Search

NASA's Transiting Exoplanet Survey Satellite (TESS) mission, has been uncovering a growing number of exoplanets orbiting nearby, bright stars. Most exoplanets that have been discovered by TESS orbit narrow-line, slow-rotating stars, facilitating the confirmation and mass determination of these worlds. We present the discovery of a hot Jupiter orbiting a rapidly rotating ($v\sin{(i)}= 35.1\pm1.0$km/s) early F3V-dwarf, HD115447 (TOI-778). The transit signal taken from Sectors 10 and 37 of TESS's initial detection of the exoplanet is combined with follow-up ground-based photometry and velocity measurements taken from Minerva-Australis, TRES, CORALIE and CHIRON to confirm and characterise TOI-778b. A joint analysis of the light curves and the radial velocity measurements yield a mass, radius, and orbital period for TOI-778b of $2.76^{+0.24}_{-0.23}$Mjup, $1.370\pm0.043$Rjup and $\sim4.63$ days, respectively. The planet orbits a bright ($V = 9.1$mag) F3-dwarf with $M=1.40\pm0.05$Msun, $R=1.70\pm0.05$Rsun, and $\log g=4.05\pm0.17$. We observed a spectroscopic transit of TOI-778b, which allowed us to derive a sky-projected spin-orbit angle of $18^{\circ}\pm11^{\circ}$, consistent with an aligned planetary system. This discovery demonstrates the capability of smaller aperture telescopes such as Minerva-Australis to detect the radial velocity signals produced by planets orbiting broad-line, rapidly rotating stars., 18 pages, 9 figures, and 4 tables. Submitted to the Astronomical Journal

We report the discovery of NGTS-21b, a massive hot Jupiter orbiting a low-mass star as part of the Next Generation Transit Survey (NGTS). The planet has a mass and radius of $2.36 \pm 0.21$ M$_{\rm J}$, and $1.33 \pm 0.03$ R$_{\rm J}$, and an orbital period of 1.543 days. The host is a K3V ($T_{\rm eff}=4660 \pm 41$, K) metal-poor (${\rm [Fe/H]}=-0.26 \pm 0.07$, dex) dwarf star with a mass and radius of $0.72 \pm 0.04$, M$_{\odot}$,and $0.86 \pm 0.04$, R$_{\odot}$. Its age and rotation period of $10.02^{+3.29}_{-7.30}$, Gyr and $17.88 \pm 0.08$, d respectively, are in accordance with the observed moderately low stellar activity level. When comparing NGTS-21b with currently known transiting hot Jupiters with similar equilibrium temperatures, it is found to have one of the largest measured radii despite its large mass. Inflation-free planetary structure models suggest the planet's atmosphere is inflated by $\sim21\%$, while inflationary models predict a radius consistent with observations, thus pointing to stellar irradiation as the probable origin of NGTS-21b's radius inflation. Additionally, NGTS-21b's bulk density ($1.25 \pm 0.15$, g/cm$^3$) is also amongst the largest within the population of metal-poor giant hosts ([Fe/H] < 0.0), helping to reveal a falling upper boundary in metallicity-planet density parameter space that is in concordance with core accretion formation models. The discovery of rare planetary systems such as NGTS-21 greatly contributes towards better constraints being placed on the formation and evolution mechanisms of massive planets orbiting low-mass stars., 12 pages, 13 figures, accepted for publication in MNRAS

We present the discovery and characterisation of an eclipsing binary identified by the Next Generation Transit Survey in the $\sim$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-characterised, 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-characterised, 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 $P_{\rm orb} = 1.09800524 \pm 0.00000038$ days, and have masses $M_{\rm pri}=0.3978\pm 0.0033$ M$_{\odot}$ and $M_{\rm sec}=0.2245\pm 0.0018$ M$_{\odot}$, radii $R_{\rm pri}=0.4037\pm 0.0048$ R$_{\odot}$ and $R_{\rm sec}=0.2759\pm 0.0055$ R$_{\odot}$, and effective temperatures $T_{\rm pri}=3372\,^{+44}_{-37}$ K and $T_{\rm sec}=3231\,^{+38}_{-31}$ 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-characterised, 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., 21 pages, 9 figures. Accepted for publication in MNRAS

