A5048568152- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- Geophysics and Gravity Measurements
- High-pressure geophysics and materials
- Ionosphere and magnetosphere dynamics
- History and Developments in Astronomy
- Geomagnetism and Paleomagnetism Studies
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Atmospheric Ozone and Climate
- Adaptive optics and wavefront sensing
- Medical Education and Admissions
- Astrophysics and Cosmic Phenomena
- Particle physics theoretical and experimental studies
- Health and Medical Research Impacts
- Electron and X-Ray Spectroscopy Techniques
- Advanced Research in Science and Engineering
- Island Studies and Pacific Affairs
- Calibration and Measurement Techniques
- Solid-state spectroscopy and crystallography
Institute of Astronomy and National Astronomical Observatory
2013-2024
Institute of Astronomy
2013-2021
Université de Toulouse
2010-2017
Centre National de la Recherche Scientifique
2010-2017
Sofia University "St. Kliment Ohridski"
2013-2017
Université Toulouse III - Paul Sabatier
2011-2016
Institut de Recherche en Astrophysique et Planétologie
2011-2016
Bulgarian Academy of Sciences
2004-2014
Observatoire Midi-Pyrénées
2010
We present the results of a major high-resolution spectropolarimetric BCool project magnetic survey 170 solar-type stars. Surface fields were detected on 67 stars, with 21 classified as mature result that increases by factor 4 number stars which have been observed. In addition, field was for 3 out 18 subgiant surveyed. For population K-dwarfs, mean value |Bl| (|Bl|mean) also found to be higher (5.7 G) than |Bl|mean measured G-dwarfs (3.2 and F-dwarfs (3.3 G). sample whole, rotation rate...
We investigate the magnetic field at surface of 48 red giants selected as promising for detection Stokes V Zeeman signatures in their spectral lines. use spectropolarimeters Narval and ESPaDOnS to detect circular polarization within photospheric absorption lines our targets least-squares deconvolution (LSD) method. also measure classical S-index activity indicator, stellar radial velocity. To infer evolutionary status interpret results, we state-of-the-art models with predictions convective...
Betelgeuse is an M supergiant with a complex and extended atmosphere, which also harbors spots giant granules at its surface. A possible magnetic field could contribute to the mass loss heating of outer atmosphere. We observed Betelgeuse, directly study infer nature field. used new-generation spectropolarimeter NARVAL least square deconvolution (LSD) method detect circular polarization within photospheric absorption lines Betelgeuse. have unambiguously detected weak Stokes V signal in...
Aims: We observe the nearby, weakly-active single giant, Pollux, in order to directly study and infer nature of its magnetic field. Methods: used new generation spectropolarimeters ESPaDOnS NARVAL detect circular polarization within photospheric absorption lines Pollux. Our observations span 18 months from 2007-2009. treated spectropolarimetric data using Least-Squares Deconvolution method create high signal-to-noise ratio mean Stokes V profiles. also measured classical activity indicator...
In order to complete the knowledge of magnetic field and its influence during transition from Asymptotic Giant Branch Planetary Nebulae stages, we have undertaken a search for fields at surface Mira stars. We used spectropolarimetric observations, collected with Narval instrument TBL, in detect - Least Squares Deconvolution method Zeeman signature visible part spectrum. present first observations S-type star chi Cyg, performed around maximum light. detected polarimetric signal Stokes V...
A sample of 19 solar-type stars, probing masses between 0.6 and 1.4 solar mass rotation periods 3.4 43 days, was regularly observed using the NARVAL spectropolarimeter at Telescope Bernard Lyot (Pic du Midi, France) 2007 2011. The Zeeman-Doppler Imaging technique is employed to reconstruct large-scale photospheric magnetic field structure targets investigate its long-term temporal evolution. We present here first results this project with observation short cycles in several showing up a...
Aims. Understanding convection in red supergiants and the mechanisms that trigger mass loss from these evolved stars are general goals of most observations Betelgeuse its inner circumstellar environment. Methods. Linear spectropolarimetry atomic lines spectrum reveals information about three-dimensional (3D) distribution brightness atmosphere. We model plasma velocities use inversion algorithms to fit observed linear polarization. Results. obtain first 3D images photosphere Betelgeuse....
Aims. We observe the slowly-rotating, active, single giant, EK Eri, to study and infer nature of its magnetic field directly.
Aims. We investigate the long-term evolution of large-scale photospheric magnetic field geometry solar-type star HD 190771. With fundamental parameters very close to those Sun except for a shorter rotation period 8.8 d, 190771 provides us with first insight into specific impact rate in dynamo generation fields 1 $M_\odot$ stars. Methods. use circularly polarized, high-resolution spectra obtained NARVAL spectropolarimeter (Observatoire du Pic Midi, France) and compute cross-correlation line...
