Related papers: The Measurement of Solar Diameter and Limb Darkeni…
Spatially unresolved observations show that the cooling phase in solar flares can be much longer than theoretical models predict. It has not yet been determined whether this is also the case for different subregions within the flare…
We present exact analytic formulae for the eclipse of a star described by quadratic or nonlinear limb darkening. In the limit that the planet radius is less than a tenth of the stellar radius, we show that the exact lightcurve can be well…
This paper is based on a dataset of many strongly polarized solar lines belonging to the ''second solar spectrum'', i.e. the spectrum near the limb in linear scattering polarization. The observations were done at the Pic du Midi Turret Dome…
Stellar limb-darkening impacts a wide range of astronomical measurements. The accuracy to which it is modelled limits the accuracy in any covariant parameters of interest, such as the radius of a transiting planet. With the ever growing…
Using data from the Michelson Doppler Imager (MDI) instrument on board the Solar and Heliospheric Observatory (SOHO), we study the large-scale velocity fields in the outer part of the solar convection zone using the ring diagram technique.…
Solar limb and disc spicule quasi- periodic motions have been reported for a long time, strongly suggesting that they are oscillating. In order to clear up the origin and possibly explain some solar limb and disc spicule quasi-periodic…
The absolute brightness temperature of the Sun at millimeter wavelengths is an important diagnostic of the solar chromosphere. Because the Sun is so bright, measurement of this property usually involves the operation of telescopes under…
We present the first parallax and luminosity measurements for an L subdwarf, the sdL7 2MASS J05325346+8246465. Observations conducted over three years by the USNO infrared astrometry program yield an astrometric distance of 26.7+/-1.2 pc…
The photometry of eclipse white-light (W-L) images showing a moving blob is interpreted for the first time together with observations from space with the PRoject for On Board Autonomy (PROBA-2) mission (ESA). An off-limb event seen with…
Near-infrared photometry of transiting extrasolar planets can be of great scientific value. It is however not straightforward to reach the necessary millimagnitude precision. Here we report on our attempts to observe transits and secondary…
We present radio observations of the Moon between $35$ and $80$ MHz to demonstrate a novel technique of interferometrically measuring large-scale diffuse emission extending far beyond the primary beam (global signal) for the first time. In…
Observations of the dynamics of solar coronal structures are necessary to investigate space weather phenomena and global heating of the corona. The profiles of high temperature lines emitted by the hot plasma are usually integrated by…
We develop a new method to measure source proper motions in microlensing events, which can partially overcome problems due to blending. It takes advantage of the fact that the source position is known precisely from the microlensing event…
We explore the radial velocity performance benefits of coupling starlight to a fast-scanning interferometer and a fast-readout spectrometer with zero readout noise. By rapidly scanning an interferometer we can decouple wavelength…
The solar spectrum is a primary reference for the study of physical processes in stars and their variation during activity cycles. In Nov 2010 an experiment with a prototype of a Laser Frequency Comb (LFC) calibration system was performed…
(Abridged) In the first part of this thesis, a general methodology for applying image deconvolution to wide-field CCD imagery. Results show that wavelet-based deconvolution can increase limiting magnitude up to 0.6 mag and improve limiting…
From 1998 to 2003 the CCD Solar Astrolabe of the Observatorio Nacional in Rio de Janeiro made more than 20000 observations of the Solar Semidiameter. In the present work similar corrections for the observational results of 2002 and 2003…
Astrometric observations of microlensing events were originally proposed to determine the lens proper motion with which the physical parameters of lenses can be better constrained. In this proceeding, we demonstrate that besides this…
A new instrument was designed to take visible-light (VL) polarized brightness ($pB$) observations of the solar corona during the 14 December 2020 total solar eclipse. The instrument, called the Coronal Imaging Polarizer (CIP), consisted of…
Eclipse shadow bands are transient intensity patterns that can appear on the ground near solar eclipse totality. This study presents a reusable image-processing framework for analyzing shadow-band video recordings collected with…