A5029729491- Stellar, planetary, and galactic studies
- Solar and Space Plasma Dynamics
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Solar Radiation and Photovoltaics
- Astronomical Observations and Instrumentation
- Atmospheric Ozone and Climate
- Calibration and Measurement Techniques
- Gamma-ray bursts and supernovae
- Atmospheric and Environmental Gas Dynamics
- Geophysics and Gravity Measurements
- Infrared Target Detection Methodologies
- Astrophysical Phenomena and Observations
- History and Developments in Astronomy
- Atmospheric chemistry and aerosols
- Adaptive optics and wavefront sensing
- Color Science and Applications
- Galaxies: Formation, Evolution, Phenomena
- Medical Imaging Techniques and Applications
- Pulsars and Gravitational Waves Research
- Inertial Sensor and Navigation
- Spectroscopy and Laser Applications
- Atomic and Molecular Physics
- Dark Matter and Cosmic Phenomena
Imperial College London
2013-2023
Kyung Hee University
2014
Max Planck Institute for Solar System Research
2000-2009
Atacama Large Millimeter Submillimeter Array
2009
Astronomical Institute of the Slovak Academy of Sciences
2009
Instituto de Astrofísica de Canarias
2009
UCL Australia
2008
Max Planck Society
2000-2004
University of Vienna
1998-2001
University of St Andrews
1995-1998
Since the discovery of transiting super-Earth CoRoT-7b, several investigations have yielded different results for number and masses planets present in system, mainly owing to star's high level activity. We re-observed CoRoT-7 January 2012 with both HARPS CoRoT, so that we now benefit simultaneous radial-velocity photometric data. This allows us use off-transit variations light curve estimate induced by suppression convective blueshift flux blocked starspots. To account activity-related...
The INT Photometric Halpha Survey of the Northern Galactic Plane (IPHAS) is a 1800 square degrees CCD survey northern Milky Way spanning latitude range -5 < b +5 (degrees) and reaching down to r' ~ 20 (10-sigma). It may increase number known emission line sources by an order magnitude. Representative observations assessment point-source data from IPHAS, now underway, are presented. obtained Wide Field Camera images in narrow-band, Sloan i' broad-band, filters. We simulate IPHAS (r' -...
The lack of long and reliable time series solar spectral irradiance (SSI) measurements makes an accurate quantification contributions to recent climate change difficult. Whereas earlier SSI observations models provided a qualitatively consistent picture the variability, by SORCE satellite suggest significantly stronger variability in ultraviolet (UV) range changes visible near-infrared (NIR) bands anti-phase with cycle. A number chemistry-climate model (CCM) simulations have shown that this...
The VST Photometric Halpha Survey of the Southern Galactic Plane and Bulge (VPHAS+) is surveying southern Milky Way in u, g, r, i at 1 arcsec angular resolution. Its footprint spans latitude range -5 < b +5 all longitudes south celestial equator. Extensions around Centre to latitudes +/-10 bring much Bulge. This ESO public survey, begun on 28th December 2011, reaches down 20th magnitude (10-sigma) will provide single-epoch digital optical photometry for 300 million stars. observing strategy...
The Sun is the only star whose surface can be directly resolved at high resolution, and therefore constitutes an excellent test case to explore physical origin of stellar radial-velocity (RV) variability. We present HARPS observations sunlight scattered off bright asteroid 4/Vesta, from which we deduced Sun's activity-driven RV variations. In parallel, Helioseismic Magnetic Imager instrument on board Solar Dynamics Observatory provided us with simultaneous spatial resolution magnetograms,...
Abstract Study Analysis Group 21 (SAG21) of NASA’s Exoplanet Exploration Program was organized to study the effect stellar contamination on space-based transmission spectroscopy, a method for studying exoplanetary atmospheres by measuring wavelength-dependent radius planet as it transits its star. Transmission spectroscopy relies precise understanding spectrum star being occulted. However, stars are not homogeneous, constant light sources but have temporally evolving photospheres and...
A model of solar irradiance variations is presented which based on the assumption that surface magnetism responsible for all total changes time scales days to years. series daily magnetograms and empirical models thermal structure magnetic features (sunspots, faculae) are combined reconstruct (and spectral) from 1996 2002. Comparisons with observational data reveal an excellent correspondence, although only contains a single free parameter. This provides strong support hypothesis caused by...
The INT/WFC Photometric H-Alpha Survey of the Northern Galactic Plane (IPHAS) is a 1800 square degrees imaging survey covering latitudes |b| < 5 deg and longitudes l = 30 to 215 in r, i H-alpha filters using Wide Field Camera (WFC) on 2.5-metre Isaac Newton Telescope (INT) La Palma. We present first quality-controlled globally-calibrated source catalogue derived from survey, providing single-epoch photometry for 219 million unique sources across 92% footprint. observations were carried out...
From observations collected with the ESPaDOnS and NARVAL spectropolarimeters, we report detection of Zeeman signatures on classical T Tauri star BP Tau. Circular polarisation in photospheric lines narrow emission tracing magnetospheric accretion are monitored throughout most rotation cycle Tau at two different epochs 2006. We observe that rotational modulation dominates temporal variations both unpolarised circularly polarised spectral proxies photosphere footpoints funnels. complete data...
The uninterrupted measurement of the total solar irradiance during last three cycles and an increasing amount spectral measurements as well imaging observations (magnetograms photometric data) have stimulated development models attributing variations to surface magnetism. Here we review current status modelling efforts based on photospheric magnetic fields. Thereby restrict ourselves study from days cycle. Phenomenological atmosphere in combination with electromagnetic radiation field...
