M-dwarf Archives

Light curve the lensing event MOA-2022-BLG-033 and the model curve. The lower panel offers a comprehensive view of the event, while the upper panel provides a close-up view of the anomaly (the region enclosed by a box in the lower panels). The colors of the data points correspond to the telescopes listed in the legend. The bottom two panels show the residuals from the models with and without considering microlens-parallax effects. -- astro-ph.EP

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

Three Low Mass-ratio Microlensing Planets Detected Through Dip Signals

by Keith CowingJanuary 18, 2025

We examined the anomalies in the light curves of the lensing events MOA-2022-BLG-033, KMT-2023-BLG-0119, and KMT-2023-BLG-1896.

X-ray images of the GJ 644/GJ 643 system from ROSAT RASS (top left), ROSAT HRI (top right), XMM-Newton EPIC (bottom left), and Chandra ACIS (bottom right). The circles are around the stellar positions extrapolated back to the epoch of the respective observations and have a radius of 15" -- astro-ph.SR

Exoplanets, -moons, -comets, Habitable Zones, Radiation, Space Weather & Heliophysics, Status Report, Stellar Cartography

X-ray Activity Of Nearby G-, K-, And M-type Stars And Implications for Planet Habitability Around M stars

by Keith CowingJanuary 14, 2025January 14, 2025

Context. The intense X-ray and UV emission of some active M stars has raised questions about the habitability of planets around M-type stars. Aims. We aim to determine the unbiased […]

Comparison of the combined exoTEDRF + Eureka! transmission spectrum to Aurora retrievals (top) and various PLATON forward models (bottom). The best-fit retrieval model is shown in the top panel with the darkness of the shading indicating the 1- and 2-σ limits, and is re-plotted in the bottom panel for comparison against the other forward models. The middle panel shows the absorption cross-sections for key molecules, which demonstrates how the spectrum is a poor fit both for CH4 and CO2. The plotted forward models include different metallicity and C/O scenarios, as well as a water-rich composition, and the inclusion of disequilibrium SO2. Forward models incorporating equilibrium chemistry are shown with dashed lines. The ‘10× Solar + SO2’ model has 108 times the equilibrium SO2 abundance as its counterpart. Offsets have been applied to the forward models at 2.8 µm to account for the best-fit offset between the NIRISS/SOSS and NIRSpec/G395M data. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Status Report, Water/Hycean Worlds & Oceanography

TOI-421 b: A Hot Sub-Neptune with a Haze-Free, Low Mean Molecular Weight Atmosphere

by Keith CowingJanuary 10, 2025January 10, 2025

Common features of sub-Neptunes atmospheres observed to date include signatures of aerosols at moderate equilibrium temperatures (~500-800 K), and a prevalence of high mean molecular weight atmospheres, perhaps indicating novel […]

The Chinese Space Station Telescope (CSST) - CNSA/Xinhua

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

Chinese Space Station Telescope: Detecting Exomoons in Free-Floating-Planet Events from Space-based Microlensing Surveys

by Keith CowingJanuary 9, 2025January 9, 2025

When a planet is ejected from its star-planet system due to dynamical interactions, its satellite may remain gravitationally bound to the planet.

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Press Release, TRAPPIST-1

The Light Of TRAPPIST-1 b Reveals New Insights On The Planet’s Nature

by Keith CowingDecember 16, 2024December 16, 2024

New TRAPPIST-1 observations with JWST underscore the complexities of confirming a planet’s atmosphere using only broadband thermal emission data. This insight takes on added significance with the newly approved “Rocky […]

Maximal (red) and minimal (blue) atmospheric heating factor vs instellation, for three values of the heat redistribution parameter: f = 0.2 (solid), 0.5 (dashed), and 1 (dotted). The locations of the four planets in Table 1 considering their instellation are marked by vertical green stripes. Modified from Fig. 11 of Wandel (2018). The allowed habitable Hatm ranges of Earth, Mars and Venus for f = 1 are marked by vertical blue strips. The effective values of Hatm for these terrestrial planets are represented by blue dots. -- astro-ph.EP

Astrogeology, Astronomy & Telescopes, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Habitable Zones, Icy Worlds, Status Report, Water/Hycean Worlds & Oceanography

Potential Interior Structures and Habitability of Super-Earth Exoplanets LHS 1140 b, K2-18 b, TOI-1452 b and TOI-1468 c

by Keith CowingDecember 12, 2024December 12, 2024

We analyze four super-Earth exoplanets, LHS 1140 b, K2-18 b, TOI-1452 b, and TOI-1468 c, which orbit M-dwarf stars in the habitable zone.

