641 research outputs found
Heavy X-ray obscuration in the most-luminous galaxies discovered by WISE
Hot Dust-Obscured Galaxies (Hot DOGs) are hyperluminous
() infrared galaxies with
extremely high (up to hundreds of K) dust temperatures. The sources powering
both their extremely high luminosities and dust temperatures are thought to be
deeply buried and rapidly accreting supermassive black holes (SMBHs). Hot DOGs
could therefore represent a key evolutionary phase in which the SMBH growth
peaks. X-ray observations can be used to study their obscuration levels and
luminosities. In this work, we present the X-ray properties of the 20
most-luminous () known Hot DOGs at
. Five of them are covered by long-exposure ( ks) Chandra and
XMM-Newton observations, with three being X-ray detected, and we study their
individual properties. One of these sources (W01160505) is a Compton-thick
candidate, with column density
derived from X-ray spectral fitting. The remaining 15 Hot DOGs have been
targeted by a Chandra snapshot (3.1 ks) survey. None of these 15 is
individually detected; therefore we applied a stacking analysis to investigate
their average emission. From hardness-ratio analysis, we constrained the
average obscuring column density and intrinsic luminosity to be
log and
, which are consistent with
results for individually detected sources. We also investigated the
and relations, finding hints that Hot
DOGs are typically X-ray weaker than expected, although larger samples of
luminous obscured QSOs are needed to derive solid conclusions.Comment: MNRAS, accepted 2017 November 29 . Received 2017 November 29 ; in
original form 2017 October 11. 15 pages, 6 figure
Explorations in anatomy: the remains from Royal London Hospital
This paper considers the faunal remains from recent excavations at the Royal London Hospital. The remains date to the beginning of the 19th century and offer an insight into the life of the hospital's patients and practices of the attached medical school. Many of the animal remains consist of partially dissected skeletons, including the unique finds of Hermann's tortoise (Testudo hermanni) and Cercopithecus monkey. The hospital diet and developments in comparative anatomy are discussed by integrating the results with documentary research. They show that zooarchaeological study of later post-medieval material can significantly enhance our understanding of the exploitation of animals in this perio
Improving Binding Specificity of Pharmacological Chaperones That Target Mutant Superoxide Dismutase-1 Linked to Familial Amyotrophic Lateral Sclerosis Using Computational Methods
We recently described a set of drug-like molecules obtained from an in silico screen that stabilize mutant superoxide dismutase-1 (SOD-1) linked to familial amyotrophic lateral sclerosis (ALS) against unfolding and aggregation but exhibited poor binding specificity toward SOD-1 in presence of blood plasma. A reasonable but not a conclusive model for the binding of these molecules was proposed on the basis of restricted docking calculations and site-directed mutagenesis of key residues at the dimer interface. A set of hydrogen bonding constraints obtained from these experiments were used to guide docking calculations with compound library around the dimer interface. A series of chemically unrelated hits were predicted, which were experimentally tested for their ability to block aggregation. At least six of the new molecules exhibited high specificity of binding toward SOD-1 in the presence of blood plasma. These molecules represent a new class of molecules for further development into clinical candidates
NuSTAR discovery of an unusually steady long-term spin-up of the Be binary 2RXP J130159.6-635806
We present spectral and timing analysis of NuSTAR observations of the
accreting X-ray pulsar 2RXP J130159.6-635806. The source was serendipitously
observed during a campaign focused on the gamma-ray binary PSR B1259-63 and was
later targeted for a dedicated observation. The spectrum has a typical shape
for accreting X-ray pulsars, consisting of a simple power law with an
exponential cutoff starting at ~7 keV with a folding energy of E_fold=~18 keV.
