• Pretty pictures
    • Exoplanet Zoo poster

  • Statistical studies of exoplanet properties (mass, radius, etc.)
    • From Super-Earths to Sub-Neptunes: observational constraints and connections to theoretical models
        Argues for three populations of exoplanets: rocky, volatile-rich, and giant. See Fig 1.
    • Quantitative Criteria for Defining Planets
        Yet another paper which attempts to define "planet," this time in the context of exoplanets. Not bad.
    • The First Evidence of a Host Star Metallicity Cut-off In The Formation of Super-Earth Planets
        Evidence that low-metallicity stars have fewer terrestrial planets than metal-rich stars. Not a surprise, just a strong illustration of the point using sample of over 100,000 stars studied by TESS.
    • Modeling Multiple Radius Valley Emergence Mechanisms With Multi-Transiting Systems
        What causes some planets to be rocky super-Earths, and others to be gas-rich sub-Neptunes? Probably some factor related to the distance from its host star at which a planet forms. These authors run simulations in which they place multiple planets at different distances from the same star, and watch how the planets evolve under different assumptions. They compare model predictions to 75 systems in which we can measure properties of multiple transiting planets, and find (sigh) that all three of their proposed models are consistent with the measurements.

  • Case studies of individual planets
    • Three super-Earths and a possible water world from TESS and ESPRESSO
        Observations with TESS and radial velocities for four planets in three systems (2 in one, 1 each in the others), all with relatively low S/N in the transits. A good illustration of the sources of uncertainty in planet radius (and mass) which then lead to uncertainties in planet composition. See Fig 18 for radius-vs-mass plot and classifications.
    • TESS Hunt for Young and Maturing Exoplanets (THYME) X: a two-planet system in the 210 Myr MELANGE-5 Association
        Observations with TESS and ground-based telescopes of a young (210 Myr), low-mass star host with two big terrestrial-sized planets circling it. Authors claim they see TTVs in transits by the outer planet ... not sure I agree. Star is bright (K = 9.1), so a good target for JWST transmission spectroscopy of the planetary atmospheres?
    • HD 21520 b: a warm sub-Neptune transiting a bright G dwarf
        TESS and CHEOPS observations of transits reveal sub-Neptune planet at 0.17 AU from sun-like star. Low-ish precision radial velocity measurements with ESPRESSO provide mass. Get R = 2.70 R(earth), M = 7.9 M(earth), density = 2.2 +/- 0.4. Would be good target for transmission spectroscopy of atmosphere due to bright V = 9.2 host star and relatively low temperature of atmosphere (T = 637 K).
    • TOI-2374 b and TOI-3071 b: two metal-rich sub-Saturns well within the Neptunian desert
        Two planets discovered by TESS transits, with followup transit photometry and radial velocities from ground-based telescopes. Both fall into the gap in radius-vs-mass diagram known as "hot Neptune desert" or "subJovian desert" or "evaporation desert." Interesting feature of paper is a graphical indication of the predicted time for the planets' atmospheres to evaporate.
    • Unveiling the internal structure and formation history of the three planets transiting HIP 29442 (TOI-469) with CHEOPS
        Study of a system with three transiting planets, using TESS and CHEOPS for radius measurements and ESPRESSO and HIRES for radial velocities. Determines physical parameters of the planets and investigates possible internal structure, chemical composition, and even age.
    • HATS-38 b and WASP-139 b join a growing group of eccentric hot Neptunes on polar orbits
        Transit photometry from TESS and a wide variety of ground-based telescopes (note in particular the very high precision from 1.2-m Euler telescope!), plus VLT/ESPRESSO spectroscopy of two host stars during transits, shows Rossiter-McLaughlin effect, indicating that both hot Neptunes have orbits with high obliquity. The authors provide evidence that these planets were driven to such orbits by the influence of a distant companion.
