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Sökning: WFRF:(Henning K) > (2020-2024)

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1.
  • Kanai, M, et al. (författare)
  • 2023
  • swepub:Mat__t
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2.
  • Kim, Jae-Young, et al. (författare)
  • Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution
  • 2020
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 640
  • Tidskriftsartikel (refereegranskat)abstract
    • 3C 279 is an archetypal blazar with a prominent radio jet that show broadband flux density variability across the entire electromagnetic spectrum. We use an ultra-high angular resolution technique - global Very Long Baseline Interferometry (VLBI) at 1.3mm (230 GHz) - to resolve the innermost jet of 3C 279 in order to study its fine-scale morphology close to the jet base where highly variable-ray emission is thought to originate, according to various models. The source was observed during four days in April 2017 with the Event Horizon Telescope at 230 GHz, including the phased Atacama Large Millimeter/submillimeter Array, at an angular resolution of ∼20 μas (at a redshift of z = 0:536 this corresponds to ∼0:13 pc ∼ 1700 Schwarzschild radii with a black hole mass MBH = 8 × 108 M⊙). Imaging and model-fitting techniques were applied to the data to parameterize the fine-scale source structure and its variation.We find a multicomponent inner jet morphology with the northernmost component elongated perpendicular to the direction of the jet, as imaged at longer wavelengths. The elongated nuclear structure is consistent on all four observing days and across diffierent imaging methods and model-fitting techniques, and therefore appears robust. Owing to its compactness and brightness, we associate the northern nuclear structure as the VLBI "core". This morphology can be interpreted as either a broad resolved jet base or a spatially bent jet.We also find significant day-to-day variations in the closure phases, which appear most pronounced on the triangles with the longest baselines. Our analysis shows that this variation is related to a systematic change of the source structure. Two inner jet components move non-radially at apparent speeds of ∼15 c and ∼20 c (∼1:3 and ∼1:7 μas day-1, respectively), which more strongly supports the scenario of traveling shocks or instabilities in a bent, possibly rotating jet. The observed apparent speeds are also coincident with the 3C 279 large-scale jet kinematics observed at longer (cm) wavelengths, suggesting no significant jet acceleration between the 1.3mm core and the outer jet. The intrinsic brightness temperature of the jet components are ≤1010 K, a magnitude or more lower than typical values seen at ≥7mm wavelengths. The low brightness temperature and morphological complexity suggest that the core region of 3C 279 becomes optically thin at short (mm) wavelengths.
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3.
  • Anderson, Emma K., 1986-, et al. (författare)
  • Fragmentation of and electron detachment from hot copper and silver dimer anions : A comparison
  • 2023
  • Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 107:6
  • Tidskriftsartikel (refereegranskat)abstract
    • We measured the spontaneous decays of internally hot copper and silver dimer anions, and , stored in one of the two ion-beam storage rings of the Double Electrostatic Ion Ring Experiment (DESIREE) at Stockholm University. A coincidence detection technique was utilized enabling essentially background-free measurements of -> Cu + Cu- and -> Ag + Ag- fragmentation rates. Furthermore, the total rates of neutral decay products (monomers and dimers) were measured and the relative contributions of fragmentation and electron emission ( -> Cu2 + e- and -> Ag2 + e-) were deduced as functions of storage time. Fragmentation is completely dominant at early times. However, after about 20 ms of storage, electron emission is observed and becomes the leading decay path after 100 ms for both dimer anions. The branching ratios between fragmentation and electron emission (vibrationally assisted autodetachment processes) are very nearly the same for and Ag-2 throughout the present storage cycle of 10 seconds. This is surprising considering the difference between the electron affinities of the neutral dimers, Cu2 and Ag2, and the difference between the and the dissociation energies.
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4.
