266 research outputs found
Price Momentum and Idiosyncratic Volatility
We find that returns to momentum investing are higher among high idiosyncratic volatility (IVol) stocks, especially high IVol losers. Higher IVol stocks also experience quicker and larger reversals. The findings are consistent with momentum profits being attributable to underreaction to firm-specific information and with IVol limiting arbitrage of the momentum effect. We also find a positive time-series relation between momentum returns and aggregate IVol. Given the long-term rise in IVol, this result helps explain the persistence of momentum profits since Jegadeesh and Titman’s (1993) study
Far Ultra-Violet Insights Into NGC 1399's Globular Cluster Population
We investigate archival Hubble Space Telescope ACS/SBC F140LP observations of
NGC~1399 to search for evidence of multiple stellar populations in
extragalactic globular clusters. Enhanced FUV populations are thought to be
indicators of He-enhanced second generation populations in globular clusters,
specifically extreme/blue horizontal branch stars. Out of 149 globular clusters
in the field of view, 58 have far ultraviolet (FUV) counterparts with
magnitudes brighter than 28.5. Six of these FUV-deteced globular clusters are
also detected in X-rays, including one ultraluminous X-ray source ( erg/s). While optically bright clusters corresponded to brighter FUV
counterparts, we observe FUV emission from both metal-rich and metal-poor
clusters, which implies that the FUV excess is not dependent on optical colour.
We also find no evidence that the cluster size influences the FUV emission. The
clusters with X-ray emission are not unusually FUV bright, which suggests that
even the ultraluminous X-ray source does not provide significant FUV
contributions. NGC 1399 is only the fourth galaxy to have its globular cluster
system probed for evidence of FUV-enhanced populations, and we compare these
clusters to previous studies of the Milky Way, M31, M87, and the brightest
cluster in M81. These sources indicate that many globular clusters likely host
extreme HB stars and/or second generation stars, and highlight the need for
more complete FUV observations of extragalactic globular cluster systems.Comment: accepted to MNRA
The X-ray Point Source Population Hosted by Globular Clusters in the Elliptical Galaxy NGC 4261
Utilising archival Chandra X-ray Observatory data and Hubble Space Telescope
globular cluster catalogues, we probe the time-domain properties of the low
mass X-ray binary population in the elliptical galaxy NGC 4261. Of the 98
unique X-ray sources identified in this study, 62 sources are within the
optical field of view and, of those, 33% are aligned with an optical cluster
counterpart. We find twenty X-ray sources coincident with globular clusters;
two are previously discovered ultra-luminous X-ray sources (ULXs) and eighteen
are low mass X-ray binaries (GCLMXBs) with erg s. ULXs
are a heterogeneous class of extremely bright X-ray binaries (
erg s) and ULXs located in globular clusters (GCULXs) and may be
indicators of black holes. Identifying these unusually X-ray bright sources and
measuring their optical properties can provide valuable constraints on the
progenitors of gravitational wave sources. We compare observations of these
sources to the twenty previously-studied GCULXs from five other early-type
galaxies, and find that GCULXs in NGC 4261 are of similar colour and luminosity
and do not significantly deviate from the rest of the sample in terms of
distance from the galaxy centre or X-ray luminosity. Both the GCULX and low
mass X-ray binary (GCLMXB) populations of NGC 4261 show long term variability;
the former may have implications for fast radio bursts originating in globular
clusters and the latter will likely introduce additional scatter into the low
mass end of GCLMXB X-ray luminosity functions.Comment: Accepted to MNRA
Metacognition across sensory modalities: Vision, warmth, and nociceptive pain
The distinctive experience of pain, beyond mere processing of nociceptive inputs, is much debated in psychology and neuroscience. One aspect of perceptual experience is captured by metacognition—the ability to monitor and evaluate one’s own mental processes. We investigated confidence in judgements about nociceptive pain (i.e. pain that arises from the activation of nociceptors by a noxious stimulus) to determine whether metacognitive processes contribute to the distinctiveness of the pain experience. Our participants made intensity judgements about noxious heat, innocuous warmth, and visual contrast (first-order, perceptual decisions) and rated their confidence in those judgements (second-order, metacognitive decisions). First-order task performance between modalities was balanced using adaptive staircase procedures. For each modality, we quantified metacognitive efficiency (meta-d’/d’)—the degree to which participants’ confidence reports were informed by the same evidence that contributed to their perceptual judgements—and metacognitive bias (mean confidence)—the participant’s tendency to report higher or lower confidence overall. We found no overall differences in metacognitive efficiency or mean confidence between modalities. Mean confidence ratings were highly correlated between all three tasks, reflecting stable inter-individual variability in metacognitive bias. However, metacognitive efficiency for pain varied independently of metacognitive efficiency for warmth and visual perception. That is, those participants who had higher metacognitive efficiency in the visual task also tended to have higher metacognitive efficiency in the warmth task, but not necessarily in the pain task. We thus suggest that some distinctive and idiosyncratic aspects of the pain experience may stem from additional variability at a metacognitive level. We further speculate that this additional variability may arise from the affective or arousal aspects of pain
Does public support help democracy survive?
