A5052810557- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Solar and Space Plasma Dynamics
- Adaptive optics and wavefront sensing
Nicolaus Copernicus Astronomical Center
2022
Polish Academy of Sciences
2022
St Petersburg University
2011-2016
University of Amsterdam
2016
Institute of Applied Astronomy
2010
Observations of individual massive stars, super-luminous supernovae, gamma-ray bursts, and gravitational-wave events involving spectacular black-hole mergers, indicate that the low-metallicity Universe is fundamentally different from our own Galaxy. Many transient phenomena will remain enigmatic until we achieve a firm understanding physics evolution stars at low metallicity (Z). The Hubble Space Telescope has devoted 500 orbits to observe 250 Z in ultraviolet (UV) with COS STIS...
Strong, globally-organized magnetic fields are found for a small fraction of O, B, and A stars. At the same time, many theoretical indirect observational studies suggested ubiquitous presence weak localized at surfaces massive However, no direct detections such have been reported yet. We carried out first comprehensive investigation spectropolarimetric signatures structured fields. These calculations applied to interpret null results recent surveys The intensity circular polarization spectra...
Context. Most O-type stars and many B show unexplained cyclical variability in their spectral lines, i.e., modulation on the rotational timescale, but not strictly periodic. The occurs so-called discrete absorption components (DACs) that accelerate through UV-wind line profiles also optical lines. For such OB no dipolar magnetic fields have been detected with upper limits of ~300 G.
Abstract Many O and B stars show unexplained cyclical variability in their winds, i.e. modulation of absorption features on the rotational timescale, but not strictly periodic over longer timescales. For these no dipolar magnetic fields have been detected, with upper limits below 300 G. Similar is also found many optical lines, which are formed at base wind. We propose that variations caused by presence multiple, transient, short-lived, corotating loops, we call “stellar prominences”....
We describe the version of Temporal Variance Spectrum (TVS, Fullerton, Gies & Bolton 1996) method with pre-smoothed line profile (smoothed Spectrum, smTVS). This introduced by Kholtygin et al. (2003) can be used to detect ultra weak variations even for very noisy stellar spectra. also how estimate mode non-radial pulsations (NRP) using TVS and smTVS different time spans. The influence rotational modulation on is considered. analysis contribution NRP in global studied.
Abstract We studied the statistical properties of magnetic fields OB stars based on recent measurements. As statistically significant characteristic field we use rms star ${\cal B}$ . The distribution functions f ( ) are evaluated. function has a power-law dependence with an index about 2-3 and fast drop below = 100 − 300 G. proposed that compact regions strong local can contribute to global O stars.
Abstract Many OB stars show unexplained cyclical variability in their winds and many optical lines, which are formed at the base of wind. For these no dipolar magnetic fields have been detected. We propose that variations caused by presence multiple, transient, short-lived, corotating loops, we call “stellar prominences”. present a simplified model representing prominences as spherical blobs fit rapid He ii λ4686 line O supergiant λ Cep for time-resolved spectra obtained 1989. Our...
Abstract We report the results of our study fast line profile variability (LPV) (hours – few days) in spectra bright OB and WR stars. All were obtained with 6-m 1-m telescope Russian Special Astrophysical Observatory (SAO) 1.8-m Bohyunsan Optical Astronomy Observatory, Korea (BOAO). detected both stochastic LPV, connected formation small-scale structures stellar wind regular LPV induced by large-scale wind.
Abstract We report the results of a search for line profile variability (LPV) in spectra OB stars. The wavelets were used looking irregular LPV program connect appearance details with formation and dissipation small-scale substructures (clumps) wind.
The results of a search for line profile variability (LPV) and polarimetric (pLPV) in spectra O stars are reported. observations were made with the 1.8-m telescope Korean Bohyunsan Optical Astronomical Observatory (BOAO) 1-m 6-m telescopes Special Astrophysical (SAO), Russia. Regular LPV all program found. We analyze connection between presence magnetic field nitrogen abundance anomalies, influence weak fields on pLPV. statistical properties mean fluxes OB studied.
We present strong evidence for a rotation period of 2.0406 d the O giant $ξ$ Persei, derived from NIV $λ$1718 wind line in 12 yr IUE data. predict that Per has magnetic dipole field, with superposed variable prominences. Favorable dates future measurements can be predicted. also analysed time-resolved He II 4686 spectra campaign 1989 by using same simplified model as before $λ$ Cephei, terms multiple spherical blobs attached to surface, called stellar prominences (Sudnik & Henrichs...
Polstar is a proposed NASA MIDEX space telescope that will provide high-resolution, simultaneous full-Stokes spectropolarimetry in the far ultraviolet, together with low-resolution linear polarimetry near ultraviolet. In this white paper, we describe unprecedented capabilities observatory would offer order to obtain unique information on magnetic and plasma properties of magnetospheres hot stars. This enable test fundamental hypothesis should act rapidly drain angular momentum, thereby...