 42 pages, 6 figures, accepted by Ap
Initial state of the recombining plasma in supernova remnant W 28
We investigate an SNR W28 with the Suzaku archive data and report the results
of spatial resolved analyses. We carry out spectral analysis using a
recombining plasma (RP) model with an element-dependent initial ionization
temperature, and obtain the ionization temperatures to be ~keV for Ne,
~keV for Mg, ~keV for Si, ~keV for S, ~keV
for Ar, ~keV for Ca, and ~keV for Fe in the RP-initial phase.
In addition to northeast regions where RP have been reported, we find that the
ionization temperature in the southeast and southwest regions show a similar
trend to the central region, in the RP-initial phase. Furthermore, the elapsed
time from the RP-initial phase to present is shorter, ~yr in the
central region and longer, -~yr in the outside regions. Our
results cannot be explained by simple scenarios of thermal conduction due to
molecular clouds or adiabatic cooling (rarefaction), and indicate that more
complex mechanism or other scenarios are required. Also, we estimate the ejecta
mass , which indicates a SNR derived a massive star.Comment: 11 pages, 5 figures. Published in PAS
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