Main Sequence Research Articles

Spectroscopic survey of faint planetary-nebula nuclei

We present spectroscopy of three hydrogen-deficient central stars of faint planetary nebulae, with effective temperatures (Teff) in excess of 100 000 K. The nucleus of RaMul 2 is a Population II Wolf-Rayet star of spectral type [WC], and the central stars of Abell 25 and StDr 138 are two new members of the PG1159 class. Our spectral analyses reveal that their atmospheres have a similar chemical composition. They are dominated by helium and carbon, which was probably caused by a late helium-shell flash. Coincidentally, the three stars have similar masses of about M = 0.53 M⊙ and hence form a post-asymptotic giant branch (AGB) evolutionary sequence of an initially early-K-type main sequence star with M = 0.8 M⊙. The central stars cover the period during which the luminosity fades from about 3000 to 250 L⊙ and the radius shrinks from about 0.15 to 0.03 R⊙. The concurrent increase of the surface gravity during this interval from log g = 5.8 to 7.2 causes the shutdown of the stellar wind from an initial mass-loss rate of log Ṁ/(M⊙ yr−1) = −6.4, as measured for the [WC] star. Along the contraction phase, we observe an increase in Teff from 112 000 K, marked by the [WC] star, to the maximum value of 140 000 K, and a subsequent cooling to 130 000 K, marked by the two PG1159 stars.

Searching for OB-type pre-supernova binary companions inside supernova remnants

Abstract We searched for OB-runaway stars inside supernova remnants (SNRs) as a pre-supernova binary companion. As the majority of massive stars are found in close binary systems, a runaway star ejected by the orbital energy after the supernova (SN) is expected to be found. Considering a binary mass fraction, q=0.25 − 1.0, the runaway star is likely to have an OB spectral type. We selected 12 SNRs at Galactic longitudes 109○ − 189○. Using Gaia astrometry we selected stars having consistent distances with those of the SNRs and showing a peculiar proper motion directed away from the central region of the SNRs. We also determined the radial distribution of the extinction towards the SNRs and estimated the spectral types of the OB-runaway candidates through Gaia and 2MASS photometry. We found two candidates among 12 SNRs. By spectroscopic observations, Gaia DR3 195632152560621440 inside SNR G166.0+4.3 was found to be an evolved A3 type star which cannot be the pre-SN binary companion to the progenitor. Gaia DR3 513927750767375872 inside SNR HB 3 is the only OB-runaway candidate (2-D space velocity of 33.3±3.3 km s−1). Based on photometric study, the star can be an early B-type main sequence star with a slightly higher extinction relative to the SNR, however, it might instead be an evolved A-type star at the same distance. The other 11 SNRs do not host an OB-runaway star within their central regions. Although the runaway search was performed in a large interval of distance and extinction, we also estimated distances to the SNRs.

Searching for gamma-ray emission from stellar flares

Abstract Flares from magnetically active dwarf stars should produce relativistic particles capable of creating γ-rays. So far, the only isolated main sequence star besides the Sun to have been detected in γ-rays is TVLM 513-46546. Detecting γ-ray flares from more dwarf stars can improve our understanding of their magnetospheric properties, and could also indicate a diminished likelihood of their planets’ habitability. In this work, we stack data from the Fermi Gamma-ray Space Telescope during a large number of events identified from optical and X-ray flare surveys. We report an upper limit of γ-ray emission from the population of flare stars. Stacking results towards control positions are consistent with a non-detection. We compare these results to observed Solar γ-ray flares and against a model of emission from neutral pion decay. The upper limit is consistent with Solar flares when scaled to the flare energies and distances of the target stars. As with Solar flares, the neutral pion decay mechanism for γ-ray production is also consistent with these results.

