Yutong Shan

• Zhang, Z. H.; Navarete, F.; Gálvez-Ortiz, M. C.; Jones, H. R.A.; Burgasser, A. J. & Cruz, P. [Vis alle 16 forfattere av denne artikkelen] (2025). Benchmark brown dwarfs - I. A blue M2 + T5 wide binary and a probable young [M4 + M4] + [T7 + T8] hierarchical quadruple. Monthly notices of the Royal Astronomical Society. ISSN 0035-8711. 542(2), s. 656–668. doi: 10.1093/mnras/staf895. Fulltekst i vitenarkiv Vis sammendrag

  Benchmark brown dwarfs in wide binary systems are crucial for characterizing substellar objects and calibrating atmospheric and evolutionary models. However, brown dwarf benchmarks with subsolar metallicity, very cool temperatures, or suitability for dynamical mass measurements are rare, limiting our understanding across the full range of mass, age, and metallicity. We present the discovery of two new multiple systems containing T dwarf companions, identified through a targeted search using CatWISE2020 and Gaia catalogues. L 122–88 AB is a wide binary comprising a mildly metal-poor M2 dwarf and a T5 dwarf, separated by 215.6 arcsec at a distance of 33.106 ± 0.014 pc. Atmospheric model fitting to the near-infrared spectrum of L 122–88 A suggests a mildly metal-poor composition ([Fe/H] = –0.2). UPM J1040–3551 AB is a candidate hierarchical quadruple system at 25.283 ± 0.013 pc, consisting of a likely astrometric binary of two M4 dwarfs and a probable unresolved spectral binary of T7 and T8 dwarfs, separated by 65.48 arcsec from the primary. The Hα emission detected in UPM J1040–3551 A indicates an age range of 0.3–2.0 Gyr. This age estimate suggests that the T8 component has a mass between 9 and 28 Jupiter masses, potentially classifying it as a planetary-mass object. These systems augment the sample of benchmark brown dwarfs, particularly in the underexplored regime of cool temperature, providing valuable opportunities for refining our understanding of substellar objects.

• Mamonova, Elena; Shan, Yutong; Kowalski, Adam F.; Wedemeyer, Sven & Werner, Stephanie (2025). Flare frequency in M dwarfs belonging to young moving groups. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 700. doi: 10.1051/0004-6361/202554614. Fulltekst i vitenarkiv Vis sammendrag

  Context. M stars are preferred targets for upcoming studies of terrestrial exoplanets aimed at obtaining their atmosphere spectra over the next decade. However, M dwarfs have long been known for their strong magnetic activity and the ability to frequently produce optical and broadband emission flares. Aims. We aim to characterise the flaring behaviour of young M dwarfs in the temporal, spectral, and energy dimensions, as well as examine the stellar parameters governing this behaviour. In this way, we aim to improve our understanding of the energy and frequency of the flare events capable of shaping the exoplanet atmosphere. Methods. Members of young moving groups (YMGs) provide a unique age-based perspective on stellar activity. By examining their flare behaviour in conjunction with rotation, mass, and Hα data, we can obtain a comprehensive understanding of flare-activity drivers in young stars. Results. We demonstrate that young stars sharing similar stellar parameters could also exhibit a broad range of flare frequency distributions. We also find that the flare behaviour shows indications of difference between optical and far ultraviolet (FUV). We propose that the period of rotation (and not the age of the star) can serve as a good proxy for assessing flaring activity. Furthermore, we recommend that instead of a simple power law for describing the flare frequency distribution, a piecewise power law can be used to describe mid-size and large flare distributions in young and active M dwarfs. Conclusions. Using known periods of rotation and fine-tuned power laws governing the flare frequency, we can produce a realistic sequence of flare events to study whether the atmosphere of small exoplanets orbiting M dwarf could withstand such activity until the emergence of life.

