2,366 research outputs found
Correlated X-ray and Optical Variability in Mkn 509
We present results of a 3 year monitoring campaign of the Seyfert 1 galaxy
Markarian 509, using X-ray data from the Rossi X-ray Timing Explorer (RXTE) and
optical data taken by the SMARTS consortium. Both light curves show significant
variations, and are strongly correlated with the optical flux leading the X-ray
flux by 15 days. The X-ray power spectrum shows a steep high-frequency slope of
-2.0, breaking to a slope of -1.0 at at timescale of 34 days. The lag from
optical to X-ray emission is most likely caused by variations in the accretion
disk propagating inward.Comment: 13 pages, 3 figures. Accepted for publication in the Astrophysical
Journa
Providing Economic Incentives in Environmental Regulation
CHAIRMAN BREGER: Let me welcome you to this AdministrativeConference colloquy on providing economic incentives in environmentallitigation
Performance, Politics and Media: How the 2010 British General Election leadership debates generated ‘talk’ amongst the electorate.
During the British General Election 2010 a major innovation was introduced in part to improve engagement: a series of three live televised leadership debates took place where the leader of each of the three main parties, Labour, Liberal Democrat and Conservative, answered questions posed by members of the public and subsequently debated issues pertinent to the questions. In this study we consider these potentially ground breaking debates as the kind of event that was likely to generate discussion. We investigate various aspects of the ‘talk’ that emerged as a result of watching the debates. As an exploratory study concerned with situated accounts of the participants experiences we take an interpretive perspective. In this paper we outline the meta-narratives (of talk) associated with the viewing of the leadership debates that were identified, concluding our analysis by suggesting that putting a live debate on television and promoting and positioning it as a major innovation is likely to mean that is how the audience will make sense of it – as a media event
An Untriggered Search for Optical Bursts
We present an untriggered search for optical bursts with the ROTSE-I
telephoto array. Observations were taken which monitor an effective 256 square
degree field continuously over 125 hours to m_{ROTSE}=15.7. The uniquely large
field, moderate limiting magnitude and fast cadence of 10 minutes permits
transient searches in a new region of sensitivity. Our search reveals no
candidate events. To quantify this result, we simulate potential optical bursts
with peak magnitude, m_{p}, at t=10 s, which fade as f=(\frac{t}{t_{0}})
^{\alpha_{t}}, where \alpha_t < 0. Simple estimates based on observational
evidence indicate that a search of this sensitivity begins to probe the
possible region occupied by GRB orphan afterglows. Our observing protocol and
image sensitivity result in a broad region of high detection efficiency for
light curves to the bright and slowly varying side of a boundary running from
[\alpha_{t},m_{p}]=[-2.0,6.0] to [-0.3,13.2]. Within this region, the
integrated rate of brief optical bursts is less than 1.1\times 10^{-8} {\rm
s}^{-1} {\rm deg}^{-2}. At 22 times the observed GRB rate from BATSE,
this suggests a limit on \frac{\theta_{opt}}{\theta_{\gamma}}\lesssim 5 where
\theta_{opt} and \theta_{\gamma} are the optical and gamma-ray collimation
angles, respectively. Several effects might explain the absence of optical
bursts, and a search of the kind described here but more sensitive by about 4
magnitudes should offer a more definitive probe.Comment: 8 pages, 6 figures, 1 tabl
Mapping Snowmelt Progression in the Upper Indus Basin with Synthetic Aperture Radar
The Indus River is a vital resource for food security, ecosystem services, hydropower, and economy for millions of people living in Pakistan, India, China, and Afghanistan. Glacier and snowmelt from the high altitude Himalaya, Karakoram, and Hindu Kush mountain ranges are the largest drivers of discharge in the upper Indus Basin (UIB), and contribute significantly to Indus flows. Complex climatology and topography, coupled with the challenges of field study and meteorological measurement in these rugged ranges, elicit notable uncertainties in predicting seasonal runoff as well as cryospheric response to changes in climate. Here we utilize Sentinel-1 synthetic aperture radar (SAR) imagery to track ablation season development of wet snow in the Shigar Watershed of the Karakoram Mountains in Pakistan from 2015 to 2018. We exploit opportune local image acquisition times to highlight diurnal differences in radar indications of wet snow, and examine the spatial and temporal contexts of radar diurnal differences for 2015, 2017, and 2018 ablation seasons. Radar classifications for each ablation season show spatial and temporal patterns that indicate a dry winter snowpack undergoing diurnal surface melt-refreeze cycles, transitioning to surface snow that remains wet both day and night, and finally snow free conditions following melt out. Diurnally differing SAR signals may offer insights into important snowpack energy balance processes that precede melt out, which could provide useful constraints for both glacier mass balance modeling and runoff forecasting in remote alpine watersheds
Protection From Clinical Peripheral Sensory Neuropathy in Alström Syndrome in Contrast to Early-Onset Type 2 Diabetes
OBJECTIVE—Alström syndrome, with type 2 diabetes, and blindness could confer a high risk of foot ulceration. Clinical testing for neuropathy in Alström syndrome and matched young-onset type 2 diabetic subjects was therefore undertaken
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