Gas, not dust: Migration of TESS/Gaia hot Jupiters possibly halted by the magnetospheres of protoplanetary disks

Context. The presence of short-period (< 10 days) planets around main sequence (MS) stars has been associated either with the dust-destruction region or with the magnetospheric gas-truncation radius in the protoplanetary disks that surround them during the pre-MS phase. However, previous analyses have only considered low-mass FGK stars, making it difficult to disentangle the two scenarios. Aims. This exploratory study is aimed at testing whether it is the inner dust or gas disk driving the location of short-period, giant planets. Methods. By combining TESS and Gaia DR3 data, we identified a sample of 47 intermediate-mass (1.5−3 M⊙) MS stars hosting confirmed and firm candidate hot Jupiters. We compared their orbits with the rough position of the inner dust and gas disks, which are well separated around their Herbig stars precursors. We also made a comparison with the orbits of confirmed hot Jupiters around a similarly extracted TESS/Gaia sample of low-mass sources (0.5−1.5 M⊙). Results. The orbits of hot Jupiters around intermediate-mass stars tend to be closer to the central sources than the inner dust disk, most generally consistent with the small magnetospheric truncation radii typical of Herbig stars (≲5 R*). A similar study considering the low-mass stars alone has been less conclusive due to the similar spatial scales of their inner dust and gas disks (≳5 R*). However, considering the whole sample, we do not find the correlation between orbit sizes and stellar luminosities that is otherwise expected if the dust-destruction radius limits the hot Jupiters’ orbits. On the contrary, the comparative analysis reveals that such orbits tend to be closer to the stellar surface for intermediate-mass stars than for low-mass stars, with both being mostly consistent with the rough sizes of the corresponding magnetospheres. Conclusion. Our results suggest that the inner gas (ad not the dust) disk limits the innermost orbits of hot Jupiters around intermediate-mass stars. These findings also provide tentative support to previous works that have claimed this is indeed the case for low-mass sources. We propose that hot Jupiters could be explained via a combination of the core-accretion paradigm and migration up to the gas-truncation radius, which may be responsible for halting inward migration regardless of the stellar mass regime. Larger samples of intermediate-mass stars with hot Jupiters are necessary to confirm our hypothesis, which implies that massive Herbig stars without magnetospheres (> 3−4 M⊙) may be the most efficient in swallowing their newborn planets.

#2465 How do renal clinicians present treatment options to older patients with advanced kidney disease and what difference does it make?

Abstract Background and Aims For older people with kidney failure, especially those with comorbidities or poor performance status, the survival benefits of dialysis are uncertain and its quality of life impact greatest. Conservative kidney management (CKM) can be a beneficial alternative. However, there is significant variation in treatment rates among older patients with kidney failure; the CKMAPPS study [1] found rates of older people receiving dialysis ranged from 5-95% across UK renal units. How clinicians communicate about treatment options influences patients’ decision-making, but this has been under-researched. The OSCAR study (Optimising Staff-Patient Communication in Advanced Renal disease) aimed to describe how kidney failure treatment options are presented by renal clinicians to older people (age 65+) with advanced chronic kidney disease (eGFR ≤20 mls/min/1.73 m2 within the last 6 months) and the implications of this for patient engagement with the decision. Method Outpatient consultations between doctors/nurses and eligible patients were recorded at 4 UK renal units with varying rates of CKM. Recorded consultations were screened to identify cases where clinicians presented treatment options for advanced kidney disease. Consultations where clinicians presented both dialysis and CKM were transcribed and analysed in detail using Conversation Analysis, focused on how dialysis and CKM were framed. Post-consultation, patients completed the Shared Decision-Making Questionnaire (SDM-Q-9). Comparisons were made between groups according to how treatment options were presented, using a non-parametric Median Test. Results A total of 110 outpatient consultations were recorded (104 audiovisual, 6 audio). Recordings included 38 doctors and nurses and 94 patients; mean patient age 77 (65-97), 33 female/61 male, mean eGFR 15 (range 4-23). Sequences where clinicians presented both dialysis and CKM as treatment options were analysed (n = 21). Two approaches to presenting CKM were identified: 1) CKM as a main option (n = 6; see Fig. 1), 2) CKM as a subordinate option (n = 15; see Fig. 2). The mean consultation length was the same in both groups (23 mins). Recurrent features of the first approach included: framing CKM as having potential personal benefits to the patient; explicitly labelling it as a treatment option; not framing it as an option preferred by or relevant to only a minority of patients. In contrast, when CKM was presented as a subordinate option, recurrent features included: framing CKM as not having benefit to the patient; not explicitly labelling CKM as a treatment option; appending CKM to the main decision-making sequence; framing CKM as an option only chosen by a minority of patients. Presenting CKM as a main option alongside dialysis was a less common approach (n = 6 vs. n = 15), but associated with more interactional opportunities for patients to ask questions about CKM, assert their perspective, and assess CKM as a relevant option, as well as significantly higher patient ratings of shared decision-making (total SDM-Q-9 score, p = 0.041). Conclusion This is the first fine-grained analysis of the relationship between the conversational practices used by clinicians and their impact on patient engagement with treatment options and ratings of shared decision-making. Despite evidence that dialysis does not reliably extend older patients’ lives at acceptable costs to quality of life, we found that clinicians tend to present dialysis as the default treatment and CKM as subordinate, if at all. Our findings demonstrate that presenting treatment options is not enough; how clinicians present options has important implications for patient engagement in shared decision-making. To provide patients with the opportunity to evaluate CKM as a valid option requires clinicians to clearly detail the advantages and disadvantages of both treatments. Study findings will form the basis of a new communication training intervention for clinicians.