Upper atmospheres of Hot Jupiters are subject to extreme radiation conditions that can result in rapid atmospheric escape. The composition and structure the upper these planets affected by high-energy spectrum host star. This emission depends on stellar type age, which thus important factors understanding behaviour exoplanetary atmospheres. In this study, we focus Extrasolar Giant Planets (EPGs) orbiting K M dwarf stars. XUV spectra for three different stars – ∊ Eridani, AD Leonis AU...
Context: The study of variations in total solar irradiance (TSI) is important for understanding how the Sun affects Earth's climate. Aims: Full-disk continuum images and magnetograms are now available three full cycles. We investigate modelled TSI compares with direct observations by building a consistent dataset. model, based only on changes photospheric magnetic flux can then be tested rotational, cyclical secular timescales. Methods: use Kitt Peak SoHO/MDI SATIRE-S model to reconstruct...
The Sun and stars with low magnetic activity levels, become photometrically brighter when their increases. Magnetically more active display the opposite behaviour get fainter We reproduce observed photometric trends in stellar variations a model that treats as hypothetical Suns coverage by features different from of Sun. presented attributes variability spectra to imbalance between contributions components solar atmosphere, such dark starspots bright faculae. A spectrum is calculated...
From observations collected with the ESPaDOnS & NARVAL spectropolarimeters at CFHT and TBL, we report detection of Zeeman signatures on prototypical classical TTauri star AATau, both in photospheric lines accretion-powered emission lines. Using time series unpolarized circularly polarized spectra, reconstruct two epochs maps magnetic field, surface brightness AATau. We find that AATau hosts a 2-3kG dipole tilted ~20deg to rotation axis, presumably dynamo origin. also show poles host large...
We report here results of spectropolarimetric observations the ~8Myr classical TTauri star (cTTS) TWHya carried out with ESPaDOnS at Canada-France-Hawaii Telescope (CFHT) in framework `Magnetic Protostars and Planets' (MaPP) programme, obtained 2 different epochs (2008 March 2010 March). Obvious Zeeman signatures are detected all times, both photospheric lines accretion-powered emission lines. Significant intrinsic variability moderate rotational modulation is observed accretion proxies....
The variation in the radiative output of Sun, described terms solar irradiance, is important to climatology. A common assumption that irradiance variability driven by its surface magnetism. Verifying this has, however, been hampered fact models based on magnetism have be calibrated observed variability. Making use realistic three-dimensional magnetohydrodynamic simulations atmosphere and state-of-the-art magnetograms from Solar Dynamics Observatory, we present a model total (TSI) does not...
The INT/WFC Photometric Hα Survey of the Northern Galactic Plane (IPHAS) is an imaging survey being carried out in Hα, r′ and i′ filters, with Wide Field Camera (WFC) on 2.5-m Isaac Newton Telescope (INT) to a depth r′= 20 (10σ). aimed at revealing large scale organization Milky Way can be applied identifying range stellar populations within it. Mapping emission line objects enables particular focus young old stages evolution ranging from early T-Tauri stars late planetary nebulae. In this...
We present a reconstruction of the spectral solar irradiance since 1700 using SATIRE-T2 (Spectral And Total Irradiance REconstructions for Telescope era version 2) model. This model uses as input magnetograms simulated with surface flux transport fed semi-synthetic records emerging sunspot groups. used statistical relationships between properties group emergence, such latitude, area, and tilt angle, cycle strength phase to produce starting in year 1700. The semisynthetic are into obtain...
We present a set of maximum-entropy reconstructions the star-spot distributions on two rapidly rotating G dwarfs in α Persei cluster, from spectra taken at William Herschel Telescope three nights 1996 October and November. Since these stars are too faint for conventional Doppler imaging, which makes use only one or few lines, we take large number photospheric metal lines available an echelle spectrum, deconvolve them into single, high signal-to-noise ratio profile. show that this technique...
We present Halpha spectropolarimetry observations of a sample 10 bright T Tauri stars, supplemented with new Herbig Ae/Be star data. A change in the linear polarisation across is detected most (9/10) and Ae (9/11) objects, which we interpret terms compact source line photons that scattered off rotating accretion disk. find consistency between position angle (PA) those imaged disk PAs from infrared millimetre imaging interferometry studies, probing much larger scales. For stars AB Aur, MWC...
From observations collected with the ESPaDOnS spectropolarimeter at Canada-France-Hawaii Telescope, we report detection of Zeeman signatures on low-mass classical TTauri star (cTTS) V2247Oph. Profile distortions and circular polarisation detected in photospheric lines can be interpreted as caused by cool spots magnetic regions surface star. The large-scale field is moderate strength highly complex; moreover, both spot distribution show significant variability a timescale only one week,...
We present an algorithm (MEAD, for 'Mapping Extinction Against Distance') which will determine intrinsic (r′−i′) colour, extinction, and distance early-A to K4 stars extracted from the IPHAS r′/i′/Hα photometric data base. These can be binned up map extinction in three dimensions across northern Galactic plane. The large size of base (∼200 million unique objects), accuracy digital photometry it contains its faint limiting magnitude (r′∼ 20) allow mapped with fine angular (∼10 arcmin) (∼ 0.1...
Aims: We investigate how well modeled solar irradiances agree with measurements from the SORCE satellite, both for total irradiance and broken down into spectral regions on timescales of several years. Methods: use SATIRE model compare (TSI) TSI between 2003 2009. Spectral over 200-1630nm is compared SIM instrument 2004 2009 during a period decline moderate activity to recent minimum in 10 nm bands three significant interest: UV integrated 200-300nm, visible 400-691nm IR 972-1630 nm....