EK Eri is one of the most slowly rotating active giants known, and has been proposed to be descendant a strongly magnetic Ap star. We have performed spectropolarimetric study over 4 photometric periods with aim inferring topology its field. used NARVAL spectropolarimeter at Bernard Lyot telescope Pic du Midi Observatory, along least-squares deconvolution method, extract high signal-to-noise ratio Stokes V profiles from timeseries 28 polarisation spectra. derived surface-averaged longitudinal...
Recent spectropolarimetric observations of otherwise ordinary G, K, and M giants revealed localized magnetic strips in the HRD coincident with regions where first dredge-up core He-burning occur. We seek to understand origin fields such late-type giant stars. In analogy dwarf stars, we focus primarily on parameters known influence generation outer convective envelope. compute classical dynamo along evolutionary tracks low- intermediate-mass stars at various metallicities using stellar models...
Betelgeuse is an M supergiant that harbors spots and giant granules at its surface presents linear polarization of continuum. We have previously discovered signatures associated with individual lines in the spectra cool evolved stars. Here, we investigate whether a similar linearly polarized spectrum exists for Betelgeuse. used spectropolarimeter Narval, combining multiple polarimetric sequences to obtain high signal-to-noise ratio lines, as well least-squares deconvolution (LSD) approach....
Aims.We report results of a quantitative colorimetric UBVRI analysis two flare events on the red dwarf EV Lac. The photometric data were obtained in September 2004, during multi-site synchronous monitoring from four observatories Ukraine, Russia, Greece, and Bulgaria. These observations confirmed presence small-scale high-frequency oscillations (HFO) initially detected by Rodonó (1974, A&A, 32, 337) recently reconfirmed authors. Here we discuss color characteristics flares HFO.
We study the fast rotating M5 giant EK Boo by means of spectropolarimetry to obtain direct and simultaneous measurements both magnetic field activity indicators, in order infer origin this fairly evolved giant. used new spectropolarimeter NARVAL at Bernard Lyot Telescope (Observatoire du Pic Midi, France) a series Stokes I V profiles for Boo. Using Least Square Deconvolution technique we were able detect Zeeman signature field. measured its longitudinal component averaged profiles. The...
Aims. We have studied the active giant V390 Aur using spectropolarimetry to obtain direct and simultaneous measurements of magnetic field activity indicators a precise insight its activity.
Aims.We have studied the active giant V390 Aur using spectropolarimetry to obtain direct and simultaneous measurements of magnetic field activity indicators in order infer origin activity.
The data were obtained using two spectropolarimeters - Narval at the Bernard Lyot Telescope, Pic du Midi, France, and ESPaDOnS CFHT, Hawaii. Thirty-eight circularly-polarized spectra have been collected in period June 2010 January 2012. Least Square Deconvolution method was applied for extracting high signal-to-noise ratio line profiles, from which we measure surface-averaged longitudinal magnetic field Bl. Chromospheric activity indicators CaII K, H_alpha, IR (854.2 nm) radial velocity...
<i>Aims. <i/>We report the detection of an unusually high lithium content in HD 232 862, a field giant classified as G8II star, and hosting magnetic field.<i>Methods. <i/>With spectropolarimeters ESPaDOnS at CFHT NARVAL TBL, we collected resolution signal-to-noise spectra three giants: KU Peg 21 018. From spectral synthesis inferred stellar parameters measured abundances that compared to predictions from evolutionary models. We also analysed Stokes <i>V<i/> signatures, looking for on these...
We present high resolution (0.06 A/px) spectroscopic observations of the recurrent nova T Coronae Borealis obtained during last 1.5 years (September 2022 -- January 2024), with 2.0m RCC telecope Rozhen National Astronomical Observatory, Bulgaria. Double-peaked emission is visible in H-alpha line after end superactive state. subtract red giant contribution and measure distance between peaks ($\Delta v_a$) line. For period July 2023 2024, we find that $\Delta v_a$ range $90 < \Delta v_a 120$...
Abstract We present high‐resolution (0.06 Å px) spectroscopic observations of the recurrent nova T Coronae Borealis obtained during last 1.5 years (September 2022–January 2024), with 2.0‐m RCC telescope Rozhen National Astronomical Observatory, Bulgaria. Double‐peaked emission is visible in line after end superactive state. subtract red giant contribution and measure distance between peaks () line. For period July 2023–January 2024, we find that range km s. Assuming from accretion disc...