The nearby TOI-270 system provides an unparalleled opportunity to observationally probe hypotheses for exoplanet formation and evolution. The system hosts one super-Earth and two sub-Neptunes near mean-motion resonances and transiting a bright (K-mag 8.25) M3V dwarf. Strangely, M-dwarf systems harbouring only super-Earths or only sub-Neptunes are ubiquitous. However, for still unknown reasons, systems with multiple planets spanning the radius valley are rare - and we know merely a handful of systems bright enough for precise mass measurements and atmospheric studies. To this end, TOI-270's planets are exceptionally favourable for detailed transit timing variation (TTV) and transmission spectroscopy observations. First, with the planets orbiting near low-order resonances (5:3 and 2:1), our extensive observing campaign with eight different observatories since 2018 yields clear TTV signals for planets c and d, with amplitudes of around 10 min and a super-period of circa 3 yr. Using dynamical models, we can thus significantly constrain their radii, mass ratios, and eccentricities. This adds to complementary radial velocity (RV) mass measurements from HARPS and ESPRESSO. Second, via HST and JWST transmission spectroscopy we can characterise and compare the atmospheres of two sub-Neptunes formed from the same protoplanetary nebula and test hypotheses like photoevaporation, core-powered mass-loss, and gas-poor formation. As one of the best-constrained small planet systems, TOI-270 can thus serve as a unique observational testbed for formation and evolution theories.

The orbits and dynamics of exoplanet systems can unveil their tales of formation, migration, star-planet interactions, and atmospheric properties. Kepler, TESS, and soon PLATO deliver an unprecedented wealth of new photometric data on this matter, while ground-based follow-up and radial velocity instruments add valuable insights. Here, I will present how we can unite and untangle all this data on exoplanets' orbits and dynamics using allesfitter. This open-source python software enables flexible and robust inference of stars and exoplanets from photometric and radial velocity data. Allesfitter offers a rich selection of orbital and transit/eclipse models, accommodating multiple exoplanets, multi-star systems, transit-timing variations, and phase curves. It can also help mitigate and/or study stellar variability, starspots, and stellar flares. I will highlight some of allesfitter's science output on examples of exoplanet dynamics (e.g., TOI-270 and TOI-216) and orbital phase curves (e.g., WASP-18 and WASP-121). With TESS' extended mission and PLATO on the horizon, a wealth of new data soon face us, allowing TTV and phase curve studies of dozens of such systems over many years.

We present the discovery of TOI-2136b, a sub-Neptune planet transiting every 7.85 days a nearby M4.5V-type star, identified through photometric measurements from the TESS mission. The host star is located $33$ pc away with a radius of $R_{\ast} = 0.34\pm0.02\ R_{\odot}$, a mass of $0.34\pm0.02\ M_{\odot}$ and an effective temperature of $\rm 3342\pm100\ K$. We estimate its stellar rotation period to be $75\pm5$ days based on archival long-term photometry. We confirm and characterize the planet based on a series of ground-based multi-wavelength photometry, high-angular-resolution imaging observations, and precise radial velocities from CFHT/SPIRou. Our joint analysis reveals that the planet has a radius of $2.19\pm0.17\ R_{\oplus}$, and a mass measurement of $6.4\pm2.4\ M_{\oplus}$. The mass and radius of TOI2136b is consistent with a broad range of compositions, from water-ice to gas-dominated worlds. TOI-2136b falls close to the radius valley for low-mass stars predicted by the thermally driven atmospheric mass loss models, making it an interesting target for future studies of its interior structure and atmospheric properties., Comment: 19 pages, 15 figures, submitted to MNRAS

