42 citations · 207 across the 25 of their papers we have counts for
28 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-driven spectral irradiance variability of Sun-like stars
N. -E. Nèmec, G. Kopp, V. Witzke +1
Granulation,caused by convection in low-mass stars like the Sun, introduces small amplitude variations in the stellar brightness on timescales of minutes to hours. Often referred t…
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…
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…
The Curious Case of Dark Faculae on M Dwarf Stars
Alexander~I. ~Shapiro, Sara~Seager, Sami~K. ~Solanki +6
The study of exoplanet atmospheres has brought a renewed interest in stellar astrophysics. Specifically, stellar magnetic activity from the host star contaminates exoplanet atmosph…
A Scalable Path to Astrometric Exomoon Discoveries with the Nautilus Space Observatory
Kevin Wagner, Sumin Seung, Dániel Apai +13
Moons orbiting exoplanets (exomoons) can be detected through the reflex motion they impart to their host planet, which is recoverable in relative star-planet astrometric time serie…
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…
Simulations of facular magnetic fields on cool stars I: Main sequence stars with solar metallicity
Tanayveer Singh Bhatia, Robert H. Cameron, Sami K. Solanki +4
Stellar convection in the presence of magnetic field affects the emergent intensity, as well as the structure and evolution of cool main-sequence dwarfs. We aim to understand the e…
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…
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…
The effect of stellar magnetic activity on measurements of morning and evening asymmetry of planetary terminator
N. Kostogryz, A. I. Shapiro, L. Carone +9
Differences in the ingress and egress shapes of transit light curves can indicate morning-evening temperature contrasts on transiting planets. Here, we pinpoint an alternative mech…
Modeling HMI observables for the study of solar oscillations
D. Fournier, N. M. Kostogryz, L. Gizon +4
Context: Helioseismology aims to infer the properties of the solar interior by analyzing observations of acoustic oscillations. The interpretation of the helioseismic data is howev…
First Calculations of Starspot Spectra based on 3D Radiative Magnetohydrodynamics Simulations
H. N. Smitha, Alexander I. Shapiro, Veronika Witzke +6
Accurate calculations of starspot spectra are essential for multiple applications in astronomy. The current standard is to represent starspot spectra by spectra of stars that are c…
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…
The PLATO Mission
Heike Rauer, Conny Aerts, Juan Cabrera +842
PLATO (PLAnetary Transits and Oscillations of stars) is ESA's M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large numb…
Stellar Surface Magnetic Fields Impact Limb Darkening
Nadiia M. Kostogryz, Alexander I. Shapiro, Veronika Witzke +8
Stars appear darker at their limbs than at their disk centers because at the limb we are viewing the higher and cooler layers of stellar photospheres. Limb darkening derived from s…
Testing MURaM and MPS-ATLAS against the quiet solar spectrum
Veronika Witzke, Alexander I. Shapiro, Nadiia M. Kostogryz +8
Three-dimensional (3D) radiative magnetohydrodynamics (MHD) simulations are the only way to model stellar atmospheres without any ad hoc parameterisations. Several 3D radiative MHD…
A roadmap for the atmospheric characterization of terrestrial exoplanets with JWST
TRAPPIST-1 JWST Community Initiative, :, Julien de Wit +80
Ultra-cool dwarf stars are abundant, long-lived, and uniquely suited to enable the atmospheric study of transiting terrestrial companions with JWST. Amongst them, the most prominen…
MPS-ATLAS library of stellar model atmospheres and spectra
N. Kostogryz, A. I Shapiro, V. Witzke +5
Stellar spectra contain a large amount of information about the conditions in stellar atmospheres. However, extracting this information is challenging and demands comprehensive num…
Can 1D radiative equilibrium models of faculae be used for calculating contamination of transmission spectra?
Veronika Witzke, Alexander I. Shapiro, Nadiia M. Kostogryz +5
The reliable characterization of planetary atmospheres with transmission spectroscopy requires realistic modeling of stellar magnetic features, since features that are attributable…
Stellar limb darkening. A new MPS-ATLAS library for Kepler, TESS, CHEOPS, and PLATO passbands
N. M. Kostogryz, V. Witzke, A. I. Shapiro +4
The detection of the first exoplanet paved the way into the era of transit photometry space missions with a revolutionary photometric precision that aim at discovering new exoplane…