It is widely believed that democracy requires public support to survive. The empirical evidence for this hypothesis is weak, however, with existing tests resting on small cross‐sectional samples and producing contradictory results. The underlying problem is that survey measures of support for democracy are fragmented across time, space, and different survey questions. In response, this article uses a Bayesian latent variable model to estimate a smooth country‐year panel of democratic support for 135 countries and up to 29 years. The article then demonstrates a positive effect of support on subsequent democratic change, while adjusting for the possible confounding effects of prior levels of democracy and unobservable time‐invariant factors. Support is, moreover, more robustly linked with the endurance of democracy than its emergence in the first place. As Lipset (1959) and Easton (1965) hypothesized over 50 years ago, public support does indeed help democracy survive
Six new candidate ultracompact X-ray binaries
Ultracompact X-ray binaries (UCXBs) appear able to sustain accretion onto the
compact accretor at rates lower than in wider X-ray binaries. This may be
understood by the smaller accretion disks in UCXBs: a lower X-ray luminosity
suffices to keep a disk completely ionized through irradiation and, thus, keep
the viscosity at a sufficiently high level to allow effective transport of
matter to the compact object. We employ this distinguishing factor on data from
RXTE and BeppoSAX to identify six new candidate UCXBs, thus increasing the
population by one quarter. The candidates are drawn from the population of
persistently accreting and type-I X-ray bursting low-mass X-ray binaries. The
X-ray bursts establish the low-mass X-ray binary nature and provide a handle on
the accretion rate. We find that the low accretion rates are supported by the
long burst recurrence times and the hard X-ray spectra of the persistent
emission as derived from the 2nd INTEGRAL catalog of soft gamma-ray sources. We
discuss the peculiar light curves of some new UCXB candidates.Comment: Section 2 corrected and improved thanks to comments by J.-P. Lasota.
Accepted for publication in Astronomy and Astrophysic
The Baryon Oscillation Spectroscopic Survey of SDSS-III
The Baryon Oscillation Spectroscopic Survey (BOSS) is designed to measure the
scale of baryon acoustic oscillations (BAO) in the clustering of matter over a
larger volume than the combined efforts of all previous spectroscopic surveys
of large scale structure. BOSS uses 1.5 million luminous galaxies as faint as
i=19.9 over 10,000 square degrees to measure BAO to redshifts z<0.7.
Observations of neutral hydrogen in the Lyman alpha forest in more than 150,000
quasar spectra (g<22) will constrain BAO over the redshift range 2.15<z<3.5.
Early results from BOSS include the first detection of the large-scale
three-dimensional clustering of the Lyman alpha forest and a strong detection
from the Data Release 9 data set of the BAO in the clustering of massive
galaxies at an effective redshift z = 0.57. We project that BOSS will yield
measurements of the angular diameter distance D_A to an accuracy of 1.0% at
redshifts z=0.3 and z=0.57 and measurements of H(z) to 1.8% and 1.7% at the
same redshifts. Forecasts for Lyman alpha forest constraints predict a
measurement of an overall dilation factor that scales the highly degenerate
D_A(z) and H^{-1}(z) parameters to an accuracy of 1.9% at z~2.5 when the survey
is complete. Here, we provide an overview of the selection of spectroscopic
targets, planning of observations, and analysis of data and data quality of
BOSS.Comment: 49 pages, 16 figures, accepted by A
The Ninth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Baryon Oscillation Spectroscopic Survey
The Sloan Digital Sky Survey III (SDSS-III) presents the first spectroscopic
data from the Baryon Oscillation Spectroscopic Survey (BOSS). This ninth data
release (DR9) of the SDSS project includes 535,995 new galaxy spectra (median
z=0.52), 102,100 new quasar spectra (median z=2.32), and 90,897 new stellar
spectra, along with the data presented in previous data releases. These spectra
were obtained with the new BOSS spectrograph and were taken between 2009
December and 2011 July. In addition, the stellar parameters pipeline, which
determines radial velocities, surface temperatures, surface gravities, and
metallicities of stars, has been updated and refined with improvements in
temperature estimates for stars with T_eff<5000 K and in metallicity estimates
for stars with [Fe/H]>-0.5. DR9 includes new stellar parameters for all stars
presented in DR8, including stars from SDSS-I and II, as well as those observed
as part of the SDSS-III Sloan Extension for Galactic Understanding and
Exploration-2 (SEGUE-2).
