M-dwarfs Archives

Absorption contributions from different molecules in a potentially inhabited TRAPPIST-1 e spectrum with surface concentrations similar to a Neoproterozoic Earth (Kaltenegger et al. 2020) and a mixing ratio of H2O fixed at 10−2 . Each color represents a molecule (see legend). Error bars illustrate noise based on the SNR, using the CO2 strongest peak as the signal value. -- astro-ph.EP

AI - Data - Apps - Cybernetics, Astrochemistry, Astrogeology, Astronomy & Telescopes, Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Habitable Zones, Imaging & Spectroscopy, Status Report, TRAPPIST-1

Machine-assisted Classification Of Potential Biosignatures In Earth-like Exoplanets Using Low Signal-to-noise Ratio Transmission Spectra

by Keith CowingApril 5, 2025April 5, 2025

The search for atmospheric biosignatures in Earth-like exoplanets is one of the most pressing challenges in observational astrobiology. Detecting biogenic gases in terrestrial planets requires high resolution and long integration […]

Top panels: evolution of CHZ and UVH for Trappist-1, Proxima Centauri, GJ 273, GJ 163, K2-18, GJ 832, GJ 357, GJ 229A, HD 40307 and Kepler-62. In each plot the vertical gray line represents the host star age found in the literature and the relative errors (the gray shaded region around the gray line). Yellow, orange and dark orange lines represent the ages at which fraction of systems with at least one rocky planet without a primordial envelope in the CHZ is equal to 20%, 30%, 40% for each system (according to NGPPS model). The dashed line represents the time where each star settled onto the main sequence. Bottom panels: evolution of the fraction of the radial extension of the CHZ that is overlapping the radial extension of the UVZ for three different values of the NUV atmospheric transmission. -- astro-ph.EP

Biophysics, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Proxima Centauri, Radiation, Space Weather & Heliophysics, Status Report, TRAPPIST-1, Water/Hycean Worlds & Oceanography

The Time Evolution Of The Ultraviolet Habitable Zone

by Keith CowingSeptember 5, 2024September 5, 2024

For stars hosting Circumstellar Habitable Zone (CHZ) exoplanets, we investigate the time-evolution of their ultraviolet habitable zone (UHZ), the annular region around a star where an exoplanet could experience a […]

Mass-Radius Diagram comparing the data from the PlanetS catalog and the data from NASA Exoplanet Archive to highlight the effects of our selection criteria and our detailed study of references. The grey dots represented the default parameters from NASA, the light blue triangles the same but filtered with our criteria on uncertainties and the blue dots correspond to the PlanetS catalog. The resulting M-R relationships from Sect.2.2 are in solid red lines with the confidence intervals represented by the shaded red areas. The transitions between the three populations are represented by the composition line of 20% water at 650 K from Luo et al. (2024) in dashed orange and the dotted black line at 138 M⊕. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Habitable Zones, Icy Worlds, Press Release, Stellar Cartography, Water/Hycean Worlds & Oceanography

From Super-Earths to Sub-Neptunes: Observational Constraints and Connections to Theoretical Models

by Keith CowingJune 7, 2024June 7, 2024

We update the PlanetS catalog of transiting planets with precise and robust mass and radius measurements and use this comprehensive catalog to explore Mass-Radius (M-R) diagrams.

Estimated rotation regimes inside the habitable zone of white dwarfs with different stellar temperatures, as a function of relative stellar flux. Colors denote different rotation regimes. Black solid line shows the inner edge of the habitable zone (RGHL, Section 4); black dashed line shows the outer edge of the habitable zone (Maximum Greenhouse Limit from Kopparapu et al. 2013); and white dotted line shows the tidal disruption limit. The stellar mass of the white dwarf is fixed at 0.6 M⊙. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Status Report, Water/Hycean Worlds & Oceanography

Novel Atmospheric Dynamics Shape Inner Edge of Habitable Zone Around White Dwarfs

by Keith CowingJune 6, 2024June 6, 2024

White dwarfs offer a unique opportunity to search nearby stellar systems for signs of life, but the habitable zone around these stars is still poorly understood. Since white dwarfs are […]