  • Boretzky, K., et al. (författare)
  • NeuLAND: The high-resolution neutron time-of-flight spectrometer for R 3 B at FAIR
  • 2021
  • Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 1014
  • Tidskriftsartikel (refereegranskat)abstract
    • NeuLAND (New Large-Area Neutron Detector) is the next-generation neutron detector for the R3B (Reactions with Relativistic Radioactive Beams) experiment at FAIR (Facility for Antiproton and Ion Research). NeuLAND detects neutrons with energies from 100 to 1000 MeV, featuring a high detection efficiency, a high spatial and time resolution, and a large multi-neutron reconstruction efficiency. This is achieved by a highly granular design of organic scintillators: 3000 individual submodules with a size of 5 × 5 × 250 cm3 are arranged in 30 double planes with 100 submodules each, providing an active area of 250 × 250 cm2 and a total depth of 3 m. The spatial resolution due to the granularity together with a time resolution of σt≤ 150 ps ensures high-resolution capabilities. In conjunction with calorimetric properties, a multi-neutron reconstruction efficiency of 50% to 70% for four-neutron events will be achieved, depending on both the emission scenario and the boundary conditions allowed for the reconstruction method. We present in this paper the final design of the detector as well as results from test measurements and simulations on which this design is based.
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5.
  • Anderson, Emma K., et al. (författare)
  • Spontaneous electron emission from hot silver dimer anions: Breakdown of the Born-Oppenheimer approximation
  • 2020
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 124
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the first experimental evidence of spontaneous electron emission from a homonuclear dimer anion through direct measurements of Ag−2 → Ag2 + e− decays on milliseconds and seconds timescales. This observation is very surprising as there is no avoided crossing between adiabatic energy curves to mediate such a process. The process is weak, yet dominates the decay signal after 100 ms when ensembles of internally hot Ag−2 ions are stored in the cryogenic ion-beam storage ring, DESIREE, for 10 s. The electron emission process is associated with an instantaneous, very large reduction of the vibrational energy of the dimer system. This represents a dramatic deviation from a Born-Oppenheimer description of dimer dynamics.
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6.
  • Najeeb, P. K., 1986-, et al. (författare)
  • Stability and Cooling of the C72- Dianion
  • 2023
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 131:11
  • Tidskriftsartikel (refereegranskat)abstract
    • We have studied the stability of the smallest long-lived all carbon molecular dianion (C72-) in new time domains and with a single ion at a time using a cryogenic electrostatic ion-beam storage ring. We observe spontaneous electron emission from internally excited dianions on millisecond timescales and monitor the survival of single colder C72- molecules on much longer timescales. We find that their intrinsic lifetime exceeds several minutes - 6 orders of magnitude longer than established from earlier experiments on C72-. This is consistent with our calculations of vertical electron detachment energies predicting one inherently stable isomer and one isomer which is stable or effectively stable behind a large Coulomb barrier for C72-→C7-+e- separation.
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7.
  • Najeeb, P. K., 1986-, et al. (författare)
  • Stability and Cooling of the C2−7 Dianion
  • 2023
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 131:11
  • Tidskriftsartikel (refereegranskat)abstract
    • We have studied the stability of the smallest long-lived all carbon molecular dianion () in new time domains and with a single ion at a time using a cryogenic electrostatic ion-beam storage ring. We observe spontaneous electron emission from internally excited dianions on millisecond timescales and monitor the survival of single colder molecules on much longer timescales. We find that their intrinsic lifetime exceeds several minutes—6 orders of magnitude longer than established from earlier experiments on . This is consistent with our calculations of vertical electron detachment energies predicting one inherently stable isomer and one isomer which is stable or effectively stable behind a large Coulomb barrier for →+e− separation.
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8.
