Dwarf Host Research Articles

Chemical composition of planetary hosts: C, N, and α-element abundances

Accurate atmospheric parameters and chemical composition of planet hosts play a major role in characterising exoplanets and understanding their formation and evolution. Our objective is to uniformly determine atmospheric parameters and chemical abundances of carbon (C), nitrogen (N), oxygen(O), and the alpha -elements, magnesium (Mg) and silicon (Si), along with C/O, N/O and Mg/Si abundance ratios for planet-hosting stars. In this analysis, we aim to investigate the potential links between stellar chemistry and the presence of planets. e tai Observatory telescope. The determination of stellar parameters was based on a standard analysis using equivalent widths and one-dimensional, plane-parallel model atmospheres calculated under the assumption of local thermodynamical equilibrium. The differential synthetic spectrum method was used to uniformly determine the carbon C(C2), nitrogen N(CN), oxygen O I magnesium Mg I, and silicon Si I elemental abundances as well as the C/O, N/O, and Mg/Si ratios. We analysed elemental abundances and ratios in dwarf and giant stars, finding that C/Fe O/Fe and Mg/Fe are lower in metal-rich dwarf hosts; whereas N/Fe is close to the Solar ratio. Giants show smaller scatter in C/Fe and O/Fe and lower than the Solar average C/Fe and C/O ratios. The (C+N+O) abundances increase with Fe/H in giant stars, with a minimal scatter. We also noted an overabundance of Mg and Si in planet-hosting stars, particularly at lower metallicities, and a lower Mg/Si ratio in stars with planets. In giants hosting high-mass planets, nitrogen shows a moderate positive relationship with planet mass. C/O and N/O ratios show moderate negative and positive slopes in giant stars, respectively. The Mg/Si ratio shows a negative correlation with planet mass across the entire stellar sample.

Climatic Effects of Ocean Salinity on M Dwarf Exoplanets

Ocean salinity is known to dramatically affect the climates of Earth-like planets orbiting Sun-like stars, with high salinity leading to less ice and higher surface temperature. However, how ocean composition impacts climate under different conditions, such as around different types of stars or at different positions within the habitable zone, has not been investigated. We used ROCKE-3D, an ocean-atmosphere general circulation model, to simulate how planetary climate responds to ocean salinities for planets with G-star versus M dwarf hosts at several stellar fluxes. We find that increasing ocean salinity from 20 to 100 g kg−1 in our model results in nonlinear ice reduction and warming on G-star planets, sometimes causing abrupt transitions to different climate states. Conversely, sea ice on M dwarf planets responds more gradually and linearly to increasing salinity. Moreover, reductions in sea ice on M dwarf planets are not accompanied by significant surface warming as on G-star planets. High salinity can modestly bolster the resilience of M dwarf planets against snowball glaciation and allow these planets to retain surface liquid water further from their host star, but the effects are muted compared to G-star planets that experience snowball bifurcation and climate hysteresis due to the ice-albedo feedback.

KMT-2023-BLG-1866Lb: Microlensing super-Earth around an M dwarf host

Aims. We aim to investigate the nature of the short-term anomaly that appears in the lensing light curve of KMT-2023-BLG-1866. The anomaly was only partly covered due to its short duration of less than a day, coupled with cloudy weather conditions and a restricted nighttime duration. Methods. Considering the intricacy of interpreting partially covered signals, we thoroughly explored all potential degenerate solutions. Through this process, we identified three planetary scenarios that account for the observed anomaly equally well. These scenarios are characterized by the specific planetary parameters: (s, q)inner = [0.9740 ± 0.0083, (2.46 ± 1.07) × 10−5], (s, q)intermediate = [0.9779 ± 0.0017, (1.56 ± 0.25) × 10−5], and (s, q)outer = [0.9894 ± 0.0107, (2.31 ± 1.29) × 10−5], where s and q denote the projected separation (scaled to the Einstein radius) and mass ratio between the planet and its host, respectively. We identify that the ambiguity between the inner and outer solutions stems from the inner-outer degeneracy, while the similarity between the intermediate solution and the others is due to an accidental degeneracy caused by incomplete anomaly coverage. Results. Through Bayesian analysis utilizing the constraints derived from measured lensing observables and blending flux, our estimation indicates that the lens system comprises a very-low-mass planet orbiting an early M-type star situated approximately (6.2–6.5) kpc from Earth in terms of median posterior values for the different solutions. The median mass of the planet host is in the range of (0.48–0.51) M⊙, and that of the planet’s mass spans a range of (2.6–4.0) ME, varying across different solutions. The detection of KMT-2023-BLG-1866Lb signifies the extension of the lensing surveys to very-low-mass planets that have been difficult to detect in earlier surveys.