H-R Diagram of TESS TOI candidates. Grey symbols are randomly chosen F, G, K stars taken from the TOI list and plotted here to give a perspective for their locations in an H-R Diagram. Red dots are M star TOIs which have already been deemed to be false positives, while blue dots show the location of the remaining M star TOI candidates. The blue dots above the main sequence are deemed to be giants and are removed from any subsequent analysis. -- astro-ph.EP

Astrogeology, Astronomy & Telescopes, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report

Demographics Of M Dwarf Binary Exoplanet Hosts Discovered by TESS

by Keith CowingDecember 12, 2024December 12, 2024

M dwarfs have become increasingly important in the detection of exoplanets and the study of Earth-sized planets and their habitability. However, 20-30% of M dwarfs have companions that can impact […]

Simulated effects of ‘bare-rock’ fresh surface albedo profiles from Hu et al. (2012a), varying regolith grain sizes of basalt, and npFe0 /graphite space weathering on simulated emission observations in the MIRI LRS bandpass (5 − 12 µm). Brightness temperature ratios in the MIRI F1500W and Spitzer IRAC2 bandpasses show similar trends. Planets too hot for solid surfaces (Tirr ≳ 1250 K) are not shown. Results are dependent on the exact stellar properties, and we include results for a GJ 367-like M1 star and a TRAPPIST-1-like M7.5 star as bounding cases defining the width of each colored band. This roughly encompasses the spread expected for M-Earths. A trend of increasing brightness temperature ratio (R) with irradiation temperature (Tirr) can be explained by grain sizes increasing with temperature or stronger space weathering on closer-in planets, as explored in §3.2. -- astro-ph.EP

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

Population-level Hypothesis Testing with Rocky Planet Emission Data: A Tentative Trend in the Brightness Temperatures of M-Earths

by Keith CowingDecember 10, 2024

Determining which rocky exoplanets have atmospheres, and why, is a key goal for JWST. So far, emission observations of individual rocky exoplanets orbiting M stars (M-Earths) have not provided definitive […]

Comparison of blue-optical data of GJ 729, for which the most data is available from our sources. Top panel: Comparison of STIS G430L, CASLEO and X-shooter spectra, as well as Swift U band photometry and the PHOENIX model spectrum. Bottom panel: Ratio between the G430L and PHOENIX spectrum. Similar trends are seen at all other stars. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Space Weather & Heliophysics, Status Report, Stellar Cartography

The Mega-MUSCLES Treasury Survey: X-ray to Infrared Spectral Energy Distributions of a Representative Sample of M dwarfs

by Keith CowingNovember 20, 2024November 20, 2024

We present 5-1×10^7 Angstrom spectral energy distributions (SEDs) for twelve M dwarf stars covering spectral types M0-M8. Our SEDs are provided for community use as a sequel to the Measurements […]

TESS target pixel file images of Sectors 17, 23, and 40, generated with tpfplotter. These sectors are shown as example of the aperture photometry performed by the SPOC pipeline, where the inclusion of the stellar companion Gl 725 B is not consistent. -- astro-ph.EP

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

Gl 725A b: A Potential Super-Earth Detected With SOPHIE and SPIRou In An M Dwarf Binary System At 3.5 pc

by Keith CowingNovember 15, 2024November 15, 2024

We report the discovery of a super-Earth candidate orbiting the nearby mid M dwarf Gl 725A using the radial velocity (RV) method.

M-dwarf

Three Low Mass-ratio Microlensing Planets Detected Through Dip Signals

X-ray Activity Of Nearby G-, K-, And M-type Stars And Implications for Planet Habitability Around M stars

TOI-421 b: A Hot Sub-Neptune with a Haze-Free, Low Mean Molecular Weight Atmosphere

Chinese Space Station Telescope: Detecting Exomoons in Free-Floating-Planet Events from Space-based Microlensing Surveys

The Light Of TRAPPIST-1 b Reveals New Insights On The Planet’s Nature

Potential Interior Structures and Habitability of Super-Earth Exoplanets LHS 1140 b, K2-18 b, TOI-1452 b and TOI-1468 c

Demographics Of M Dwarf Binary Exoplanet Hosts Discovered by TESS

Population-level Hypothesis Testing with Rocky Planet Emission Data: A Tentative Trend in the Brightness Temperatures of M-Earths

The Mega-MUSCLES Treasury Survey: X-ray to Infrared Spectral Energy Distributions of a Representative Sample of M dwarfs

Gl 725A b: A Potential Super-Earth Detected With SOPHIE and SPIRou In An M Dwarf Binary System At 3.5 pc

Ancient Layers On Mars Exposed By A Crater Within A Crater In Terra Sirenum

Send Your Name to Titan Aboard NASA’s Dragonfly Astrobiology Mission

Reconciling Giant Impacts with the Radius Valley: The Role of Silicate-Hydrogen Miscibility for Sub-Neptunes

Comprehensive Visible and Near-infrared Keck and Gemini Monitoring and Characterization of Interstellar Comet 3I/ATLAS during its Encounter with the Solar System

ExoVetter and a TESS Exoplanet Transit Search of Kepler Stars as Ground Truth