#1165 Targeted-release budesonide can preserve the glomerular filtration rate in patients diagnosed with IgA nephropathy after 3 months of administration.

Abstract Background and Aims The four-hit hypothesis constitutes the main immunological sequence of the IgA nephropathy (IgAN) pathogenesis. However, the activation of intestinal-renal axis is considered the initial step during IgA nephropathy (IgAN) pathogenesis. Aim of this prospective pilot study is to evaluate parameters which influence early response to targeted release budesonide. Method Adult IgAN patients, diagnosed the last 10 years, maintaining eGFR >30 ml/min/1.73m2 and Uprotein >750 mg/24 hr, despite standard supportive treatment, commenced on budesonide 16 mg/d, and followed for 3 months. Renal biopsies were re-evaluated and scored according to Oxford classification, parameters of renal function recorded at time of diagnosis (T-d),at the beginning of treatment (T0), and 3 months later (T3). Results Fifteen IgAN patients, M/F:12/3, Mean age: 52 (34-74) years from two different departments fulfilled the criteria and they have already started on budesonide treatment, 51.6 ± 45 months following diagnosis. eGFR had declined from T-d to T0, 57.43 ± 10.58 to 49.23 ± 13.63 ml/min/1.73 m2, p = 0.03, and Uprot was stable 3.33 ± 1.16 to Uprot = 2.98 ± 1.19 gr/24 hrs, p = NS. During the 3 first months of budesonide (T3), eGFR showed slight improvement, eGFR = 54.38 ± 13.67 while Uprot remained stable 3.17 ± 1,04 gr/24 hrs. Improvement in renal function was not associated with any of histologic findings, but was remarkably more evident within patients with <4 years of diagnosis, eGFR from 62 ± 5.2 to 73 ± 2.4, compared to change in the eGFR from 23 ± 5.6 ml/min/1.73 m2 to 25 ± 3.6 ml/min/1.73 m2. Conclusion Our preliminary findings suggest that, independent of renal histology, budesonide treatment showed a trend in improving renal function, mainly in patients with relatively short time from diagnosis. So, budesonide can

Precise Mass, Orbital Motion, and Stellar Properties of the M-dwarf Binary LP 349−25AB