    • Characterisation of the Warm-Jupiter TOI-1130 system with CHEOPS and photo-dynamical approach
        Transit light curves from CHEOPS, TESS, and ground-based instruments, combined with radial velcity measurements from the literature, show a two-planet system with strong transit-timing variations due to their mutual gravitational influence. One turns out to be a gas giant, the other a Neptune-ish planet. Their orbital periods are close to a 2::1 ratio. A nice illustration of the power of CHEOPS.
    • A hot-Jupiter progenitor on a super-eccentric retrograde orbit
        Jupiter-mass object in very eccentric (e = 0.94) and _retrograde_ orbit, which is probably evolving pretty rapidly into a smaller and more circular orbit. An example of planetary migration, caught in the act?
    • JWST reveals a rapid and strong day side variability of 55 Cancri e
        Multiple observations in the near-IR of secondary occultations (planet goes behind star) reveal _very_ different depths. Something weird must be going on with the planet, if the observations are correct.
    • Revisiting the dynamical masses of the transiting planets in the young AU Mic system: Potential AU Mic b inflation at ~20 Myr
        Using public photometric and spectroscopic data, the authors perform joint fits to the three planets circling AU Mic, and model its stellar activity as well. They find a low density for innermost planet, and a high density for the next planet outwards. They place limits on the rate at which the innermost planet's atmosphere may be disappearing due to stellar radiation.
    • Climate Change in Hell: Long-Term Variation in Transits of the Evaporating Planet K2-22b
        The authors combine measurements of transits of this system over a long period of time, from 2014 to 2024, from a collection of different telescopes. They find that no transits are observed at some of the predicted times, leading them to conclude that there is time-variable obscuration by dust clouds, rather than by a planet itself; the dust may be created and destroyed on short time scales, causing the transits to disappear at some times.
    • A transiting multi-planet system in the 61 million year old association Theia 116
        The authors discover via TESS two planets transiting a G4V (sun-like) star in a young stellar association; they estimate the age of the system to be 61 Myr. They find that these young planets are larger than is typical for their orbital distances/periods, and model the gradual decrease in planetary radius over time (due to cooling off and escape of atmosphere).
    • TESS discovery of two super-Earths orbiting the M-dwarf stars TOI-6002 an d TOI-5713 near the radius valley
        The authors announce the confirmation of two TESS candidates as real exoplanets, one each in two low-mass M-star host systems. The planets both lie close to the habitable region of their hosts, and the systems are relatively close to Earth (32 and 40 pc), so these could be interesting for future followup studies of all sorts.
    • Searching for Neutral Hydrogen Escape from the 120 Myr Old Sub-Neptune HIP94235b using HST
        The authors use HST/STIS to look at this transiting sub-Neptune, hoping to see evidence of hydrogen escaping from its atmosphere due to stellar radiation. They don't see any evidence, and can place upper limits on the rate of evaporation of the planet's atmosphere. Could be important as a check on models for the evolution of planetary atmospheres over long time scales.
    • An extended low-density atmosphere around the Jupiter-sized planet WASP-193 b
      and TESS Spots a Super-puff: The Remarkably Low Density of TOI-1420b
        • Two recent discoveries of planets (hot/warm Jupiters) with very low densities: one is the "Cotton Candy" planet. WASP-139b's atmosphere appears more extended than it ought to be ... why is that?

