Valeriy Vasilyev
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View article: Separating Flare and Secondary Atmospheric Signals with <tt>RADYN</tt> Modeling of Near-infrared JWST Transmission Spectroscopy Observations of TRAPPIST-1
Separating Flare and Secondary Atmospheric Signals with RADYN Modeling of Near-infrared JWST Transmission Spectroscopy Observations of TRAPPIST-1 Open
Although TRAPPIST-1’s temperate planets have the highest transmission signals of any known system, flares contaminate 50%–70% of transits at the 1000 ppm level, far above 100 ppm secondary atmospheric signals. Efforts to mitigate flare con…
View article: Solar flares versus solar energetic particle events: Probabilistic projections to extreme events
Solar flares versus solar energetic particle events: Probabilistic projections to extreme events Open
Aims. Terrestrial cosmogenic isotope records yield that extreme solar particle events (ESPEs) are relatively rare, occurring approximately once every 1500 years. In contrast, stellar observations show that superflares on solar-like stars m…
View article: Sensitivity of spectral lines to granulation: The Sun
Sensitivity of spectral lines to granulation: The Sun Open
The intrinsic variability of stars, due to acoustic oscillations, surface granulation, and magnetic activity, introduces radial velocity (RV) jitter in spectral lines, obscuring true planetary signals and hindering the detection of Earth-l…
View article: Flares on TRAPPIST-1 Reveal the Spectrum of Magnetic Features on Its Surface
Flares on TRAPPIST-1 Reveal the Spectrum of Magnetic Features on Its Surface Open
TRAPPIST-1 is an M8 dwarf hosting seven known exoplanets and is currently one of the most frequently observed targets of the James Webb Space Telescope (JWST). However, it is notoriously active, and its surface is believed to be covered by…
View article: Detectability of Solar Rotation Period across Various Wavelengths
Detectability of Solar Rotation Period across Various Wavelengths Open
The light curves of old G dwarfs obtained in the visible and near-infrared wavelength ranges are highly irregular. This significantly complicates the detectability of the rotation periods of stars similar to the Sun in large photometric su…
View article: Sun-like stars produce superflares roughly once per century
Sun-like stars produce superflares roughly once per century Open
Stellar superflares are energetic outbursts of electromagnetic radiation that are similar to solar flares but release more energy, up to 10 36 erg on main-sequence stars. It is unknown whether the Sun can generate superflares and, if so, h…
View article: Reliable Transmission Spectrum Extraction with a Three-parameter Limb-darkening Law
Reliable Transmission Spectrum Extraction with a Three-parameter Limb-darkening Law Open
Stellar limb darkening must be properly accounted for to accurately determine the radii of exoplanets at various wavelengths. The standard approach to address limb darkening involves either using laws with coefficients from modeled stellar…
View article: Reliable Transmission Spectrum Extraction with a Three-Parameter Limb Darkening Law
Reliable Transmission Spectrum Extraction with a Three-Parameter Limb Darkening Law Open
Stellar limb darkening must be properly accounted for to accurately determine the radii of exoplanets at various wavelengths. The standard approach to address limb darkening involves either using laws with coefficients from modelled stella…
View article: Detecting stellar activity cycles in <i>p</i>-mode travel times
Detecting stellar activity cycles in <i>p</i>-mode travel times Open
Context. The 11 yr solar cycle is known to affect the global modes of solar acoustic oscillations. In particular, p mode frequencies increase with solar activity. Aims. We propose a new method to detect the solar cycle from the p -mode aut…
View article: Detecting stellar activity cycles in p-mode travel times: Proof of concept using SOHO/VIRGO solar observations
Detecting stellar activity cycles in p-mode travel times: Proof of concept using SOHO/VIRGO solar observations Open
The eleven year solar cycle is known to affect the global modes of solar acoustic oscillations. In particular, p mode frequencies increase with solar activity. We propose a new method to detect the solar cycle from the p-mode autocorrelati…
View article: Superflares on solar-like stars
Superflares on solar-like stars Open
Context. Over the past years, thousands of stellar flares have been detected by harvesting data from large photometric surveys. These detections, however, do not account for potential sources of contamination such as background stars or sm…
View article: Superflares on solar-like stars: A new method for identifying the true flare sources in photometric surveys
Superflares on solar-like stars: A new method for identifying the true flare sources in photometric surveys Open
Over the past years, thousands of stellar flares have been detected by harvesting data from large photometric surveys. These detections, however, do not account for potential sources of contamination such as background stars appearing in t…
View article: Spectroscopic properties of a two-dimensional time-dependent Cepheid model
Spectroscopic properties of a two-dimensional time-dependent Cepheid model Open
\nContext. Standard spectroscopic analyses of variable stars are based on hydrostatic 1D model atmospheres. This quasi-static approach has not been theoretically validated. Aim. We aim at investigating the validity of the quasi-static appr…
View article: Spectroscopic properties of a two-dimensional time-dependent Cepheid model
Spectroscopic properties of a two-dimensional time-dependent Cepheid model Open
Context. Standard spectroscopic analyses of variable stars are based on hydrostatic 1D model atmospheres. This quasi-static approach has not been theoretically validated. Aim. We aim at investigating the validity of the quasi-static approx…
View article: Spectroscopic properties of a two-dimensional time-dependent Cepheid model II. Determination of stellar parameters and abundances
Spectroscopic properties of a two-dimensional time-dependent Cepheid model II. Determination of stellar parameters and abundances Open
Standard spectroscopic analyses of variable stars are based on hydrostatic one-dimensional model atmospheres. This quasi-static approach has theoretically not been validated. We aim at investigating the validity of the quasi-static approxi…