75 research outputs found
Report of the x ray and gamma ray sensors panel
Overall five major areas of technology are recommended for development in order to meet the science requirements of the Astrotech 21 mission set. These are: detectors for high resolution gamma ray spectroscopy, cryogenic detectors for improved x ray spectral and spatial resolution, advanced x ray charge coupled devices (CCDs) for higher energy resolution and larger format, extension to higher energies, liquid and solid position sensitive detectors for improving stopping power in the energy range 5 to 500 keV and 0.2 to 2 MeV. Development plans designed to achieve the desired capabilities on the time scales required by the technology freeze dates have been recommended in each of these areas
CHIRON - A Fiber Fed Spectrometer for Precise Radial Velocities
The CHIRON optical high-resolution echelle spectrometer was commissioned at
the 1.5m telescope at CTIO in 2011. The instrument was designed for high
throughput and stability, with the goal of monitoring radial velocities of
bright stars with high precision and high cadence for the discovery of low-mass
exoplanets. Spectral resolution of R=79,000 is attained when using a slicer
with a total (including telescope and detector) efficiency of 6% or higher,
while a resolution of R=136,000 is available for bright stars. A fixed spectral
range of 415 to 880 nm is covered. The echelle grating is housed in a vacuum
enclosure and the instrument temperature is stabilized to +-0.2deg. Stable
illumination is provided by an octagonal multimode fiber with excellent
light-scrambling properties. An iodine cell is used for wavelength calibration.
We describe the main optics, fiber feed, detector, exposure-meter, and other
aspects of the instrument, as well as the observing procedure and data
reduction.Comment: 15 pages, 10 figures. Accepted by PAS
Fiber scrambling for high-resolution spectrographs. I. Lick Observatory
In this paper, we report all results obtained with a fiber scrambler on the
Hamilton spectrograph at Lick Observatory. We demonstrate an improvement in the
stability of the instrumental profile using this fiber scrambler. Additionally,
we present data obtained with a double scrambler that further improves the
stability of the instrument by a factor 2. These results show that errors
related to the coupling between the telescope and the spectrograph are the
dominant source of instrumental profile variability at Lick Observatory. In
particular, we show a strong correlation between instrumental profile
variations and hour angle, most likely due to pointing-dependent illumination
of the spectrograph optics
Environmental variation drives continental-scale synchrony of European beech reproduction.
Spatial synchrony is the tendency of spatially separated populations to display similar temporal fluctuations. Synchrony affects regional ecosystem functioning, but it remains difficult to disentangle its underlying mechanisms. We leveraged regression on distance matrices and geography of synchrony to understand the processes driving synchrony of European beech masting over the European continent. Masting in beech shows distance-decay, but significant synchrony is maintained at spatial scales of up to 1,500 km. The spatial synchrony of the weather cues that drive interannual variation in reproduction also explains the regional spatial synchrony of masting. Proximity played no apparent role in influencing beech masting synchrony after controlling for synchrony in environmental variation. Synchrony of beech reproduction shows a clear biogeographical pattern, decreasing from the northwest to southeast Europe. Synchrony networks for weather cues resemble networks for beech masting, indicating that the geographical structure of weather synchrony underlies the biogeography of masting synchrony. Our results support the hypothesis that environmental factors, the Moran effect, are key drivers of spatial synchrony in beech seed production at regional scales. The geographical patterns of regional synchronization of masting have implications for regional forest production, gene flow, carbon cycling, disease dynamics, biodiversity, and conservation
Searching for keV Sterile Neutrino Dark Matter with X-ray Microcalorimeter Sounding Rockets
High-resolution X-ray spectrometers onboard suborbital sounding rockets can
search for dark matter candidates that produce X-ray lines, such as decaying
keV-scale sterile neutrinos. Even with exposure times and effective areas far
smaller than XMM-Newton and Chandra observations, high-resolution, wide
field-of-view observations with sounding rockets have competitive sensitivity
to decaying sterile neutrinos. We analyze a subset of the 2011 observation by
the X-ray Quantum Calorimeter instrument centered on Galactic coordinates l =
165, b = -5 with an effective exposure of 106 seconds, obtaining a limit on the
sterile neutrino mixing angle of sin^2(2 theta) < 7.2e-10 at 95% CL for a 7 keV
neutrino. Better sensitivity at the level of sin^2(2 theta) ~ 2.1e-11 at 95\%
CL for a 7 keV neutrino is achievable with future 300-second observations of
the galactic center by the Micro-X instrument, providing a definitive test of
the sterile neutrino interpretation of the reported 3.56 keV excess from galaxy
clusters.Comment: 13 pages, 13 figures, submitted to Ap
- …