• Hatalova, Petra; Brodholt, John Peter; Brasser, Ramon; Shan, Yutong & Werner, Stephanie C. (2025). The compositional diversity of rocky exoplanets around K-dwarf stars. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 694. doi: 10.1051/0004-6361/202451070. Fulltekst i vitenarkiv Vis sammendrag

  Context. The mass-radius distribution of currently known exoplanets suggests a fascinating variety in terms of their chemical compositions. Still, the interior structures and compositions of rocky exoplanets are essentially inaccessible to observations. Here, we present a model that combines planet formation simulations with equilibrium condensation models to estimate the interior composition and structure of exoplanets around K-dwarf stars. Aims. In a previous study, we reproduced the observed population of close-in super-Earths around K-dwarf stars with suitable initial conditions. However, the masses and radii of these simulated planets are not self-consistent, since the radius information is postprocessed based on an assumed constant average density (3 g cm−3). In this work, we have incorporated compositions into the N-body simulations using the chemistry of the protoplanetary disk from equilibrium condensation sequences, together with thermodynamics of the various mineral phases. This has allowed us to develop models of likely interior structures, bulk densities, and, thus, radii for rocky exoplanets. Methods. We selected the outcomes of ten N-body simulations around a 0.8 M⊙ star that best reproduced the observed population. We employed stellar abundances from six K-dwarf stars with a range of metallicities. Based on the condensation sequence and the temperature-pressure profile of a disk, we assigned bulk elemental compositions to planetesimals and then tracked materials accreted onto planets during their formation. Results. We have obtained a set of planets with more realistic radii determinations than those purely based on one preset density for all bodies. We formed various types of planets: i) Ca- and Al-rich(er), ii) Mg-depleted, iii) fully oxidized core-less planets, iv) planets similar to Earth or Mars in composition and core size, and v) planets with different core mass fractions (from significantly smaller than the Martian core to significantly larger than the Earth’s core); however, we do not have Mercury-like planet with a huge core.

• Rauer, Heike; Aerts, Conny; Cabrera, Juan; Deleuil, Magali; et, al., including: & Erikson, Anders [Vis alle 847 forfattere av denne artikkelen] (2025). The PLATO mission. Experimental astronomy (Print). ISSN 0922-6435. 59. doi: 10.1007/s10686-025-09985-9. Fulltekst i vitenarkiv Vis sammendrag

  PLATO (PLAnetary Transits and Oscillations of stars) is ESA’s M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large number of stars. PLATO will detect small planets (down to <2R) around bright stars (<11 mag), including terrestrial planets in the habitable zone of solar-like stars. With the complement of radial velocity observations from the ground, planets will be characterised for their radius, mass, and age with high accuracy (5%, 10%, 10% for an Earth-Sun combination respectively). PLATO will provide us with a large-scale catalogue of well-characterised small planets up to intermediate orbital periods, relevant for a meaningful comparison to planet formation theories and to better understand planet evolution. It will make possible comparative exoplanetology to place our Solar System planets in a broader context. In parallel, PLATO will study (host) stars using asteroseismology, allowing us to determine the stellar properties with high accuracy, substantially enhancing our knowledge of stellar structure and evolution. The payload instrument consists of 26 cameras with 12cm aperture each. For at least four years, the mission will perform high-precision photometric measurements. Here we review the science objectives, present PLATO‘s target samples and fields, provide an overview of expected core science performance as well as a description of the instrument and the mission profile towards the end of the serial production of the flight cameras. PLATO is scheduled for a launch date end 2026. This overview therefore provides a summary of the mission to the community in preparation of the upcoming operational phases.

• Kaur, Simranpreet; Viganò, Daniele; Béjar, Víctor J. S.; Monge, Álvaro Sánchez; Morata, Òscar & Kansabanik, Devojyoti [Vis alle 21 forfattere av denne artikkelen] (2024). Hints of auroral and magnetospheric polarized radio emission from the scallop-shell star 2MASS J05082729-2101444. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 691. doi: 10.1051/0004-6361/202452037. Fulltekst i vitenarkiv Vis sammendrag

  Scallop-shell stars, a recently discovered class of young M dwarfs, show complex optical light curves that are characterized by periodic dips as well as other features that are stable over tens to hundreds of rotation cycles. The origin of these features is not well-understood. 2MASS J05082729−2101444 is a ∼25 Myr old scallop-shell star that was identified using TESS data; it has a photometric period of 6.73 h that has been attributed to rotation. Of the ∼50 recently confirmed scallop-shell stars, it is one of the few detected at radio frequencies between 1 and 8 GHz. We observed this rare system with the upgraded Giant Meterwave Radio Telescope at 575–720 MHz, covering 88% of the photometric period in each of the two observations scheduled almost a month apart in 2023. We detected approximately millijansky emission from the target in both epochs, with a significant circular polarization fraction: |V/I|∼20 − 50%. The 3.5-minute phase-folded light curves show unique variability in circular polarization. We detected an approximately hour-long helicity reversal during both epochs, and the reversals had similar amplitudes, lengths, and (possibly) occured at similar phases. These results suggest two emission components: The first is a persistent, moderately polarized component possibly ascribable to gyro-synchrotron emission driven by centrifugal breakout events. The second is a highly polarized, short burst-like component that is likely due to an electron cyclotron maser (ECM); it is indicative of auroral emission and is potentially responsible for the helicity reversal. To explain this, we discuss the different origins of the plasma responsible for the radio emission, including the possibility that the occulting material is acting as a plasma source. Future coordinated multifrequency radio and optical observations can further constrain the underlying scenario, as well as the magnetic geometry of the system, if we assume an ECM-like auroral emission.

