43 research outputs found
X-ray Evolution of SN 1987A
The X-ray observations of SN 1987A over the previous 20 years have seen the
emergence of soft X-rays from the interaction of the explosion shock wave with
the ambient medium. This shock wave is now interacting strongly with the inner
ring and might have passed already the highest density regions. The emission
can be described by thermal models with two temperatures, with perhaps some but
little change over time. Relative to the elemental abundances prevailing in the
LMC the inner ring shows an overabundance of Si and S compared to the lighter
elements and Fe, which suggests that the ring consists of highly processed
matter dredged up in a binary merger event well before the explosion. The X-ray
lightcurves between 0.5--2 keV and 3--10 keV differ significantly in slope,
with the latter being much flatter but very similar to the radio light curve.Comment: 10 pages, 9 figures; review talk to appear in the AIP Proceedings of
the Conference " Supernova 1987A: 20 Years after - Supernovae and Gamma-Ray
Bursters" held in Aspen Co USA, Feb 19-23, 200
Grazing Incidence Reflection and Scattering of MeV Protons
Treating protons as de Broglie waves shows that up to a few MeV energies
protons experience total external reflection using the index of refraction
concept for the target earlier applied to electrons. Angular scattering
distributions can be explained by random surface scattering as known for
X-rays. Applied to the {\it{Chandra}} and {\it{XMM-Newton}} X-ray telescopes
the calculated reflection efficiencies can explain the observed degradation of
the X-ray CCDs for both missions. Some discussion about the possibility of
realizing imaging sub-MeV and MeV proton optics is presented.Comment: 7 pages, 3 figures, updated version of a paper accepted for
publication in the SPIE Conference Proceedings 6688, 200
RX-J0852−4622: THE NEAREST HISTORICAL SUPERNOVA REMNANT – AGAIN
RX-J0852−4622, a supernova remnant, is demonstrated to be closer than 500 pc, based on the measurements of the angular radius, the angular expansion rate and the TeV g-ray flux. This is a new method of limiting the distance to any supernova remnant with hadronic induced TeV g-ray flux. The progenitor star of RX-J0852−4622 probably exploded in its blue supergiant wind, like SN 1987A, preceeded by a red supergiant phase. A cool dense shell, expected around the outskirts of the red wind, my have been identified. The distance (200 pc) and age (680 yr) of the supernova remnant, originally proposed, are supported
Overabundance of Calcium in the young SNR RX J08524622: evidence of over-production of Ti
Recently, COMPTEL has detected -rays of 1157 keV from Ti in
the direction of the SNR RX J08524622 (Iyudin et al. 1998). Since Ti
is a product of explosive nucleosynthesis and its half lifetime \tau\sb{1/2}
is about 60 yrs, RX J08524622 must be a young supernova remnant and
radiation is dominated by the ejecta rather than by interstellar matter. We
have detected an X-ray emission line at keV which is thought to
come from highly ionized Ca. The emission line is so far only seen in the
north-west shell region of RX J08524622. The X-ray spectrum can be well
fitted with that of thin hot plasma of cosmic abundances except that of Ca,
which is overabundant by a factor of . Assuming that most of Ca is
Ca, which originates from Ti by radioactive decay, we estimate a
total Ca mass of about . Combining the amount of
Ca and the observed flux of the Ti -ray line, the age of
RX J08524622 is around 1000 yrs.Comment: 14 pages, 5figures, accepted for publication of PAS
Discovery of Non Thermal X-Rays from the Northwest Shell of the New SNR RX J1713.7-3946: The Second SN1006 ?
