A5056341479- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Adaptive optics and wavefront sensing
- Geomagnetism and Paleomagnetism Studies
- Geophysics and Gravity Measurements
- Atmospheric Ozone and Climate
- High-pressure geophysics and materials
- Pulsars and Gravitational Waves Research
- Atomic and Molecular Physics
- Calibration and Measurement Techniques
- Scientific Research and Discoveries
- Astrophysical Phenomena and Observations
- Inertial Sensor and Navigation
- Atomic and Subatomic Physics Research
- Nuclear Physics and Applications
- Advanced MRI Techniques and Applications
- Spectroscopy and Laser Applications
- Astronomical and nuclear sciences
- Ionosphere and magnetosphere dynamics
- Space Technology and Applications
Uppsala University
2015-2024
University of Helsinki
2009-2022
Turku Centre for Computer Science
2022
University of Turku
2022
Aalto University
2022
Max Planck Institute for Solar System Research
2022
University of Göttingen
2017
Astronomy and Space
2006-2013
Leibniz Institute for Astrophysics Potsdam
2009
Friedrich-Alexander-Universität Erlangen-Nürnberg
2006
The MiMeS (Magnetism in Massive Stars) project is a large-scale, high-resolution, sensitive spectropolarimetric investigation of the magnetic properties O- and early B-type stars. Initiated 2008 completed 2013, was supported by three Large Program allocations, as well various programmes initiated independent principal investigators, archival resources. Ultimately, over 4800 circularly polarized spectra 560 O B stars were collected with instruments ESPaDOnS (Echelle SpectroPolarimetric Device...
We present the analysis performed on spectropolarimetric data of 97 O-type targets included in framework MiMeS (Magnetism Massive Stars) Survey. Mean Least-Squares Deconvolved Stokes I and V line profiles were extracted for each observation, from which we measured radial velocity, rotational non-rotational broadening velocities, longitudinal magnetic field. The investigation led to discovery 2 new multi-line spectroscopic systems (HD46106, HD204827) confirmed presence a suspected companion...
Context . General circulation models of gas giant exoplanets predict equatorial jets that drive inhomogeneities in the atmospheric physical parameters across planetary surface. Aims We studied transmission spectrum hot Jupiter WASP-127 b during one transit K band with CRIRES + Methods Telluric and stellar signals were removed from data using SYSREM signal was investigated cross-correlation technique. After detecting a spectral indicative inhomogeneities, we employed Bayesian retrieval...
We describe our latest Magnetic Doppler Imaging (MDI) code capable of simultaneously reconstructing the magnetic field vector and chemical composition distribution over stellar surface. Input data consists polarization measurements in line profiles reconstruction is performed by solving regularized inverse problem. The incorporates developments radiative transfer, optimization parallel computing techniques. have also developed a new regularization method that allows application MDI to...
Magnetic fields play a fundamental role for interior and atmospheric properties of M dwarfs greatly influence terrestrial planets orbiting in the habitable zones these low-mass stars. Determination strength topology magnetic fields, both on stellar surfaces throughout extended magnetospheres, is key ingredient advancing planetary science. Here modern methods field measurements applied to M-dwarf stars are reviewed, with an emphasis direct diagnostics based interpretation Zeeman effect...
Magnetic confinement of stellar winds leads to the formation magnetospheres, which can be sculpted into Centrifugal Magnetospheres (CMs) by rotational support corotating plasma. The conditions required for CMs magnetic early B-type stars yield detectable emission in H$\alpha$ -- principal diagnostic these structures are poorly constrained. A key reason is that no detailed study and evolution this population has yet been performed. Using newly determined periods, modern measurements,...
ABSTRACT Numerous magnetic hot stars exhibit gyrosynchrotron radio emission. The source electrons were previously thought to be accelerated relativistic velocities in the current sheet formed middle magnetosphere by wind opening field lines. However, a lack of dependence luminosity on power, and strong rotation, has recently challenged this paradigm. We have collected all measurements early-type available literature. When constraints and/or rotational period are not available, we determined...
The CRyogenic InfraRed Echelle Spectrograph (CRIRES) Upgrade project CRIRES$^{+}$ extended the capabilities of CRIRES. It transformed this VLT instrument into a cross-dispersed spectrograph to increase wavelength range that is covered simultaneously by up factor ten. In addition, new detector focal plane array three Hawaii 2RG detectors with 5.3 $\mu$m cutoff replaced existing detectors. Amongst many other improvements, spectropolarimetric unit was added and calibration system has been...
Context. When observing the atmospheres of transiting exoplanets using high-resolution spectroscopy, aim is to detect well-resolved spectral features with high signal-to-noise ratios (S/Ns), as possible today modern spectrographs. However, obtaining such high-quality observations comes a trade-off: lower cadence fewer, longer exposures across transit collects more photons thanks reduced overheads, enhancing S/N each observation, while higher several shorter minimises feature smearing due...
We present the first investigation of structure stellar surface magnetic field using line profiles in all four Stokes parameters. extract information about geometry and abundance distributions chemically peculiar star 53 Cam by modelling time-series high-resolution spectropolarimetric observations with help a new Doppler imaging code. This combination unique parameter data state-of-the-art technique makes it possible to infer topology directly from rotational variability spectra. In we...
