During most of their life, stars fuse hydrogen into helium in their cores. Mixing of chemical elements in the radiative envelope of stars with a convective

In this paper we present the results of our search for and study of z 6 galaxy candidates behind the third Frontier Fields (FF) cluster, MACSJ0717.5+3745, and its parallel field, combining data from Hubble and Spitzer. We select 39 candidates using the Lyman Break technique, for which the clear non-detection in optical make the extreme mid-z interlopers hypothesis unlikely. We also take benefit from z 6 samples selected using previous Frontier Fields datasets of Abell 2744 and MACS0416 to improve the constraints on the properties of very high-redshift objects. We compute the redshift and the physical properties, such emission lines properties, star formation rate, reddening, and stellar mass for all Frontier Fields objects from their spectral energy distribution using templates including nebular emission lines. We study the relationship between several physical properties and confirm the trend already observed in previous surveys for evolution of star formation rate with galaxy mass, and between the size and the UV luminosity of our candidates. The analysis of the evolution of the UV Luminosity Function with redshift seems more compatible with an evolution of density. Moreover, no robust z ≥8.5 object is selected behind the cluster field, and few z∼9 candidates have been selected in the two previous datasets from this legacy survey, suggesting a strong evolution in the number density of galaxies between z∼8 and 9. Thanks to the use of the lensing cluster, we study the evolution of the star formation rate density produced by galaxies with L>0.03L , and confirm the strong decrease observed between z∼8 and 9.

We searched for z7 Lyman-break galaxies in the optical-to-mid-infrared Hubble Frontier Field and associated parallel field observations of the strong-lensing cluster MACS J0416−2403. We discovered 22 candidates, of which 6 lie at z9 and 1 lies at z10. Based on the Hubble and Spitzer photometry, all have secure photometric redshifts and a negligible probability of being at lower redshifts according to their peak-probability ratios, . This substantial increase in the number of known high-redshift galaxies allows a solid determination of the luminosity function (LF) at z8. The number of high-z candidates in the parallel field is considerably higher than that in the Abell 2744 parallel field. Our candidates have median stellar masses of * ~-+ M log 8.44 0.31 0.55 ( ) M e , star formation rates (SFRs) of ~-+ 1.8 0.4 0.5 M e yr −1 , and SFR-weighted ages of  -+ 300 Myr 140 70. Finally, we are able to put strong constraints on the z=7, 8, 9, and 10 LFs. One of the objects in the cluster field is a z ; 10 candidate, with a magnification of μ∼20±13. This object is likely the faintest z∼10 object known to date, allowing a first look into the extreme faint end (L∼0.04 L * ) of the z∼10 LF (It is named "Tayna" in the Aymara language).

Context. Intermediate-to high-mass stars are the least numerous types of stars, and they are less well understood than their more numerous low-mass counterparts in terms of their internal physical processes. Modelling the photometric variability of a large sample of main-sequence intermediate-to high-mass stars in eclipsing binary systems will help to improve the models for such stars. Aims. Our goal is to compose a homogeneously compiled sample of main-sequence intermediate-to high-mass OBA-type dwarfs in eclipsing binary systems from TESS photometry. We search for binaries with and without pulsations and determine their approximate ephemerides. Methods. Our selection starts from a catalogue of dwarfs with colours corresponding to those of OBA-type dwarfs in the TESS Input Catalog. We develop a new automated method aimed at detecting eclipsing binaries in the presence of a strong pulsational and/or rotational signal relative to the eclipse depths and apply it to publicly available 30-minute cadence TESS light curves. Results. Using targets with TESS magnitudes below 15 and cuts in the 2MASS magnitude bands of J − H < 0.045 and J − K < 0.06 as the most stringent criteria, we arrive at a total of 189 981 intermediate-to high-mass candidates, 91193 of which have light curves from at least one of two data reduction pipelines. The eclipsing binary detection and subsequent manual check for false positives resulted in 3155 unique OBA-type eclipsing binary candidates. Conclusions. Our sample of eclipsing binary stars in the intermediate-to high-mass regime allows for future binary (and asteroseismic) modelling with the aim to better understand the internal physical processes in this hot part of the main sequence.