A5029204635- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Solar and Space Plasma Dynamics
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Geomagnetism and Paleomagnetism Studies
- Pulsars and Gravitational Waves Research
- Mechanics and Biomechanics Studies
- Adaptive optics and wavefront sensing
- Particle accelerators and beam dynamics
- Particle Accelerators and Free-Electron Lasers
- Geophysics and Gravity Measurements
- Astrophysics and Cosmic Phenomena
- Photocathodes and Microchannel Plates
- Molecular Spectroscopy and Structure
- Chemical Thermodynamics and Molecular Structure
- Spectroscopy and Laser Applications
- Geophysics and Sensor Technology
- Cardiac Valve Diseases and Treatments
- Lung Cancer Diagnosis and Treatment
- High-pressure geophysics and materials
- Laser Design and Applications
Leibniz Institute for Astrophysics Potsdam
2015-2024
University of Florence
2022
Aarhus University
2022
University of Potsdam
2017
University of Oulu
2003-2009
University of Turku
2008-2009
Nordic Optical Telescope
2003
We study the time variations of cycles 20 active stars based on decades-long photometric or spectroscopic observations. A method time-frequency analysis, as discussed in a companion paper, is applied to data. Fifteen definitely show multiple cycles; records rest are too short verify timescale for second cycle. The typically systematic changes. For three stars, we found two each them that not harmonics, and which vary parallel, indicating common physical mechanism arising from dynamo...
The "B fields in OB stars" (BOB) collaboration is based on an ESO Large Programme, to study the occurrence rate, properties, and ultimately origin of magnetic massive stars. In framework this programme, we carried out low-resolution spectropolarimetric observations a large sample stars using FORS2 installed at VLT 8-m telescope. We determined field values with two completely independent reduction analysis pipelines. Our in-depth measurements shows that differences between our pipelines are...
We have used two robotic telescopes to obtain time-series high-resolution spectroscopy and V I and/or by photometry for a sample of 60 active stars. Orbital solutions are presented 26 SB2 19 SB1 systems with unprecedented phase coverage accuracy. The total 6,609 R=55,000 echelle spectra also systematically determine effective temperatures, gravities, metallicities, rotational velocities, lithium abundances absolute H{\alpha}-core fluxes as function time. is infer unspotted brightness, - b y...
The Herbig Ae/Be star HD,190073 is one of the very few magnetic stars for which close low-mass companions have been reported. Previously published field measurements indicated an annual change in configuration. We aim to study detail spectral and variability this characterise its magnetosphere first time. Newly acquired archival spectropolarimetric observations are combined determine a more precise period constrain geometry field. hydrogen line profiles studied using dynamical spectra....
Recent observations of the accretion disk around Herbig Ae/Be star HD,169142 have revealed its complex and asymmetric morphology that indicates presence planets. The knowledge magnetic field structure in host stars is indispensable for our understanding magnetospheric interaction between central stars, circumstellar (CS) environment, planetary companions. We want to study geometry HD,169142. measured mean longitudinal from high-resolution ESPaDOnS HARPS-pol spectra using least-squares...
Stars with very low levels of magnetic activity provide an opportunity for a more quantitative comparison the Sun during its Maunder minimum. We employ spectra from RAVE survey in search particularly low-activity stars goal identifying candidates so-called Maunder-minimum stars. Spectra were used to measure relative flux cores Ca ii infrared-triplet (IRT) lines. Those converted absolute emission-line fluxes and corrected target high-resolution STELLA ultra-high-resolution PEPSI spectra....
White-light flares are magnetically driven localized brightenings on the surfaces of stars. Their temporal, spectral, and statistical properties present a treasury physical information about stellar magnetic fields. The spatial distributions spots associated flaring regions help constrain dynamo theories. Moreover, thought to crucially affect habitability exoplanets that orbit these Measuring location stars other than Sun is challenging due lack resolution. Here we four fully convective...
We present comprehensive photometric R-band observations of the fading optical afterglow X-Ray Flash XRF050824, from 11 minutes to 104 days after burst. The lightcurve resembles lightcurves long duration Gamma-Ray Bursts (GRBs), i.e., a power-law albeit with rather shallow slope alpha=0.6. Our late images reveal host galaxy rest-frame B-band luminosity corresponding roughly 0.5 Lstar. star-formation rate as determined [O II] emission line is about 1.8 Msun per year. When accounting for...
We report the detection of a magnetic field in helium-strong star CPD-57 3509 (B2 IV), member Galactic open cluster NGC3293, and characterise star's atmospheric fundamental parameters. Spectropolarimetric observations with FORS2 HARPSpol are analysed using two independent approaches to quantify strength. A high-S/N FLAMES/GIRAFFE spectrum is hybrid non-LTE model atmosphere technique. Comparison stellar evolution models constrains parameters star. obtain firm surface averaged longitudinal...