We present the evidence for abundance stratification in atmosphere of rapidly oscillating Ap star γ Equ. Ca, Cr, Fe, Ba, Si, Na seem to be overabundant deeper atmospheric layers, but normal underabundant upper layers with a transition typical line forming region . This profile agrees well diffusion theory Ca and developed cool magnetic stars weak mass loss yr-1. Pr Nd from rare earth elements have an opposite profile. Their is more than 6 dex higher above layers. further discuss implications...
Context.The photospheres of about 5–10% the upper main sequence stars exhibit remarkable chemical anomalies. Many these chemically peculiar (CP) have a global magnetic field, origin which is still matter debate.
We present new absolute trigonometric parallaxes and proper motions for seven Pop II variable stars: five RR Lyr variables; RZ Cep, XZ Cyg, SU Dra, Lyr, UV Oct; two type 2 Cepheids; VY Pyx {\kappa} Pav. obtained these results with astrometric data from Fine Guidance Sensors, white-light interfer- ometers on Hubble Space Telescope. find in milliseconds of arc: 2.12\pm0.16 mas; 1.67\pm0.17 1.42\pm0.16 3.77\pm0.13 Oct, 1.71\pm0.10 Pyx, 6.44\pm0.23 Pav, 5.57\pm0.28 an average {\sigma}{\pi}/{\pi}...
Near-UV observations of the planet host star WASP-12 uncovered apparent absence normally conspicuous core emission Mg2 h&k resonance lines. This anomaly could be due either to (1) a lack stellar activity, which would unprecedented for solar-like imputed age WASP-12; or (2) extrinsic absorption, from intervening interstellar medium (ISM) material within system itself, presumably ablated extreme hot Jupiter WASP-12b. HIRES archival spectra Ca2 H&K lines show broad depressions in line cores,...
Context. The late-B, magnetic, chemically peculiar star CU Vir is one of the fastest rotators among intermediate-mass stars with strong fossil magnetic fields. It shows a prominent rotational modulation spectral energy distribution and absorption line profiles due to chemical spots exhibits unique, strongly beamed variable radio emission.
Global magnetic fields of active solar-like stars are, nowadays, routinely detected with spectropolarimetric measurements and are mapped Zeeman Doppler imaging (ZDI). However, due to the cancellation opposite field polarities, polarimetry only captures a tiny fraction flux cannot assess overall stellar surface if it is dominated by small-scale component. The analysis broadening in high-resolution intensity spectra can reveal these hidden complex fields. Historically, there were very few...
Aims. The goal of this work is to study the magnetic fields six young solar-analogue stars both individually, and collectively, search for possible field trends with age. If such are found, they can be used understand magnetism in context stellar evolution solar-like past Sun solar system. This also important atmospheric inner planets, Earth particular.
Abstract The nearby M dwarf binary GJ65 AB, also known as BL Cet and UV Cet, is a unique benchmark for investigation of dynamo-driven activity low-mass stars. Magnetic was repeatedly assessed by indirect means, such studies flares, photometric variability, X-ray, radio emission. Here, we present direct analysis large-scale local surface magnetic fields in both components. Interpreting high-resolution circular polarization spectra (sensitive to field geometry) uncovered remarkable difference...
We present the first results from Transiting Exoplanet Survey Satellite (TESS) on rotational and pulsational variability of magnetic chemically peculiar A-type stars. analyse TESS 2-min cadence data sectors 1 2 a sample 83 Five new rapidly oscillating Ap (roAp) stars are announced. One these pulsates with periods around 4.7 min, making it shortest period roAp star known to date. Four out five multiperiodic. Three singly periodic one show presence mode splitting. Individual frequencies...
Rapidly rotating early-type stars with strong magnetic fields frequently show H$\alpha$ emission originating in Centrifugal Magnetospheres (CMs), circumstellar structures which centrifugal support due to magnetically enforced corotation of the confined plasma enables it accumulate high densities. It is not currently known whether CM escapes via Breakout (CB), or by an unidentified leakage mechanism. We have conducted first comprehensive examination properties all display CM-pattern emission....
The rotation rates of main-sequence stars slow over time as they gradually lose angular momentum to their magnetized stellar winds. rate loss depends on the strength and morphology magnetic field, mass-loss rate, period, mass, radius. Previous observations suggested a shift in between two F-type with similar but very different ages (88 Leo rho CrB). In this Letter, we identify comparable transition an evolutionary sequence solar analogs 2-7 Gyr. We present new spectropolarimetry 18 Sco 16...
The dayside atmospheres of ultra-hot Jupiters (UHJs) are predicted to possess temperature inversion layers with extremely high temperatures at altitudes. We observed the thermal emission spectra WASP-18b and WASP-76b new CRIRES+ high-resolution spectrograph near-infrared wavelengths. Using cross-correlation technique, we detected strong CO lines in both planets, which confirms existence inversions on their hemispheres. two planets first UHJs orbiting F-type stars detected; previous...
Abstract During the first half of their main-sequence lifetimes, stars rapidly lose angular momentum to magnetized winds, a process known as magnetic braking. Recent observations suggest substantial decrease in braking efficiency when reach critical value Rossby number, stellar rotation period normalized by convective overturn timescale. Cooler have deeper convection zones with longer times, reaching this number at slower rates. The nature and timing transition weakened previously been...