  • Schuller, F., et al. (författare)
  • The SEDIGISM survey: First Data Release and overview of the Galactic structure
  • 2021
  • Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 500:3, s. 3064-3082
  • Tidskriftsartikel (refereegranskat)abstract
    • The SEDIGISM (Structure, Excitation and Dynamics of the Inner Galactic InterstellarMedium) survey used the APEX telescope to map 84 deg(2) of the Galactic plane between l = -60 degrees and +31 degrees in several molecular transitions, including (CO)-C-13(2 - 1) and (CO)-O-18(2 - 1), thus probing the moderately dense (similar to 10(3) cm(-3)) component of the interstellar medium. With an angular resolution of 30 arcsec and a typical 1 sigma sensitivity of 0.8-1.0K at 0.25 km s(-1) velocity resolution, it gives access to a wide range of structures, from individual star-forming clumps to giant molecular clouds and complexes. The coverage includes a good fraction of the first and fourth Galactic quadrants, allowing us to constrain the large-scale distribution of cold molecular gas in the inner Galaxy. In this paper, we provide an updated overview of the full survey and the data reduction procedures used. We also assess the quality of these data and describe the data products that are being made publicly available as part of this First Data Release (DR1). We present integrated maps and position-velocity maps of the molecular gas and use these to investigate the correlation between the molecular gas and the large-scale structural features of the Milky Way such as the spiral arms, Galactic bar and Galactic Centre. We find that approximately 60 per cent of the molecular gas is associated with the spiral arms and these appear as strong intensity peaks in the derived Galactocentric distribution. We also find strong peaks in intensity at specific longitudes that correspond to the Galactic Centre and well-known star-forming complexes, revealing that the 13CO emission is concentrated in a small number of complexes rather than evenly distributed along spiral arms.
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9.
  • Weigelt, G., et al. (författare)
  • VLTI-MATISSE chromatic aperture-synthesis imaging of eta Carinae's stellar wind across the Br alpha line Periastron passage observations in February 2020
  • 2021
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 652
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. Eta Carinae is a highly eccentric, massive binary system (semimajor axis similar to 15.5 au) with powerful stellar winds and a phase-dependent wind-wind collision (WWC) zone. The primary star, eta Car A, is a luminous blue variable (LBV); the secondary, eta Car B, is a Wolf-Rayet or O star with a faster but less dense wind. Aperture-synthesis imaging allows us to study the mass loss from the enigmatic LBV eta Car. Understanding LBVs is a crucial step toward improving our knowledge about massive stars and their evolution. Aims. Our aim is to study the intensity distribution and kinematics of eta Car's WWC zone. Methods. Using the VLTI-MATISSE mid-infrared interferometry instrument, we perform Br alpha imaging of eta Car's distorted wind. Results. We present the first VLTI-MATISSE aperture-synthesis images of eta Car A's stellar windin several spectral channels distributed across the Br alpha 4.052 mu m line (spectral resolving power R similar to 960). Our observations were performed close to periastron passage in February 2020 (orbital phase similar to 14.0022). The reconstructed iso-velocity images show the dependence of the primary stellar wind on wavelength or line-of-sight (LOS) velocity with a spatial resolution of 6 mas (similar to 14 au). The radius of the faintest outer wind regions is similar to 26 mas (similar to 60 au). At several negative LOS velocities, the primary stellar wind is less extended to the northwest than in other directions. This asymmetry is most likely caused by the WWC. Therefore, we see both the velocity field of the undisturbed primary wind and the WWC cavity. In continuum spectral channels, the primary star wind is more compact than in line channels. A fit of the observed continuum visibilities with the visibilities of a stellar wind CMFGEN model (CMFGEN is an atmosphere code developed to model the spectra of a variety of objects) provides a full width at half maximum fit diameter of the primary stellar wind of 2.84 +/- 0.06 mas (6.54 +/- 0.14 au). We comparethe derived intensity distributions with the CMFGEN stellar wind model and hydrodynamic WWC models.
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10.
  • Chiavassa, A., et al. (författare)
  • The extended atmosphere and circumstellar environment of the cool evolved star VX Sagittarii as seen by MATISSE star
  • 2022
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 658
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. VX Sgr is a cool, evolved, and luminous red star whose stellar parameters are difficult to determine, which affects its classification.Aims. We aim to spatially resolve the photospheric extent as well as the circumstellar environment.Methods. We used interferometric observations obtained with the MATISSE instrument in the L (3-4 mu m), M (4.5-5 mu m), and N (8-13 mu m) bands. We reconstructed monochromatic images using the MIRA software. We used 3D radiation-hydrodynamics simulations carried out with (COBOLD)-B-5 and a uniform disc model to estimate the apparent diameter and interpret the stellar surface structures. Moreover, we employed the radiative transfer codes OPTIM3D and RADMC3D to compute the spectral energy distribution for the L, M, and N bands, respectively.Results. MATISSE observations unveil, for the first time, the morphology of VX Sgr across the L, M, and N bands. The reconstructed images show a complex morphology with brighter areas whose characteristics depend on the wavelength probed. We measured the angular diameter as a function of the wavelength and showed that the photospheric extent in the L and M bands depends on the opacity through the atmosphere. In addition to this, we also concluded that the observed photospheric inhomogeneities can be interpreted as convection-related surface structures. The comparison in the N band yielded a qualitative agreement between the N-band spectrum and simple dust radiative transfer simulations. However, it is not possible to firmly conclude on the interpretation of the current data because of the difficulty in constraing the model parameters using the limited accuracy of our absolute flux calibration.Conclusions. MATISSE observations and the derived reconstructed images unveil the appearance of VX Sgr's stellar surface and circumstellar environment across a very large spectral domain for the first time.