LP 349−25 is a well-studied close stellar binary system comprised of two late M dwarf stars, where both stars are close to the limit between star and brown dwarf. This system was previously identified as a source of gigahertz radio emission. We observed LP 349−25AB over 11 epochs in 2020–2022, detecting both components in this nearby binary system using the Very Long Baseline Array (VLBA). We fit simultaneously the VLBA absolute astrometric positions together with existing relative astrometric observations derived from optical/infrared observations with a set of algorithms that use nonlinear least-squares, genetic algorithm, and Markov Chain Monte Carlo methods to determine the orbital parameters of the two components. We find the masses of the primary and secondary components to be 0.08188 ± 0.00061 M ⊙ and 0.06411 ± 0.00049 M ⊙, respectively, representing one of the most precise mass estimates of any ultracool dwarf (UCD) to date. The primary is a UCD of 85.71 ± 0.64 M Jup, while the secondary has a mass consistent with being a brown dwarf of 67.11 ± 0.51 M Jup. This is one of the very few direct detections of a brown dwarf with VLBA observations. We also find a distance to the binary system of 14.122 ± 0.057 pc. Using stellar evolutionary models, we find the model-derived stellar parameters of both stars. In particular, we obtain a model-derived age of 262 Myr for the system, which indicates that LP 349−25AB is composed of two pre–main-sequence stars. In addition, we find that the secondary star is significantly less evolved than the primary star.

The Population of Massive Stars in Active Galactic Nuclei Disks

Gravitational instability in the outskirts of active galactic nuclei (AGN) disks leads to disk fragmentation and formation of ∼300 M ⊙ supermassive stars with potentially long lifetimes. Alternatively, stars can be captured ex situ and grow from gas accretion in the AGN disk. However, the number density distribution throughout the disk is limited by thermal feedback as their luminosities provide the dominant heating source. We derive equilibrium stellar surface density profiles under two limiting contexts: in the case where the stellar lifetimes are prolonged, due to the recycling of hydrogen-rich disk gas, only the fraction of gas converted into heat is removed from the disk accretion flow. Alternatively, if stellar composition recycling is inefficient and stars can evolve off the main sequence, the disk accretion rate is quenched toward smaller radii resembling a classical starburst disk, albeit the effective removal rate depends not only on the stellar lifetime, but also the mass of stellar remnants. For AGNs with central supermassive black hole masses of ∼106–108 M ⊙ accreting at ∼0.1 Eddington efficiency, we estimate a total number of 103–105 massive stars and the rate of stellar mergers to be 10−3 to 1 yr−1. We initiate the detailed study of the interaction between a swarm of massive stars through hydro and N-body simulations to provide better prescriptions of dynamical processes in AGN disks, and to constrain more accurate estimates of the stellar population.

How Reliable are Rotation Period Determinations from TESS Data?

Gyrochronology is the empirical relation between rotation and age. NASA's Transiting Exoplanet Survey Satellite (TESS), Kepler, and K2 missions have observed thousands of wide main sequence binaries. Since components of a binary are coeval, their rotation periods should be consistent with gyrochronology models. However, the usefulness of gyrochronology depends upon reliable rotation periods. We explore the reliability of rotation period determinations for a sample of wide binary components from the TESS cycle 3. Wide binaries with the most reliable rotation period determinations provide a strong basis for testing whether the gyrochronology empirical relation derived from open clusters is also valid for field stars.

Evolutionary nature of puffed-up stripped star binaries and their occurrence in stellar populations

The majority of massive stars are formed in multiple systems, and at some point during their life, they interact with their companions via mass transfer. This interaction typically leads to the primary shedding its outer envelope, resulting in the formation of a "stripped star". Classically, stripped stars are expected to quickly contract to become hot and UV-bright helium stars. Surprisingly, recent optical spectroscopic surveys have unveiled many stripped stars that are much larger and cooler, appearing "puffed up" and overlapping with the Main Sequence (MS) in the Hertzsprung-Russell diagram. Here, we study the evolutionary nature of puffed-up stripped (PS) stars and the duration of this enigmatic phase using the stellar-evolution code MESA. We computed grids of binary models at four metallicities: Solar (Z$_ odot $ = 0.017), Large Magellanic Cloud (LMC, Z=0.0068), Small Magellanic Cloud (SMC, Z = 0.0034), and Z = 0.1Z$_ Contrary to previous assumptions, we find that stripped stars regain thermal equilibrium shortly after the end of mass transfer and maintain it during most of the PS phase. Their further contraction towards hot and compact He stars is determined by the rate at which the residual H-rich envelope is depleted, with the main agents being H-shell burning (dominant for M lesssim 50 and mass-loss in winds. The duration of the PS star phase is approximately 10<!PCT!> of the core-He burning lifetime (1<!PCT!> total lifetime) and up to 100 times more than the thermal timescale. It decreases with increasing mass and luminosity and increases with metallicity. We explored several factors influencing PS star lifetimes: orbital period, mass ratio, winds, and semiconvection. We further carried out a simple binary population synthesis estimation, finding that sim 0.5 – 0.7<!PCT!> of all the stars with log (L/L$_ > 3.7 may, in fact, be PS stars. Our results indicate that tens to hundreds of PS stars in post-interaction binaries may be hiding in the MS population, disguised as 'normal' stars: sim 100 (sim 280) in the SMC (LMC) and sim 1500 in the Milky Way . Their true nature may be revealed by spectroscopically measured low surface gravities, high N enrichment, and likely slow rotation rates.