Transit light curves of K2-25 b taken with MuSCAT2 & 3 in 𝑔, 𝑟, 𝑖, 𝑧-band (from top to bottom) on each observing night. 𝑁T number is shown next to each light curve. In each subplot, observed data points are shown in grey points, and best-fit transit + baseline models derived by GP regression are indicated in coloured lines. The shaded regions indicate the 1𝜎 error of the GP model. -- astro-ph.EP

Exoplanets, -moons, -comets, Imaging & Spectroscopy, Space Weather & Heliophysics, Status Report

Characterization of Starspots on a Young M-dwarf K2-25: Multi-band Observations of Stellar Photometric Variability and Planetary Transits

by Keith CowingMarch 22, 2024March 22, 2024

Detailed atmospheric characterization of exoplanets by transmission spectroscopy requires careful consideration of stellar surface inhomogeneities induced by starspots.

Phase-folded light curve of EBLM J0608−59 (TOI-1338, BEBOP-1) from the WASP project. The data in blue are phase-binned and offset vertically to make the transit at phase 0 easier to see in this automatically-generated diagnostic plot. This system was first flagged as an EBLM system by Amaury Triaud on 2010-07-02 based on follow-up radial velocity meausurements obtained with the CORALIE spectrograph on the Swiss Euler 1.2-m telescope. This binary would later be discovered to host two circumbinary planets, one identified from a transit observed in the TESS light curve [7] and the other long-period planet identified from radial-velocity measurements obtained by the BEBOP project [8]. -- astro-ph.SR

Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

The EBLM Project — From False Positives to Benchmark Stars and Circumbinary Exoplanet

by Keith CowingNovember 30, 2023November 30, 2023

The EBLM project aims to characterise very low-mass stars that are companions to solar-type stars in eclipsing binaries. We describe the history and motivation for this project, the methodology we […]

Relations between Hα, X-ray, and white-light energies for solar and stellar flares. (left) The relation between Hα and Bolometric X-ray energies (0.1–100 keV = 0.124–124 ˚A). Data of superflares on the G-dwarf EK Dra detected in this study are represented by red squares. Other solar and stellar data are taken from Kawai et al. (2022). The function fitted to the observational data with a power-law is shown by the cyan line. (right) The relation between bolometric white-light and Hα energies. Data of superflares on the G-dwarf EK Dra, which are associated with filament/prominence eruptions, are represented by filled red squares, whereas those without eruptions are represented by open red squares (this study, Namekata et al. 2022d, Namekata et al. 2022c). For E1, the total energy including the blueshift component is plotted as the upper limit, with the radiative energy of the central component from the two-component fit being plotted as the lower limit. Data of M-dwarf flares are taken from Maehara et al. (2021), Namizaki et al. (2023), and (Notsu et al. 2023). Solar flare data are taken from Namekata et al. (2022a). The function fitted to the observational data, excluding flare E1, with a power-law is shown by the cyan line. -- astro-ph.SR

Astronomy & Telescopes, Exoplanets, -moons, -comets, Habitable Zones, Radiation, Space Weather & Heliophysics, Status Report

Multi-wavelength Campaign Observations of a Young Solar-type Star, EK Draconis I. Discovery of Prominence Eruptions Associated with Superflares

by Keith CowingNovember 15, 2023

Young solar-type stars frequently produce superflares, serving as a unique window into the young Sun-Earth environments. Large solar flares are closely linked to coronal mass ejections (CMEs) associated with filament/prominence […]

Upper left panel: Comparison of our work to the model results of Mikal-Evans (2022) who assumed a cloud-less Archean-Earth. Grey shading indicated the wavelength range of the figure below. Lower left panel: The transmission spectra of TRAPPIST-1e observed with HST/WFC3 during two different transits (see Zhang et al. 2018). The green lines show our wet alive model results during the Carrington-like event (solid lines - scenario [5], dashed lines - scenario [6]), while the blue lines correspond to the Archean-Earth scenario of Mikal-Evans (2022). Right panel: Comparison of the corresponding assumed atmospheric temperature profiles. -- astro-ph.EP

