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Short-period gas giant planets have been shown to be significantly rarer for host stars less massive than the Sun. We report the discovery of two transiting giant planets – TOI-2379 b and TOI-2384 b – with low-mass (early M) host stars. Both planets were detected using Transiting Exoplanet Survey Satellite photometry and for both the transit signal was validated using ground-based photometric facilities. We confirm the planetary nature of these companions and measure their masses using radial velocity observations. We find that TOI-2379 b has an orbital period of 5.469 d and a mass and radius of |$5.76\pm 0.20$|  M |$_{J}$| and |$1.046\pm 0.023$|  R |$_{J}$| and TOI-2384 b has an orbital period of 2.136 d and a mass and radius of |$1.966\pm 0.059$|  M |$_{J}$| and |$1.025\pm 0.021$|  R |$_{J}$|⁠. TOI-2379 b and TOI-2384 b have the highest and third highest planet-to-star mass ratios, respectively, out of all transiting exoplanets with a low-mass host star, placing them uniquely among the population of known exoplanets and making them highly important pieces of the puzzle for understanding the extremes of giant planet formation. [ABSTRACT FROM AUTHOR]

Planets orbiting binary systems are relatively unexplored compared to those around single stars. Detections of circumbinary planets and planetary systems offer a first detailed view into our understanding of circumbinary planet formation and dynamical evolution. The BEBOP (binaries escorted by orbiting planets) radial velocity survey plays a special role in this adventure as it focuses on eclipsing single-lined binaries with an FGK dwarf primary and M dwarf secondary allowing for the highest radial velocity precision using the HARPS and SOPHIE spectrographs. We obtained 4512 high-resolution spectra for the 179 targets in the BEBOP survey which we used to derive the stellar atmospheric parameters using both equivalent widths and spectral synthesis. We furthermore derive stellar masses, radii, and ages for all targets. With this work, we present the first homogeneous catalogue of precise stellar parameters for these eclipsing single-lined binaries. [ABSTRACT FROM AUTHOR]

We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a bright (V  = 12.6 mag, K  = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors 42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory, as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of 12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy. [ABSTRACT FROM AUTHOR]

In the hunt for Earth-like exoplanets, it is crucial to have reliable host star parameters, as they have a direct impact on the accuracy and precision of the inferred parameters for any discovered exoplanet. For stars with masses between 0.35 and 0.5 M⊙, an unexplained radius inflation is observed relative to typical stellar models. However, for fully convective objects with a mass below 0.35 M⊙, it is not known whether this radius inflation is present, as there are fewer objects with accurate measurements in this regime. Low-mass eclipsing binaries present a unique opportunity to determine empirical masses and radii for these low-mass stars. Here, we report on such a star, EBLM J2114−39 B. We have used HARPS and FEROS radial velocities and TESS photometry to perform a joint fit of the data and produce one of the most precise estimates of a very low mass star's parameters. Using a precise and accurate radius for the primary star using Gaia DR3 data, we determine J2114−39 to be a M 1 = 0.998 ± 0.052 M⊙ primary star hosting a fully convective secondary with mass |$M_2~=~0.0993~\pm 0.0033~\, \mathrm{M_{\odot }}$|⁠ , which lies in a poorly populated region of parameter space. With a radius |$R_2 =~0.1250~\pm 0.0016~\, \mathrm{R_{\odot }}$|⁠ , similar to TRAPPIST-1, we see no significant evidence of radius inflation in this system when compared to stellar evolution models. We speculate that stellar models in the regime where radius inflation is observed might be affected by how convective overshooting is treated. [ABSTRACT FROM AUTHOR]