The impact of radiative levitation on mode excitation of main-sequence B-type pulsators

Numerical computations of stellar oscillations for models representative of B-type stars predict fewer modes to be excited than observations reveal from modern space-based photometric data. One shortcoming of state-of-the-art evolution models of B-type stars that may cause a lack of excited modes is the absence of microscopic diffusion in most such models. We investigate whether the inclusion of microscopic diffusion in stellar models of B-type stars, notably radiative levitation experienced by isotopes, leads to extra mode driving by the opacity mechanism compared to the case of models that do not include microscopic diffusion. We consider the case of slowly to moderately rotating stars and use non-rotating equilibrium models, while we account for (uniform) rotation in the computations of the pulsation frequencies. We calculate 1D stellar structure and evolution models with and without microscopic diffusion and examine the effect of radiative levitation on mode excitation, for both low-radial order pressure and gravity modes and for high-radial order gravity modes. As is common practice in asteroseismology, rotation is included in the pulsation computations according to the mode's frequency regime. For modes having frequencies below twice the rotation frequency, that is, modes in the sub-inertial regime, we adopt the traditional approximation of rotation. For modes in the super-inertial regime with frequency above twice the rotation frequency, rotation is treated perturbatively up to first order in the rotation. We consider macroscopic envelope mixing induced by internal gravity waves to compute the modes and study its effect on the surface abundances. We find systematically more modes to be excited for the stellar models including microscopic diffusion compared to those without it, in agreement with observational findings of pulsating B-type dwarfs. Furthermore, the models with microscopic diffusion predict that excited modes occur earlier on in the evolution compared to modes without it. In order to maintain realistic surface abundances during the main sequence, we include macroscopic envelope mixing by internal gravity waves. Along with microscopic diffusion, such macroscopic envelope mixing ensures both more excited modes and surface abundances consistent with spectroscopic studies of B-type stars. While radiative levitation has so far largely been neglected in stellar evolution computations of B-type stars for computational convenience, it impacts mode excitation predictions for stellar models of such stars. We conclude that the process of radiative levitation is able to reduce the discrepancy between predicted and observed excited pulsation modes in B-type stars.

Rapidly rotating Population III stellar models as a source of primary nitrogen

The first stars might have been fast rotators. This would have important consequences for their radiative, mechanical, and chemical feedback. We discuss the impact of fast initial rotation on the evolution of massive Population III models and on their nitrogen and oxygen stellar yields. We explore the evolution of Population III stars with initial masses in the range of 9 msol ini msol starting with an initial rotation on the zero-age main sequence equal to 70<!PCT!> of the critical one. We find that with the physics of rotation considered here, our rapidly rotating Population III stellar models do not follow a homogeneous evolution. They lose very little mass in the case in which mechanical winds are switched on when the surface rotation becomes equal to or larger than the critical velocity. The impact on the ionising flux appears to be modest when compared to moderately rotating models. Fast rotation favours, in models with initial masses above sim 20 msol the appearance of a very extended intermediate convective zone around the H-burning shell during the core He-burning phase. This shell has important consequences for the sizes of the He- and CO-cores, and thus impacts the final fate of stars. Moreover, it has a strong impact on nucleosynthesis, boosting the production of primary 14N. Fast initial rotation significantly impacts the chemical feedback of Population III stars. Observations of extremely metal-poor stars and/or starbursting regions are essential to provide constraints on the properties of the first stars.

