The nature of a primary jet within a circumbinary disc outflow in a young stellar system

Most stars form in binaries, and both stars may grow by accreting material from a circumbinary disc onto their own discs. We suspect that in many cases a wide molecular wind will envelope a collimated atomic jet emanating from close to an orbiting young star. This so-called Circumbinary Scenario is explored here in order to find common identifiable properties. The dynamical set up is studied with three dimensional simulations with chemistry and cooling included. We extract the properties on scales of order 100 AU and compare to the Co-Orbital Scenario in which the wind and jet sources are in orbit. We find that the rapid orbital motion generates a wide ionised sheath around the jet core with a large opening angle at the base. This is independent of the presence of the surrounding molecular outflow. However, the atomic jet is recollimated beyond ∼ 55 AU when the molecular outflow restricts the motion of the ambient medium which, in turn, confines the jet. These physical properties are related to the optical Hα imaging, providing a means of distinguishing between models. The high excitation sheath and recollimation region can be explored on these scales through the next generation of instruments. However, in general, the amount and location of the ionised material, whether in the knots or the sheath, will depend on several parameters including the orbital period, axis alignment and pulse amplitude

The Numerical Modelling Of Scenarios For The Herbig-Haro Object HH30

The classical T-Tauri star HH30 in Taurus-Auriga exhibits a well-collimated plume of hot, optically-emitting atomic and partially ionised Hydrogen, and also a colder, dense, wide-angle molecular Hydrogen ouflow. Observations suggest HH30 is a binary system system, surrounded by a circumbinary accretion disc. We investigated the propagation and interaction of dual atomic and molecular outflows from HH30, using a series of numerical simulations with parameters informed by observational campaigns. These 3-dimensional models were computed using the established Eulerian astrophysics code ZEUS-MP, with in-house modifications and an enhanced chemistry and cooling module. These simulations assumed off-domain launch and tracked the evolution of the jets over spatial scale of ~ 100 AU, and with a timescale ~ 100 - 200 years. The propagation in this region is of special interest, as this is where the greatest difference between the two scenarios is likely to emerge. Our work here differs from "classical" simulations of jet propagation by virtue of one or both outflow sources moving in an orbit. Two competing scenarios were investigated, in which the morphology of the light-year scale outflow from HH30 is explained by different kinds of motion of the atomic outflow source, and in which the launch site of the molecular outflow differs. In both cases a velocity-pulsed atomic jet emerges from the more massive binary object. In the Orbital scenario, the orbital motion of the primary explains the morphology seen at large scale, while the molecular flow is launched from the secondary partner; in the Precessional scenario, precession of the primary dominates the morphology, while launch of the molecular flow is from the inner edge of the circumbinary disc. The binary orbit and inner depletion zone of the circumbinary disc differs between the scenarios, with the Precessional scenario having a much smaller orbit and correspondingly reduced inner depletion zone. Clearly identifiable structural differences emerge between the simulated models. We compared the effects of the two different kinds of perturbing molecular outflow on the faster atomic jet; position, velocity, line mass per unit length, temperature and other variables, as a function of distance x (AU) from the binary source. Linear and quadratic fit functions were determined to facilitate comparison with observation. These quantify the expected behaviours of the atomic jet in the presence of the two different kinds of molecular flow. Where the fit function domains overlap direct comparisons may be drawn; where 26 < x < 42 AU, the average velocity as a function of distance is Vx(x) = (1.39×10^?1 ±2.15×10^?3)x + (246.82±1.29) km s^?1 in the Precessional model, while in the Orbital model we find Vx(x) = (?3.26 ± 0.26)x + (269.57 ± 6.75) km s^?1. In the region 10 < x < 60 AU, the Precessional model has temperature dependence T(x) = (64.53 ± 12.54)x + (3535 ± 330) K. Whilst in the same region of the Orbital model, T(x) = (401.99 ± 333.19)x + (4258.4 ± 1340.3) K. Synthetic Mass-Velocity Spectra have been generated for our models, to investigate distinguishing features of these spectra in the presence of the two different types of molecular outflow. The shallow-angle spectra matching the aspect angle of HH30 itself are examined and the link between outflow scenario and time variability discussed. Spectra from the same dual outflow systems observed at different aspect angles to the sky plane are given, to provide a means to confirm these senarios in other HH30-like T-Tauri stars. Using code written in-house to calculate emission using rate coefficients for photon production, we generated synthetic observations; spatially resolved images, velocity channel maps and position-velocity diagrams. The morphology of the synthetic images from the two scenarios when compared to HST R-band imaging of HH30 suggests that the Orbital case is unlikely, whilst the Precessional case is supported