• Tabernero, H.M.; Shan, Yutong; Caballero, J.A.; Duque-Arribas, C.; Montes, D. & Hernández, Hernandez González [Vis alle 16 forfattere av denne artikkelen] (2024). The CARMENES search for exoplanets around M dwarfs: Magnesium and silicon abundances of K7- M5.5 stars. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 689. doi: 10.1051/0004-6361/202450054. Fulltekst i vitenarkiv Vis sammendrag

  We present the abundances of magnesium (Mg) and silicon (Si) for 314 dwarf stars with spectral types in the interval K7.0–M5.5 (Teff range ≈ 4200–3050 K) observed with the CARMENES high-resolution spectrograph at the 3.5 m telescope at the Calar Alto Observatory. Our analysis employs the BT-Settl model atmospheres, the radiative transfer code Turbospectrum, and a state-of-the-art selection of atomic and molecular data. These Mg and Si abundances are critical for understanding both the chemical evolution and assembly of the Milky Way and the formation and composition of rocky planets. Our chemical abundances show a line-to-line scatter at the level of 0.1 dex for all studied spectral types. The typical error bar of our chemical abundance measurements is ± 0.11 dex (Mg) and ± 0.16 dex (Si) for all spectral types based on the comparison of the results obtained for stellar components of multiple systems. The derived abundances are consistent with the galactic evolution trends and observed chemical abundance distribution of earlier FGK-type stars in the solar neighbourhood. Besides, our analysis provides compatible abundances for stars in multiple systems. In addition, we studied the abundances of different galactic stellar populations. In this paper, we also explore the relation of the Mg and Si abundances of stars with and without known planets.

• Shan, Yutong; Revilla, D.; Skrzypinski, S.L.; Dreizler, S.; Béjar, V.J.S. & Caballero, J.A. [Vis alle 43 forfattere av denne artikkelen] (2024). CARMENES input catalog of M dwarfs: VII. New rotation periods for the survey stars and their correlations with stellar activity. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 684. doi: 10.1051/0004-6361/202346794. Fulltekst i vitenarkiv Vis sammendrag

  Aims. Knowledge of rotation periods (Prot) is important for understanding the magnetic activity and angular momentum evolution of late-type stars, as well as for evaluating radial velocity signals of potential exoplanets and identifying false positives. We measured photometric and spectroscopic Prot for a large sample of nearby bright M dwarfs with spectral types from M0 to M9, as part of our continual effort to fully characterize the Guaranteed Time Observation programme stars of the CARMENES survey. Methods. We analyse light curves chiefly from the SuperWASP survey and TESS data. We supplemented these with our own follow-up photometric monitoring programme from ground-based facilities, as well as spectroscopic indicator time series derived directly from the CARMENES spectra. Results. From our own analysis, we determined Prot for 129 stars. Combined with the literature, we tabulated Prot for 261 stars, or 75% of our sample. We developed a framework to evaluate the plausibility of all periods available for this sample by comparing them with activity signatures and checking for consistency between multiple measurements. We find that 166 of these stars have independent evidence that confirmed their Prot. There are inconsistencies in 27 periods, which we classify as debated. A further 68 periods are identified as provisional detections that could benefit from independent verification. We provide an empirical relation for the Prot uncertainty as a function of the Prot value, based on the dispersion of the measurements. We show that published formal errors seem to be often underestimated for periods longwards of ∼10 d. We examined rotation–activity relations with emission in X-rays, Hα, Ca II H&K, and surface magnetic field strengths for this sample of M dwarfs. We find overall agreement with previous works, as well as tentative differences in the partially versus fully convective subsamples. We show Prot as a function of stellar mass, age, and galactic kinematics. With the notable exception of three transiting planet systems and TZ Ari, all known planet hosts in this sample have Prot ≳ 15 d. Conclusions. Inherent challenges in determining accurate and precise stellar Prot means independent verification is important, especially for inactive M dwarfs. Evidence of potential mass dependence in activity–rotation relations would suggest physical changes in the magnetic dynamo that warrants further investigation using larger samples of M dwarfs on both sides of the fully convective boundary. Important limitations need to be overcome before the radial velocity technique can be routinely used to detect and study planets around young and active stars.