LHS 1140 b Is a Potentially Habitable Water World

LHS 1140 b is a small planet orbiting in the habitable zone of its M4.5V dwarf host. Recent mass and radius constraints have indicated that it has either a thick H2-rich atmosphere or substantial water by mass. Here we present a transmission spectrum of LHS 1140 b between 1.7 and 5.2 μm, obtained using the NIRSpec instrument on JWST. By combining spectral retrievals and self-consistent atmospheric models, we show that the transmission spectrum is inconsistent with H2-rich atmospheres with varied size and metallicity, leaving a water world as the remaining scenario to explain the planet’s low density. Specifically, a H2-rich atmosphere would result in prominent spectral features of CH4 or CO2 on this planet, but they are not seen in the transmission spectrum. Instead, the data favor a high mean molecular weight atmosphere (possibly N2 dominated with H2O and CO2) with a modest confidence. Forming the planet by accreting C- and N-bearing ices could naturally give rise to a CO2- or N2-dominated atmosphere, and if the planet evolves to or has the climate-stabilizing mechanism to maintain a moderate-size CO2/N2-dominated atmosphere, the planet could have liquid-water oceans. Our models suggest CO2 absorption features with an expected signal of 20 ppm at 4.2 μm. As the existence of an atmosphere on TRAPPIST-1 planets is uncertain, LHS 1140 b may well present the best current opportunity to detect and characterize a habitable world.

Atmospheric Retrievals of the Phase-resolved Spectra of Irradiated Brown Dwarfs WD-0137B and EPIC-2122B

We present an atmospheric retrieval analysis of Hubble Space Telescope/Wide Field Camera 3/G141 spectroscopic phase curve observations of two brown dwarfs, WD-0137B and EPIC-2122B, in ultrashort period orbits around white dwarf hosts. These systems are analogous to hot and ultra-hot Jupiter systems, enabling a unique and high-precision comparison to exoplanet systems. We use the PHOENIX Exoplanet Retrieval Algorithm retrieval suite to test various analysis setups, including joint-phase retrievals, multiple temperature structures, and nonuniform abundances. We find that WD-0137B has a dayside that closely resembles that of other ultra-hot Jupiters with inverted temperature structures and H− opacity, but quickly transitions to a mostly noninverted temperature structure on the nightside. Meanwhile, EPIC-2122B’s atmosphere remains inverted at all constrained longitudes, with dominant H− opacity. Retrievals with multiple temperature profiles and nonuniform vertical abundances were generally not statistically justified for this data set, but retrievals with dayside-dilution factors were found to be justified. Retrieving all phases simultaneously with a linear combination of a dayside and nightside atmosphere was found to be an adequate representation of the entire phase curve once a longitudinal temperature gradient free parameter was included in the retrieval. Comparing to global circulation models, we attribute behavior in the 1D retrievals to the inclined viewing geometry of the systems, which results in always-visible irradiated and inverted portions of the atmosphere contaminating spectra measured from the nightside hemisphere. This study sheds light on the similarities between these irradiated brown dwarf systems and hot and ultra-hot Jupiters, but also their unique differences, including the influence of the inclined viewing geometry.

Stellar Populations of AGN-host Dwarf Galaxies Selected with Different Methods

In this paper we investigate the stellar populations and star formation histories of 235 active galactic nucleus (AGN)-host dwarf galaxies, consisting of four samples identified separately with different methods (i.e., radio, X-ray, mid-IR and variability), utilizing the synthesis code STARLIGHT and spectra from the Sloan Digital Sky Survey Data Release 8. Our results show that the variability sample is the oldest, while the mid-IR sample is the youngest, for which the luminosity at 4020 Å is dominated (>50%) by the young population (t < 108 yr). The light-weighted mean stellar age of the whole sample is in general about 0.7 dex younger than the optical sample studied in Cai et al. We compare the population results between fitting models with and without a power-law (PL) component and find that the neglect of a PL component would lead to an under- and over-estimation by 0.2 and 0.1 dex for the light- and mass-weighted mean stellar age, respectively, for our sample of dwarf galaxies, which has a mean fractional contribution of ∼16% from the AGN. In addition, we obtain further evidence for a possible suppression of star formation in the host galaxy by the central AGN. We also find that there exists an anti-correlation between the extinction-corrected [O iii] luminosity and light-weighted mean stellar age, confirming our previous finding that there is a physical connection between AGN and star-forming activities in AGN-host dwarfs.