HIP 41378 f is a temperate $9.2\pm0.1 R_{\oplus}$ planet with period of 542.08 days and an extremely low density of $0.09\pm0.02$ g cm$^{-3}$. It transits the bright star HIP 41378 (V=8.93), making it an exciting target for atmospheric characterization including transmission spectroscopy. HIP 41378 was monitored photometrically between the dates of 2019 November 19 and November 28. We detected a transit of HIP 41378 f with NGTS, just the third transit ever detected for this planet, which confirms the orbital period. This is also the first ground-based detection of a transit of HIP 41378 f. Additional ground-based photometry was also obtained and used to constrain the time of the transit. The transit was measured to occur 1.50 hours earlier than predicted. We use an analytic transit timing variation (TTV) model to show the observed TTV can be explained by interactions between HIP 41378 e and HIP 41378 f. Using our TTV model, we predict the epochs of future transits of HIP 41378 f, with derived transit centres of T$_{C,4} = 2459355.087^{+0.031}_{-0.022}$ (May 2021) and T$_{C,5} = 2459897.078^{+0.114}_{-0.060}$ (Nov 2022)., Comment: Accepted for publication in MNRAS Letters. 6 pages, 2 figures

We are using precise radial velocities from CORALIE together with precision photometry from the Next Generation Transit Survey (NGTS) to follow up stars with single-transit events detected with the Transiting Exoplanet Survey Satellite (TESS). As part of this survey we identified a single transit on the star TIC-320687387, a bright (T=11.6) G-dwarf observed by TESS in Sector 13 and 27. From subsequent monitoring of TIC-320687387 with CORALIE, NGTS, and Lesedi we determined that the companion, TIC-320687387 B,is a very low-mass star with a mass of $96.2 \pm _{2.0}^{1.9} M_J$ and radius of $1.14 \pm _{0.02}^{0.02} R_J$ placing it close to the hydrogen burning limit ($\sim 80 M_J$). TIC-320687387 B has a wide and eccentric orbit, with a period of 29.77381 days and an eccentricity of $0.366 \pm 0.003$. Eclipsing systems such as TIC-320687387 AB allow us to test stellar evolution models for low-mass stars, which in turn are needed to calculate accurate masses and radii for exoplanets orbiting single low-mass stars. The wide orbit of TIC-320687387 B makes it particularly valuable as its evolution can be assumed to be free from perturbations caused by tidal interactions with its G-type host star., Comment: 9 pages, 6 figures, 4 tables. Submitted to MNRAS

We report the discovery of four new hot Jupiters with the Next Generation Transit Survey (NGTS). NGTS-15b, NGTS-16b, NGTS-17b, and NGTS-18b are short-period ($P, Accepted for publication in MNRAS