• Ruh, H.L.; Zechmeister, M.; Reiners, A.; Nagel, E.; Shan, Yutong & Cifuentes, C. [Vis alle 22 forfattere av denne artikkelen] (2024). The CARMENES search for exoplanets around M dwarfs: The impact of rotation and magnetic fields on the radial velocity jitter in cool stars. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 692. doi: 10.1051/0004-6361/202450836. Fulltekst i vitenarkiv Vis sammendrag

  Context. Radial velocity (RV) jitter represents an intrinsic limitation on the precision of Doppler searches for exoplanets that can originate from both instrumental and astrophysical sources. Aims. We aim to determine the RV jitter floor in M dwarfs and investigate the stellar properties that lead to RV jitter induced by stellar activity. Methods. We determined the RV jitter in 239 M dwarfs from the CARMENES survey that are predominantly of mid to late spectral type and solar metallicity. We also investigated the correlation between stellar rotation and magnetic fields with RV jitter. Results. The median jitter in the CARMENES sample is 3.1 m s−1, and it is 2.3 m s−1 for stars with an upper limit of 2 km s−1 on their projected rotation velocities. We provide a relation between the stellar equatorial rotation velocity and RV jitter in M dwarfs based on a subsample of 129 well-characterized CARMENES stars. RV jitter induced by stellar rotation dominates for stars with equatorial rotation velocities greater than 1 km s−1. A jitter floor of 2 m s−1 dominates in stars with equatorial rotation velocities below 1 km s−1. This jitter floor likely contains contributions from stellar jitter, instrumental jitter, and undetected companions. We study the impact of the average magnetic field and the distributions of magnetic filling factors on the RV jitter. We find a series of stars with excess RV jitter and distinctive distributions of magnetic filling factors. These stars are characterized by a dominant magnetic field component between 2 to 4 kG. Conclusions. An RV jitter floor can be distinguished from RV jitter induced by activity and rotation based on the stellar equatorial rotation velocity. RV jitter induced by activity and rotation primarily depends on the equatorial rotation velocity. This RV jitter is also related to the distribution of magnetic filling factors, and this emphasizes the role of the magnetic field in the generation of RV jitter.

• Mamonova, Elena; Shan, Yutong; Hatalova, Petra & Werner, Stephanie C. (2024). Planets similar in size are often dissimilar in interior. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 685. doi: 10.1051/0004-6361/202347049. Fulltekst i vitenarkiv Vis sammendrag

  The number of discovered exoplanets now exceeds 5500 allowing statistical analyses of planetary systems. Multi-planet systems are mini-laboratories of planet formation and evolution, and analysing their system architectures can help us to constrain the physics of these processes. Recent works have found evidence of significant intrasystem uniformity in planet properties such as radius, mass, and orbital spacing, collectively termed ‘peas in a pod’ trends. In particular, correlations in radius and mass have been interpreted as implying uniformity in planet bulk density and composition within a system. However, the samples used to assess trends in mass tend to be small and biased. In this paper, we re-evaluate correlations in planet properties in a large sample of systems with at least two planets for which mass and radius have been directly measured, and therefore bulk density can be calculated. Our sample was assembled using the most up-to-date exoplanet catalogue data, and we compute the relevant statistics while using a procedure to ‘weight’ the data points according to measurement precision. We find a moderate correlation in radius and a weak correlation in the densities of adjacent planets. However, masses of neighbouring planets show no overall correlation in our main sample and a weak correlation among pairs of planets similar in size or pairs restricted to Mp<100 M⊕, Rp<10 R⊕. Similarly, we show that the intrasystem dispersion in radius is typically less than that in mass and density. We identify ranges in stellar host properties that correlate with stronger uniformity in pairs of adjacent planets: low Teff for planet masses, and low metallicity and old age for planet densities. Furthermore, we explore whether peas in a pod trends extend into planet compositions or interior structures. For small neighbouring planets with similar radii, we show that their masses and interior structures are often disparate, indicating that even within the same system, similarity in radii is not necessarily a good proxy for similarity in composition or the physical nature of the planets.