A dusty rain falls on the nova V959 Monocerotis

Abstract We present archival and ground-based infrared observations of the γ-ray-emitting nova V959 Mon, covering the period 100–4205 days after the 2012 eruption. We use these data to determine that the secondary in the nova system is a G5 main sequence star. Data from the NEOWISE survey reveal a significant increase in the emission at 3.4$\, \mu$m and 4.6$\, \mu$m at late (≳ 600 days) times, which we interpret as emission by dust. Other interpretations are considered but cannot be reconciled with the data. The presence of such late dust emission, and in particular its variation with time, are unprecedented in the context of novae. The behaviour of the dust emission suggests a qualitative interpretation in which ejecta from the 2012 eruption encounter denser pre-eruption circumbinary material, giving rise to Rayleigh-Taylor instabilities that cause clumps of dust-bearing material to fall back towards the central binary, the dust undergoing destruction by chemisputtering as it does so. The observed rise in the dust temperature, the decline in the nova-dust distance and in the dust mass, are consistent with this interpretation. Not all novae are expected to show this behaviour, but inspection of resources such as NEOWISE might reveal other novae post-eruption that do.

Molecular gas scaling relations for local star-forming galaxies in the low-M_* regime

We derived molecular gas fractions ($f_ mol =M_ mol /M_*$) and depletion times ($ mol = M_ mol SFR $) for 353 galaxies representative of the local star-forming population with $10^ \,M_ < M_* < \,M_ drawn from the ALLSMOG and xCOLDGASS surveys of CO(2-1) and CO(1-0) line emission. By adding constraints from low-mass galaxies and upper limits for CO non-detections, we find the median molecular gas fraction of the local star-forming population to be constant at $ f_ mol $, challenging previous reports of increased molecular gas fractions in low-mass galaxies. Above $M_* \,M_ we find the $f_ mol $ versus $M_*$ relation to be sensitive to the selection criteria for star-forming galaxies. We tested the robustness of our results against different prescriptions for the CO-to-H$_2$ conversion factor and different selection criteria for star-forming galaxies. The depletion timescale $ mol $ weakly depends on $M_*$, following a power law with a best-fit slope of . This suggests that small variations in specific star formation rate ($ sSFR=SFR /M_*$) across the local main sequence of star-forming galaxies with $M_* < 10^ \,M_ are mainly driven by differences in the efficiency of converting the available molecular gas into stars. We tested these results against a possible dependence of $f_ mol $ and $ mol $ on the surrounding (group) environment of the targets by splitting them into centrals, satellites, and isolated galaxies, and find no significant variation between these populations. We conclude that the group environment is unlikely to have a large systematic effect on the molecular gas content of star-forming galaxies in the local Universe.

Impact of main sequence mass loss on the appearance, structure, and evolution of Wolf-Rayet stars

Stellar winds are one of the most important drivers of massive star evolution and are a vital source of chemical, mechanical, and radiative feedback on the galactic scale. Despite its significance, mass loss remains a major uncertainty in stellar evolution models. In particular, the interdependencies between the different approaches and the subsequent evolutionary stages and predicted observable phenomena are far from being systematically understood. In this study, we examine the impact of main sequence mass loss on the structure of massive stars throughout their entire evolution. Particular focus is placed on the consequences in terms of entrance into the Wolf-Rayet regime and the subsequent evolution. Using the Geneva stellar evolution code (GENEC), we computed grids of single, nonrotating stellar models at solar and Large Magellanic Cloud (LMC) metallicities of initial masses between 20 and 120 solar masses, with two representative prescriptions for high and low main sequence mass loss. We obtain detailed numerical predictions regarding the structure and evolution of massive stars, and infer the role of main sequence mass loss by comparison of the mass-loss rate prescriptions. We present implications for the overall evolutionary trajectory, including the evolution of WR stars, as well as the effect on stellar yields and stellar populations. Mass loss during the main sequence plays an important role because of its ability to affect the sequence and duration of all subsequent phases. We identify several distinct evolutionary paths for massive stars, which are significantly influenced by the chosen main sequence mass-loss description. We also discuss the impact of uncertainties ---other than that regarding mass loss--- on the evolution, in particular those relating to convection. We further demonstrate that not only the total mass loss but also the specific mass-loss history throughout a star's life is a crucial determinant of many aspects, such as the resulting stellar yields.