The astrometry error introduced in the DR8 imaging catalogs has been
corrected in the DR9 data products. The next data release for SDSS-III will be
in Summer 2013, which will present the first data from the Apache Point
Observatory Galactic Evolution Experiment (APOGEE) along with another year of
data from BOSS, followed by the final SDSS-III data release in December 2014.Comment: 9 figures; 2 tables. Submitted to ApJS. DR9 is available at
http://www.sdss3.org/dr
The Proprioceptive Map of the Arm Is Systematic and Stable, but Idiosyncratic
Visual and somatosensory signals participate together in providing an estimate of the hand's spatial location. While the ability of subjects to identify the spatial location of their hand based on visual and proprioceptive signals has previously been characterized, relatively few studies have examined in detail the spatial structure of the proprioceptive map of the arm. Here, we reconstructed and analyzed the spatial structure of the estimation errors that resulted when subjects reported the location of their unseen hand across a 2D horizontal workspace. Hand position estimation was mapped under four conditions: with and without tactile feedback, and with the right and left hands. In the task, we moved each subject's hand to one of 100 targets in the workspace while their eyes were closed. Then, we either a) applied tactile stimulation to the fingertip by allowing the index finger to touch the target or b) as a control, hovered the fingertip 2 cm above the target. After returning the hand to a neutral position, subjects opened their eyes to verbally report where their fingertip had been. We measured and analyzed both the direction and magnitude of the resulting estimation errors. Tactile feedback reduced the magnitude of these estimation errors, but did not change their overall structure. In addition, the spatial structure of these errors was idiosyncratic: each subject had a unique pattern of errors that was stable between hands and over time. Finally, we found that at the population level the magnitude of the estimation errors had a characteristic distribution over the workspace: errors were smallest closer to the body. The stability of estimation errors across conditions and time suggests the brain constructs a proprioceptive map that is reliable, even if it is not necessarily accurate. The idiosyncrasy across subjects emphasizes that each individual constructs a map that is unique to their own experiences
The Baryon Oscillation Spectroscopic Survey of SDSS-III
The Baryon Oscillation Spectroscopic Survey (BOSS) is designed to measure the scale of baryon acoustic oscillations (BAO) in the clustering of matter over a larger volume than the combined efforts of all previous spectroscopic surveys of large-scale structure. BOSS uses 1.5 million luminous galaxies as faint as i = 19.9 over 10,000 deg(2) to measure BAO to redshifts z < 0.7. Observations of neutral hydrogen in the Ly alpha forest in more than 150,000 quasar spectra (g < 22) will constrain BAO over the redshift range 2.15 < z < 3.5. Early results from BOSS include the first detection of the large-scale three-dimensional clustering of the Ly alpha forest and a strong detection from the Data Release 9 data set of the BAO in the clustering of massive galaxies at an effective redshift z = 0.57. We project that BOSS will yield measurements of the angular diameter distance d(A) to an accuracy of 1.0% at redshifts z = 0.3 and z = 0.57 and measurements of H(z) to 1.8% and 1.7% at the same redshifts. Forecasts for Ly alpha forest constraints predict a measurement of an overall dilation factor that scales the highly degenerate D-A(z) and H-1(z) parameters to an accuracy of 1.9% at z similar to 2.5 when the survey is complete. Here, we provide an overview of the selection of spectroscopic targets, planning of observations, and analysis of data and data quality of BOSS
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