1,038 research outputs found
Notes on Bonds: Illiquidity Feedback During the Financial Crisis
This paper traces the evolution of extreme illiquidity discounts among Treasury securities during the financial crisis; bonds fell more than six percent below more-liquid but otherwise identical notes. Using high-resolution data on market quality and trader identities and characteristics, we find that the discounts amplify through feedback loops, where cheaper, less-liquid securities flow to investors with longer horizons, thereby increasing their illiquidity and thus their appeal to these investors. The effect of the widened liquidity gap on transactions costs is further amplified by a surge in the price liquidity providers charged for access to their balance sheets in the crisis
Discovery of Non-radial pulsations in PQ Andromedae
We have detected pulsations in time-series photometry of the WZ Sge dwarf
nova PQ And. The strongest peak in the power spectrum occurs at a period of
10.5 minutes. Similar periods have been observed in other WZ Sge systems and
are attributed to ZZ Ceti type non-radial pulsations. There is no indication in
the photometry of an approximately 1.7 hour orbital period as reported in
previous spectroscopic observations.Comment: 7 pages, 5 figure
Abundance analysis of the slow nova PW Vulpeculae 1984
We determine the elemental abundances for the ejecta of the slow nova PW Vul
1984. Our technique uses a minimization of the emission line fits of a
photoionization model to available ultraviolet, optical and infrared spectra.
We find the following abundances (by number) with respect to solar: He/H = 1.0
0.4, C/H = 7.0 , N/H = 85 and O/H = 6
. In addition, there is weak evidence for solar Ne and Mg and twice
solar Fe. Previous studies (Saizar et al. 1991 and Andre\"{a} et al. 1991,
1994) of PW Vul have yielded considerable differences in their derived
elemental abundances for the ejecta. Our abundances fall in between the
previous studies. To explain the discrepant abundances, we analyze in detail
the data and methods used to obtain the previous results. The abundances of
Saizar et al. (1991) are significantly smaller then our values because of the
lower electron temperature used by Saizar et al. in deriving elemental
abundances from ion abundances. Andre\"{a} et al. (1991) used an ionization
correction method to obtain their abundances and verified their results with a
photoionization model (Andre\"{a} et al. 1994). Our analysis of their data
shows that the absolute fluxes of the optical emission lines used by Andre\"{a}
are underestimated by 15% leading to a factor of 2 increase in their derived
abundances. We also find the photoionization model used by Andre\"{a} et al.
(1994) predicts 2 times more carbon than the photoionization code we used even
when fitting the same data with similar model parameters.Comment: 9 pages, figures not included, full text with figures available at
ftp://calvin.physast.uga.edu/pub/preprints/PW-Vul.ps.gz, MNRAS, in pres
Elemental Abundances in the Ejecta of Old Classical Novae from Late-Epoch Spitzer Spectra
We present Spitzer Space Telescope mid-infrared IRS spectra, supplemented by
ground-based optical observations, of the classical novae V1974 Cyg, V382 Vel,
and V1494 Aql more than 11, 8, and 4 years after outburst respectively. The
spectra are dominated by forbidden emission from neon and oxygen, though in
some cases, there are weak signatures of magnesium, sulfur, and argon. We
investigate the geometry and distribution of the late time ejecta by
examination of the emission line profiles. Using nebular analysis in the low
density regime, we estimate lower limits on the abundances in these novae. In
V1974 Cyg and V382 Vel, our observations confirm the abundance estimates
presented by other authors and support the claims that these eruptions occurred
on ONe white dwarfs. We report the first detection of neon emission in V1494
Aql and show that the system most likely contains a CO white dwarf.Comment: 22 pages, 12 figure
Pan-chromatic observations of the remarkable nova LMC 2012
We present the results of an intensive multiwavelength campaign on nova LMC
2012. This nova evolved very rapidly in all observed wavelengths. The time to
fall two magnitudes in the V band was only 2 days. In X-rays the super soft
phase began 135 days after discovery and ended around day 50 after
discovery. During the super soft phase, the \Swift/XRT and \Chandra\ spectra
were consistent with the underlying white dwarf being very hot, 1 MK,
and luminous, 10 erg s. The UV, optical, and near-IR
photometry showed a periodic variation after the initial and rapid fading had
ended. Timing analysis revealed a consistent 19.240.03 hr period in all
UV, optical, and near-IR bands with amplitudes of 0.3 magnitudes which
we associate with the orbital period of the central binary. No periods were
detected in the corresponding X-ray data sets. A moderately high inclination
system, = 6010^{\arcdeg}, was inferred from the early optical
emission lines. The {\it HST}/STIS UV spectra were highly unusual with only the
\ion{N}{5} (1240\AA) line present and superposed on a blue continuum. The lack
of emission lines and the observed UV and optical continua from four epochs can
be fit with a low mass ejection event, 10 M, from a hot
and massive white dwarf near the Chandrasekhar limit. The white dwarf, in turn,
significantly illuminated its subgiant companion which provided the bulk of the
observed UV/optical continuum emission at the later dates. The inferred extreme
white dwarf characteristics and low mass ejection event favor nova LMC 2012
being a recurrent nova of the U Sco subclass.Comment: 18 figures, 6 tables (one online only containing all the photometry
Role of Predicted Metalloprotease Motif of Jab1/Csn5 in Cleavage of Nedd8 from Cul1
COP9 signalosome (CSN) cleaves the ubiquitin-like protein Nedd8 from the Cul1 subunit of SCF ubiquitin ligases. The Jab1/MPN domain metalloenzyme (JAMM) motif in the Jab1/Csn5 subunit was found to underlie CSN's Nedd8 isopeptidase activity. JAMM is found in proteins from archaea, bacteria, and eukaryotes, including the Rpn11 subunit of the 26S proteasome. Metal chelators and point mutations within JAMM abolished CSN-dependent cleavage of Nedd8 from Cul1, yet had little effect on CSN complex assembly. Optimal SCF activity in yeast and both viability and proper photoreceptor cell (R cell) development in Drosophila melanogaster required an intact Csn5 JAMM domain. We propose that JAMM isopeptidases play important roles in a variety of physiological pathways
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