PHL 5038AB: Is the brown dwarf causing pollution of its white dwarf host star?

Abstract We present new results on PHL 5038AB, a widely separated binary system composed of a white dwarf and a brown dwarf, refining the white and brown dwarf parameters and determining the binary separation to be $66^{+12}_{-24}$ AU. New spectra of the white dwarf show calcium absorption lines suggesting the hydrogen-rich atmosphere is weakly polluted, inferring the presence of planetesimals in the system, which we determine are in an S-type orbit around the white dwarf in orbits closer than 17-32 AU. We do not detect any infrared excess that would indicate the presence of a disc, suggesting all dust present has either been totally accreted or is optically thin. In this system, we suggest the metal pollution in the white dwarf atmosphere can be directly attributed to the presence of the brown dwarf companion disrupting the orbits of planetesimals within the system.

Fast Outflows and Luminous He ii Emission in Dwarf Galaxies with Active Galactic Nuclei (AGN)

While stellar processes are believed to be the main source of feedback in dwarf galaxies, the accumulating discoveries of active galactic nuclei (AGN) in dwarf galaxies over recent years arouse the interest to also consider AGN feedback in them. Fast, AGN-driven outflows, a major mechanism of AGN feedback, have indeed been discovered in dwarf galaxies and may be powerful enough to provide feedback to their dwarf hosts. In this paper, we search for outflows traced by the blueshifted ultraviolet absorption features in three dwarf galaxies with AGN from the sample examined in our previous ground-based study. We confirm outflows traced by blueshifted absorption features in two objects and tentatively detect an outflow in the third object. In one object where the outflow is clearly detected in multiple species, photoionization modeling suggests that this outflow is located ∼0.5 kpc from the AGN, implying a galactic-scale impact. This outflow is much faster and possesses a higher kinetic energy outflow rate than starburst-driven outflows in sources with similar star formation rates, and is likely energetic enough to provide negative feedback to its host galaxy as predicted by simulations. Much broader (∼4000 km s−1) absorption features are also discovered in this object, which may have the same origin as that of broad absorption lines in quasars. Additionally, strong He ii λ1640 emission is detected in both objects where the transition falls in the wavelength coverage and is consistent with an AGN origin. In one of these two objects, a blueshifted He ii λ1640 emission line is clearly detected, likely tracing a highly ionized AGN wind.

OGLE-2014-BLG-0221Lb: A Jupiter Mass Ratio Companion Orbiting Either a Late-type Star or a Stellar Remnant

We present the analysis of the microlensing event OGLE-2014-BLG-0221, a planetary candidate event discovered in 2014. The photometric light curve is best described by a binary-lens single-source model. Our light-curve modeling finds two degenerate models, with event timescales of t E ∼ 70 days and ∼110 days. These timescales are relatively long, indicating that the discovered system would possess a substantial mass. The two models are similar in their planetary parameters with a Jupiter mass ratio of q ∼ 10−3 and a separation of s ∼ 1.1. Bayesian inference is used to estimate the physical parameters of the lens, revealing that the shorter timescale model predicts 65% and 25% probabilities of a late-type star and white dwarf host, respectively, while the longer timescale model favors a black hole host with a probability ranging from 60% to 95%, under the assumption that stars and stellar remnants have equal probabilities of hosting companions with planetary mass ratios. If the lens is a remnant, this would be the second planet found by microlensing around a stellar remnant. The current separation between the source and lens stars is 41–139 mas depending on the models. This indicates the event is now ready for high-angular-resolution follow-up observations to rule out either of the models. If precise astrometric measurements are conducted in multiple bands, the centroid shift due to the color difference between the source and lens would be detected in the luminous lens scenario.

Discovery of Magnetically Guided Metal Accretion onto a Polluted White Dwarf

Dynamically active planetary systems orbit a significant fraction of white dwarf stars. These stars often exhibit surface metals accreted from debris disks, which are detected through infrared excess or transiting structures. However, the full journey of a planetesimal from star-grazing orbit to final dissolution in the host star is poorly understood. Here, we report the discovery that the cool metal-polluted star WD 0816–310 has cannibalized heavy elements from a planetary body similar in size to Vesta, and where accretion and horizontal mixing processes have clearly been controlled by the stellar magnetic field. Our observations unveil periodic and synchronized variations in metal line strength and magnetic field intensity, implying a correlation between the local surface density of metals and the magnetic field structure. Specifically, the data point to a likely persistent concentration of metals near a magnetic pole. These findings demonstrate that magnetic fields may play a fundamental role in the final stages of exoplanetary bodies that are recycled into their white dwarf hosts.