Exoplanets, -moons, -comets, Imaging & Spectroscopy, Radiation, Space Weather & Heliophysics, Status Report, TRAPPIST-1

Impact of Cosmic Rays on Atmospheric Ion Chemistry and Spectral Transmission Features of TRAPPIST-1e

by Keith CowingNovember 10, 2023November 10, 2023

Ongoing observing projects like the James Webb Space Telescope (JWST) and future missions offer the chance to characterize Earth-like exoplanetary atmospheres. Thereby, M-dwarfs are preferred targets for transit observations, for […]

Schematic diagram of the idealised planetary system considered in this work with equally spaced planets (brown circles, semi-major axis ai) scattering comets (small dark blue circles) from the snow-line. The blue region represents the volatile-rich region of the disc where comets occur, and the green region represents the habitable zone. Low velocity cometary impacts onto habitable planets will follow the lower arrows, which sketch the dynamically cold scattering between adjacent planets. The dynamically hot scattering as shown by the upper arrows, will result in high velocity impacts. -- astro-ph.EP

Astrochemistry, Astrogeology, Biochemistry & Organic Chemistry, Comets and Asteroids, Exoplanets, -moons, -comets, Meteorites & Asteroids, Panspermia, Status Report

Can Comets Deliver Prebiotic Molecules To Rocky Exoplanets?

by Keith CowingOctober 23, 2023October 20, 2023

In this work we consider the potential of cometary impacts to deliver complex organic molecules and the prebiotic building blocks required for life to rocky exoplanets. Numerical experiments have demonstrated […]

Evolution of the inertial-frame mode frequencies σ in units of the dynamical frequency Ωdyn (top panel) and the absolute value of the ℓ = m = 2 tidal overlap coefficients Qℓ,m (bottom panel) for the set of f-modes and i-modes we include during the pre-MS to MS evolution of the Prot,0 = 5 day (left) and 1 day (right) sets of stellar models. In the bottom panel, a subset of these modes are plotted. For the Prot,0 = 1 day models, i-modes that experience avoided crossings are plotted with a circle marker in the bottom panel. -- astro-ph.EP

Exoplanets, -moons, -comets, Habitable Zones, Status Report, TRAPPIST-1

Tidal Migration Of Exoplanets Around M-dwarfs: Frequency-dependent Tidal Dissipation

by Keith CowingOctober 10, 2023October 10, 2023

The orbital architectures of short-period exoplanet systems are shaped by tidal dissipation in their host stars.

M-dwarfs

Machine-assisted Classification Of Potential Biosignatures In Earth-like Exoplanets Using Low Signal-to-noise Ratio Transmission Spectra

The Time Evolution Of The Ultraviolet Habitable Zone

From Super-Earths to Sub-Neptunes: Observational Constraints and Connections to Theoretical Models

Novel Atmospheric Dynamics Shape Inner Edge of Habitable Zone Around White Dwarfs

Characterization of Starspots on a Young M-dwarf K2-25: Multi-band Observations of Stellar Photometric Variability and Planetary Transits

The EBLM Project — From False Positives to Benchmark Stars and Circumbinary Exoplanet

Multi-wavelength Campaign Observations of a Young Solar-type Star, EK Draconis I. Discovery of Prominence Eruptions Associated with Superflares

Impact of Cosmic Rays on Atmospheric Ion Chemistry and Spectral Transmission Features of TRAPPIST-1e

Can Comets Deliver Prebiotic Molecules To Rocky Exoplanets?

Tidal Migration Of Exoplanets Around M-dwarfs: Frequency-dependent Tidal Dissipation

Our Local Star

Decolonizing Technosignatures: Reimagining Technosignatures Through An Indigenist Lens

The Role Of Minerals In Prebiotic Evolution: Implications For Identifying Worlds With The Potential For Life’s Origin

Climates Of Temperate Rocky Planets With He-dominated Atmospheres

Aerosols And Hydrocarbons In The Atmosphere Of A White Dwarf Planet