Abstract We discuss activity phenomena observed in the spot distribution on young single solar‐type stars LQ Hya, AB Dor and EK Dra. These include cyclic variations of mean level, differential rotation, persistent active longitudes separated by 180° flip‐flop cycles. A comparison with sunspot reveals many similarities between Sun solar analogs. Our results confirm presence very dwarfs allow for studying evolution stellar magnetic during main‐sequence stage. (© 2005 WILEY‐VCH Verlag GmbH...
We analyse photometric observations of the young active dwarf AB Dor, spanning more than 20 years. Similar to solar analog LQ Hya, Dor shows long-lived, nonaxisymmetric spot distribution – longitudes in opposite hemispheres. The migrate nonlinearly fixed reference frame, because differential rotation and changes mean latitudes. At least two activity cycles are found data. One cycle originates from repeating switches between about (2–3)-year intervals. This results flip-flop 5.5 years, which...
We analyse photometric observations of the young active star EK Dra, altogether about 21 years. Similar to ZAMS stars LQ Hya and AB Dor, Dra shows long-lived, non-axisymmetric spot distribution with longitudes on opposite hemispheres. At least two activity cycle can be found from data. The first originates repeated switches between in (2–2.25)-year intervals, resulting a (4–4.5) second is order 10.5 years comes migration longitudes. Our data cover consecutive cycles. periodicity also present...
The origin and evolution of magnetism in OB stars is far from being well understood. With approximately 70 magnetic known, any new object with unusual characteristics may turn out to be a key piece the puzzle. We report detection an exceptionally strong field He-strong B2IV star CPD-62 2124. Spectropolarimetric FORS2 HARPSpol observations were analysed by two independent teams procedures, concluding on longitudinal 5.2 kG. quantitative characterisation stellar atmosphere yields effective...
Context: HD 54879 (O9.7 V) is one of a dozen O-stars for which an organized atmospheric magnetic field has been detected. To gain insights into the interplay between atmospheres, winds, and fields massive stars, we acquired UV X-ray data using Hubble Space Telescope XMM-Newton satellite. In addition, 35 optical amateur spectra were secured to study variability 54879. A multiwavelength (X-ray optical) spectral analysis performed Potsdam Wolf-Rayet (PoWR) model atmosphere code xspec software....
The detection of exoplanets using any method is prone to confusion due the intrinsic variability host star. We investigate effect cool starspots on detectability around solar-like stars radial velocity method. For investigating this activity-caused "jitter" we calculate synthetic spectra radiative transfer, known stellar atomic and molecular lines, different surface spot configurations, an added planetary signal. Here, methods are described in detail, tested compared previously published...
ABSTRACT Although significant progress has been achieved in recent surveys of the magnetism massive stars, origin detected magnetic fields remains to be least understood topic their studies. We present an analysis 61 high-resolution spectropolarimetric observations 36 systems with O-type primaries, among them 10 known particle-accelerating colliding-wind binaries exhibiting synchrotron radio emission. Our sample consists multiple components at different evolutionary stages wide and tight...
Aims. In this paper we analyse photometric and spectroscopic observations of the young active dwarf V889 Her. We present new surface temperature maps, compare them to earlier published Doppler as well results obtained from long-term photometry.
RX J0806+15 has recently been identified as the binary system with shortest known orbital period. We present a series of observations including new optical taken one month apart. Using these and archival data we find that period this is decreasing over time. Our measurements imply f_dot = 6.11x10^-16 Hz/s, which in agreement rate expected from gravitational radiation for two white dwarfs orbiting at given However, smaller value 3.14x10^-16 Hz/s cannot be ruled out. result supports idea 321.5...
Context.As a young solar analogue, EK Draconis provides an opportunity to study the magnetic activity of infant Sun.
Aims. We present the first temperature surface map of EK Dra from very-high-resolution spectra obtained with Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at Large Binocular Telescope. Methods. Changes in spectral line profiles are inverted to a stellar using our i Map code. The long-term photometric record is employed compare previously published maps. Results. Four cool spots were reconstructed, but no polar spot was seen. difference photosphere between 990 280 K. Two...
Models of magnetically-driven accretion and outflows reproduce many observational properties T Tauri stars. This concept is not well established for the more massive Herbig Ae/Be We intend to examine magnetospheric in stars search rotational modulation using spectroscopic signatures, this first paper concentrating on well-studied Ae star HD101412. used near-infrared observations magnetic HD101412 test character its disk/star interaction. reduced analyzed 30 spectra HD101412, acquired with...
Since its discovery more than half a century ago Przybylski's star (HD101065) continues to excite the astronomical community by unusual nature of spectrum, exhibiting exotic element abundances. This was also first magnetic chemically peculiar A-type for which presence rapid oscillations established. Our analysis newly acquired and historic longitudinal field measurements indicates that is with respect extremely slow rotation. Adopting dipolar structure using sine wave fit all reported values...