75 research outputs found
The spectral evolution of AT 2018dyb and the presence of metal lines in tidal disruption events
We present light curves and spectra of the tidal disruption event (TDE)
ASASSN-18pg / AT 2018dyb spanning a period of one year. The event shows a
plethora of strong emission lines, including the Balmer series, He II, He I and
metal lines of O III 3760 and N III 4100, 4640
(blended with He II). The latter lines are consistent with originating from the
Bowen fluorescence mechanism. By analyzing literature spectra of past events,
we conclude that these lines are common in TDEs. The spectral diversity of
optical TDEs is thus larger than previously thought and includes N-rich events
besides H- and He-rich events. We study how the spectral lines evolve with
time, by means of their width, relative strength, and velocity offsets. The
velocity width of the lines starts at 13000 km s and decreases
with time. The ratio of He II to N III increases with time. The same is true
for ASASSN-14li, which has a very similar spectrum to AT 2018dyb but its lines
are narrower by a factor of 2. We estimate a black hole mass of
= by using the -
relation. This is consistent with the black hole mass derived using the MOSFiT
transient fitting code. The detection of strong Bowen lines in the optical
spectrum is an indirect proof for extreme ultraviolet and (reprocessed) X-ray
radiation and favors an accretion origin for the TDE optical luminosity. A
model where photons escape after multiple scatterings through a super-Eddington
thick disk and its optically thick wind, viewed at an angle close to the disk
plane, is consistent with the observations.Comment: Accepted version. Updated with new photometry and spectra, including
an X-shooter spectrum used to determine the BH mass. Two more figures added
and line measurements tabulated. No significant scientific updates and the
conclusions remain unaffecte
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure
The genetic architecture of the human cerebral cortex
The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder
The Science Performance of JWST as Characterized in Commissioning
This paper characterizes the actual science performance of the James Webb
Space Telescope (JWST), as determined from the six month commissioning period.
We summarize the performance of the spacecraft, telescope, science instruments,
and ground system, with an emphasis on differences from pre-launch
expectations. Commissioning has made clear that JWST is fully capable of
achieving the discoveries for which it was built. Moreover, almost across the
board, the science performance of JWST is better than expected; in most cases,
JWST will go deeper faster than expected. The telescope and instrument suite
have demonstrated the sensitivity, stability, image quality, and spectral range
that are necessary to transform our understanding of the cosmos through
observations spanning from near-earth asteroids to the most distant galaxies.Comment: 5th version as accepted to PASP; 31 pages, 18 figures;
https://iopscience.iop.org/article/10.1088/1538-3873/acb29
A SARS-CoV-2 protein interaction map reveals targets for drug repurposing
The novel coronavirus SARS-CoV-2, the causative agent of COVID-19 respiratory disease, has infected over 2.3 million people, killed over 160,000, and caused worldwide social and economic disruption1,2. There are currently no antiviral drugs with proven clinical efficacy, nor are there vaccines for its prevention, and these efforts are hampered by limited knowledge of the molecular details of SARS-CoV-2 infection. To address this, we cloned, tagged and expressed 26 of the 29 SARS-CoV-2 proteins in human cells and identified the human proteins physically associated with each using affinity-purification mass spectrometry (AP-MS), identifying 332 high-confidence SARS-CoV-2-human protein-protein interactions (PPIs). Among these, we identify 66 druggable human proteins or host factors targeted by 69 compounds (29 FDA-approved drugs, 12 drugs in clinical trials, and 28 preclinical compounds). Screening a subset of these in multiple viral assays identified two sets of pharmacological agents that displayed antiviral activity: inhibitors of mRNA translation and predicted regulators of the Sigma1 and Sigma2 receptors. Further studies of these host factor targeting agents, including their combination with drugs that directly target viral enzymes, could lead to a therapeutic regimen to treat COVID-19
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