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A spectroscopic technique employing an iodine absorption cell (I_2) to superimpose a reference spectrum onto a stellar spectrum is currently the most widely adopted approach to obtain precision radial velocities of solar-type stars. It has…
We present precise relative radial velocity (RV) measurements for the rapidly oscillating Ap (roAp) star 33 Librae measured from high resolution data spanning the wavelength interval 5000--6200 A. We find that pulsational radial velocity…
The atmosphere of a transiting planet shields the stellar radiation providing us with a powerful method to estimate its size and density. In particular, because of their high ionization energy, atoms with high atomic number (Z) absorb…
The gravitational redshift induced by stellar surface gravity is notoriously difficult to measure for non-degenerate stars, since its amplitude is small in comparison with the typical Doppler shift induced by stellar radial velocity. In…
Radio-loud active galactic nuclei (AGN) are among the most luminous objects in the Universe, emitting radiation from low-energy radio waves to high energy $\gamma$-rays. They are well known to exhibit flux variations at nearly all…
Spectroscopic observations are a crucial step in driving major discoveries in the era of time-domain surveys. However, the pace of current spectroscopic surveys is increasingly unable to meet the demands of rapidly advancing large-scale…
The present paper describes the first results of an observational program intended to refine and extend the existing vsini measurements of metal-poor stars, with anemphasis on field evolved stars. The survey was carried out with the FEROS…
Aims. The Radial Velocity Spectrometer (RVS) on board the ESA satellite mission Gaia has no calibration device. Therefore, the radial velocity zero point needs to be calibrated with stars that are proved to be stable at a level of 300 m/s…
Transit and radial velocity searches are two techniques for identifying nearby extrasolar planets to Earth that transit bright stars. Identifying a robust sample of these exoplanets around bright stars for detailed atmospheric…
We present radial velocities for 29 B- and A-type stars in the field of the nearby association Perseus OB2. The velocities are derived from spectra obtained with AURELIE, via cross correlation with radial velocity standards matched as…
This research note presents a comparison of radial velocities between the RAVE DR5 data release with Gaia DR2. RAVE DR5 and Gaia DR2 have 450587 stars in common. In particular we would like to shed light on a small subset of joint targets…
Stellar active regions, including spots and faculae, can create radial velocity (RV) signals that interfere with the detection and mass measurements of low mass exoplanets. In doing so, these active regions affect each spectral line…
We attempt to measure possible miscalibration of the wavelength scale of the VLT-UVES spectrograph. We take spectra of QSO HE0515-4414 through the UVES iodine cell which contains thousands of well-calibrated iodine lines and compare these…
We present the second data release of the Radial Velocity Experiment (RAVE), an ambitious spectroscopic survey to measure radial velocities (RVs) and stellar atmosphere parameters of up to one million stars using the 6dF multi-object…
The dependence of the long-term optical/UV variability on the spectral and the fundamental physical parameters for radio-quiet active galactic nuclei (AGNs) is investigated. The multi-epoch repeated photometric scanning data in the…
We present accurate, spatially resolved imaging of radio spectra at the bases of jets in eleven low-luminosity (Fanaroff-Riley I) radio galaxies, derived from Very Large Array (VLA) observations. We pay careful attention to calibration and…
FU Orionis objects are a class of young stars with important bursts in luminosity and which show evidence of accretion and ejection activity. It is generally accepted that they are surrounded by a Keplerian circumstellar disk and an…
Using a sample of 213,713 stars from the Radial Velocity Experiment (RAVE) survey, limited to a distance of 2 kpc from the Sun and to |z|<1 kpc, we report the detection of a velocity gradient of disc stars in the fourth quadrant, directed…
Ultraviolet flare emission can drive photochemistry in exoplanet atmospheres and even serve as the primary source of uncertainty in atmospheric retrievals. Additionally, flare energy budgets are not well-understood due to a paucity of…
Both Uranus and Neptune are thought to have strong zonal winds with velocities of several hundred meters per second. These wind velocities, however, assume solid-body rotation periods based on Voyager 2 measurements of periodic variations…