• González-Álvarez, E.; Kemmer, J.; Chaturvedi, P.; Caballero, J.A.; Quirrenbach, A. & Amado, P.J. [Vis alle 32 forfattere av denne artikkelen] (2023). The CARMENES search for exoplanets around M dwarfs: A sub-Neptunian mass planet in the habitable zone of HN Lib. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202346276. Fulltekst i vitenarkiv Vis sammendrag

  We report the discovery of HN Lib b, a sub-Neptunian mass planet orbiting the nearby ( d ≈ = 6.25 pc) M4.0 V star HN Lib detected by our CARMENES radial-velocity (RV) survey. We determined a planetary minimum mass of M b sin i = 5.46 ± 0.75 M ⊕ and an orbital period of P b = 36.116 ± 0.029 d, using ~5 yr of CARMENES data, as well as archival RVs from HARPS and HIRES spanning more than 13 yr. The flux received by the planet equals half the instellation on Earth, which places it in the middle of the conservative habitable zone (HZ) of its host star. The RV data show evidence for another planet candidate with M [c] sin i = 9.7 ± 1.9 M ⊕ and P [c] = 113.46 ± 0.20 d. The long-term stability of the signal and the fact that the best model for our data is a two-planet model with an independent activity component stand as strong arguments for establishing a planetary origin. However, we cannot rule out stellar activity due to its proximity to the rotation period of HN Lib, which we measured using CARMENES activity indicators and photometric data from a ground-based multi-site campaign as well as archival data. The discovery adds HN Lib b to the shortlist of super-Earth planets in the habitable zone of M dwarfs, but HN Lib [c] probably cannot be inhabited because, if confirmed, it would most likely be an icy giant.

• Gorrini, P.; Kemmer, J.; Dreizler, S.; Burn, R.; Hirano, T. & Pozuelos, F.J. [Vis alle 39 forfattere av denne artikkelen] (2023). Planetary companions orbiting the M dwarfs GJ 724 and GJ 3988: A CARMENES and IRD collaboration. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 680. doi: 10.1051/0004-6361/202347108. Fulltekst i vitenarkiv Vis sammendrag

  We report the discovery of two exoplanets around the M dwarfs GJ 724 and GJ 3988 using the radial velocity (RV) method. We obtained a total of 153 3.5 m Calar Alto/CARMENES spectra for both targets and measured their RVs and activity indicators. We also added archival ESO/HARPS data for GJ 724 and infrared RV measurements from Subaru/IRD for GJ 3988. We searched for periodic and stable signals to subsequently construct Keplerian models, considering different numbers of planets, and we selected the best models based on their Bayesian evidence. Gaussian process (GP) regression was included in some models to account for activity signals. For both systems, the best model corresponds to one single planet. The minimum masses are 10.75 −0.87 +0.96 and 3.69 −0.41 +0.42 Earth-masses for GJ 724 b and GJ 3988 b, respectively. Both planets have short periods ( P &lt; 10 d) and, therefore, they orbit their star closely ( a &lt; 0.05 au). GJ 724 b has an eccentric orbit ( e = 0.577 −0.052 +0.055 ), whereas the orbit of GJ 3988 b is circular. The high eccentricity of GJ 724 b makes it the most eccentric single exoplanet (to this date) around an M dwarf. Thus, we suggest a further analysis to understand its configuration in the context of planetary formation and architecture. In contrast, GJ 3988 b is an example of a common type of planet around mid-M dwarfs.

