H-alpha Activity of Old M Dwarfs: Stellar Cycles and Mean Activity Levels For 93 Low-Mass Stars in the Solar Neighborhood

Through the McDonald Observatory M Dwarf Planet Search, we have acquired nearly 3,000 high-resolution spectra of 93 late-type (K5-M5) stars over more than a decade using HET/HRS. This sample provides a unique opportunity to investigate the occurrence of long-term stellar activity cycles for low-mass stars. In this paper, we examine the stellar activity of our targets as reflected in the H-alpha feature. We have identified periodic signals for 6 stars, with periods ranging from days to more than 10 years, and find long-term trends for 7 others. Stellar cycles with P > 1 year are present for at least 5% of our targets. Additionally, we present an analysis of the time-averaged activity levels of our sample, and search for correlations with other stellar properties. In particular, we find that more massive, earlier type (M0-M2) stars tend to be more active than later type dwarfs. Furthermore, high-metallicity stars tend to be more active at a given stellar mass. We also evaluate H-alpha variability as a tracer of activity-induced radial velocity (RV) variation. For the M dwarf GJ 1170, H-alpha variation reveals stellar activity patterns matching those seen in the RVs, mimicking the signal of a giant planet, and we find evidence that the previously identified stellar activity cycle of GJ 581 may be responsible for the recently retracted planet f (Vogt et al. 2012) in that system. In general, though, we find that H-alpha is not frequently correlated with RV at the precision (typically 6-7 m/s) of our measurements.Comment: Submitted to ApJ. Reflects comments from a positive refere

Secretly Eccentric: The Giant Planet and Activity Cycle of GJ 328

We announce the discovery of a ~2 Jupiter-mass planet in an eccentric 11-year orbit around the K7/M0 dwarf GJ 328. Our result is based on 10 years' worth of radial velocity (RV) data from the Hobby-Eberly and Harlan J. Smith telescopes at McDonald Observatory, and from the Keck Telescope at Mauna Kea. Our analysis of GJ 328's magnetic activity via the Na I D features reveals a long-period stellar activity cycle, which creates an additional signal in the star's RV curve with amplitude 6-10 m/s. After correcting for this stellar RV contribution, we see that the orbit of the planet is more eccentric than suggested by the raw RV data. GJ 328b is currently the most massive, longest-period planet discovered around a low-mass dwarf.Comment: Accepted for publication in Ap

Stellar Activity and its Implications for Exoplanet Detection on GJ 176

We present an in-depth analysis of stellar activity and its effects on radial velocity (RV) for the M2 dwarf GJ 176 based on spectra taken over 10 years from the High Resolution Spectrograph on the Hobby-Eberly Telescope. These data are supplemented with spectra from previous observations with the HIRES and HARPS spectrographs, and V- and R-band photometry taken over 6 years at the Dyer and Fairborn observatories. Previous studies of GJ 176 revealed a super-Earth exoplanet in an 8.8-day orbit. However, the velocities of this star are also known to be contaminated by activity, particularly at the 39-day stellar rotation period. We have examined the magnetic activity of GJ 176 using the sodium I D lines, which have been shown to be a sensitive activity tracer in cool stars. In addition to rotational modulation, we see evidence of a long-term trend in our Na I D index, which may be part of a long-period activity cycle. The sodium index is well correlated with our RVs, and we show that this activity trend drives a corresponding slope in RV. Interestingly, the rotation signal remains in phase in photometry, but not in the spectral activity indicators. We interpret this phenomenon as the result of one or more large spot complexes or active regions which dominate the photometric variability, while the spectral indices are driven by the overall magnetic activity across the stellar surface. In light of these results, we discuss the potential for correcting activity signals in the RVs of M dwarfs.Comment: Accepted for publication in Ap

Evaluation with Simulation of Lucerne-Based Cropping Systems to Combat Dryland Salinity in Australia

Dryland salinity is one of the most significant forms of land degradation that farmers face in Australia. There are currently 2.5 million ha affected by dryland salinity in Australia, and this may rise to 15 million ha over the next 30 to 100 years if no action is taken. National field experiments suggest that adoption of cropping systems that integrate deep-rooted perennials, such as lucerne, are important to reduce dryland salinity. This paper reports simulation results with APSIM (The Agricultural Production Systems Simulator), that have been used to explore climate, soil and agronomic factors affecting effectiveness of lucerne-based phase and companion cropping systems in sustaining crop yield and reducing deep-water drainage in South Australia

Small Manufacturer Strategic Decision Making Assistance Tool (SMSDM): a Case Study of a Small Oklahoma Manufacturer

