60 research outputs found
K Corrections For Type Ia Supernovae and a Test for Spatial Variation of the Hubble Constant
Cross-filter K corrections for a sample of "normal" Type Ia supernovae (SNe)
have been calculated for a range of epochs. With appropriate filter choices,
the combined statistical and systematic K correction dispersion of the full
sample lies within 0.05 mag for redshifts z<0.7. This narrow dispersion of the
calculated K correction allows the Type Ia to be used as a cosmological probe.
We use the K corrections with observations of seven SNe at redshifts 0.3 < z
<0.5 to bound the possible difference between the locally measured Hubble
constant (H_L) and the true cosmological Hubble constant (H_0).Comment: 6 pages, 3 Postscript figures, uuencoded uses crckapb.sty and
psfig.sty. To appear in Thermonuclear Supernovae (NATO ASI), eds. R. Canal,
P. Ruiz-LaPuente, and J. Isern. Postscript version is also available at
http://www-supernova.lbl.gov
Implications For The Hubble Constant from the First Seven Supernovae at z >= 0.35
The Supernova Cosmology Project has discovered over twenty-eight supernovae
(SNe) at 0.35 <z < 0.65 in an ongoing program that uses Type Ia SNe as
high-redshift distance indicators. Here we present measurements of the ratio
between the locally observed and global Hubble constants, H_0^L/H_0^G, based on
the first 7 SNe of this high-redshift data set compared with 18 SNe at z <= 0.1
from the Calan/Tololo survey. If Omega_M <= 1, then light-curve-width corrected
SN magnitudes yield H_0^L/H_0^G < 1.10 (95% confidence level) in both a
Lambda=0 and a flat universe. The analysis using the SNe Ia as standard candles
without a light-curve-width correction yields similar results. These results
rule out the hypothesis that the discrepant ages of the Universe derived from
globular clusters and recent measurements of the Hubble constant are
attributable to a locally underdense bubble. Using the
Cepheid-distance-calibrated absolute magnitudes for SNe Ia of Sandage (1996},
we can also measure the global Hubble constant, H_0^G. If Omega_M >= 0.2, we
find that H_0^G < 70 km/s/Mpc in a Lambda=0 universe and H_0^G < 78 km/s/Mpc in
a flat universe, correcting the distant and local SN apparent magnitudes for
light curve width. Lower results for H_0^G are obtained if the magnitudes are
not width corrected.Comment: 13 pages, 2 Postscript figures. Preprint also available at
http://www-supernova.lbl.gov . To appear in ApJ Letter
The Type Ia Supernova Rate at z ~ 0.4
We present the first measurement of the rate of Type Ia supernovae at high
redshift. The result is derived using a large subset of data from the Supernova
Cosmology Project as described in more detail at this meeting by Perlmutter et
al. (1996). We present our methods for estimating the numbers of galaxies and
the number of solar luminosities to which the survey is sensitive, the
supernova detection efficiency and hence the control time. We derive a
rest-frame Type Ia supernova rate at z~0.4 of 0.82^+0.54_-0.37 ^+0.42_-0.32 h^2
SNu where the first uncertainty is statistical and the second includes
systematic effects.Comment: 9 pages, 3 Postscript figures, uuencoded uses crckapb.sty and
psfig.sty. To appear in Thermonuclear Supernovae (NATO ASI), eds. R. Canal,
P. Ruiz-LaPuente, and J. Isern. Postscript version is also available at
http://www-supernova.lbl.gov
The Type Ia Supernova Rate at z
We present the first measurement of the rate of Type Ia supernovae at high
redshift. The result is derived using a large subset of data from the Supernova
Cosmology Project. Three supernovae were discovered in a surveyed area of 1.7
square degrees. The survey spanned a week baseline and used images
with limiting magnitude of . We present our methods for
estimating the numbers of galaxies and the number of solar luminosities to
which the survey is sensitive, and the supernova detection efficiency which is
used to determine the control time, the effective time for which the survey is
sensitive to a Type Ia event. We derive a rest-frame Type Ia supernova rate at
of SNu (1 SNu
= 1 SN per century per \Lbsun), where the first uncertainty is
statistical and the second includes systematic effects. For the purposes of
observers, we also determine the rate of SNe, per sky area surveyed, to be SNe\ for SN magnitudes in
the range .Comment: 33 pages, To be published in December 10, 1996 issue of ApJ Vol 47
Scheduled Discoveries of 7+ High-Redshift Supernovae: First Cosmology Results and Bounds on q_0
Our search for high-redshift Type Ia supernovae discovered, in its first
years, a sample of seven supernovae. Using a "batch" search strategy, almost
all were discovered before maximum light and were observed over the peak of
their light curves. The spectra and light curves indicate that almost all were
Type Ia supernovae at redshifts z = 0.35 -- 0.5. These high-redshift supernovae
can provide a distance indicator and "standard clock" to study the cosmological
parameters q_0, Lambda, Omega_0, and H_0. This presentation and the following
presentations of Kim et al. (1996), Goldhaber et al. (1996), and Pain et al.