TIaRA TESS 1: estimating exoplanet yields from Years 1 and 3 SPOC light curves

ABSTRACT We present a study of the detection efficiency for the TESS mission, focusing on the yield of longer period transiting exoplanets (P &amp;gt; 25 d). We created the Transit Investigation and Recoverability Application (TIaRA) pipeline to use real TESS data with injected transits to create sensitivity maps which we combine with occurrence rates derived from Kepler. This allows us to predict longer period exoplanet yields, which will help design follow-up photometric and spectroscopic programs, such as the NGTS (Next Generation Transit Survey) Monotransit Program. For the TESS Years 1 and 3 SPOC (Science Processing Operations Centre) FFI (Full Frame Image) light curves, we find $2271^{+241}_{-138}$ exoplanets should be detectable around AFGKM dwarf host stars. We find $215^{+37}_{-23}$ exoplanets should be detected from single-transit events or ‘monotransits’. An additional $113^{+22}_{-13}$ detections should result from ‘biennial duotransit’ events with one transit in Year 1 and a second in Year 3. We also find that K dwarf stars yield the most detections by TESS per star observed. When comparing our results to the TOI (TESS objects of interest) catalogue, we find our predictions agree within 1σ of the number of discovered systems with periods between 0.78 and 6.25 d and agree to 2σ for periods between 6.25 and 25 d. Beyond periods of 25 d, we predict $403^{+64}_{-38}$ detections, which is three times as many detections as there are in the TOI catalogue with &amp;gt;3σ confidence. This indicates a significant number of long-period planets yet to be discovered from TESS data as monotransits or biennial duotransits.

A Population of Short-duration Gamma-Ray Bursts with Dwarf Host Galaxies

We present a population of 11 of the faintest (>25.5 AB mag) short gamma-ray burst (GRB) host galaxies. We model their sparse available observations using the stellar population inference code Prospector-β and develop a novel implementation to incorporate the galaxy mass–radius relation. Assuming these hosts are randomly drawn from the galaxy population and conditioning this draw on their observed flux and size in a few photometric bands, we determine that these hosts have dwarf galaxy stellar masses of 7.0≲log(M*/M⊙)≲9.1 . This is striking as only 14% of short GRB hosts with previous inferred stellar masses had M * ≲ 109 M ⊙. We further show these short GRBs have smaller physical and host-normalized offsets than the rest of the population, suggesting that the majority of their neutron star (NS) merger progenitors were retained within their hosts. The presumably shallow potentials of these hosts translate to small escape velocities of ∼5.5–80 km s−1, indicative of either low postsupernova systemic velocities or short inspiral times. While short GRBs with identified dwarf host galaxies now comprise ≈14% of the total Swift-detected population, a number are likely missing in the current population, as larger systemic velocities (observed from the Galactic NS population) would result in highly offset short GRBs and less secure host associations. However, the revelation of a population of short GRBs retained in low-mass host galaxies offers a natural explanation for the observed r-process enrichment via NS mergers in Local Group dwarf galaxies, and has implications for gravitational-wave follow-up strategies.

Keck/KCWI spectroscopy of globular clusters in local volume dwarf galaxies

Abstract A number of nearby dwarf galaxies have globular cluster (GC) candidates that require spectroscopic confirmation. Here, we present Keck telescope spectra for 15 known GCs and GC candidates that may be associated with a host dwarf galaxy and an additional 3 GCs in the halo of M31 that are candidates for accretion from a now-disrupted dwarf galaxy. We confirm six star clusters (of intermediate-to-old age) to be associated with NGC 247. The vast bulk of its GC system remains to be studied spectroscopically. We also confirm the GC candidates in F8D1 and DDO190, finding both to be young star clusters. The three M31 halo GCs all have radial velocities consistent with M31 and are old and very metal-poor. Their ages and metallicities are consistent with accretion from a low-mass satellite galaxy. Finally, three objects are found to be background galaxies – two are projected near NGC 247 and one (candidate GCC7) is near the IKN dwarf. The IKN dwarf thus has only five confirmed GCs but still a remarkable specific frequency of 124.