FRBs from rapid spindown neutron stars

Abstract A fast radio burst (FRB) localized to a globular cluster (GC) challenges FRB models involving ordinary young magnetars. In this paper, we examine the rapid spindown millisecond neutron star (NS) scenario, which favours the dynamic environment in GCs. Fast spindown corresponds to a larger magnetic field than regular millisecond pulsars, which empirically favours giant pulse (GP) emission. The kinetic energy in millisecond NSs can readily exceed the magnetic energy in magnetars. The high inferred isotropic luminosity of most FRBs is challenging to explain in spin-down powered pulsars. A recent observation of a GP from the Crab pulsar, on the other hand, suggests highly Doppler-beamed emission, making the required energy orders of magnitude smaller than estimated with isotropic assumptions. Considering this strong beaming effect, GPs from a recycled pulsar with a modest magnetic field could explain the energetics and burst rates for a wide range of FRBs. The short life span accounts for a paucity of bright FRBs in the Milky Way neighbourhood. We point out that tidal disruption spin-up from a main sequence star can provide sufficient accretion rate to recycle a NS with mild magnetic field. It can also explain the observed source density and the spatial offset in the GC for FRB 20200120E. Frequency variation in the scattering tail for some of the brightest FRBs is expected in this scenario.

The Gaia-ESO Survey: No sign of multiple stellar populations in open clusters from their sodium and oxygen abundances

The light element (anti-)correlations shown by globular clusters (GCs) are the main spectroscopic signature of multiple stellar populations. These internal abundance variations provide us with fundamental constraints on the formation mechanism of stellar clusters. Using $Gaia$-ESO, the largest and most homogeneous survey of open clusters (OCs), we intend to check whether these stellar aggregates display the same patterns. Based on previous studies of many GCs, several young and massive clusters in the Magellanic Clouds, as well as a few OCs, we do not expect to find any anti-correlation, given the low mass of Milky Way OCs. We used the results based on UVES spectra of stars in $Gaia$-ESO to derive the distribution of Na and O abundances and see whether they show an unexplained dispersion or whether they are anti-correlated. By selecting only high-probability members with high-precision stellar parameters, we ended up with more than 700 stars in 74 OCs. We examined the O-Na distribution in 28 OCs with at least 4 stars available as well as the Na distribution in 24 OCs, with at least 10 stars available. We find that the distribution of Na abundances is compatible with a single-value population, within the errors. The few apparent exceptions can be explained by differences in the evolutionary phase (main sequence and giant post first dredge-up episode) or by difficulties in analysing low gravity giants. We did not find any indication of an Na-O anti-correlation in any of the clusters for which O has been derived. Based on the very small spread we find, OCs maintain the status of single stellar populations. However, a definitive answer requires studying more elements and larger samples covering different evolutionary phases. This will be possible with the next generation of large surveys.

