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An infrared excess over the stellar photospheric emission of main-sequence stars has been found in interferometric surveys, commonly attributed to the presence of hot exozodiacal dust (HEZD). While submicrometer-sized grains in close vicinity to their host star have been inferred to be responsible for the found near-infrared excesses, the presence and amount of larger grains as part of the dust distributions are weakly constrained. We quantify how many larger grains (above-micrometer-sized) could be present in addition to submicrometer-sized grains, while being consistent with observational constraints. This is important in order to distinguish between various scenarios for the origin of HEZD and to better estimate its observational appearance when observed with future instruments. We extended a model suitable to reproduce current observations of HEZD to investigate a bimodal size distribution. By deriving the characteristics of dust distributions whose observables are consistent with observational limits from interferometric measurements in the $K$ and $N$ bands we constrained the radii of sub- and above-micrometer-sized grains as well as their mass, number, and flux density ratios. In the most extreme cases of some of the investigated systems, large grains $\gtrsim 10\,\mu$m might dominate the mass budget of HEZD while contributing up to 25$\,$% of the total flux density originating from the dust at a wavelength of 2.13$\,\mu$m and up to 50$\,$% at a wavelength of 4.1$\,\mu$m; at a wavelength of 11.1$\,\mu$m their emission might clearly dominate over the emission of small grains. While it is not possible to detect such hot-dust distributions using ALMA, the ngVLA might allow us to detect HEZD at millimeter wavelengths. Large dust grains might have a more important impact on the observational appearance of HEZD than previously assumed, especially at longer wavelengths., Comment: Accepted for publication in Astronomy & Astrophysics. 18 pages, 7 figures

Aims. We analyze whether the effects of secular perturbations, originating from a substellar companion, on the dust dynamics in a debris disk can be investigated with spatially resolved observations. Methods. We numerically simulated the collisional evolution of narrow and eccentric cold planetesimal belts around a star of spectral type A3V that are secularly perturbed by a companion that orbits either closer to or farther from the star than the belt. Based on the resulting spatial dust distributions, we simulated spatially resolved maps of their surface brightness in the $K$, $N$, and $Q$ bands and at wavelengths of 70$\mu$m and 1300$\mu$m. Results. Assuming a nearby debris disk seen face-on, we find that the brightness distribution varies significantly with observing wavelength, for example between the $N$ and $Q$ band. This can be explained by the varying relative contribution of the emission of the smallest grains near the blowout limit. The orbits of both the small grains that form the halo and the large grains close to the parent belt precess due to the secular perturbations induced by a companion orbiting inward of the belt. The halo, being composed of older grains, trails the belt. The magnitude of the trailing decreases with increasing perturber mass and hence with increasing strength of the perturbation, a trend we recovered in synthetic maps of surface brightness by fitting ellipses to lines of constant brightness. Systems with an outer perturber do not show a uniform halo precession since the orbits of small grains are strongly altered. We identified features of the brightness distributions suitable for distinguishing between systems with a potentially detectable inner or outer perturber, especially with a combined observation with JWST/MIRI in the $Q$ band tracing small grain emission and with ALMA at mm wavelengths tracing the position of the parent planetesimal belt., Comment: Article and corrigendum published in A&A. 27 pages, 22 figures. New version: minor plot layout updates and attached corrigendum. Reason for corrigendum: The original article has a typo in the sensitivity of JWST/MIRI at 10$\mu$m and an error in the calculation of its sensitivity at 21$\mu$m. The required exposure times at 21$\mu$m are shorter than stated. The main conclusions are not affected

Statistical analyses from exoplanet surveys around low-mass stars indicate that super-Earth and Neptune-mass planets are more frequent than gas giants around such stars, in agreement with core accretion theory of planet formation. Using precise radial velocities derived from visual and near-infrared spectra, we report the discovery of a giant planet with a minimum mass of 0.46 Jupiter masses in an eccentric 204-day orbit around the very low-mass star GJ 3512. Dynamical models show that the high eccentricity of the orbit is most likely explained from planet-planet interactions. The reported planetary system challenges current formation theories and puts stringent constraints on the accretion and migration rates of planet formation and evolution models, indicating that disc instability may be more efficient in forming planets than previously thought., Comment: Manuscript author version. 41 pages, 11 figures

Context. Teegarden's Star is the brightest and one of the nearest ultra-cool dwarfs in the solar neighbourhood. For its late spectral type (M7.0V), the star shows relatively little activity and is a prime target for near-infrared radial velocity surveys such as CARMENES. Aims. As part of the CARMENES search for exoplanets around M dwarfs, we obtained more than 200 radial-velocity measurements of Teegarden's Star and analysed them for planetary signals. Methods. We find periodic variability in the radial velocities of Teegarden's Star. We also studied photometric measurements to rule out stellar brightness variations mimicking planetary signals. Results. We find evidence for two planet candidates, each with $1.1M_\oplus$ minimum mass, orbiting at periods of 4.91 and 11.4 d, respectively. No evidence for planetary transits could be found in archival and follow-up photometry. Small photometric variability is suggestive of slow rotation and old age. Conclusions. The two planets are among the lowest-mass planets discovered so far, and they are the first Earth-mass planets around an ultra-cool dwarf for which the masses have been determined using radial velocities., Comment: A&A 627, A49. 26 pages, 17 figures, 6 tables. Press release available at http://www.astro.physik.uni-goettingen.de/~zechmeister/teegarden/teegarden.html. v2: two authors and one reference added