Detection of Low Mass-ratio Stellar Binary Systems

O- and B-type stars are often found in binary systems, but the low binary mass-ratio regime is relatively unexplored due to observational difficulties. Binary systems with low mass-ratios may have formed through fragmentation of the circumstellar disk rather than molecular cloud core fragmen- tation. We describe a new technique sensitive to G- and K-type companions to early B stars, a mass-ratio of roughly 0.1, using high-resolution, high signal-to-noise spectra. We apply this technique to a sample of archived VLT/CRIRES observations of nearby B-stars in the CO bandhead near 2300 nm. While there are no unambiguous binary detections in our sample, we identify HIP 92855 and HIP 26713 as binary candidates warranting follow-up observations. We use our non-detections to determine upper limits to the frequency of FGK stars orbiting early B-type primaries.Comment: 13 pages, 7 figures Accepted to the Astrophysical Journa

Correcting For Telluric Absorption: Methods, Case Studies, And Release Of The TelFit Code

Ground-based astronomical spectra are contaminated by the Earth's atmosphere to varying degrees in all spectral regions. We present a Python code that can accurately fit a model to the telluric absorption spectrum present in astronomical data, with residuals of similar to 3%-5% of the continuum for moderately strong lines. We demonstrate the quality of the correction by fitting the telluric spectrum in a nearly featureless A0V star, HIP 20264, as well as to a series of dwarf M star spectra near the 819 nm sodium doublet. We directly compare the results to an empirical telluric correction of HIP 20264 and find that our model-fitting procedure is at least as good and sometimes more accurate. The telluric correction code, which we make freely available to the astronomical community, can be used as a replacement for telluric standard star observations for many purposes.UT Austin Hutchinson fellowshipUniversity of TexasAstronom

Hot Stars With Cool Companions

Young intermediate-mass stars have become high-priority targets for direct-imaging planet searches following the recent discoveries of planets orbiting e.g. HR 8799 and Beta Pictoris. Close stellar companions to these stars can affect the formation and orbital evolution of any planets, and so a census of the multiplicity properties of nearby intermediate mass stars is needed. Additionally, the multiplicity can help constrain the important binary star formation physics. We report initial results from a spectroscopic survey of 400 nearby A- and B-type stars. We search for companions by cross-correlating high resolution and high signal-to-noise ratio echelle spectra of the targets stars against model spectra for F- to M-type stars. We have so far found 18 new candidate companions, and have detected the spectral lines of the secondary in 4 known spectroscopic binary systems. We present the distribution of mass-ratios for close companions, and find that it differs from the distribution for wide ($a < 100$ AU) intermediate-mass binaries, which may indicate a different formation mechanism for the two populations.Comment: Submitted as part of the 18th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun Proceedings of Lowell Observatory (9-13 June 2014

Effects of Energy Development on Movements, Home Ranges, and Resource Selection of White-Tailed Deer in the Western Dakotas

Oil and natural gas development has increased in recent years and research is needed to assess potential impacts on white-tailed deer (Odocoileus virginianus) populations. Our objectives were to document movements, home ranges, and resource selection of female white-tailed deer in response to energy development in the western Dakotas. Our study areas included Dunn County, North Dakota, an area with current oil and gas development, and Grant County, North Dakota, and Perkins County, South Dakota, areas without current oil and gas development. We captured and fitted 150 female deer with Very High Frequency (VHF) collars across study sites, and monitored movements through radio telemetry from March 2014 to December 2015. We collected 10,729 locations from radio collared individuals, documented seasonal movements, generated 50 and 95% home ranges, mapped and ground-verified habitats within home ranges, and conducted resource selection analysis using design II (population level) and design III (home range level) analyses. Overall 50 and 95% summer home ranges were 0.79 and 3.38 km2, respectively, overall 50 and 95% winter home ranges were 2.0 and 7.9 km2, respectively, for migrators, and overall 50 and 95% annual home ranges were 1.09 and 4.74 km2, respectively, for resident deer. Overall mean migration distance was 8.0 km. We suspect that home ranges and seasonal movements were influenced by habitat availability, food availability, and weather and environmental conditions. We found that at the population level, deer commonly selected areas with agricultural crops (i.e., corn and sunflowers), wetlands, and forests in summer, and areas with agricultural crops and forests in winter. At the home range level, deer generally selected forests and wetlands in summer as well as forests in winter. We found that deer in Dunn County avoided developed areas at the population level during summer 2015, as well as during summers at the home range level. We compared the distance from home range centroids and random points to oil and gas well pads within the Dunn County study area and found that home range centroids averaged 1.57 km farther from well pads than random points, indicating that white-tailed deer in Dunn County were avoiding well pads. Our results showed that white-tailed deer home ranges in Dunn County were being affected by oil and gas development, and further monitoring is needed to assess continued effects on deer populations

Collecting Space Use Data to Improve the UX of Library Space

Collecting data about where people are and what they are doing is an easy entry point into exploring the UX of library space. This article examines projects at two academic libraries where space use data was collected multiple times per day for several months. The two projects were designed and carried out independently but had the same purpose: to better understand how students were using library spaces so that we could improve student experiences. Collecting space use data provided a baseline understanding of user behavior in these spaces. Similar to web analytics, this baseline can be useful on its own or used in conjunction with other forms of user research

Sensitivity of an image plate system in the XUV (60 eV < E < 900 eV)

Phosphor imaging plates (IPs) have been calibrated and proven useful for quantitative x-ray imaging in the 1 to over 1000 keV energy range. In this paper we report on calibration measurements made at XUV energies in the 60 to 900 eV energy range using beamline 6.3.2 at the Advanced Light Source at Lawrence Berkeley National Laboratory. We measured a sensitivity of ~25 plus or minus 15 counts/pJ over the stated energy range which is compatible with the sensitivity of Si photodiodes that are used for time-resolved measurements. Our measurements at 900 eV are consistent with the measurements made by Meadowcroft et al. at ~1 keV.Comment: 7 pages, 2 figure