• Timmermann, Anina; Shan, Yutong; Reiners, Ansgar & Pack, Andreas (2023). Revisiting equilibrium condensation and rocky planet compositions: Introducing the ECCO PLANETS code. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 676. doi: 10.1051/0004-6361/202244850. Fulltekst i vitenarkiv Vis sammendrag

  Context . The bulk composition of exoplanets cannot yet be directly observed. Equilibrium condensation simulations help us better understand the composition of the planets’ building blocks and their relation to the composition of their host star. Aims . We introduce ECCO PLANETS , an open-source Python code that simulates condensation in the protoplanetary disk. Our aim is to analyse how well a simplistic model can reproduce the main characteristics of rocky planet formation. For this purpose, we revisited condensation temperatures ( T c ) as a means to study disk chemistry, and explored their sensitivity to variations in pressure ( p ) and elemental abundance pattern. We also examined the bulk compositions of rocky planets around chemically diverse stars. Methods . Our T - p -dependent chemical equilibrium model is based on a Gibbs free energy minimisation. We derived condensation temperatures for Solar System parameters with a simulation limited to the most common chemical species. We assessed their change (∆ T c ) as a result of p -variation between 10 −6 and 0.1 bar. To analyse the influence of the abundance pattern, key element ratios were varied, and the results were validated using solar neighbourhood stars. To derive the bulk compositions of planets, we explored three different planetary feeding-zone (FZ) models and compared their output to an external n -body simulation. Results . Our model reproduces the external results well in all tests. For common planet-building elements, we derive a T c that is within ±5 K of literature values, taking a wider spectrum of components into account. The T c is sensitive to variations in p and the abundance pattern. For most elements, it rises with p and metallicity. The tested pressure range (10 −6 − 0.1 bar) corresponds to ∆ T c ≈ +350 K, and for −0.3 ≤ [M/H] ≤ 0.4 we find ∆ T c ≈ +100 K. An increase in C/O from 0.1 to 0.7 results in a decrease of ∆ T c ≈ −100 K. Other element ratios are less influential. Dynamic planetary accretion can be emulated well with any FZ model. Their width can be adapted to reproduce gradual changes in planetary composition.

• Ribas, I.; Reiners, A.; Zechmeister, M.; Caballero, J.A.; Morales, J.C. & Sabotta, S. [Vis alle 105 forfattere av denne artikkelen] (2023). The CARMENES search for exoplanets around M dwarfs: Guaranteed time observations Data Release 1 (2016-2020). Astronomy and Astrophysics (A & A). ISSN 0004-6361. 670. doi: 10.1051/0004-6361/202244879. Fulltekst i vitenarkiv Vis sammendrag

  Context. The CARMENES instrument, installed at the 3.5 m telescope of the Calar Alto Observatory in Almería, Spain, was conceived to deliver high-accuracy radial velocity (RV) measurements with long-term stability to search for temperate rocky planets around a sample of nearby cool stars. Moreover, the broad wavelength coverage was designed to provide a range of stellar activity indicators to assess the nature of potential RV signals and to provide valuable spectral information to help characterise the stellar targets. Aims. We describe the CARMENES guaranteed time observations (GTO), spanning from 2016 to 2020, during which 19 633 spectra for a sample of 362 targets were collected. We present the CARMENES Data Release 1 (DR1), which makes public all observations obtained during the GTO of the CARMENES survey. Methods. The CARMENES survey target selection was aimed at minimising biases, and about 70% of all known M dwarfs within 10 pc and accessible from Calar Alto were included. The data were pipeline-processed, and high-level data products, including 18 642 precise RVs for 345 targets, were derived. Time series data of spectroscopic activity indicators were also obtained. Results. We discuss the characteristics of the CARMENES data, the statistical properties of the stellar sample, and the spectroscopic measurements. We show examples of the use of CARMENES data and provide a contextual view of the exoplanet population revealed by the survey, including 33 new planets, 17 re-analysed planets, and 26 confirmed planets from transiting candidate follow-up. A subsample of 238 targets was used to derive updated planet occurrence rates, yielding an overall average of 1.44 ± 0.20 planets with 1 M⊕ < Mpl sin i < 1000 M⊕ and 1 day < Porb < 1000 days per star, and indicating that nearly every M dwarf hosts at least one planet. All the DR1 raw data, pipeline-processed data, and high-level data products are publicly available online. Conclusions. CARMENES data have proven very useful for identifying and measuring planetary companions. They are also suitable for a variety of additional applications, such as the determination of stellar fundamental and atmospheric properties, the characterisation of stellar activity, and the study of exoplanet atmospheres.