There is also an indication of the presence of a 6.4 keV iron line in the
spectrum at the ~3 sigma significance level. NuSTAR measurements of the
pulsation period reveal that the pulsar has undergone a strong and steady
spin-up for the last 20 years. The pulsed fraction is estimated to be ~80%, and
is constant with energy up to 40 keV. The power density spectrum shows a break
towards higher frequencies relative to the current spin period. This, together
with steady persistent luminosity, points to a long-term mass accretion rate
high enough to bring the pulsar out of spin equilibrium.Comment: 13 pages, 7 figures, accepted for publication in The Astrophysical
Journa
The AllWISE Motion Survey, Part 2
We use the AllWISE Data Release to continue our search for WISE-detected
motions. In this paper, we publish another 27,846 motion objects, bringing the
total number to 48,000 when objects found during our original AllWISE motion
survey are included. We use this list, along with the lists of confirmed
WISE-based motion objects from the recent papers by Luhman and by Schneider et
al. and candidate motion objects from the recent paper by Gagne et al. to
search for widely separated, common-proper-motion systems. We identify 1,039
such candidate systems. All 48,000 objects are further analyzed using
color-color and color-mag plots to provide possible characterizations prior to
spectroscopic follow-up. We present spectra of 172 of these, supplemented with
new spectra of 23 comparison objects from the literature, and provide
classifications and physical interpretations of interesting sources. Highlights
include: (1) the identification of three G/K dwarfs that can be used as
standard candles to study clumpiness and grain size in nearby molecular clouds
because these objects are currently moving behind the clouds, (2) the
confirmation/discovery of several M, L, and T dwarfs and one white dwarf whose
spectrophotometric distance estimates place them 5-20 pc from the Sun, (3) the
suggestion that the Na 'D' line be used as a diagnostic tool for interpreting
and classifying metal-poor late-M and L dwarfs, (4) the recognition of a triple
system including a carbon dwarf and late-M subdwarf, for which model fits of
the late-M subdwarf (giving [Fe/H] ~ -1.0) provide a measured metallicity for
the carbon star, and (5) a possible 24-pc-distant K5 dwarf + peculiar red L5
system with an apparent physical separation of 0.1 pc.Comment: 62 pages with 80 figures, accepted for publication in The
Astrophysical Journal Supplement Series, 23 Mar 2016; second version fixes a
few small typos and corrects the footnotes for Table
The NuSTAR Extragalactic Survey: First Direct Measurements of the Greater Than Or Similar To 10 Kev X-Ray Luminosity Function For Active Galactic Nuclei At z \u3e 0.1
We present the first direct measurements of the rest-frame 10–40 keV X-ray luminosity function (XLF) of active galactic nuclei (AGNs) based on a sample of 94 sources at 0.1 \u3c z \u3c 3, selected at 8–24 keV energies from sources in the Nuclear Spectroscopic Telescope Array (NuSTAR) extragalactic survey program. Our results are consistent with the strong evolution of the AGN population seen in prior, lower-energy studies of the XLF. However, different models of the intrinsic distribution of absorption, which are used to correct for selection biases, give significantly different predictions for the total number of sources in our sample, leading to small, systematic differences in our binned estimates of the XLF. Adopting a model with a lower intrinsic fraction of Compton-thick sources and a larger population of sources with column densities cm−2 or a model with stronger Compton reflection component (with a relative normalization of R ~ 2 at all luminosities) can bring extrapolations of the XLF from 2–10 keV into agreement with our NuSTAR sample. Ultimately, X-ray spectral analysis of the NuSTAR sources is required to break this degeneracy between the distribution of absorbing column densities and the strength of the Compton reflection component and thus refine our measurements of the XLF. Furthermore, the models that successfully describe the high-redshift population seen by NuSTAR tend to over-predict previous, high-energy measurements of the local XLF, indicating that there is evolution of the AGN population that is not fully captured by the current models
South Korea's automotive labour regime, Hyundai Motors’ global production network and trade‐based integration with the European Union
This article explores the interrelationship between global production networks(GPNs) and free trade agreements (FTAs) in the South Korean auto industry and its employment relations. It focuses on the production network of the Hyundai Motor Group (HMG) — the third biggest automobile manufacturer in the world — and the FTA between the EU and South Korea. This was the first of the EU’s ‘new generation’ FTAs, which among other things contained provisions designed to protect and promote labour standards. The article’s argument is twofold. First, that HMG’s production network and Korea’s political economy (of which HMG is a crucial part) limited the possibilities for the FTA’s labour provisions to take effect. Second, that the commercial provisions in this same FTA simultaneously eroded HMG’s domestic market and corporate profitability, leading to adverse consequences for auto workers in the more
insecure and low-paid jobs. In making this argument, the article advances a multiscalar conceptualization of the labour regime as an analytical intermediary between GPNs and FTAs. It also provides one of the first empirical studies of the EU–South Korea FTA in terms of employment relations, drawing on 105 interviews with trade unions, employer associations, automobile companies and state officials across both parties
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