Ongoing ground-based radial-velocity observations seeking to detect circumbinary planets focus on single-lined binaries even though over 9 in every 10 binary systems in the solar neighbourhood are double lined. Double-lined binaries are on average brighter, and should in principle yield more precise radial velocities. However, as the two stars orbit one another, they produce a time-varying blending of their weak spectral lines. This makes an accurate measure of radial velocities difficult, producing a typical scatter of |$10{\!-\!}15~\rm m\, s^{-1}$|⁠. This extra noise prevents the detection of most orbiting circumbinary planets. We develop two new data-driven approaches to disentangle the two stellar components of a double-lined binary, and extract accurate and precise radial velocities. Both approaches use a Gaussian process regression, with the first one working in the spectral domain, whereas the second works on cross-correlated spectra. We apply our new methods to TIC 172900988, a proposed circumbinary system with a double-lined binary, and detect a circumbinary planet with an orbital period of |$150~\rm d$|⁠ , different than previously proposed. We also measure a significant residual scatter, which we speculate is caused by stellar activity. We show that our two data-driven methods outperform the traditionally used TODCOR and TODMOR, for that particular binary system. [ABSTRACT FROM AUTHOR]

A new generation of observatories is enabling detailed study of exoplanetary atmospheres and the diversity of alien climates, allowing us to seek evidence for extraterrestrial biological and geological processes. Now is therefore the time to identify the most unique planets to be characterized with these instruments. In this context, we report on the discovery and validation of TOI-715 b, a |$R_{\rm b}=1.55\pm 0.06\rm R_{\oplus }$| planet orbiting its nearby (42 pc) M4 host (TOI-715/TIC 271971130) with a period |$P_{\rm b} = 19.288004_{-0.000024}^{+0.000027}$| d. TOI-715 b was first identified by TESS and validated using ground-based photometry, high-resolution imaging and statistical validation. The planet's orbital period combined with the stellar effective temperature |$T_{\rm eff}=3075\pm 75~\rm K$| give this planet an installation |$S_{\rm b} = 0.67_{-0.20}^{+0.15}~\rm S_\oplus$|⁠ , placing it within the most conservative definitions of the habitable zone for rocky planets. TOI-715 b's radius falls exactly between two measured locations of the M-dwarf radius valley; characterizing its mass and composition will help understand the true nature of the radius valley for low-mass stars. We demonstrate TOI-715 b is amenable for characterization using precise radial velocities and transmission spectroscopy. Additionally, we reveal a second candidate planet in the system, TIC 271971130.02, with a potential orbital period of |$P_{02} = 25.60712_{-0.00036}^{+0.00031}$| d and a radius of |$R_{02} = 1.066\pm 0.092\, \rm R_{\oplus }$|⁠ , just inside the outer boundary of the habitable zone, and near a 4:3 orbital period commensurability. Should this second planet be confirmed, it would represent the smallest habitable zone planet discovered by TESS to date. [ABSTRACT FROM AUTHOR]

In the last decade, a dozen close-in giant planets have been discovered orbiting stars with spectral types ranging from M0 to M4, a mystery since known formation pathways do not predict the existence of such systems. Here, we confirm TOI-4860 b, a Jupiter-sized planet orbiting an M4.5 host, a star at the transition between fully and partially convective interiors. First identified with TESS data, we validate the transiting companion's planetary nature through multicolour photometry from the TRAPPIST-South/North, SPECULOOS, and MuSCAT3 facilities. Our analysis yields a radius of |$0.76\pm 0.02~\rm R_{Jup}$| for the planet, a mass of |$0.34~\rm M_\odot$| for the star, and an orbital period of |$1.52~\rm d$|⁠. Using the newly commissioned SPIRIT InGaAs camera at the SPECULOOS-South Observatory, we collect infrared photometry in zYJ that spans the time of secondary eclipse. These observations do not detect a secondary eclipse, placing an upper limit on the brightness of the companion. The planetary nature of the companion is further confirmed through high-resolution spectroscopy obtained with the IRD spectrograph at Subaru Telescope, from which we measure a mass of |$0.67\pm 0.14~\rm M_{Jup}$|⁠. Based on its overall density, TOI-4860 b appears to be rich in heavy elements, like its host star. [ABSTRACT FROM AUTHOR]