  • Combining amateur and pro datasets: nice examples of typical small-telescope transit curves vs. TESS transit curves.
    • Enhancing Exoplanet Ephemerides by Leveraging Professional and Citizen Science Data: A Test Case with WASP-77A b
    • TOI-2374 b and TOI-3071 b: two metal-rich sub-Saturns well within the Neptunian desert

  • Importance of CHEOPS for long-duration observations: a) because it's in space, not on the ground b) because it can be pointed to a target a particular time, unlike TESS
    • HIP 41378 observed by CHEOPS: Where is planet d?
    • TOI-757 b: an eccentric transiting mini-Neptune on a 17.5-d orbit
        This paper doesn't pertain to long-duration CHEOPS observations, but does show a very nice side-by-side comparison of TESS and CHEOPS light curves of a target.

  • Examples of spectra of individual exoplanets
    • HST SHEL: Enabling Comparative Exoplanetology with HST/STIS
        Explanation of reduction procedure, and comparison of spectra of four exoplanets to previous work. None show strong, obvious features ...
    • Sulfur Dioxide and Other Molecular Species in the Atmosphere of the Sub-Neptune GJ 3470 b
        Combines new JWST transmission spectra with older HST spectra over range 1.1 - 5.0 microns to detect presence of H20, CH4, CO2, SO2, some of which are not in equilibrium abundances. Star has magnitude V=12.3.
    • Phase-resolving the absorption signatures of water and carbon monoxide in the atmosphere of the ultra-hot Jupiter WASP-121b with GEMINI-S/IGRINS
        GEMINI spectra 1.4 - 2.4 microns during three transits of hot Jup provides strong evidence for changes in absorption spec as function of phase angle. Allows one to separate contributions from different limbs (leading and trailing) of the planet. Ingenious technique -- for explanation and nice figures, see
        Decomposing the iron cross-correlation signal of the ultra-hot Jupiter WASP-76b in transmission using 3D Monte Carlo radiative transfer
        by Wardenier, J. P., et al., MNRAS 506, 1258 (2021).
    • Evidence for Morning-to-Evening Limb Asymmetry on the Cool Low-Density Exoplanet WASP-107b
        JWST/NIRCam data on warm giant planet WASP 107b, which has a relatively low equlibrium temperature of 770 K. The authors use a technique to separate contributions from the morning and evening limbs of the planet. They find 3-sigma evidence for a difference in the two limbs at 2.7 and 3.3 microns. The technique is described in
        Constraining Mornings and Evenings on Distant Worlds: A new Semianalytical Approach and Prospects with Transmission Spectroscopy
        by Espinoza, N, and Jones, K., AJ, 162, 165 (2021).
    • Latitudinal Asymmetry in the Dayside Atmosphere of WASP-43b
        JWST/NIR-Spec measurements of hot Jupiter very close to its host star. Daytime temp approx 2000 K, nighttime temp approx 1000 K. The authors use a slightly different sort of analysis of the lightcurve over a full orbit, plus Spitzer obs, to make a (very) low-res map of the brightness of the planet. They create "eigenmaps" of the planet's surface/atmosphere and fit the observed light curves with weighted combinations of contributions from the eigenmaps.
    • IGRINS observations of WASP-127 b: H2O, CO, and super-Solar atmospheric metallicity in the inflated sub-Saturn
        Gemini transmission spectroscopy of a hot sub-Saturn, showing evidence for H2O, CO, and possibly H2S. Nice illustrations of the lengths to which astronomers must go to pull information out of very faint features in the spectra.
    • Transmission Spectroscopy of the Habitable Zone Exoplanet LHS 1140 b with JWST/NIRISS
        JWST NIRISS transmission spectroscopy (0.6 - 2.7 microns) of a super-Earth/sub-Neptune in habitable zone of M4.5 dwarf. Many active areas on photosphere of star complicate analysis. Weak evidence for an atmosphere of N2 or CO2, can rule out some types of thick H2 atmos.
    • Hydrogen sulfide and metal-enriched atmosphere for a Jupiter-mass exoplanet
        JWST near-IR transit spectroscopy of hot Jupiter HD 189773b. The spectrum shows signatures of several molecules: H2O, CO2, CO, H2S. The atmosphere of the planet has larger metallacity than the Sun, but a smaller ratio of carbon to other elements.
    • Sulphur dioxide in the mid-infrared transmission spectrum of WASP-39b
        JWST near-IR transit spectroscopy of hot Saturn WASP-39b. Clear evidence for SO2 and H2O, as well as super-solar metallicity.
    • A Benchmark JWST Near-Infrared Spectrum for the Exoplanet WASP-39b
        Transit spectroscopy from JWST (near-IR), as well as light curves from ground-based optical telescopes, analyzed together. Authors find evidence for many species in the atmosphere of this hot Saturn: CO, CO2, H2O, SO2, Na, K.
    • Four HD 209458 b transits through CRIRES+: Detection of H2O and non-detections of C2H2, CH4, and HCN
        Transit spectroscopy from ground-based VLT (near-IR) during four transits of the hot Jupiter HD 209458b. Authors find evidence for H2O, but no other species. This suggests a low C/O ratio in the atmosphere.

