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Current theories of planetary evolution predict that infant giant planets have large radii and very low densities before they slowly contract to reach their final size after about several hundred million years1,2. These theoretical expectations remain untested so far as the detection and characterization of very young planets is extremely challenging due to the intense stellar activity of their host stars3,4. Only the recent discoveries of young planetary transiting systems allow initial constraints to be placed on evolutionary models5,6,7. With an estimated age of 20 million years, V1298 Tau is one of the youngest solar-type stars known to host transiting planets; it harbours a system composed of four planets, two Neptune-sized, one Saturn-sized and one Jupiter-sized8,9. Here we report a multi-instrument radial velocity campaign of V1298 Tau, which allowed us to determine the masses of two of the planets in the system. We find that the two outermost giant planets, V1298 Tau b and e (0.64 ± 0.19 and 1.16 ± 0.30 Jupiter masses, respectively), seem to contradict our knowledge of early-stages planetary evolution. According to models, they should reach their mass–radius combination only hundreds of millions of years after formation. This result suggests that giant planets can contract much more quickly than usually assumed. © 2021, The Author(s), under exclusive licence to Springer Nature Limited., A.S.M. acknowledges financial support from the Spanish Ministry of Science and Innovation (MICINN) under the 2019 Juan de la Cierva Programme. J.I.G.H. acknowledges financial support from the Spanish MICINN under the 2013 Ramón y Cajal programme RYC-2013-14875. A.S.M., J.I.G.H., R.R., B.T.-P., N.L., M.R.Z.O., E.G.-A., J.A.C., P.J.A. and I.R. acknowledge financial support from the Spanish Ministry of Science and Innovation through projects AYA2017-86389-P, PID2019-109522GB-C53, PID2019-109522GB-C51, AYA2016-79425-C3-3-P, PID2019-109522GB-C52 and PGC2018-098153-B-C33. M.D. acknowledges financial support from the FP7-SPACE Project ETAEARTH (GA no. 313014). A.M., D.L., G.M., A.S. and S.D. acknowledge partial contribution from the agreement ASI-INAF no. 2018-16-HH.0. S.B., D.L., G.M. and D.T. acknowledge partial contribution from the agreement ASI-INAF no. 2021-5-HH.0. P.J.A. acknowledges financial support from the project SEV-2017-0709. S.D., V.D., S.B. and D.T. acknowledge support from the PRIN-INAF 2019 ‘Planetary systems at young ages’ (PLATEA). D.S.A. thanks the Leverhulme Trust for financial support. I.R. acknowledges the support of the Generalitat de Catalunya/CERCA programme. E.G.-A acknowledges support from the Spanish State Research Agency (AEI) project no. MDM-2017-0737 Unidad de Excelencia ‘María de Maeztu’ Centro de Astrobiología (CAB, CSIC/INTA). D.T. acknowledges the support of the Italian National Institute of Astrophysics (INAF) through the INAF Main Stream project ‘Ariel and the astrochemical link between circumstellar discs and planets’ (CUP: C54I19000700005). E.E.-B. acknowledges financial support from the European Union and the State Agency of Investigation of the Spanish Ministry of Science and Innovation (MICINN) under grant PRE2020-093107 of the Pre-Doc Program for the Training of Doctors (FPI-SO) through FEDER, FSE and FDCAN funds. This work is based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated by the Fundación Galileo Galilei (FGG) of the Istituto Nazionale di Astrofisica (INAF) at the Observatorio del Roque de los Muchachos (La Palma, Canary Islands, Spain). CARMENES is an instrument at the Centro Astronómico Hispano-Alemán (CAHA) at Calar Alto (Almería, Spain), operated jointly by the Junta de Andalucía and the Instituto de Astrofísica de Andalucía (CSIC). This work is based on data obtained with the STELLA robotic telescopes in Tenerife, an AIP facility jointly operated by AIP and IAC. This work makes use of observations from the LCOGT network.

We present an analysis of the red giant component of the recurrent nova V3890 Sgr, using data obtained before and after its 2019 eruption. Its effective temperature is $T_{\rm eff}=3050\pm$200 K for $\log{g}=0.7$, although there are modest changes in $T_{\rm eff}$. There is an overabundance of both carbon ($0.20\pm0.05$~dex) and sodium ($1.0\pm0.3$~dex) relative to their solar values, possibly the result of ejecta from the 1990 nova eruption being entrained into the red giant photosphere. We find $^{12}$C/$^{13}$C $=25\pm2$, a value similar to that found in red giants in other recurrent novae. The interpretation of the quiescent spectrum in the 5--38$\,mu$m region requires the presence of photospheric SiO absorption and cool ($\sim400$~K) dust in the red giant environment. The spectrum in the region of the Na{\sc i} D lines is complex, and includes at least six interstellar components, together with likely evidence for interaction between ejecta from the 2019 eruption and material accumulated in the plane of the binary. Three recurrent novae with giant secondaries have been shown to have environments with different dust content, but photospheres with similar $^{12}$C/$^{13}$C ratios. The SiO fundamental bands most likely have a photospheric origin in the all three stars., Accepted for publication in MNRAS on 22 July 2022. 15 pages, 11 figs