The propose was to design an informative analytical tool for small Oklahoma manufacturing firms that would assist in their strategic planning and decision making processes. The specific objectives were to: 1) determine the probability of a positive cash flow and profit for a small Oklahoma manufacturer under different product mixes and production practice scenarios; 2) analyze seasonal sales variability of a small Oklahoma manufacture and determine its effect on the manufacturer's monthly cash flow and profit given various product mixes; and 3) determine the importance of variability in prices of key inputs, primarily steel, on cash flow and profit. Data was obtained for a small Oklahoma manufacturer and the Bureau of Labor Statistics. The program Simetar was used to run cash flow simulations and project cash flow probabilities for a case study. An informative analytical tool for small Oklahoma manufacturers was successfully created and used to run six simulations. Cash flow projections for the case study show that the firm has a cash flow problem during summer months of the year. The negative cash flow for the summer months was found to be most directly related to variability in product sales. Steel price variability did affect cash flows negatively during the summer months also but was less of a factor than sales variability. The firm had the highest projected annual cash flows when producing one newly designed product and two of the standard products while manufacturing when products are ordered.Department of Agricultural Economic

Revisiting rho 1 Cancri e: A New Mass Determination Of The Transiting super-Earth

We present a mass determination for the transiting super-Earth rho 1 Cancri e based on nearly 700 precise radial velocity (RV) measurements. This extensive RV data set consists of data collected by the McDonald Observatory planet search and published data from Lick and Keck observatories (Fischer et al. 2008). We obtained 212 RV measurements with the Tull Coude Spectrograph at the Harlan J. Smith 2.7 m Telescope and combined them with a new Doppler reduction of the 131 spectra that we have taken in 2003-2004 with the High-Resolution-Spectrograph (HRS) at the Hobby-Eberly Telescope (HET) for the original discovery of rho 1 Cancri e. Using this large data set we obtain a 5-planet Keplerian orbital solution for the system and measure an RV semi-amplitude of K = 6.29 +/- 0.21 m/s for rho 1 Cnc e and determine a mass of 8.37 +/- 0.38 M_Earth. The uncertainty in mass is thus less than 5%. This planet was previously found to transit its parent star (Winn et al. 2011, Demory et al. 2011), which allowed them to estimate its radius. Combined with the latest radius estimate from Gillon et al. (2012), we obtain a mean density of rho = 4.50 +/- 0.20 g/cm^3. The location of rho 1 Cnc e in the mass-radius diagram suggests that the planet contains a significant amount of volitales, possibly a water-rich envelope surrounding a rocky core.Comment: 16 pages, 5 figures, accepted for publication in the Astrophysical Journal (the 300+ RV measurements will be published as online tables or can be obtained from the author

94 GHz Radar Backscatter Characteristics of Alpine Glacier Ice

Acknowledgments William D. Harcourt would like to thank PhD studentship funding from SAGES and EP281 SRC (grant number: EP/R513337/1). Funding for this study was obtained from the Scot282 tish Alliance for Geoscience, Environment and Society (SAGES) Small Grant Scheme. We would like to thank the staff at the Rhˆonegletscher Eisgrotte Cafe for enabling en284 trance to the field site and supporting the field activities, as well as the VAW Glaciol285 ogy Group and Glacier Monitoring in Switzerland groups for providing aerial photogram metry data over Rhˆonegletscher. Thanks also to Josu´e Gehring, Alexis Berne and Etienne Vignon for assisting with collection and delivery of our equipment at Ecole Polytechnique D´ed´erale de Lausanne (EPFL).Peer reviewedPublisher PD

Heavy cannabis use is associated with low bone mineral density and an increased risk of fractures

Purpose: To investigate possible associations between recreational cannabis use and bone health in humans.  Methods: Cross-sectional study of individuals recruited from primary care in the UK between 2011 and 2014. Cases were regular smokers of cannabis divided into moderate (n=56) and heavy user (n=144) subgroups depending on whether they reported fewer or more than 5000 cannabis smoking episodes during their lifetime. Controls comprised 114 cigarette smokers.  Results: Heavy cannabis users had lower total hip bone mineral density (mean ± SD Z-score: -0.20±0.9 vs. +0.2±0.9, p<0.0005), lower spine bone mineral density (-0.5±1.2 vs. 0.0±1.2, p<0.0005) and lower BMI (26.5±6.0 vs 29.0±7.0, p=0.01) than controls. Fracture rate was also increased in heavy users (rate ratio=2.17, 95% confidence interval 1.59 to 2.95; p<0.001). When compared with controls, CTX serum concentrations were raised in heavy cannabis users (0.3±0.1 vs. 0.2±0.1 pg/ml, p=0.045) as were P1NP concentrations (47.1±19.2 vs. 41.2±17.8 pg/ml, p=0.01). Serum 25(OH)D concentrations were reduced in heavy users compared with controls (25.3±16.8 vs. 36.9±26.7 nmol/l, p=0.002). Multiple regression analysis revealed that heavy cannabis use was an independent predictor of spine bone mineral density accounting for 5.4% of the variance (p=0.035) and total hip bone mineral density accounting for 5.8% of the variance (p=0.001) but mediation analysis suggested that the effect on spine bone mineral density was indirect and mediated through low BMI.  Conclusion: Heavy cannabis use is associated with low bone mineral density, low BMI, high bone turnover and an increased risk of fracture. Heavy cannabis use negatively impacts on bone health both directly and indirectly through an effect on BMI