Sounding stellar cycles with Kepler - preliminary results from ground-based chromospheric activity measurements

Due to its unique long-term coverage and high photometric precision, observations from the Kepler asteroseismic investigation will provide us with the possibility to sound stellar cycles in a number of solar-type stars with asteroseismology. By comparing these measurements with conventional ground-based chromospheric activity measurements we might be able to increase our understanding of the relation between the chromospheric changes and the changes in the eigenmodes. In parallel with the Kepler observations we have therefore started a programme at the Nordic Optical Telescope to observe and monitor chromospheric activity in the stars that are most likely to be selected for observations for the whole satellite mission. The ground-based observations presented here can be used both to guide the selection of the special Kepler targets and as the first step in a monitoring programme for stellar cycles. Also, the chromospheric activity measurements obtained from the ground-based observations can be compared with stellar parameters such as ages and rotation in order to improve stellar evolution models.Comment: submitted to the proceedings of the IAU symposium No. 264, 200

Cuidados com a nutrição da melancia em Rondônia.

Esta publicação teve como objetivo informar sobre o tratamento adequado para a nutrição da melancia, no que se refere a amostra de solo para análise química, calagem, adubação (adubação orgânica e química).bitstream/item/23258/1/Cot301-melancia.pd

Age and helium content of the open cluster NGC 6791 from multiple eclipsing binary members. I. Measurements, methods, and first results

Earlier measurements of the masses and radii of the detached eclipsing binary V20 in the open cluster NGC 6791 were accurate enough to demonstrate that there are significant differences between current stellar models. Here we improve on those results and add measurements of two additional detached eclipsing binaries, the cluster members V18 and V80. The enlarged sample sets much tighter constraints on the properties of stellar models than has hitherto been possible, thereby improving both the accuracy and precision of the cluster age. We employed (i) high-resolution UVES spectroscopy of V18, V20 and V80 to determine their spectroscopic effective temperatures, [Fe/H] values, and spectroscopic orbital elements, and (ii) time-series photometry from the Nordic Optical Telescope to obtain the photometric elements. The masses and radii of the V18 and V20 components are found to high accuracy, with errors on the masses in the range 0.27-0.36% and errors on the radii in the range 0.61-0.92%. V80 is found to be magnetically active, and more observations are needed to determine its parameters accurately. The metallicity of NGC 6791 is measured from disentangled spectra of the binaries and a few single stars to be [Fe/H]= +0.29 \pm 0.03 (random) \pm 0.07 (systematic). The cluster reddening and apparent distance modulus are found to be E(B - V) = 0.160 \pm 0.025 and (m - M)V = 13.51 \pm 0.06 . A first model comparison shows that we can constrain the helium content of the NGC 6791 stars, and thus reach a more accurate age than previously possible. It may be possible to constrain additional parameters, in particular the C, N, and O abundances. This will be investigated in paper II.Comment: Accepted for publication in A&

Detection of Solar-like Oscillations in the G7 Giant Star xi Hya

We report the firm discovery of solar-like oscillations in a giant star. We monitored the star xi Hya (G7III) continuously during one month with the CORALIE spectrograph attached to the 1.2m Swiss Euler telescope. The 433 high-precision radial-velocity measurements clearly reveal multiple oscillation frequencies in the range 50 - 130 uHz, corresponding to periods between 2.0 and 5.5 hours. The amplitudes of the strongest modes are slightly smaller than 2 m/s. Current model calculations are compatible with the detected modes.Comment: 4 pages, 4 figures, accepted for publication as a letter in A&

Plasma wave measurements for the Mariner to Venus and Mercury Final report of the Plasma Wave Instrument Science Advisory Team for the 1973 Mercury/Venus mission design

Very low frequency electric and magnetic wave measurements for Mariner Venus Mercury 1973 missio

Fixed-delay Interferometry for Doppler Extra-solar Planet Detection

We present a new technique based on fixed-delay interferometry for high throughput, high precision and multi-object Doppler radial velocity (RV) surveys for extra-solar planets. The Doppler measurements are conducted through monitoring the stellar fringe phase shifts of the interferometer. High Doppler sensitivity is achieved through optimizing the optical delay in the interferometer and reducing photon noise by measuring multiple fringes over a broadband. This broadband operation is performed through coupling the interferometer with a low to medium resolution post-disperser. The total Doppler sensitivity of this approach is, in theory, independent of dispersing power of the post-disperser, which allows development of new generation RV machines with much reduced size, high stability and low cost compared to echelles. This technique has the potential to improve RV survey efficiency by 2-3 orders of magnitude over cross-dispersed echelle spectroscopy approach to allow a full sky RV survey for planets once the instrument is operated as a multi-object instrument and optimized for high throughput. The simple interferometer response potentially allows this technique to be operated at other wavelengths independent of popular iodine reference sources to search for planets around early type stars, white dwarfs, and M, L and T dwarfs for the first time.Comment: Accepted to ApJ Letters for publication, 11 pages, 2 figure