4,860 research outputs found
Ejecta in SN 1006: The knotty issue
The 1988 IUE SWP observations of a faint sdOB star situated behind the remnant of the supernova of AD 1006 are presented. These spectra along with IUE spectra of the star taken between 1982 and 1986 provide a detailed look at the elemental composition and dynamical properties of the SN 1006 remnant. Over the 6 years there were no significant changes in the absorption features associated with the remnant at 1281, 1330, or 1420 A. While the lack of variability in these absorption lines makes it impossible to decide whether the ejecta is distributed smoothly or in knots, it is clear that the 1281 A feature is a blend, requiring either S II absorption redshifted at 6000 km/sec plus Si II 1260 at 5200 km/sec, or else 2 individual Si absorbing regions
The 2D Distribution of Iron Rich Ejecta in the Remnant of SN 1885 in M31
We present Hubble Space Telescope (HST) ultraviolet Fe I and Fe II images of
the remnant of Supernova 1885 (S And) which is observed in absorption against
the bulge of the Andromeda galaxy, M31. We compare these Fe I and Fe II
absorption line images to previous HST absorption images of S And, of which the
highest quality and theoretically cleanest is Ca II H & K. Because the remnant
is still in free expansion, these images provide a 2D look at the distribution
of iron synthesized in this probable Type Ia explosion, thus providing insights
and constraints for theoretical SN Ia models. The Fe I images show extended
absorption offset to the east from the remnant's center as defined by Ca II
images and is likely an ionization effect due to self-shielding. More
significant is the remnant's apparent Fe II distribution which consists of four
streams or plumes of Fe-rich material seen in absorption that extend from
remnant center out to about 10,000 km/s. This is in contrast to the remnant's
Ca II absorption, which is concentrated in a clumpy, roughly spherical shell at
1000 to 5000 km/s but which extends out to 12,500 km/s. The observed
distributions of Ca and Fe rich ejecta in the SN 1885 remnant are consistent
with delayed detonation white dwarf models. The largely spherical symmetry of
the Ca-rich layer argues against a highly anisotropic explosion as might result
from a violent merger of two white dwarfs.Comment: 14 pages, 8 figures, and 1 table; revised to match ApJ published
versio
An Ultraviolet Fe II Image of SN 1885 in M31
Ultraviolet imaging of the remnant of Supernova 1885 in M31 with the Hubble
Space Telescope using the F255W filter on the WFPC2 reveals a dark spot of Fe
II absorption at the remnant's known position in the bulge of M31. The diameter
of the absorbing spot is 0"55 +- 0"15, slightly smaller than, but consistent
with, the 0"70 +- 0"05 diameter measured in the higher quality WFPC2 Ca II
absorption image previously reported by us. The measured ratio of flux inside
to outside SNR 1885 in the Fe II image is 0.24 +- 0.17, consistent with the
ratio 0.33 +- 0.04 expected on the basis of a model fit to the previously
obtained near-UV FOS spectrum. The observed depth of Fe II absorption suggests
that Fe II is fully saturated, with an iron mass in the range M_Fe = 0.1-1.0
Msun. Besides Fe, ion species Mg I, Mg II, and Mn I probably make some
contribution to the absorption from the SN 1885 remnant in the F255W image.Comment: 7 pages, including 2 embedded PostScript figures, emulateapj.sty,
submitted to Ap
A high resolution UV absorption spectrum of supernova ejecta in SN1006
We report a high resolution, far-ultraviolet, STIS E140M spectrum of the
strong, broad Si II, III, and IV features produced by the ejecta of SN1006 seen
in absorption against the background Schweizer-Middleditch star. The spectrum
confirms the extreme sharpness of the red edge of the redshifted Si II 1260 A
feature, supporting the idea that this edge represents the location of the
reverse shock moving into the freely expanding ejecta. The expansion velocity
of ejecta at the reverse shock is measured to be 7026 +-3(relative)
+-10(absolute) km/s. If the shock model is correct, then the expansion velocity
should be decreasing at the observable rate of 2.7 +-0.1 km/s per year. The
pre-shock velocity, post-shock velocity, and post-shock velocity dispersion are
