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

Centralized Versus Decentralized Team Coordination Using Dynamic Scripting

Computer generated forces (CGFs) must display realistic behavior for tactical training simulations to yield an effective training experience. Tradionally, the behavior of CGFs is scripted. However, there are three drawbacks, viz. (1) scripting limits the adaptive behavior of CGFs, (2) creating scripts is difficult and (3) it requires scarce domain expertise. A promising machine learning technique is the dynamic scripting of CGF behavior. In simulating air combat scenarios, team behavior is important, both with and without communication. While dynamic scripting has been reported to be effective in creating behavior for single fighters, it has not often been used for team coordination. The dynamic scripting technique is sufficiently flexible to be used for different team coordination methods. In this paper, we report the first results on centralized coordination of dynamically scripted air combat teams, and compare these results to a decentralized approach from earlier work. We find that using the centralized approach leads to higher performance and more efficient learning, although creativity of the solutions seems bounded by the reduced complexity

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

Arterial stiffness index beta and cardio-ankle vascular index inherently depend on blood pressure but can be readily corrected

Objectives: Arterial stiffness index beta and cardio-ankle vascular index (CAVI) are widely accepted to quantify the intrinsic exponent (beta(0)) of the blood pressure (BP)-diameter relationship. CAVI and b assume an exponential relationship between pressure (P) and diameter (d). We aim to demonstrate that, under this assumption, beta and CAVI as currently implemented are inherently BP-dependent and to provide corrected, BP-independent forms of CAVI and beta.Methods and results: In P = P(ref)e(beta 0[(d/dref)-1)], usually reference pressure (P-ref) and reference diameter (d(ref)) are substituted with DBP and diastolic diameter to accommodate measurements. Consequently, the resulting exponent is not equal to the pressure-independent beta(0). CAVI does not only suffer from this 'reference pressure' effect, but also from the linear approximation of (dP=dd). For example, assuming beta(0) = 7, an increase of SBP/DBP from 110/70 to 170/120mmHg increased beta by 8.1% and CAVI by 14.3%. We derived corrected forms of b and of CAVI (CAVI(0)) that indeed did not change with BP and represent the pressure-independent beta(0). To substantiate the BP effect on CAVI in a typical follow-up study, we realistically simulated patients (n = 161) before and following BP-lowering 'treatment' (assuming no follow-up change in intrinsic beta(0) and therefore in actual P-d relationship). Lowering BP from 160 +/- 14/111 +/- 11 to 120 +/- 15/79 +/- 11 mmHg (p &lt;0.001) resulted in a significant CAVI decrease (from 8.1 +/- 2.0 to 7.7 +/- 2.1, p = 0.008); CAVI(0) did not change (9.8 +/- 2.4 and 9.9 +/- 2.6, p = 0.499).Conclusion: beta and CAVI as currently implemented are inherently BP-dependent, potentially leading to erroneous conclusions in arterial stiffness trials. BP-independent forms are presented to readily overcome this problem.</p

MASCARA-2 b: A hot Jupiter transiting the mV=7.6m_V=7.6 A-star HD185603

In this paper we present MASCARA-2 b, a hot Jupiter transiting the $m_V=7.6$ A2 star HD 185603. Since early 2015, MASCARA has taken more than 1.6 million flux measurements of the star, corresponding to a total of almost 3000 hours of observations, revealing a periodic dimming in the flux with a depth of $1.3\%$. Photometric follow-up observations were performed with the NITES and IAC80 telescopes and spectroscopic measurements were obtained with the Hertzsprung SONG telescope. We find MASCARA-2 b orbits HD 185603 with a period of $3.474119^{+0.000005}_{-0.000006}~\rm{days}$ at a distance of $0.057 \pm 0.006~\rm{AU}$, has a radius of $1.83 \pm 0.07~\rm{R}_{\rm{J}}$ and place a $99\%$ upper limit on the mass of $< 17~\rm{M}_{\rm{J}}$. HD 185603 is a rapidly rotating early-type star with an effective temperature of $8980^{+90}_{-130}~\rm{K}$ and a mass and radius of $1.89^{+0.06}_{-0.05}~M_\odot$, $1.60 \pm 0.06~R_\odot$, respectively. Contrary to most other hot Jupiters transiting early-type stars, the projected planet orbital axis and stellar spin axis are found to be aligned with $\lambda=0.6 \pm 4^\circ$. The brightness of the host star and the high equilibrium temperature, $2260 \pm 50~\rm{K}$, of MASCARA-2 b make it a suitable target for atmospheric studies from the ground and space. Of particular interest is the detection of TiO, which has recently been detected in the similarly hot planets WASP-33 b and WASP-19 b.Comment: 8 pages, 4 figures, Accepted for publication in A&

Data calibration for the MASCARA and bRing instruments

Aims: MASCARA and bRing are photometric surveys designed to detect variability caused by exoplanets in stars with $m_V < 8.4$. Such variability signals are typically small and require an accurate calibration algorithm, tailored to the survey, in order to be detected. This paper presents the methods developed to calibrate the raw photometry of the MASCARA and bRing stations and characterizes the performance of the methods and instruments. Methods: For the primary calibration a modified version of the coarse decorrelation algorithm is used, which corrects for the extinction due to the earth's atmosphere, the camera transmission, and intrapixel variations. Residual trends are removed from the light curves of individual stars using empirical secondary calibration methods. In order to optimize these methods, as well as characterize the performance of the instruments, transit signals were injected in the data. Results: After optimal calibration an RMS scatter of 10 mmag at $m_V \sim 7.5$ is achieved in the light curves. By injecting transit signals with periods between one and five days in the MASCARA data obtained by the La Palma station over the course of one year, we demonstrate that MASCARA La Palma is able to recover 84.0, 60.5 and 20.7% of signals with depths of 2, 1 and 0.5% respectively, with a strong dependency on the observed declination, recovering 65.4% of all transit signals at $\delta > 0^\circ$ versus 35.8% at $\delta < 0^\circ$. Using the full three years of data obtained by MASCARA La Palma to date, similar recovery rates are extended to periods up to ten days. We derive a preliminary occurrence rate for hot Jupiters around A-stars of ${>} 0.4 \%$, knowing that many hot Jupiters are still overlooked. In the era of TESS, MASCARA and bRing will provide an interesting synergy for finding long-period (${>} 13.5$ days) transiting gas-giant planets around the brightest stars.Comment: 18 pages, 17 figures, accepted for publication in A&