We present an analysis of the first 20 second cadence light curves obtained by the TESS space telescope during its extended mission. We find improved precision of 20 second data compared to 2 minute data for bright stars when binned to the same cadence (˜10%-25% better for T ? 8 mag, reaching equal precision at T ˜ 13 mag), consistent with pre-flight expectations based on differences in cosmic-ray mitigation algorithms. We present two results enabled by this improvement. First, we use 20 second data to detect oscillations in three solar analogs (? Pav, ? Tuc, and p Men) and use asteroseismology to measure their radii, masses, densities, and ages to ˜1%, ˜3%, ˜1%, and ˜20% respectively, including systematic errors. Combining our asteroseismic ages with chromospheric activity measurements, we find evidence that the spread in the activity-age relation is linked to stellar mass and thus the depth of the convection zone. Second, we combine 20 second data and published radial velocities to recharacterize p Men c, which is now the closest transiting exoplanet for which detailed asteroseismology of the host star is possible. We show that p Men c is located at the upper edge of the planet radius valley for its orbital period, confirming that it has likely retained a volatile atmosphere and that the "asteroseismic radius valley"remains devoid of planets. Our analysis favors a low eccentricity for p Men c (, D.H. acknowledges support from the Alfred P. Sloan Foundation, the National Aeronautics and Space Administration (80NSSC19K0379, 80NSSC21K0652), and the National Science Foundation (AST-1717000). T.S.M. acknowledges support from NASA grant 80NSSC20K0458. Computational time at the Texas Advanced Computing Center was provided through XSEDE allocation TG-AST090107. A.C. acknowledges support from the National Science Foundation through the Graduate Research Fellowship Program (DGE 1842402). W.H.B. performed computations using the University of Birmingham's BlueBEAR High Performance Computing service. T.R.B. acknowledges support from the Australian Research Council through Discovery Project DP210103119. Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (Grant DNRF106). M.S.C. and M.D. acknowledge the support by FCT/MCTES through the research grants UIDB/04434/2020, UIDP/04434/2020 and PTDC/FIS-AST/30389/2017, and by FEDER—Fundo Europeu de Desenvolvimento Regional through COMPETE2020—Programa Operacional Competitividade e Internacionalização (grant: POCI-01-0145-FEDER-030389). T.L.C. is supported by Fundação para a Ciência e a Tecnologia (FCT) in the form of a work contract (CEECIND/00476/2018). M.S.C. is supported by national funds through FCT in the form of a work contract. H.K. and E.P. acknowledge the grant from the European Social Fund via the Lithuanian Science Council (LMTLT) grant No. 09.3.3-LMT-K-712-01-0103. R.A.G. and S.N.B. acknowledge the support received from the CNES with the PLATO and GOLF grants. B.N. acknowledges postdoctoral funding from the Alexander von Humboldt Foundation and "Branco Weiss fellowship Science in Society" through the SEISMIC stellar interior physics group. S.M. acknowledges support by the Spanish Ministry of Science and Innovation with the Ramon y Cajal fellowship number RYC-2015-17697 and the grant number PID2019-107187GB-I00. T.W. acknowledges support from the B-type Strategic Priority Program of the Chinese Academy of Sciences (grant No. XDB41000000) from the NSFC of China (grant Nos. 11773064, 11873084, and 11521303), from the Youth Innovation Promotion Association of Chinese Academy of Sciences, and from the Ten Thousand Talents Program of Yunnan for Top-notch Young Talents. T.W. also gratefully acknowledges the computing time granted by the Yunnan Observatories and provided by the facilities at the Yunnan Observatories Supercomputing Platform. T.D. acknowledges support from MIT's Kavli Institute as a Kavli postdoctoral fellow.

All stars produce explosive surface events such as flares and coronal mass ejections. These events are driven by the release of energy stored in coronal magnetic fields, generated by the stellar dynamo. However, it remains unclear if the energy deposition in the magnetic fields is driven by direct or alternating currents. Recently, we presented observational measurements of the flare intensity distributions for a sample of $\sim10^5$ stars across the main sequence observed by $\textit{TESS}$, all of which exhibited power-law distributions similar to those observed in the Sun, albeit with varying slopes. Here we investigate the mechanisms required to produce such a distribution of flaring events via direct current energy deposition, in which coronal magnetic fields braid, reconnect, and produce flares. We adopt a topological model for this process which produces a power-law distribution of energetic flaring events. We expand this model to include the Coriolis effect, which we demonstrate produces a shallower distribution of flare energies in stars that rotate more rapidly (corresponding to a weaker decline in occurrence rates toward increasing flare energies). We present tentative evidence for the predicted rotation-power-law index correlation in the observations. We advocate for future observations of stellar flares that would improve our measurements of the power-law exponents, and yield key insights into the underlying dynamo mechanisms that underpin the self-similar flare intensity distributions., Comment: 19 pages, 11 figures, accepted for publication in ApJ