Binary outflows from young stars: interaction of co-orbital jet and wind

Jets from young stellar objects provide insight into the workings of the beating heart at the centre of star-forming cores. In some cases, multiple pulsed outflows are detected such as the atomic and molecular jets from a proposed binary system in the T Tauri star HH 30. We investigate here the development and propagation of duelling atomic and molecular outflows stemming from the two stars in co-orbit. We perform a series of numerical experiments with the ZEUS-MP code with enhanced cooling and chemistry modules. The aim of this work is to identify signatures on scales of the order of 100 au. The jet sources are off the grid domain and so it is the propagation and interaction from ∼20 au out to 100 au simulated here. We find that the molecular flow from the orbiting source significantly disturbs the atomic jet, deflecting and twisting the jet and disrupting the jet knots. Regions of high ionization are generated as the atomic jet rams through the dense molecular outflow. Synthetic images in atomic and molecular lines are presented, which demonstrate identifying signatures. In particular, the structure within the atomic jet is lost and H α may trace the walls of the present CO cavity or where the walls have been recently. These results provide a framework for the interpretation of upcoming high-resolution observations

A survey for variable young stars with small telescopes: IX - Evolution of spot properties on YSOs in IC 5070

We present spot properties on 32 periodic young stellar objects in IC 5070. Long term, ∼5 yr, light curves in the V, R, and I-bands are obtained through the HOYS (Hunting Outbursting Young Stars) citizen science project. These are dissected into six months long slices, with 3 months oversampling, to measure 234 sets of amplitudes in all filters. We fit 180 of these with reliable spot solutions. Two thirds of spot solutions are cold spots, the lowest is 2150 K below the stellar temperature. One third are warm spots that are above the stellar temperature by less than ∼2000 K. Cold and warm spots have maximum surface coverage values of 40 per cent, although only 16 per cent of warm spots are above 20 per cent surface coverage as opposed to 60 per cent of the cold spots. Warm spots are most likely caused by a combination of plages and low density accretion columns, most common on objects without inner disc excess emission in K − W2. Five small hot spot solutions have &amp;lt;3 percent coverage and are 3000 – 5000 K above the stellar temperature. These are attributed to accretion, and four of them occur on the same object. The majority of our objects are likely to be accreting. However, we observe very few accretion hot spots as either the accretion is not stable on our timescale or the photometry is dominated by other features. We do not identify cyclical spot behaviour on the targets. We additionally identify and discuss a number of objects that have interesting amplitudes, phase changes, or spot properties

A survey for variable young stars with small telescopes – VIII. Properties of 1687 Gaia selected members in 21 nearby clusters

The Hunting Outbursting Young Stars (HOYS) project performs long-term, optical, multi-filter, high cadence monitoring of 25 nearby young clusters and star forming regions. Utilising Gaia DR3 data we have identified about 17000 potential young stellar members in 45 coherent astrometric groups in these fields. Twenty one of them are clear young groups or clusters of stars within one kiloparsec and they contain 9143 Gaia selected potential members. The cluster distances, proper motions and membership numbers are determined. We analyse long term (≈ 7 yr) V, R, and I-band light curves from HOYS for 1687 of the potential cluster members. One quarter of the stars are variable in all three optical filters, and two thirds of these have light curves that are symmetric around the mean. Light curves affected by obscuration from circumstellar materials are more common than those affected by accretion bursts, by a factor of 2 – 4. The variability fraction in the clusters ranges from 10 to almost 100 percent, and correlates positively with the fraction of stars with detectable inner disks, indicating that a lot of variability is driven by the disk. About one in six variables shows detectable periodicity, mostly caused by magnetic spots. Two thirds of the periodic variables with disk excess emission are slow rotators, and amongst the stars without disk excess two thirds are fast rotators – in agreement with rotation being slowed down by the presence of a disk

Whole-genome sequencing reveals host factors underlying critical COVID-19

Altres ajuts: Department of Health and Social Care (DHSC); Illumina; LifeArc; Medical Research Council (MRC); UKRI; Sepsis Research (the Fiona Elizabeth Agnew Trust); the Intensive Care Society, Wellcome Trust Senior Research Fellowship (223164/Z/21/Z); BBSRC Institute Program Support Grant to the Roslin Institute (BBS/E/D/20002172, BBS/E/D/10002070, BBS/E/D/30002275); UKRI grants (MC_PC_20004, MC_PC_19025, MC_PC_1905, MRNO2995X/1); UK Research and Innovation (MC_PC_20029); the Wellcome PhD training fellowship for clinicians (204979/Z/16/Z); the Edinburgh Clinical Academic Track (ECAT) programme; the National Institute for Health Research, the Wellcome Trust; the MRC; Cancer Research UK; the DHSC; NHS England; the Smilow family; the National Center for Advancing Translational Sciences of the National Institutes of Health (CTSA award number UL1TR001878); the Perelman School of Medicine at the University of Pennsylvania; National Institute on Aging (NIA U01AG009740); the National Institute on Aging (RC2 AG036495, RC4 AG039029); the Common Fund of the Office of the Director of the National Institutes of Health; NCI; NHGRI; NHLBI; NIDA; NIMH; NINDS.Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care or hospitalization after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes-including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)-in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease