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We present the discovery of NGTS-1b, a hot-Jupiter transiting an early M-dwarf host (T eff, * =3916 +71 −63 K) in a P = 2.647 d orbit discovered as part of the Next Generation Transit Survey (NGTS). The planet has a mass of 0.812 +0.066 −0.075 M J making it the most massive planet ever discovered transiting an M-dwarf. The radius of the planet is 1.33 +0.61 −0.33 R J . Since the transit is grazing, we determine this radius by modelling the data and placing a prior on the density from the population of known gas giant planets. NGTS-1b is the third transiting giant planet found around an M-dwarf, reinforcing the notion that close-in gas giants can form and migrate similar to the known population of hot Jupiters around solar type stars. The host star shows no signs of activity, and the kinematics hint at the star being from the thick disk population. With a deep (2.5%) transit around a K = 11.9 host, NGTS-1b will be a strong candidate to probe giant planet composition around M-dwarfs via JWST transmission spectroscopy.

About one out of 200 Sun-like stars has a planet with an orbital period shorter than one day: an ultrashort-period planet (Sanchis-Ojeda et al. 2014;Winn et al. 2018). All of the previously known ultrashort-period planets are either hot Jupiters, with sizes above 10 Earth radii (R ⊕ ), or apparently rocky planets smaller than 2 R ⊕ . Such lack of planets of intermediate size (the "hot Neptune desert") has been interpreted as the inability of low-mass planets to retain any hydrogen/helium (H/He) envelope in the face of strong stellar irradiation. Here, we report the discovery of an ultra-short-period planet with a radius of 4.6 R ⊕ and a mass of 29 M ⊕ , firmly in the hot Neptune desert. Data from the Transiting Exoplanet Survey Satellite (Ricker et al. 2015) revealed transits of the bright Sun-like star LTT 9779 every 0.79 days. The planet's mean density is similar to that of Neptune, and according to thermal evolution models, it has a H/He-rich envelope constituting 9.0 +2.7 −2.9 % of the total mass. With an equilibrium temperature around 2000 K, it is unclear how this "ultra-hot Neptune" managed to retain such an envelope. Follow-up observations of the planet's atmosphere to better understand its origin and physical nature will be facilitated by the star's brightness (V mag = 9.8).

Context. The detection and subsequent characterisation of exoplanets are intimately linked to the characteristics of their host star. Therefore, it is necessary to study the star in detail in order to understand the formation history and characteristics of their companion(s). Aims. Our aims were to develop a community tool that allows the automated calculation of stellar parameters for a large number of stars, using high resolution echelle spectra and minimal photometric magnitudes, and introduce the first catalogue of these measurements in this work. Methods. We measured the equivalent widths of several iron lines and used them to solve the radiative transfer equation assuming local thermodynamic equilibrium in order to obtain the atmospheric parameters (T eff , [Fe/H], log g and ξ t ). We then used these values to derive the abundance of 11 chemical elements in the stellar photosphere (Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Ni, Cu and Zn). Rotation and macroturbulent velocity were obtained using temperature calibrators and synthetic line profiles to match the observed spectra of five absorption lines. Finally, by interpolating in a grid of MIST isochrones, we are able to derive the mass, radius and age for each star using a Bayesian approach. Results. Our SPECIES code obtains bulk parameters that are in good agreement with measured values from different existing catalogues, including when different methods are used to derive them. We find excellent agreement with previous works that used similar methodologies, in particular when the T eff is calculated using model fitting to the spectra themselves. We find discrepancies in the chemical abundances for some elements with respect to other works, which could be produced by differences in T eff , or in the line list or the atomic line data used to derive them. We also obtained analytic relations to describe the correlations between different parameters, and we implemented new methods to better handle these correlations, which provides a better description of the uncertainties associated with the measurements.

We report the discovery of a radial velocity signal that can be interpreted as a planetary-mass candidate orbiting the K dwarf HD26965, with an orbital period of 42.364±0.015 days, or alternatively, as the presence of residual, uncorrected rotational activity in the data. Observations include data from HIRES, PFS, CHIRON, and HARPS, where 1,111 measurements were made over 16 years. Our best solution for HD26965 b is consistent with a super-Earth that has a minimum mass of 6.92±0.79 M ⊕ orbiting at a distance of 0.215±0.008 AU from its host star. We have analyzed the correlation between spectral activity indicators and the radial velocities from each instrument, showing moderate correlations that we include in our model. From this analysis, we recover a ∼38 day signal, which matches some literature values of the stellar rotation period. However, from independent Mt. Wilson HK data for this star, we find evidence for a significant 42 day signal after subtraction of longer period magnetic cycles, casting doubt on the planetary hypothesis for this period. Although our statistical model strongly suggests that the 42-day signal is Doppler in origin, we conclude that the residual effects of stellar rotation are difficult to fully model and remove from this dataset, highlighting the difficulties to disentangle small planetary signals and photospheric noise, particularly when the orbital periods are close to the rotation period of the star. This study serves as an excellent test case for future works that aim to detect small planets orbiting 'Sun-like' stars using radial velocity measurements.

We report the discovery of NGTS-4b, a sub-Neptune-sized planet transiting a 13th magnitude K-dwarf in a 1.34 d orbit. NGTS-4b has a mass M=20.6 ± 3.0 M ⊕ and radius R=3.18 ± 0.26 R ⊕ , which places it well within the so-called "Neptunian Desert". The mean density of the planet (3.45 ± 0.95 g cm −3 ) is consistent with a composition of 100 % H 2 O or a rocky core with a volatile envelope. NGTS-4b is likely to suffer significant mass loss due to relatively strong EUV/X-ray irradiation. Its survival in the Neptunian desert may be due to an unusually high core mass, or it may have avoided the most intense X-ray irradiation by migrating after the initial activity of its host star had subsided. With a transit depth of 0.13 ± 0.02%, NGTS-4b represents the shallowest transiting system ever discovered from the ground, and is the smallest planet discovered in a wide-field ground-based photometric survey.

We report the detection of a transiting hot Neptune exoplanet orbiting TOI-824 (SCR J1448-5735), a nearby (d=64 pc) K4V star, using data from the Transiting Exoplanet Survey Satellite. The newly discovered planet has a radius R p =2.93±0.20 Å R and an orbital period of 1.393 days. Radial velocity measurements using the Planet Finder Spectrograph and the High Accuracy Radial velocity Planet Searcher spectrograph confirm the existence of the planet, and we estimate its mass to be 18.47±1.84 Å M . The planet's mean density is r p =4.03 -+ 0.78 0.98 g cm 3 , making it more than twice as dense as Neptune. TOI-824 bʼs high equilibrium temperature makes the planet likely to have a cloud-free atmosphere, and thus it is an excellent candidate for follow-up atmospheric studies. The detectability of TOI-824 b's atmosphere from both ground and space is promising and could lead to the detailed characterization of the most irradiated small planet at the edge of the hot Neptune desert that has retained its atmosphere to date. Unified Astronomy Thesaurus concepts: Exoplanet astronomy (486); Exoplanet detection methods (489); Exoplanets (498); Transit photometry (1709); Radial velocity (1332); Stellar properties (1624)

Aims. We investigate the nature of multiple supernova hosting galaxies, and the types of events that they produce. Methods. Using all known historical supernovae, we split host galaxies into samples containing single or multiple events. These samples are then characterised in terms of their relative supernova fractions and host properties. Results. In multiple supernova hosts the ratio of type Ia to core-collapse events is lower than in single supernova hosts. For corecollapse events there is a suggestion that the ratio of types Ibc to type II events is higher in multiples than within single supernova hosts. This second increase is dominated by an increase in the number of SNIb. Within multiple supernova hosts, supernovae of any given type appear to "prefer" to explode in galaxies that are host to the same type of SN. We also find that multiple SN hosts have higher T-type morphologies. Conclusions. While our results suffer from low number statistics, we speculate that their simplest interpretation is that star formation within galaxies is generally of an episodic and bursty nature. This leads to the supernovae detected within any particular galaxy to be dominated by those with progenitors of a specific age, rather than a random selection from standard relative supernova rates, as the latter would be expected if star formation was of a long-term continuous nature. We further discuss the supernova progenitor and star formation properties that may be important for understanding these trends, and also comment on a range of important selection effects within our sample.