(1996) will discuss observation strategies and rates, analysis and calibration
issues, the sources of measurement uncertainty, and the cosmological
implications, including bounds on q_0, of these first high-redshift supernovae
from our ongoing search.Comment: 15 pages, 6 Postscript figures, uuencoded uses crckapb.sty and
psfig.sty. To appear in Thermonuclear Supernovae (NATO ASI), eds. R. Canal,
P. Ruiz-LaPuente, and J. Isern. Postscript version is also available at
http://www-supernova.lbl.gov
A supernova at z = 0.458 and implications for measuring the cosmological deceleration
We have begun a program to discover high-redshift supernovae (z \approx 0.25--0.5), and study them with follow-up photometry and spectroscopy. We report here our first discovery, a supernova at z = 0.458. The photometry for this supernova closely matches the lightcurve calculated for this redshift from the template of well-observed nearby Type Ia supernovae. We discuss the measurement of the deceleration parameter q_0 using such high-redshift supernovae, and give the best fit value assuming this one supernova is a normal, unextincted Type Ia. We describe the main sources of error in such a measurement of q_0, and ways to reduce these errors
<i>Gaia</i> Data Release 1. Summary of the astrometric, photometric, and survey properties
Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7.
Aims. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release.
Methods. The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue.
Results. Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the HIPPARCOS and Tycho-2 catalogues – a realisation of the Tycho-Gaia Astrometric Solution (TGAS) – and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of ∼3000 Cepheid and RR-Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr−1 for the proper motions. A systematic component of ∼0.3 mas should be added to the parallax uncertainties. For the subset of ∼94 000 HIPPARCOS stars in the primary data set, the proper motions are much more precise at about 0.06 mas yr−1. For the secondary astrometric data set, the typical uncertainty of the positions is ∼10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to ∼0.03 mag over the magnitude range 5 to 20.7.
Conclusions. Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data
Shared and Distinct Genomics of Chronic Thromboembolic Pulmonary Hypertension and Pulmonary Embolism.
RATIONALE: Chronic Thromboembolic Pulmonary Hypertension involves formation and non-resolution of thrombus, dysregulated inflammation, angiogenesis and the development of a small vessel vasculopathy. OBJECTIVES: We aimed to establish the genetic basis of chronic thromboembolic pulmonary hypertension to gain insight into its pathophysiological contributors. METHODS: We conducted a genome-wide association study on 1907 European cases and 10363 European controls. We co-analysed our results with existing results from genome-wide association studies on deep vein thrombosis, pulmonary embolism and idiopathic pulmonary arterial hypertension. MEASUREMENTS AND MAIN RESULTS: Our primary association study revealed genetic associations at the ABO, FGG, F11, MYH7B, and HLA-DRA loci. Through our co-analysis we demonstrate further associations with chronic thromboembolic pulmonary hypertension at the F2, TSPAN15, SLC44A2 and F5 loci but find no statistically significant associations shared with idiopathic pulmonary arterial hypertension. CONCLUSIONS: Chronic thromboembolic pulmonary hypertension is a partially heritable polygenic disease, with related though distinct genetic associations to pulmonary embolism and to deep vein thrombosis
Altered TMPRSS2 usage by SARS-CoV-2 Omicron impacts infectivity and fusogenicity
The SARS-CoV-2 Omicron BA.1 variant emerged in 20211 and has multiple mutations in its spike protein2. Here we show that the spike protein of Omicron has a higher affinity for ACE2 compared with Delta, and a marked change in its antigenicity increases Omicron’s evasion of therapeutic monoclonal and vaccine-elicited polyclonal neutralizing antibodies after two doses. mRNA vaccination as a third vaccine dose rescues and broadens neutralization. Importantly, the antiviral drugs remdesivir and molnupiravir retain efficacy against Omicron BA.1. Replication was similar for Omicron and Delta virus isolates in human nasal epithelial cultures. However, in lung cells and gut cells, Omicron demonstrated lower replication. Omicron spike protein was less efficiently cleaved compared with Delta. The differences in replication were mapped to the entry efficiency of the virus on the basis of spike-pseudotyped virus assays. The defect in entry of Omicron pseudotyped virus to specific cell types effectively correlated with higher cellular RNA expression of TMPRSS2, and deletion of TMPRSS2 affected Delta entry to a greater extent than Omicron. Furthermore, drug inhibitors targeting specific entry pathways3 demonstrated that the Omicron spike inefficiently uses the cellular protease TMPRSS2, which promotes cell entry through plasma membrane fusion, with greater dependency on cell entry through the endocytic pathway. Consistent with suboptimal S1/S2 cleavage and inability to use TMPRSS2, syncytium formation by the Omicron spike was substantially impaired compared with the Delta spike. The less efficient spike cleavage of Omicron at S1/S2 is associated with a shift in cellular tropism away from TMPRSS2-expressing cells, with implications for altered pathogenesis
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