all measured from the Si II 1260 A feature, and consistency of these velocities
with the shock jump conditions implies that there is little or no electron
heating in this fast (2680 km/s) Si-rich shock.Comment: 9 pages, 5 embedded postscript fig
HST Images and Spectra of the Remnant of SN 1885 in M31
Near UV HST images of the remnant of SN 1885 (S And) in M31 show a 0"70 +-
0"05 diameter absorption disk silhouetted against M31's central bulge, at SN
1885's historically reported position. The disk's size corresponds to a linear
diameter of 2.5 +- 0.4 pc at a distance of 725 +- 70 kpc, implying an average
expansion velocity of 11000 +- 2000 km/s over 110 years. Low-dispersion FOS
spectra over 3200-4800 A; reveal that the absorption arises principally from Ca
II H & K (equivalent width ~215 A;) with weaker absorption features of Ca I
4227 A; and Fe I 3720 A;. The flux at Ca II line center indicates a foreground
starlight fraction of 0.21, which places SNR 1885 some 64 pc to the near side
of the midpoint of the M31 bulge, comparable to its projected 55 pc distance
from the nucleus. The absorption line profiles suggest an approximately
spherically symmetric, bell-shaped density distribution of supernova ejecta
freely expanding at up to 13100 +- 1500 km/s. We estimate Ca I, Ca II, and Fe I
masses of 2.9(+2.4,-0.6) x 10^-4 M_o, 0.005(+0.016,-0.002) M_o, and
0.013(+0.010,-0.005) M_o respectively. If the ionization state of iron is
similar to the observed ionization state of calcium, M_CaII/M_CaI = 16(+42,-5),
then the mass of Fe II is 0.21(+0.74,-0.08) M_o, consistent with that expected
for either normal or subluminous SN Ia.Comment: 8 pages, including 4 embedded EPS figures, emulateapj.sty style file.
Color image at http://casa.colorado.edu/~mcl/sand.shtml . Submitted to Ap
Arctic–CHAMP: A program to study Arctic hydrology and its role in global change
The Arctic constitutes a unique and important environment that is central to the dynamics and evolution of the Earth system. The Arctic water cycle, which controls countless physical, chemical, and biotic processes, is also unique and important. These processes, in turn, regulate the climate, habitat, and natural resources that are of great importance to both native and industrial societies. Comprehensive understanding of water cycling across the Arctic and its linkage to global biogeophysical dynamics is a scientific as well as strategic policy imperative
Arctic–CHAMP: A program to study Arctic hydrology and its role in global change
The Arctic constitutes a unique and important environment that is central to the dynamics and evolution of the Earth system. The Arctic water cycle, which controls countless physical, chemical, and biotic processes, is also unique and important. These processes, in turn, regulate the climate, habitat, and natural resources that are of great importance to both native and industrial societies. Comprehensive understanding of water cycling across the Arctic and its linkage to global biogeophysical dynamics is a scientific as well as strategic policy imperative
Chemical and Physical Properties of Tumor-Affected Sitka Spruce
The chemical composition, fiber properties, and pulpability of a Sitka spruce (Picea sitchensis) massive trunk and root tumor were compared with normal second-growth wood. In general appearance the tumored tissue looked like normal wood in that it had annual rings and definite sapwood and heartwood zones. However, the trunk tumor showed no visible evidence of compression wood, whereas the trunk of the affected tree above and below the tumor contained about 30% compression wood. The tumor tracheids were short, curved, and twisted; and numerous traumatic resin canals were present. The wood rays and bark showed no apparent abnormalities. Paper prepared from kraft pulp tumor wood was lower in burst, tear, tensile, and opacity, and higher in fold and shrinkage, density and air resistance compared to pulp from the second-growth control. Chemical analysis indicated that the tumor-affected tree had a higher hemicellulose content, primarily as galactan-containing polymers, than the second-growth control. The factor causing the tumor growth was not ascertained in this study
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