Measurement of stellar and substellar winds using white dwarf hosts

ABSTRACT White dwarfs stars are known to be polluted by their active planetary systems, but little attention has been paid to the accretion of wind from low-mass companions. The capture of stellar or substellar wind by white dwarfs is one of few methods available to astronomers which can assess mass-loss rates from unevolved stars and brown dwarfs, and the only known method to extract their chemical compositions. In this work, four white dwarfs with closely orbiting, L-type brown dwarf companions are studied to place limits on the accretion of a substellar wind, with one case of a detection, and at an extremely non-solar abundance mNa/mCa &amp;gt; 900. The mass-loss rates and upper limits are tied to accretion in the white dwarfs, based on limiting cases for how the wind is captured, and compared with known cases of wind pollution from close M dwarf companions, which manifest in solar proportions between all elements detected. For wind captured in a Bondi–Hoyle flow, mass-loss limits $\dot{M}\lesssim 5\times 10^{-17}$ ${\rm M}_\odot \, {\rm yr}^{-1}$ are established for three L dwarfs, while for M dwarfs polluting their hosts, winds in the range 10−13−10−16 ${\rm M}_\odot \, {\rm yr}^{-1}$ are found. The latter compares well with the $\dot{M}\sim 10^{-13} {\!-\!} 10^{-15}$ ${\rm M}_\odot \, {\rm yr}^{-1}$ estimates obtained for nearby, isolated M dwarfs using Ly$\alpha$ to probe their astropsheres. These results demonstrate that white dwarfs are highly sensitive stellar and substellar wind detectors, where further work on the actual captured wind flow is needed.

HIP 33609 b: An Eccentric Brown Dwarf Transiting a V = 7.3 Rapidly Rotating B Star

We present the discovery and characterization of HIP 33609 b, a transiting warm brown dwarf orbiting a late B star, discovered by NASA's Transiting Exoplanet Survey Satellite as TOI-588 b. HIP 33609 b is a large (R b = R J) brown dwarf on a highly eccentric (e = ) orbit with a 39 days period. The host star is a bright (V = 7.3 mag), T eff = 10,400 K star with a mass of M * = M ⊙ and radius of R * = R ⊙, making it the hottest transiting brown dwarf host star discovered to date. We obtained radial velocity measurements from the CHIRON spectrograph confirming the companion's mass of M b = M J as well as the host star's rotation rate ( km s−1). We also present the discovery of a new comoving group of stars, designated as MELANGE-6, and determine that HIP 33609 is a member. We use a combination of rotation periods and isochrone models fit to the cluster members to estimate an age of 150 ± 25 Myr. With a measured mass, radius, and age, HIP 33609 b becomes a benchmark for substellar evolutionary models.

The orbital eccentricity distribution of planets orbiting M dwarfs

We investigate the underlying distribution of orbital eccentricities for planets around early-to-mid M dwarf host stars. We employ a sample of 163 planets around early- to mid-M dwarfs across 101 systems detected by NASA's Kepler Mission. We constrain the orbital eccentricity for each planet by leveraging the Kepler lightcurve together with a stellar density prior, constructed using metallicity from spectroscopy, Ks magnitude from 2MASS, and stellar parallax from Gaia. Within a Bayesian hierarchical framework, we extract the underlying eccentricity distribution, assuming alternately Rayleigh, half-Gaussian, and Beta functions for both single- and multi-transit systems. We described the eccentricity distribution for apparently single-transiting planetary systems with a Rayleigh distribution with [Formula: see text], and for multitransit systems with [Formula: see text]. The data suggest the possibility of distinct dynamically warmer and cooler subpopulations within the single-transit distribution: The single-transit data prefer a mixture model composed of two distinct Rayleigh distributions with [Formula: see text] and [Formula: see text] over a single Rayleigh distribution, with 7:1 odds. We contextualize our findings within a planet formation framework, by comparing them to analogous results in the literature for planets orbiting FGK stars. By combining our derived eccentricity distribution with other M dwarf demographic constraints, we estimate the underlying eccentricity distribution for the population of early- to mid-M dwarf planets in the local neighborhood.