89 New Ultracool Dwarf Comoving Companions Identified with the Backyard Worlds: Planet 9 Citizen Science Project

We report the identification of 89 new systems containing ultracool dwarf companions to main-sequence stars and white dwarfs, using the citizen science project Backyard Worlds: Planet 9 and cross-reference between Gaia and CatWISE2020. 32 of these companions and 33 host stars were followed up with spectroscopic observations, with companion spectral types ranging from M7–T9 and host spectral types ranging from G2–M9. These systems exhibit diverse characteristics, from young to old ages, blue to very red spectral morphologies, potential membership to known young moving groups, and evidence of spectral binarity in nine companions. 20 of the host stars in our sample show evidence for higher-order multiplicity, with an additional 11 host stars being resolved binaries themselves. We compare this sample’s characteristics with those of the known stellar binary and exoplanet populations, and find our sample begins to fill in the gap between directly imaged exoplanets and stellar binaries on mass ratio–binding energy plots. With this study, we increase the population of ultracool dwarf companions to FGK stars by ∼42%, and more than triple the known population of ultracool dwarf companions with separations larger than 1000 au, providing excellent targets for future atmospheric retrievals.

Blink Lagophthalmos in Graves Orbitopathy.

To investigate the relationship between the kinematics of spontaneous blinks and the anterior area of the levator palpebrae superioris muscle in patients with Graves orbitopathy (GO). This is a case-control study. The authors measured the margin reflex distance of the upper eyelid (margin reflex distance 1), the kinematics of spontaneous blinks, and the anterior area of levator palpebrae superioris muscle in CT coronal scans of patients with Graves upper eyelid retraction (GO) and a control group. The eye with the greatest margin reflex distance 1 was selected for analysis in each group. A total of 68 participants were included, with 36 in the GO group and 32 in the control group. In the GO group, the mean margin reflex distance 1 measured 6.5 mm, while in the control group, it was 3.9 mm. Almost all parameters related to the closing phase of spontaneous blinking activity, including amplitude, velocity, blinking rate, and interblink time, did not differ between the two groups. However, the effectiveness of the blink's amplitude (ratio of blink amplitude to margin reflex distance 1) and the main sequence (relationship between amplitude and velocity) were significantly reduced in the GO group compared with the control group. The area of the levator palpebrae superioris muscle was significantly larger in GO than in controls, with 71.4% of patients' muscles outside of the maximum range of the controls. In patients with GO, there is a reduction in blinking effectiveness, also known as blink lagophthalmos, which is a factor in the common occurrence of ocular surface symptoms. The increase in velocity with amplitude is also reduced in GO.

Probing the inner Galactic halo with blue horizontal-branch stars

Context. Stars that are found on the blue horizontal-branch (BHB) evolved from low-mass stars that have completed their core hydrogen-burning main sequence (MS) stage and undergone the helium flash at the end of their red giant phase. Hence, they are very old objects that can be used as markers in studying galactic structure and formation history. The fact that their luminosity is virtually constant at all effective temperatures also makes them good standard candles. Aims. We have compiled a catalogue of BHB stars with stellar parameters calculated from spectral energy distributions (SEDs) constructed using data from multiple large-scale photometric surveys. In addition, we update our previous Gaia Early Data Release 3 (EDR3) catalogue of BHB stars with parallax errors less than 20% by using the SED results to define the selection criteria. The purpose of these catalogues is to create a set of BHB star candidates with reliable stellar parameters. In addition, they provide a more complete full-sky catalogue with candidate objects found along the whole BHB from where RR-Lyrae are found on the instability strip to the extreme horizontal-branch (EHB). Methods. We selected a large dataset of Gaia Data Release 3 (DR3) objects based only on their position on the colour-magnitude diagram (CMD), along with the tangential velocity and parallax errors. The SEDs were then used to evaluate contamination levels in the dataset and derive optimised data quality acceptance constraints. This allowed us to extend the Gaia DR3 colour and absolute magnitude criteria further towards the EHB. The level of contamination found using SED analysis was confirmed by acquiring spectra using the Ondrejov Echelle spectrograph, attached to the Perek 2m telescope at the Astronomical Institute of the Czech Academy of Sciences. Results. We present a catalogue of 9172 Galactic halo BHB candidate stars with atmospheric and stellar parameters calculated from synthetic SEDs. We also present an extended Gaia DR3-based catalogue of 22 335 BHB candidate stars with a wider range of effective temperatures and Gaia DR3 parallax errors of less than 20%. This represents an increase of 33% compared to the our 2021 catalogue, with a contamination level of 10%.