M-dwarfs are the most abundant stars in the galaxy and popular targets for exoplanet searches. However, their intrinsic faintness and complex spectra inhibit precise characterization. We only know of dozens of M-dwarfs with fundamental parameters of mass, radius, and effective temperature characterized to better than a few per cent. Eclipsing binaries remain the most robust means of stellar characterization. Here we present two targets from the Eclipsing Binary Low Mass (EBLM) survey that were observed with K2: EBLM J0055-00 and EBLM J2217-04. Combined with HARPS and CORALIE spectroscopy, we measure M-dwarf masses with precisions better than 5 per cent, radii better than 3 per cent, and effective temperatures on order 1 per cent. However, our fits require invoking a model to derive parameters for the primary star and fitting the M-dwarf using the transit and radial velocity observations. By investigating three popular stellar models, we determine that the model uncertainty in the primary star is of similar magnitude to the statistical uncertainty in the model fits of the secondary M-dwarf. Therefore, whilst these can be considered benchmark M-dwarfs, we caution the community to consider model uncertainty when pushing the limits of precise stellar characterization. [ABSTRACT FROM AUTHOR]

We report on the discovery and characterization of three planets orbiting the F8 star HD 28109, which sits comfortably in |${TESS}$| 's continuous viewing zone. The two outer planets have periods of |$\rm 56.0067 \pm 0.0003~d$| and |$\rm 84.2597_{-0.0008}^{+0.0010}~d$|⁠ , which implies a period ratio very close to that of the first-order 3:2 mean motion resonance, exciting transit timing variations (TTVs) of up to |$\rm 60\, min$|⁠. These two planets were first identified by |${TESS}$|⁠ , and we identified a third planet in the |${TESS}$| photometry with a period of |$\rm 22.8911 \pm 0.0004~d$|⁠. We confirm the planetary nature of all three planetary candidates using ground-based photometry from Hazelwood , |${ASTEP}$|⁠ , and LCO , including a full detection of the |$\rm \sim 9\, h$| transit of HD 28109 c from Antarctica. The radii of the three planets are |${\it R}_b=2.199_{-0.10}^{+0.098} ~{\rm R}_{\oplus }$|⁠ , |${\it R}_c=4.23\pm 0.11~ {\rm R}_{\oplus }$|⁠ , and |${\it R}_d=3.25\pm 0.11 ~{\rm R}_{\oplus }$|⁠ ; we characterize their masses using TTVs and precise radial velocities from ESPRESSO and HARPS, and find them to be |${\it M}_b=18.5_{-7.6}^{+9.1}~M_{\oplus }$|⁠ , |${\it M}_c=7.9_{-3.0}^{+4.2}~{\rm M}_{\oplus }$|⁠ , and |${\it M}_d=5.7_{-2.1}^{+2.7}~{\rm M}_{\oplus }$|⁠ , making planet b a dense, massive planet while c and d are both underdense. We also demonstrate that the two outer planets are ripe for atmospheric characterization using transmission spectroscopy, especially given their position in the CVZ of James Webb Space Telescope. The data obtained to date are consistent with resonant (librating) and non-resonant (circulating) solutions; additional observations will show whether the pair is actually locked in resonance or just near-resonant. [ABSTRACT FROM AUTHOR]

BEBOP is a radial-velocity survey that monitors a sample of single-lined eclipsing binaries, in search of circumbinary planets by using high-resolution spectrographs. Here, we describe and test the methods we use to identify planetary signals within the BEBOP data and establish how we quantify our sensitivity to circumbinary planets by producing detection limits. This process is made easier and more robust by using a diffusive nested sampler. In the process of testing our methods, we notice that contrary to popular wisdom, assuming circular orbits in calculating detection limits for a radial-velocity survey provides overoptimistic detection limits by up to |$40{{\ \rm per\ cent}}$| in semi-amplitude with implications for all radial-velocity surveys. We perform example analyses using three BEBOP targets from our Southern HARPS survey. We demonstrate for the first time a repeated ability to reach a residual root mean squared scatter of |$3\, \rm m\, s^{-1}$| (after removing the binary signal), and find that we are sensitive to circumbinary planets with masses down to that of Neptune and Saturn, for orbital periods up to |$1000\, \rm d$|⁠. [ABSTRACT FROM AUTHOR]

