1,839 research outputs found
High-Resolution Measurements of Intersystem Bands of Carbon Monoxide toward X Persei
In an echelle spectrum of X Per acquired with the Space Telescope Imaging
Spectrograph we have identified individual rotational lines of 11
triplet-singlet (intersystem) absorption bands of ^12CO. Four bands provide
first detections for interstellar clouds. From a comparison with the zeta Oph
sight line we find that X Per is obscured by a higher 12CO column density of
1.4 x 10^16 cm-2. Together with the high spectral resolution of 1.3 km s-1,
this allows (i) an improved measurement of previously published f-values for
seven bands, and (ii) an extraction of the first astrophysical oscillator
strengths for d-X (8-0), (9-0), and (10-0), as well as for e-X (12-0). The
^13CO d-X (12-0) band, previously suspected to exist toward zeta Oph, is now
readily resolved and modeled. Our derived intersystem f-values for ^12CO
include a few mild (leq 34%) disagreements with recent predictions from a
perturbation analysis calculated for the interstellar excitation temperature.
Overall, the comparison confirms the superiority of employing multiple singlet
levels in the calculations of mixing coefficients over previous single-level
predictions.Comment: 11 pages (incl. 1 figure). Accepted by ApJ Letter
WISeREP - An Interactive Supernova Data Repository
We have entered an era of massive data sets in astronomy. In particular, the
number of supernova (SN) discoveries and classifications has substantially
increased over the years from few tens to thousands per year. It is no longer
the case that observations of a few prototypical events encapsulate most
spectroscopic information about SNe, motivating the development of modern tools
to collect, archive, organize and distribute spectra in general, and SN spectra
in particular. For this reason we have developed the Weizmann Interactive
Supernova data REPository - WISeREP - an SQL-based database (DB) with an
interactive web-based graphical interface. The system serves as an archive of
high quality SN spectra, including both historical (legacy) data as well as
data that is accumulated by ongoing modern programs. The archive provides
information about objects, their spectra, and related meta-data. Utilizing
interactive plots, we provide a graphical interface to visualize data, perform
line identification of the major relevant species, determine object redshifts,
classify SNe and measure expansion velocities. Guest users may view and
download spectra or other data that have been placed in the public domain.
Registered users may also view and download data that are proprietary to
specific programs with which they are associated. The DB currently holds >8000
spectra, of which >5000 are public; the latter include published spectra from
the Palomar Transient Factory, all of the SUSPECT archive, the
Caltech-Core-Collapse Program, the CfA SN spectra archive and published spectra
from the UC Berkeley SNDB repository. It offers an efficient and convenient way
to archive data and share it with colleagues, and we expect that data stored in
this way will be easy to access, increasing its visibility, usefulness and
scientific impact.Comment: To be published in PASP. WISeREP:
http://www.weizmann.ac.il/astrophysics/wiserep
Entangled coherent states by mixing squeezed vacuum and coherent light
Entangled coherent states are shown to emerge, with high fidelity, when
mixing coherent and squeezed vacuum states of light on a beam-splitter. These
maximally entangled states, where photons bunch at the exit of a beamsplitter,
are measured experimentally by Fock-state projections. Entanglement is examined
theoretically using a Bell-type nonlocality test and compared with ideal
entangled coherent states. We experimentally show nearly perfect similarity
with entangled coherent states for an optimal ratio of coherent and squeezed
vacuum light. In our scheme, entangled coherent states are generated
deterministically with small amplitudes, which could be beneficial, for
example, in deterministic distribution of entanglement over long distances.Comment: 6 pages, 6 figures, comments are welcom
The Effective Tax Rate of the Largest US and EU Multinationals
The United States has the second highest statutory corporate tax rate in the Organization for Economic Co-Operation and Development (OECD) (after Japan).1 This has not always been the case. After the Tax Reform Act of 1986 lowered the U.S. rate from 46% to 34%,2 the United States had one of the lowest statutory corporate tax rates in the OECD.3 In the past twenty-five years, however, the U.S. rate has remained essentially unchanged (it was raised to 35% in 1993),4 while most other OECD countries reduced their statutory rate so that the OECD average statutory corporate tax rate is 25.1%
The Effective Tax Rate of the Largest US and EU Multinationals
This paper compares the effective tax rates of the 100 largest US multinationals to the 100 largest EU multinationals for the period 2001-2010, based on financial disclosures. The paper finds that despite the higher US statutory rate the effective tax rates are comparable and that EU multinationals tend to have a higher effective tax rate. The likely explanation is that EU corporate taxes have a broader base. The paper concludes that current US tax law does not subject US based multinationals to a competitive disadvantage against their EU based competitors
FUSE Measurements of Interstellar Fluorine
The source of fluorine is not well understood, although core-collapse
supernovae, Wolf-Rayet stars, and asymptotic giant branch stars have been
suggested. A search for evidence of the nu process during Type II supernovae is
presented. Absorption from interstellar F I is seen in spectra of HD 208440 and
HD 209339A acquired with the Far Ultraviolet Spectroscopic Explorer. In order
to extract the column density for F I from the line at 954 A, absorption from
H2 has to be modeled and then removed. Our analysis indicates that for H2
column densities less than about 3 x 10^20 cm^-2, the amount of F I can be
determined from lambda 954. For these two sight lines, there is no clear
indication for enhanced F abundances resulting from the nu process in a region
shaped by past supernovae.Comment: 17 pages, 4 figures, accepted for publication in Ap
Localization of Multi-Dimensional Wigner Distributions
A well known result of P. Flandrin states that a Gaussian uniquely maximizes
the integral of the Wigner distribution over every centered disc in the phase
plane. While there is no difficulty in generalizing this result to
higher-dimensional poly-discs, the generalization to balls is less obvious. In
this note we provide such a generalization.Comment: Minor corrections, to appear in the Journal of Mathematical Physic
A pre-outburst signal in the long-term optical light curve of the recurrent nova RS Ophiuchi
Recurrent novae are binary stars in which a white dwarf accretes matter from a less evolved companion, either a red giant or a main-sequence star. They have dramatic optical brightenings of around 5–6 mag in V in less than a day, several times a century. These occur at variable and unpredictable intervals, and are followed by an optical decline over several weeks and activity from the X-ray to the radio. The unpredictability of recurrent novae and related stellar types can hamper systematic study of their outbursts. Here we analyse the long-term light curve of RS Ophiuchi, a recurrent nova with six confirmed outbursts, most recently in 2006 February. We confirm the previously suspected 1945 outburst, largely obscured in a seasonal gap. We also find a signal via wavelet analysis that can be used to predict an incipient outburst up to a few hundred days before hand. This has never before been possible. In addition, this may suggest that the preferred thermonuclear runaway mechanism for the outbursts will have to be modified, as no pre-outburst signal is anticipated in that case. If our result indeed points to gaps in our understanding of how outbursts are driven, we will need to study such objects carefully to determine if the white dwarf is growing in mass, an essential factor if these systems are to become Type Ia supernovae. Determining the likelihood of recurrent novae being an important source population will have implications for stellar and galaxy evolution
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