We present ground- and space-based photometric observations of TOI-270 (L231-32), a system of three transiting planets consisting of one super-Earth and two sub-Neptunes discovered by TESS around a bright (K-mag = 8.25) M3V dwarf. The planets orbit near low-order mean-motion resonances (5:3 and 2:1) and are thus expected to exhibit large transit timing variations (TTVs). Following an extensive observing campaign using eight different observatories between 2018 and 2020, we now report a clear detection of TTVs for planets c and d, with amplitudes of ∼10 min and a super-period of ∼3 yr, as well as significantly refined estimates of the radii and mean orbital periods of all three planets. Dynamical modelling of the TTVs alone puts strong constraints on the mass ratio of planets c and d and on their eccentricities. When incorporating recently published constraints from radial velocity observations, we obtain masses of $M_{\mathrm{b}}=1.48\pm 0.18\, M_\oplus$, $M_{\mathrm{c}}=6.20\pm 0.31\, M_\oplus$, and $M_{\mathrm{d}}=4.20\pm 0.16\, M_\oplus$ for planets b, c, and d, respectively. We also detect small but significant eccentricities for all three planets : eb = 0.0167 ± 0.0084, ec = 0.0044 ± 0.0006, and ed = 0.0066 ± 0.0020. Our findings imply an Earth-like rocky composition for the inner planet, and Earth-like cores with an additional He/H2O atmosphere for the outer two. TOI-270 is now one of the best constrained systems of small transiting planets, and it remains an excellent target for atmospheric characterization.

The recent detection of the M dwarf GJ 1151 at 144 MHz low radio frequencies using LOFAR has been interpreted as evidence of an exoplanet magnetically interacting with its host star. This would be the first exoplanet detected around a main sequence star by a radio telescope. Radial velocity confirmation of such a planet has proven inconclusive, and it remains possible that the radio emission could be generated by a stellar coronal process. Using data from TESS, we shed light on this question by probing the stellar activity and flares of GJ 1151 as well as fourteen other M dwarfs detected by LOFAR. GJ 1151 and three other star-planet interaction candidates are found to be inactive, with no rotational modulation and few, if any, flares. The remainder of the LOFAR detected M dwarfs flare frequently. We consider it unlikely that stellar activity is responsible for the bright, circularly-polarized emission from GJ 1151 and its three analogs, and support the star-planet magnetic interaction interpretation., ApJL: https://iopscience.iop.org/article/10.3847/2041-8213/ac230c

We present the bright (V$_{mag} = 9.12$), multi-planet system TOI-431, characterised with photometry and radial velocities. We estimate the stellar rotation period to be $30.5 \pm 0.7$ days using archival photometry and radial velocities. TOI-431b is a super-Earth with a period of 0.49 days, a radius of 1.28 $\pm$ 0.04 R$_{\oplus}$, a mass of $3.07 \pm 0.35$ M$_{\oplus}$, and a density of $8.0 \pm 1.0$ g cm$^{-3}$; TOI-431d is a sub-Neptune with a period of 12.46 days, a radius of $3.29 \pm 0.09$ R$_{\oplus}$, a mass of $9.90^{+1.53}_{-1.49}$ M$_{\oplus}$, and a density of $1.36 \pm 0.25$ g cm$^{-3}$. We find a third planet, TOI-431c, in the HARPS radial velocity data, but it is not seen to transit in the TESS light curves. It has an $M \sin i$ of $2.83^{+0.41}_{-0.34}$ M$_{\oplus}$, and a period of 4.85 days. TOI-431d likely has an extended atmosphere and is one of the most well-suited TESS discoveries for atmospheric characterisation, while the super-Earth TOI-431b may be a stripped core. These planets straddle the radius gap, presenting an interesting case-study for atmospheric evolution, and TOI-431b is a prime TESS discovery for the study of rocky planet phase curves., Comment: 21 pages, 11 figures, 3 appendices, accepted for publication in MNRAS