The radial velocity method is amongst the most robust and most established means of detecting exoplanets. Yet, it has so far failed to detect circumbinary planets despite their relatively high occurrence rates. Here, we report velocimetric measurements of Kepler-16A, obtained with the SOPHIE spectrograph, at the Observatoire de Haute-Provence's 193cm telescope, collected during the BEBOP survey for circumbinary planets. Our measurements mark the first radial velocity detection of a circumbinary planet, independently determining the mass of Kepler-16 (AB) b to be |$0.313 \pm 0.039\, {\rm M}_{\rm Jup}$|⁠ , a value in agreement with eclipse timing variations. Our observations demonstrate the capability to achieve photon-noise precision and accuracy on single-lined binaries, with our final precision reaching |$\rm 1.5~m\, s^{-1}$| on the binary and planetary signals. Our analysis paves the way for more circumbinary planet detections using radial velocities which will increase the relatively small sample of currently known systems to statistically relevant numbers, using a method that also provides weaker detection biases. Our data also contain a long-term radial velocity signal, which we associate with the magnetic cycle of the primary star. [ABSTRACT FROM AUTHOR]

We present the discovery and characterization of an eclipsing binary identified by the Next Generation Transit Survey in the ∼115-Myr-old Blanco 1 open cluster. NGTS J0002−29 comprises three M dwarfs: a short-period binary and a companion in a wider orbit. This system is the first well-characterized, low-mass eclipsing binary in Blanco 1. With a low mass ratio, a tertiary companion, and binary components that straddle the fully convective boundary, it is an important benchmark system, and one of only two well-characterized, low-mass eclipsing binaries at this age. We simultaneously model light curves from NGTS, TESS , SPECULOOS, and SAAO, radial velocities from VLT/UVES and Keck/HIRES, and the system's spectral energy distribution. We find that the binary components travel on circular orbits around their common centre of mass in P orb = 1.098 005 24 ± 0.000 000 38 d, and have masses M pri = 0.3978 ± 0.0033 M⊙ and M sec = 0.2245 ± 0.0018 M⊙, radii R pri = 0.4037 ± 0.0048 R⊙ and R sec = 0.2759 ± 0.0055 R⊙, and effective temperatures |$T_{\rm pri}=\mbox{$3372\, ^{+44}_{-37}$}$| K and |$T_{\rm sec}=\mbox{$3231\, ^{+38}_{-31}$}$| K. We compare these properties to the predictions of seven stellar evolution models, which typically imply an inflated primary. The system joins a list of 19 well-characterized, low-mass, sub-Gyr, stellar-mass eclipsing binaries, which constitute some of the strongest observational tests of stellar evolution theory at low masses and young ages. [ABSTRACT FROM AUTHOR]

Colour–magnitude diagrams provide a convenient way of comparing populations of similar objects. When well populated with precise measurements, they allow quick inferences to be made about the bulk properties of an astronomic object simply from its proximity on a diagram to other objects. We present here a python toolkit that allows a user to produce colour–magnitude diagrams of transiting exoplanets, comparing planets to populations of ultra-cool dwarfs, of directly imaged exoplanets, to theoretical models of planetary atmospheres, and to other transiting exoplanets. Using a selection of near- and mid-infrared colour–magnitude diagrams, we show how outliers can be identified for further investigation, and how emerging subpopulations can be identified. Additionally, we present evidence that observed differences in the Spitzer 's 4.5  μ m flux, between irradiated Jupiters and field brown dwarfs, might be attributed to phosphine, which is susceptible to photolysis. The presence of phosphine in low-irradiation environments may negate the need for thermal inversions to explain eclipse measurements. We speculate that the anomalously low 4.5  μ m flux of the nightside of HD 189733b and the daysides of GJ 436b and GJ 3470b might be caused by phosphine absorption. Finally, we use our toolkit to include Hubble Wide Field Camera 3 spectra, creating a new photometric band called the 'Water band' (WJH band) in the process. We show that the colour index [ WJH − H ] can be used to constrain the C/O ratio of exoplanets, showing that future observations with James Webb Space Telescope and Ariel will be able to distinguish these populations if they exist, and select members for future follow-up. [ABSTRACT FROM AUTHOR]