34 citations · 71 across the 15 of their papers we have counts for
17 papers
Magnetic Activity as a Driver of Low-gravity-like Spectral Morphology in Late-M Dwarfs
Chia-Lung Lin, Daniel Apai, Benjamin V. Rackham +7
We present a systematic investigation of the connection between magnetic activity and the low-surface-gravity-like near-infrared spectral morphology of late-M dwarfs. Our sample in…
Granulation in Color: The Chromatic Stellar Flicker of LTT-9779 and WASP-121
William C. Waalkes, Nadiia Kostogryz, Valeriy Vasilyev +9
Granulation is a persistent feature of stars with outer convective layers and is the photospheric signature of near-surface convective energy transport. In disk-integrated observat…
Leveraging Impact Parameter to Mitigate the Transit Light Source Effect: Early Insights from TRAPPIST-1
Ana Glidden, Alexander I. Shapiro, Sara Seager +19
Stellar activity complicates exoplanet transmission spectra, particularly for smaller planets around M dwarfs with JWST. The transit light source (TLS) effect, the imprinting of sp…
Mapping Stellar Heterogeneities with the Nautilus Space Observatory
Adina D. Feinstein, Jeff Valenti, Julien de Wit +9
Stellar photospheric heterogeneities, such as starspots and faculae, are a fundamental limitation for exoplanet transmission spectroscopy. Inhomogeneous surfaces can imprint wavele…
Nautilus: Fast Time-Resolved Spectroscopy of GKM Stellar Flares and Their Implications for Planetary Habitability
Chia-Lung Lin, Adina D. Feinstein, Jeff Valenti +10
Low-mass GKM dwarfs are prime targets for finding habitable-zone Earth-sized planets, but their frequent flares, especially on M~dwarfs, can strongly affect planetary atmospheres t…
Effect of surface magnetic fields on limb darkening in main-sequence stars
N. Kostogryz, A. I. Shapiro, V. Witzke +5
Context.Stellar limb darkening encodes the thermal and radiative structure of stellar photospheres and is a key ingredient in modeling transit light curves and transmission spectra…
A single power law for the TRAPPIST-1 flare distribution across four orders of magnitude in energy
Valeriy Vasilyev, Alexander I. Shapiro, Nadiia Kostogryz +10
TRAPPIST-1 is an ultra-cool dwarf that flares frequently. These flares shape the surrounding planets' high-energy irradiation environments, with consequences for atmospheric chemis…
Sensitivity of spectral lines to granulation: from the Sun to K-type stars
V. Vasilyev, K. Sowmya, A. I. Shapiro +7
Stellar granulation produces radial-velocity (RV) jitter at the 1 m/s level in Sun-like stars, limiting Earth-analog detection. A route beyond this limit is to weight spectral line…
Linking Solar Magnetism, Extreme Solar Particle Events and Stellar Superflares
Valeriy Vasilyev, Natalie Krivova, Ilya Usoskin
The magnetic field of the Sun drives a wide range of eruptive phenomena, from small-scale nanoflares to large flares and coronal mass ejections (CMEs). While direct observations of…
Molecular hydrogen controls the temperatures of flares on TRAPPIST-1
Alexander I. Shapiro Nadiia Kostogryz Sara Seager Veronika Witzke Julien de Wit Valeriy Vasilyev Astrid M. Veronig Robert Cameron Hardi Peter Sami K. Solanki
Early JWST observations of TRAPPIST-1 have revealed an unexpected puzzle: energetic white-light flares ( erg) reach temperatures of only 3500--4000\,K, ne…
Separating flare and secondary atmospheric signals with RADYN modeling of near-infrared JWST transmission spectroscopy observations of TRAPPIST-1
Ward S. Howard, Adam F. Kowalski, Michael Radica +10
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 se…
Flares on TRAPPIST-1 reveal the spectrum of magnetic features on its surface
Valeriy Vasilyev, Nadiia Kostogryz, Alexander I. Shapiro +11
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 notor…
Detectability of Solar Rotation Period Across Various Wavelengths
Valeriy Vasilyev, Timo Reinhold, Alexander I. Shapiro +3
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…
Sun-like stars produce superflares roughly once per century
Valeriy Vasilyev, Timo Reinhold, Alexander I. Shapiro +7
Stellar superflares are energetic outbursts of electromagnetic radiation, similar to solar flares but releasing more energy, up to erg on main sequence stars. It is unkno…
Reliable Transmission Spectrum Extraction with a Three-Parameter Limb Darkening Law
Rosa E. Keers, Alexander I. Shapiro, Nadiia M. Kostogryz +7
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 involv…
Detecting stellar activity cycles in p-mode travel times: Proof of concept using SOHO/VIRGO solar observations
Valeriy Vasilyev, Laurent Gizon
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 met…
Spectroscopic properties of a two-dimensional time-dependent Cepheid model I. Description and validation of the model
V. Vasilyev, H. -G. Ludwig, B. Freytag +2
Standard spectroscopic analyses of Cepheid variables are based on hydrostatic one-dimensional model atmospheres, with convection treated using various formulations of mixing-length…