Nuclear star clusters as probes of dark matter haloes: the case of the Sagittarius dwarf spheroidal galaxy

ABSTRACT The Sagittarius dwarf spheroidal (Sgr dSph) galaxy is currently being accreted and disrupted by the tidal field of the Milky Way. Recent observations have shown that the central region of the dwarf hosts at least three different stellar populations, ranging from old and metal-poor over intermediate metal-rich to young metal-rich. While the intermediate-age metal-rich population has been identified as part of the galaxy, the oldest and youngest populations belong to M54, the nuclear star cluster (NSC) of the Sgr dSph galaxy. The old metal-poor component of M54 has been interpreted as at least one decayed globular cluster (GC) that was initially orbiting its host galaxy. The youngest population formed in situ from gas accreted into M54 after its arrival at the centre of the host. In this work, we use the observed properties of M54 to explore the shape of the inner density profile of the Sgr dSph galaxy. To do so, we simulate the decay of M54 towards the centre of the dark matter (DM) halo of its host. We model the DM density profile using different central slopes, and we compare the results of the simulations to the most recent observations of the structural properties of M54. From this comparison, we conclude that a GC that decays in a DM halo with a density profile ∝ r−γ and γ ≤ 1 shows a rotational signal and flattening comparable to those observed for M54. Steeper profiles produce, instead, highly rotating and more flattened NSCs which do not match the properties of M54.

There’s More to Life than O2: Simulating the Detectability of a Range of Molecules for Ground-based, High-resolution Spectroscopy of Transiting Terrestrial Exoplanets

Within the next decade, atmospheric O2 on Earth-like M-dwarf planets may be accessible with visible–near-infrared (NIR), high-spectral-resolution, ground-based extremely large telescope (ELT) instruments. However, the prospects for using ELTs to detect environmental properties that provide context for O2 have not been thoroughly explored. Additional molecules may help indicate planetary habitability, rule out abiotically generated O2, or reveal alternative biosignatures. To understand the accessibility of environmental context using ELT spectra, we simulate high-resolution transit transmission spectra of previously generated evolved terrestrial atmospheres. We consider inhabited preindustrial and Archean Earth–like atmospheres, and lifeless worlds with abiotic O2 buildup from CO2 and H2O photolysis. All atmospheres are self-consistent with M2V–M8V dwarf host stars. Our simulations include explicit treatment of systematic and telluric effects to model high-resolution spectra for Giant Magellan Telescope (GMT), Thirty Meter Telescope (TMT), and European ELT (E-ELT) configurations for systems 5 and 12 pc from Earth. Using the cross-correlation technique, we determine the detectability of major species in these atmospheres: O2, O3, CH4, CO2, CO, H2O, and C2H6. Our results suggest that CH4 and CO2 are the most accessible molecules for terrestrial planets transiting a range of M-dwarf hosts using an E-ELT-, TMT-, or GMT-sized telescope, and that the O2 NIR and H2O 0.9 μm bands may also be accessible with more observation time. Although this technique still faces considerable challenges, the ELTs will provide access to the atmospheres of terrestrial planets transiting earlier-type M-dwarf hosts that may not be possible using JWST.

A Nonrepeating Fast Radio Burst in a Dwarf Host Galaxy

We present the discovery of an as yet nonrepeating fast radio burst (FRB), FRB 20210117A, with the Australian Square Kilometre Array Pathfinder (ASKAP), as a part of the Commensal Real-time ASKAP Fast Transients Survey. The subarcsecond localization of the burst led to the identification of its host galaxy at z = 0.214(1). This redshift is much lower than what would be expected for a source dispersion measure (DM) of 729 pc cm−3, given typical contributions from the intergalactic medium and the host galaxy. Optical observations reveal the host to be a dwarf galaxy with little ongoing star formation—very different to the dwarf host galaxies of the known repeating FRBs 20121102A and 20190520B. We find an excess DM contribution from the host and attribute it to the FRB’s local environment. We do not find any radio emission from the FRB site or host galaxy. The low magnetized environment and the lack of a persistent radio source indicate that the FRB source is older than those found in other dwarf host galaxies, establishing the diversity of FRB sources in dwarf galaxy environments. We find our observations to be fully consistent with the “hypernebula” model, where the FRB is powered by an accretion jet from a hyperaccreting black hole. Finally, our high time resolution analysis reveals burst characteristics similar to those seen in repeating FRBs. We encourage follow-up observations of FRB 20210117A to establish any repeating nature.

The CARMENES search for exoplanets around M dwarfs

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⊕ &lt; Mpl sin i &lt; 1000 M⊕ and 1 day &lt; Porb &lt; 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.