  • Sky background references
    • Expected Sky Background @ TAO site
    • The 1997 reference of diffuse night sky brightness by Leinert et al., A&AS, 127, 1 (1998)

  • Detectors and instruments and software in general
    • Multi-Amplifier Sensing Charge-coupled Devices for Next Generation Spectroscopy
        Using multiple amplifiers to read out each pixel many times can decrease the readnoise without taking any additional time.
    • The high-contrast performance of the Keck Planet Imager and Characterizer
        by Wang, J. J., et al., arXiv 2406.15028 (2024).
        Describes the performance of an instrument with high spatial resolution and high angular resolution, designed to measure properties of directly-imaged exoplanet atmospheres by reflected light (not transmission spectroscopy).
    • The Lowell Observatory Solar Telescope: A fiber feed into the EXtreme PREcision Spectrometer
        by Llama, J., et al., arXiv 2407.07967 (2024).
        Describes a device to send sunlight into the EXPRES high-precision RV spectrometer at Lowell Observatory, so that we can study the Sun in the same way we study other stars. Finds RMS around 70 cm/s, plus what appears to me to be systematic changes as a function of solar activity. A good warning for those who look for terrestrial exoplanets via RV.
    • The SHERLOCK pipeline: new exoplanet candidates in the WASP-16, HAT-P-27, HAT-P-26, and TOI-2411 systems
        by Devora-Pajares, M., et al., arXiv 2407.14602 (2024).
        An end-to-end pipeline designed for the "common man" to investigate possible exoplanets based on transit measurements. Starts with extracting data from archives, fitting baselines, finding candidates, testing periods, and all that stuff.

        Provides a good overview of all the steps involved in the process of finding and analyzing exoplanets via the transit method. Might be nice as a review.

    • The ANTARESS workflow I. Optimal extraction of spatially resolved stellar spectra with high-resolution transit spectroscopy
        by Bourrier, V., et al., arXiv 2407.19012 (2024).
        VERY detailed, step-by-step description of methods to be used in the reduction and analysis of transit spectroscopy, particularly based on echelle spectra. Uses two real datasets -- HD 209458b and WASP-76b -- as examples to illustrate its methods. Should be a good reference for those interested in doing this sort of thing.
    • TESSILATOR: a one-stop shop for measuring TESS rotation periods
        by Binks, A. S., et al., arXiv 2407.18761 (2024).
        Not really useful for exoplanets, but I'll include it anyway. This package claims to allow one to download, correct, and measure TESS data on any source, then look for periodic variations, with a single command-line command.
    • Machine-assisted classification of potential biosignatures in earth-like exoplanets using low signal-to-noise ratio transmission spectra
        by Duque-Castano, D. S., et al., arXiv 2407.19167 (2024)
        The authors create simulations of observations of exoplanet atmosphere with JWST/NIRSpec PRISM, and use them to determine the number of observations required to detect various gases reliably. The key to their paper is the use of machine learning to deal with very low signal-to-noise data.
    • Detecting exoplanet transits with the next generation of X-ray telescopes
        by Cilley, R., et al., arXiv 2408.06417 (2024)
        A discussion of the feasibility of detecting exoplanet transits using X-ray telescopes. Only one such exoplanet has been detected in this way so far (HD 189733b). The authors look ahead to the next generation of X-ray telescopes and estimate the number of systems they could detect; seems to be small, of order 10-20. Note that expected transit light curves are double-dipped, due to limb-BRIGHTENING in stars of type F and later.

  • Can one use timing residuals in the maxima of a variable star to detect exoplanets circling it?
    • The β Pictoris b Hill sphere transit campaign. Paper II: Searching for the signatures of the β Pictoris exoplanets through time delay analysis of the Δ Scuti pulsations by Zieba, S., et al., finds that the answer is "no" for beta Pic (and provides discouraging evidence about the long-term stability of this delta-Scuti variable)
    • Modeling the Solar System as an Observed Multi-Transit System I: Characterization Limits from Analytic Timing Variations by Lindor, B., and Agol, E., tests the ability of observers to detect unseen planets via transit timing variations. It uses the Solar System as a test case. Provides some decent examples of the required precision in timing for various purposes.

  • Papers related even vaguely to habitability and life
    • Dynamical Viability Assessment for Habitable Worlds Observatory Targets by Kane, S. R., et al. (2024). The authors look at 30 nearby exoplanet systems and ask if a terrestrial planet, added to the system at an orbital radius which would yield Earth-like conditions, would be stable.
    • A Radio Technosignature Search of TRAPPIST-1 with the Allen Telescope Array by Tusay, N., et al. (2024). Search for radio signals emitted by planets in the TRAPPIST-1 system at special times. No positive results, alas.