10,109 research outputs found
Investigation of Electrochemistry of High Energy Compounds in Organic Electrolytes. Bibliography on Propylene Carbonate, Gamma- Butyrolactone, and Related Subjects Supplement to Third Progress Report
Bibliography on electrochemistry of high energy compounds in organic electrolyte
Early and Late-Time Observations of SN 2008ha: Additional Constraints for the Progenitor and Explosion
We present a new maximum-light optical spectrum of the the extremely low
luminosity and exceptionally low energy Type Ia supernova (SN Ia) 2008ha,
obtained one week before the earliest published spectrum. Previous observations
of SN 2008ha were unable to distinguish between a massive star and white dwarf
origin for the SN. The new maximum-light spectrum, obtained one week before the
earliest previously published spectrum, unambiguously shows features
corresponding to intermediate mass elements, including silicon, sulfur, and
carbon. Although strong silicon features are seen in some core-collapse SNe,
sulfur features, which are a signature of carbon/oxygen burning, have always
been observed to be weak in such events. It is therefore likely that SN 2008ha
was the result of a thermonuclear explosion of a carbon-oxygen white dwarf.
Carbon features at maximum light show that unburned material is present to
significant depths in the SN ejecta, strengthening the case that SN 2008ha was
a failed deflagration. We also present late-time imaging and spectroscopy that
are consistent with this scenario.Comment: ApJL, accepted. 5 pages, 3 figure
Swift UVOT Grism Observations of Nearby Type Ia Supernovae - I. Observations and Data Reduction
Ultraviolet (UV) observations of Type Ia supernovae (SNe Ia) are useful tools
for understanding progenitor systems and explosion physics. In particular, UV
spectra of SNe Ia, which probe the outermost layers, are strongly affected by
the progenitor metallicity. In this work, we present 120 Neil Gehrels Swift
Observatory UV spectra of 39 nearby SNe Ia. This sample is the largest UV
(lambda < 2900 A) spectroscopic sample of SNe Ia to date, doubling the number
of UV spectra and tripling the number of SNe with UV spectra. The sample spans
nearly the full range of SN Ia light-curve shapes (delta m(B) ~ 0.6-1.8 mag).
The fast turnaround of Swift allows us to obtain UV spectra at very early
times, with 13 out of 39 SNe having their first spectra observed >~ 1 week
before peak brightness and the earliest epoch being 16.5 days before peak
brightness. The slitless design of the Swift UV grism complicates the data
reduction, which requires separating SN light from underlying host-galaxy light
and occasional overlapping stellar light. We present a new data-reduction
procedure to mitigate these issues, producing spectra that are significantly
improved over those of standard methods. For a subset of the spectra we have
nearly simultaneous Hubble Space Telescope UV spectra; the Swift spectra are
consistent with these comparison data.Comment: Accepted for publication in MNRA
An Examination of the Perceptions of Traditional and Nontraditional Student Engagement at a Community College in Southern Appalachia
Abstract is available to download
On the Progenitor and Supernova of the SN 2002cx-like Supernova 2008ge
We present observations of supernova (SN) 2008ge, which is spectroscopically
similar to the peculiar SN 2002cx, and its pre-explosion site that indicate
that its progenitor was probably a white dwarf. NGC 1527, the host galaxy of SN
2008ge, is an S0 galaxy with no evidence of star formation or massive stars.
Astrometrically matching late-time imaging of SN 2008ge to pre-explosion HST
imaging, we constrain the luminosity of the progenitor star. Since SN 2008ge
has no indication of hydrogen or helium in its spectrum, its progenitor must
have lost its outer layers before exploding, requiring that it be a white
dwarf, a Wolf-Rayet star, or a lower-mass star in a binary system. Observations
of the host galaxy show no signs of individual massive stars, star clusters, or
H II regions at the SN position or anywhere else, making a Wolf-Rayet
progenitor unlikely. Late-time spectroscopy of SN 2008ge show strong [Fe II]
lines with large velocity widths compared to other members of this class at
similar epochs. These previously unseen features indicate that a significant
amount of the SN ejecta is Fe (presumably the result of radioactive decay of
56Ni generated in the SN), further supporting a thermonuclear explosion.
Placing the observations of SN 2008ge in the context of observations of other
objects in the class of SN, we suggest that the progenitor was most likely a
white dwarf.Comment: 9 pages, 6 figures, accepted by A
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