Context. We embarked on a high-resolution optical spectroscopic survey of bright Transiting Exoplanet Survey Satellite (TESS) stars around the Northern Ecliptic Pole (NEP), dubbed the Vatican-Potsdam-NEP (VPNEP) survey. Aims. Our NEP coverage comprises ≈770 square degrees with 1067 stars, of which 352 are bona fide dwarf stars and 715 are giant stars, all cooler than spectral type F0 and brighter than V = 8m.5. Our aim is to characterize these stars for the benefit of future studies in the community. Methods. We analyzed the spectra via comparisons with synthetic spectra. Particular line profiles were analyzed by means of eigenprofiles, equivalent widths, and relative emission-line fluxes (when applicable). Results. Two R = 200 000 spectra were obtained for each of the dwarf stars with the Vatican Advanced Technology Telescope (VATT) and the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI), with typically three R = 55 000 spectra obtained for the giant stars with STELLA and the STELLA Echelle Spectrograph (SES). Combined with V-band magnitudes, Gaia EDR3 parallaxes, and isochrones from the Padova and Trieste Stellar Evolutionary Code, the spectra can be used to obtain radial velocities, effective temperatures, gravities, rotational and turbulence broadenings, stellar masses and ages, and abundances for 27 chemical elements, as well as isotope ratios for lithium and carbon, line bisector spans, convective blue-shifts (when feasible), and levels of magnetic activity from Hα, Hβ, and the Ca II infrared triplet. In this initial paper, we discuss our analysis tools and biases, presenting our first results from a pilot sub-sample of 54 stars (27 bona-fide dwarf stars observed with VATT+PEPSI and 27 bona-fide giant stars observed with STELLA+SES) and making all reduced spectra available to the community. We carried out a follow-up error analysis, including systematic biases and standard deviations based on a joint target sample for both facilities, as well as a comparison with external data sources.

Active regions are the most prominent manifestations of solar magnetic fields; their generation and dissipation are fundamental problems in solar physics. Light bridges are commonly present during sunspot decay, but a comprehensive picture of their role in the removal of photospheric magnetic field is still missing. We study the three dimensional configuration of a sunspot and in particular its light bridge during one of the last stages of its decay. We present the magnetic and thermodynamical stratification inferred from full Stokes inversions of the photospheric Si I 10827 \AA\ and Ca I 10839 \AA\ lines obtained with the GREGOR Infrared Spectrograph of the GREGOR telescope at Observatorio del Teide, Tenerife, Spain. The analysis is complemented by a study of continuum images covering the disk passage of the active region, which are provided by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. The sunspot shows a light bridge with penumbral continuum intensity that separates the central umbra from a smaller umbra. We find that in this region the magnetic field lines form a canopy with lower magnetic field strength in the inner part. The photospheric light bridge is dominated by gas pressure (high-$\beta$), as opposed to the surrounding umbra where the magnetic pressure is higher. A convective flow is observed in the light bridge. This flow is able to bend the magnetic field lines and to produce field reversals. The field lines close above the light bridge and become as vertical and strong as in the surrounding umbra. We conclude that it develops because of two highly magnetized regions which come closer during the sunspot evolution., Comment: Accepted for publication in A&A

We present the first Doppler image for both stellar components of the F9+G0 ZAMS binary σ 2 CrB and found evidence for the coexistence of cool and warm spots on both stars. Cool spots appear mainly at polar or high latitudes while a confined equatorial warm belt appears on the trailing hemisphere of each of the two stars with respect to the orbital motion. We also present an update of the TempMap imaging code that allows us to solve the stellar surface temperature distribution on both binary components simultaneously, including photometric input. Several test reconstructions are performed to demonstrate its reliability and robustness. Our new orbital solution results in very precise masses for both components - good to 0.4% - and confirms the spectral classifications of F9 and G0 for the primary and secondary, respectively. The visual component, σ 1 CrB, seems to be G4 rather than G0. All three components are on or very close to the ZAMS which is also confirmed by the relatively high lithium abundance of about twenty times the solar abundance. Photometric light variations are detected with a period of 1.157 ± 0.002 days that we interpret to be the rotation period of both binary components. A 0. m 04 dimming in y together with a reddening of 0. m 01 in b − y during the year 2000 suggests a long-term spot variability compatible with a period of at least 260 days.