We report ASCA results of a featureless X-ray spectrum from RX J1713.7-3946,
a new shell-like SNR discovered with the ROSAT all sky survey. The northwest
part of RX J1713.7-3946 was in the field of the ASCA Galactic Plane Survey
Project and was found to exhibit a shell-like structure. The spectrum, however
shows neither line emission nor any signature of a thermal origin. Instead, a
power-law model with a photon index of 2.4-2.5 gives reasonable fit to the
spectrum, suggesting a non-thermal origin. Together with the similarity to
SN1006, we propose that RX J1713.7-3946 is the second example, after SN1006, of
a synchrotron X-ray radiation from a shell of SNRs. Since the synchrotron
X-rays suggest existence of extremely high energy charged particles in the SNR
shell, our discovery should have strong impact on the origin of the cosmic
X-rays.Comment: 4 pages, 3 postscript figure
Galactic SNR candidates in the ROSAT all-sky survey
Identified radio supernova remnants (SNRs) in the Galaxy comprise an
incomplete sample of the SNR population due to various selection effects. ROSAT
performed the first all-sky survey with an imaging X-ray telescope, and thus
provides another window for finding SNRs and compact objects that may reside
within them. Performing a search for extended X-ray sources in the ROSAT
all-sky survey database about 350 objects were identified as SNR candidates in
recent years (Busser 1998). Continuing this systematic search, we have
reanalysed the ROSAT all-sky survey (RASS) data of these candidates and
correlated the results with radio surveys like NVSS, ATNF, Molonglo and
Effelsberg. A further correlation with SIMBAD and NED was performed for
subsequent identification purposes. About 50 of the 350 candidates turned out
to be likely galaxies or clusters of galaxies. We found 14 RASS sources which
are very promising SNR candidates and are currently subject of further
follow-up studies. We will provide the details of the identification campaign
and present first results.Comment: 4 pages, 1 figures, appears in "Neutron Stars in Supernova Remnants"
(ASP Conference Proceedings), eds P. O. Slane and B. M. Gaensler, 2002, p.39
XMM-Newton observation of the eclipsing binary Algol
We present an {\sl XMM-Newton} observation of the eclipsing binary Algol
which contains an X-ray dark B8V primary and an X-ray bright K2IV secondary.
The observation covered the optical secondary eclipse and captured an X-ray
flare that was eclipsed by the B star. The EPIC and RGS spectra of Algol in its
quiescent state are described by a two-temperature plasma model. The cool
component has a temperature around 6.4 K while that of the hot
component ranges from 2 to 4.0 K. Coronal abundances of C, N, O,
Ne, Mg, Si and Fe were obtained for each component for both the quiescent and
the flare phases, with generally upper limits for S and Ar, and C, N, and O for
the hot component. F-tests show that the abundances need not to be different
between the cool and the hot component and between the quiescent and the flare
phase with the exception of Fe. Whereas the Fe abundance of the cool component
remains constant at 0.14, the hot component shows an Fe abundance of
0.28, which increases to 0.44 during the flare. This increase is
expected from the chromospheric evaporation model. The absorbing column density
of the quiescent emission is 2.5 cm, while that of
the flare-only emission is significantly lower and consistent with the column
density of the interstellar medium. This observation substantiates earlier
suggestions of the presence of X-ray absorbing material in the Algol system.Comment: 15 pages, 9 figures, Accpted by RA
Probing Elemental Abundances in SNR 1987A Using XMM-Newton
We report on the latest (2007 Jan) observations of supernova remnant (SNR)
1987A from the XMM-Newton mission. Since the 2003 May observations of Haberl et
al. (2006), 11 emission lines have experienced increases in flux by factors ~ 3
to 10, with the 775 eV line of O VIII showing the greatest increase; we have
observed 6 lines of Fe XVII and Fe XVIII previously unreported by XMM-Newton. A
two-shock model representing plasmas in non-equilibrium ionization is fitted to
the EPIC-pn spectra, yielding temperatures of ~ 0.4 and ~ 3 keV, as well as
elemental abundances for N, O, Ne, Mg, Si, S and Fe. We demonstrate that the
abundance ratio of N and O can be constrained to less than ~20% accuracy.
Within the same confidence interval, the same analysis suggests that the C+N+O
abundance varies from ~ 1.1 to 1.4 X 10^-4. Normalizing our obtained abundances
by the Large Magellanic Cloud (LMC) values of Hughes, Hayashi & Koyama (1998),
we find that O, Ne, Mg and Fe are under-abundant, while Si and S are
over-abundant, consistent with the findings of Aschenbach (2007). Such a result
has implications for both the single-star and binary accretion/merger models
for the progenitor of SNR 1987A. In the context of the binary merger scenario
proposed by Morris & Podsiadlowski (2006, 2007), material forming the inner,
equatorial ring was expelled after the merger, implying that either our derived
Fe abundance is inconsistent with typical LMC values or that iron is
under-abundant at the site of the progenitor star of SNR 1987A.Comment: 14 pages, 10 diagrams (2 omitted). Accepted by Ap