• Kossakowski, D.; Kürster, M.; Trifonov, T.; Henning, Th.; Kemmer, J. & Caballero, J.A. [Vis alle 50 forfattere av denne artikkelen] (2023). The CARMENES search for exoplanets around M dwarfs: Wolf 1069 b: Earth-mass planet in the habitable zone of a nearby, very low-mass star. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 670. doi: 10.1051/0004-6361/202245322. Fulltekst i vitenarkiv Vis sammendrag

  We present the discovery of an Earth-mass planet (Mb sin i = 1.26 ± 0.21 M⊕) on a 15.6 d orbit of a relatively nearby (d ~ 9.6 pc) and low-mass (0.167 ± 0.011 M⊙) M5.0 V star, Wolf 1069. Sitting at a separation of 0.0672 ± 0.0014 au away from the host star puts Wolf 1069 b in the habitable zone (HZ), receiving an incident flux of S = 0.652 ± 0.029 S⊕. The planetary signal was detected using telluric-corrected radial-velocity (RV) data from the CARMENES spectrograph, amounting to a total of 262 spectroscopic observations covering almost four years. There are additional long-period signals in the RVs, one of which we attribute to the stellar rotation period. This is possible thanks to our photometric analysis including new, well-sampled monitoring campaigns undergone with the OSN and TJO facilities that supplement archival photometry (i.e., from MEarth and SuperWASP), and this yielded an updated rotational period range of Prot = 150–170 d, with a likely value at 169.3−3.6+3.7. The stellar activity indicators provided by the CARMENES spectra likewise demonstrate evidence for the slow rotation period, though not as accurately due to possible factors such as signal aliasing or spot evolution. Our detectability limits indicate that additional planets more massive than one Earth mass with orbital periods of less than 10 days can be ruled out, suggesting that perhaps Wolf 1069 b had a violent formation history. This planet is also the sixth closest Earth-mass planet situated in the conservative HZ, after Proxima Centauri b, GJ 1061 d, Teegarden’s Star c, and GJ 1002 b and c. Despite not transiting, Wolf 1069 b is nonetheless a very promising target for future three-dimensional climate models to investigate various habitability cases as well as for sub-m s−1 RV campaigns to search for potential inner sub-Earth-mass planets in order to test planet formation theories.

• Reiners, A.; Shulyak, D.; Käpylä, P.J.; Ribas, I.; Nagel, E. & Zechmeister, M. [Vis alle 19 forfattere av denne artikkelen] (2022). Magnetism, rotation, and nonthermal emission in cool stars: Average magnetic field measurements in 292 M dwarfs. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 662. doi: 10.1051/0004-6361/202243251. Fulltekst i vitenarkiv
• Schlecker, M.; Burn, R.; Sabotta, S.; Seifert, A.; Henning, T. & Emsenhuber, A. [Vis alle 10 forfattere av denne artikkelen] (2022). RV-detected planets around M dwarfs: Challenges for core accretion models. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 664. doi: 10.1051/0004-6361/202142543. Fulltekst i vitenarkiv Vis sammendrag

  Context. Planet formation is sensitive to the conditions in protoplanetary disks, for which scaling laws as a function of stellar mass are known. Aims. We aim to test whether the observed population of planets around low-mass stars can be explained by these trends, or if separate formation channels are needed. Methods. We address this question by confronting a state-of-the-art planet population synthesis model with a sample of planets around M dwarfs observed by the HARPS and CARMENES radial velocity (RV) surveys. To account for detection biases, we performed injection and retrieval experiments on the actual RV data to produce synthetic observations of planets that we simulated following the core accretion paradigm. Results. These simulations robustly yield the previously reported high occurrence of rocky planets around M dwarfs and generally agree with their planetary mass function. In contrast, our simulations cannot reproduce a population of giant planets around stars less massive than 0.5 solar masses. This potentially indicates an alternative formation channel for giant planets around the least massive stars that cannot be explained with current core accretion theories. We further find a stellar mass dependency in the detection rate of short-period planets. A lack of close-in planets around the earlier-type stars ( M * &gt; 0.4 M ⊙ ) in our sample remains unexplained by our model and indicates dissimilar planet migration barriers in disks of different spectral subtypes. Conclusions. Both discrepancies can be attributed to gaps in our understanding of planet migration in nascent M dwarf systems. They underline the different conditions around young stars of different spectral subtypes, and the importance of taking these differences into account when studying planet formation.

