7,074 research outputs found
Multiwavelength optical observations of chromospherically active binary systems V. FF UMa (2RE J0933+624): a system with orbital period variation
This is the fifth paper in a series aimed at studying the chromospheres of
active binary systems using several optical spectroscopic indicators to obtain
or improve orbital solution and fundamental stellar parameters. We present here
the study of FF UMa (2RE J0933+624), a recently discovered, X-ray/EUV selected,
active binary with strong H_alpha emission. The objectives of this work are, to
find orbital solutions and define stellar parameters from precise radial
velocities and carry out an extensive study of the optical indicators of
chromospheric activity. We obtained high resolution echelle spectroscopic
observations during five observing runs from 1998 to 2004. We found radial
velocities by cross correlation with radial velocity standard stars to achieve
the best orbital solution. We also measured rotational velocity by
cross-correlation techniques and have studied the kinematic by galactic space-
velocity components (U, V, W) and Eggen criteria. Finally, we have determined
the chromospheric contribution in optical spectroscopic indicators, from Ca II
H & K to Ca II IRT lines, using the spectral subtraction technique. We have
found that this system presents an orbital period variation, higher than
previously detected in other RS CVn systems. We determined an improved orbital
solution, finding a circular orbit with a period of 3.274 days. We derived the
stellar parameters, confirming the subgiant nature of the primary component and
obtained rotational velocities (vsini), of 33.57 km/s and 32.38 km/s for the
primary and secondary components respectively. From our kinematic study, we can
deduce its membership to the Castor moving group. Finally, the activity study
has given us a better understanding of the possible mechanisms that produce the
orbital period variation.Comment: Latex file with 16 pages, 18 figures. Available at
http://www.ucm.es/info/Astrof/invest/actividad/actividad_pub.html Accepted
for publication in: Astronomy & Astrophysics (A&A
A new technique based on mini-UAS for estimating water and bottom radiance contributions in optically shallow waters
The mapping of nearshore bathymetry based on spaceborne radiometers is commonly used for QC ocean colour products in littoral waters. However, the accuracy of these estimates is relatively poor with respect to those derived from Lidar systems due in part to the large uncertainties of bottom depth retrievals caused by changes on bottom reflectivity. Here, we present a method based on mini unmanned aerial vehicles (UAS) images for discriminating bottom-reflected and water radiance components by taking advantage of shadows created by different
structures sitting on the bottom boundary. Aerial surveys were done with a drone Draganfly X4P during October 1 2013 in optically shallow waters of the Saint Lawrence Estuary, and during low tide. Colour images with a spatial resolution
of 3 mm were obtained with an Olympus EPM-1 camera at 10 m height. Preliminary results showed an increase of the relative difference between bright and dark pixels (dP) toward the red wavelengths of the camera's receiver. This is
suggesting that dP values can be potentially used as a quantitative proxy of bottom reflectivity after removing artefacts related to Fresnel reflection and bottom adjacency effects.Peer ReviewedPostprint (published version
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