This research is based on data collected under the NGTS project at the ESO La Silla Paranal Observatory. The NGTS facility is funded by a consortium of institutes consisting of the University of Warwick, the University of Leicester, Queen’s University Belfast, the University of Geneva, the Deutsches Zentrum fur Luft- und Raumfahrt e.V. (DLR; under the ‘Grosinvestition GI-NGTS’), the University of Cambridge, together with the UK Science and Technology Facilities Council (STFC; project reference ST/M001962/1). JAGJ is supported by STFC PhD studentship 1763096. PJW and RGW are supported by the STFC consolidated grant ST/P000495/1. AMB acknowledges the support of the Institute of Advanced Study, University of Warwick, and is also supported by the STFC consolidated grant ST/P000320/1. MNG is supported by the STFC award reference 1490409 as well as the Isaac Newton Studentship. CEP acknowledges support from the European Research Council under the SeismoSun Research Project No. 321141. JSJ acknowledges support by Fondecyt grant 1161218 and partial support by CATA-Basal (PB06, CONICYT). DYK acknowledges support by the STFC consolidated grant ST/P000320/1. GMK is supported by the Royal Society as a Royal Society University Research Fellow. We also acknowledge and thank the ISSI team led by AMB for useful discussions. This publication makes use of data products from the 2MASS, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This publication makes use of data products from the WISE, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. The national facility capability for SkyMapper has been funded through ARC LIEF grant LE130100104 from the Australian Research Council, awarded to the University of Sydney, the Australian National University, Swinburne University of Technology, the University of Queensland, the University of Western Australia, the University of Melbourne, Curtin University of Technology, Monash University and the Australian Astronomical Observatory. SkyMapper is owned and operated by the Australian National University’s Research School of Astronomy and Astrophysics. The survey data were processed and provided by the SkyMapper Team at the ANU. The SkyMapper node of the All-Sky Virtual Observatory (ASVO) is hosted at the National Computational Infrastructure (NCI). Development and support the SkyMapper node of the ASVO has been funded in part by Astronomy Australia Limited (AAL) and the Australian Government through the Commonwealth’s Education Investment Fund (EIF) and National Collaborative Research Infrastructure Strategy (NCRIS), particularly the National eResearch Collaboration Tools and Resources (NeCTAR) and the Australian National Data Service Projects (ANDS). This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.

Stellar Flares and Habitable(?) Worlds from the TESS Primary Mission On our search for habitable worlds, we have to account for explosive stellar flaring and coronal mass ejections (CMEs) impacting exoplanets’ surface (or cloud) habitability. These stellar outbursts are a double-edged sword. On the one hand, flares and CMEs are capable of stripping off atmospheres and extinguishing existing biology. On the other hand, flares might be the (only) means to deliver the trigger energy for prebiotic chemistry and initiate life. In this talk, I will highlight our TESS study of all stellar flares from Years 1 & 2 of the mission, driven by the "stella" convolutional neural network. Where manual vetting would have taken a lifetime, and conventional outlier detection would have missed the smallest flares, state-of-the-art machine learning approaches allow us a fast, efficient, and probabilistic characterization of flares. I will also discuss flaring as a function of stellar type, age, rotation, spot coverage, and other factors. Finally, I will link our findings to prebiotic chemistry and ozone sterilization, identifying which worlds might lie just in the right regime between too much and too little flaring. With the TESS extended mission and increased cadences (20s, 2min and 10min), stellar flare studies and new exoplanet discoveries will ultimately aid in defining criteria for exoplanet habitability.

Context: The sub-Jovian or Neptunian desert is a previously-identified region of parameter space where there is a relative dearth of intermediate-mass planets at short orbital periods. Aims: We present the discovery of a new transiting planetary system within the Neptunian desert, NGTS-14. Methods: Transits of NGTS-14Ab were discovered in photometry from the Next Generation Transit Survey (NGTS). Follow-up transit photometry was conducted from several ground-based facilities, as well as extracted from TESS full-frame images. We combine radial velocities from the HARPS spectrograph with the photometry in a global analysis to determine the system parameters. Results: NGTS-14Ab has a radius about 30 per cent larger than that of Neptune ($0.444\pm0.030~\mathrm{R_{Jup}}$), and is around 70 per cent more massive than Neptune ($0.092 \pm 0.012~\mathrm{M_{Jup}}$). It transits the main-sequence K1 star, NGTS-14A, with a period of 3.54 days, just far enough to have maintained at least some of its primordial atmosphere. We have also identified a possible long-period stellar mass companion to the system, NGTS-14B, and we investigate the binarity of exoplanet host stars inside and outside the Neptunian desert using Gaia., 11 pages, 7 figures. Accepted for publication in A&A