• Luque, R.; Fulton, B.J.; Kunimoto, M.; Amado, P.J.; Gorrini, P. & Dreizler, S. [Vis alle 67 forfattere av denne artikkelen] (2022). The HD 260655 system: Two rocky worlds transiting a bright M dwarf at 10 pc. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 664. doi: 10.1051/0004-6361/202243834. Fulltekst i vitenarkiv
• Caballero, J.A.; González-Álvarez, E.; Brady, M.; Trifonov, T.; Ellis, T.G. & Dorn, C. [Vis alle 67 forfattere av denne artikkelen] (2022). A detailed analysis of the Gl 486 planetary system. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 665. doi: 10.1051/0004-6361/202243548. Fulltekst i vitenarkiv Vis sammendrag

  Context . The Gl 486 system consists of a very nearby, relatively bright, weakly active M3.5 V star at just 8 pc with a warm transiting rocky planet of about 1.3 R ⊕ and 3.0 M ⊕ . It is ideal for both transmission and emission spectroscopy and for testing interior models of telluric planets. Aims . To prepare for future studies, we aim to thoroughly characterise the planetary system with new accurate and precise data collected with state-of-the-art photometers from space and spectrometers and interferometers from the ground. Methods . We collected light curves of seven new transits observed with the CHEOPS space mission and new radial velocities obtained with MAROON-X at the 8.1 m Gemini North telescope and CARMENES at the 3.5 m Calar Alto telescope, together with previously published spectroscopic and photometric data from the two spectrographs and TESS. We also performed near-infrared interferometric observations with the CHARA Array and new photometric monitoring with a suite of smaller telescopes (AstroLAB, LCOGT, OSN, TJO). This extraordinary and rich data set was the input for our comprehensive analysis. Results . From interferometry, we measure a limb-darkened disc angular size of the star Gl 486 at θ LDD = 0.390 ± 0.018 mas. Together with a corrected Gaia EDR3 parallax, we obtain a stellar radius R * = 0.339 ± 0.015 R ⊕ . We also measure a stellar rotation period at P rot = 49.9 ± 5.5 days, an upper limit to its XUV (5-920 A) flux informed by new Hubble /STIS data, and, for the first time, a variety of element abundances (Fe, Mg, Si, V, Sr, Zr, Rb) and C/O ratio. Moreover, we imposed restrictive constraints on the presence of additional components, either stellar or sub-stellar, in the system. With the input stellar parameters and the radial-velocity and transit data, we determine the radius and mass of the planet Gl 486 b at R p = 1.343 −0.062 +0.063 R ⊕ and M p = 3.00 −0.12 +0.13 M ⊕ , with relative uncertainties of the planet radius and mass of 4.7% and 4.2%, respectively. From the planet parameters and the stellar element abundances, we infer the most probable models of planet internal structure and composition, which are consistent with a relatively small metallic core with respect to the Earth, a deep silicate mantle, and a thin volatile upper layer. With all these ingredients, we outline prospects for Gl 486 b atmospheric studies, especially with forthcoming James Webb Space Telescope ( Webb ) observations.

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• Akerholt, Line Nybakk; Spilker, Andri & Shan, Yutong (2025). Astronomy libraries "In the middle of everyting" under severe pressure - coping or reinventing? doi: 10.5281/ZENODO.17749494. Fulltekst i vitenarkiv Vis sammendrag

  In 2010 we presented the talk "In Between or in the Middle of Everything" - since then, rapid technological development, sequential reorganizations, and changes in the handling of costs at the university level, have influenced our tasks and roles. Academic subject librarians and their special knowledge competes with the larger and more generic trends and constraints in the university library organizations. With this poster we wish to point out strategies and activities for maintaining focus on astronomy and the greater STEM librarian fellowship.

• Shan, Yutong; Zechmeister, Mathias; Reiners, Ansgar; Ilyin, Ilya & Strassmeier, Klaus (2024). The PEPSI ultra-high resolution spectral library of M dwarfs. Fulltekst i vitenarkiv
• Shan, Yutong; Hatalova, Petra; Tabernero, Hugo; Timmermann, Anina; Mamonova, Elena & Werner, Stephanie C. (2024). Current limitations in chemical abundance measurements for M dwarfs and implications for exoplanet characterisation. Fulltekst i vitenarkiv
• Shan, Yutong; Wedemeyer, Sven; Werner, Stephanie C. & Mamonova, Elena (2024). En leteaksjon av en annen verden: Kavliprisen i astrofysikk for 2024 hedrer forskerne som har pionert studien av eksoplaneter. Bladet Astronomi. Fulltekst i vitenarkiv

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