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11.
  • Eklund, Gustav, 1990-, et al. (författare)
  • Experimental lifetime of the a1Δ electronically excited state of CH−
  • 2022
  • Ingår i: Physical Review Research. - : American Physical Society (APS). - 2643-1564. ; 4:1
  • Tidskriftsartikel (refereegranskat)abstract
    • By repeatedly probing the a1Δ excited state and the X3Σ− ground-state populations in a beam of CH− ions stored in a cryogenic ion-beam storage ring for 100 s, we extract an intrinsic lifetime of 14.9±0.5 s for this excited state. This is far longer than all earlier experimental and theoretical results, exposing large difficulties in measuring and calculating slow decays and the need for benchmark quality experiments.
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12.
  • Gobel, K., et al. (författare)
  • Coulomb dissociation of 16O into 4He and 12C
  • 2020
  • Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 1668:1
  • Konferensbidrag (refereegranskat)abstract
    • We measured the Coulomb dissociation of 16O into 4He and 12C at the R3B setup in a first campaign within FAIR Phase 0 at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt. The goal was to improve the accuracy of the experimental data for the 12C(a,?)16O fusion reaction and to reach lower center-ofmass energies than measured so far. The experiment required beam intensities of 109 16O ions per second at an energy of 500 MeV/nucleon. The rare case of Coulomb breakup into 12C and 4He posed another challenge: The magnetic rigidities of the particles are so close because of the same mass-To-charge-number ratio A/Z = 2 for 16O, 12C and 4He. Hence, radical changes of the R3B setup were necessary. All detectors had slits to allow the passage of the unreacted 16O ions, while 4He and 12C would hit the detectors' active areas depending on the scattering angle and their relative energies. We developed and built detectors based on organic scintillators to track and identify the reaction products with sufficient precision.
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13.
  • Heil, M., et al. (författare)
  • A new Time-of-flight detector for the R 3 B setup
  • 2022
  • Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-601X .- 1434-6001. ; 58:12
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the design, prototype developments and test results of the new time-of-flight detector (ToFD) which is part of the R3B experimental setup at GSI and FAIR, Darmstadt, Germany. The ToFD detector is able to detect heavy-ion residues of all charges at relativistic energies with a relative energy precision σΔE/ ΔE of up to 1% and a time precision of up to 14 ps (sigma). Together with an elaborate particle-tracking system, the full identification of relativistic ions from hydrogen up to uranium in mass and nuclear charge is possible.
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14.
  • Lee, Jason W. L., et al. (författare)
  • Cooling dynamics of energized naphthalene and azulene radical cations
  • 2023
  • Ingår i: Journal of Chemical Physics. - 0021-9606 .- 1089-7690. ; 158:17
  • Tidskriftsartikel (refereegranskat)abstract
    • Naphthalene and azulene are isomeric polycyclic aromatic hydrocarbons (PAHs) and are topical in the context of astrochemistry due to the recent discovery of substituted naphthalenes in the Taurus Molecular Cloud-1 (TMC-1). Here, the thermal- and photo-induced isomerization, dissociation, and radiative cooling dynamics of energized (vibrationally hot) naphthalene (Np+) and azulene (Az(+)) radical cations, occurring over the microsecond to seconds timescale, are investigated using a cryogenic electrostatic ion storage ring, affording molecular cloud in a box conditions. Measurement of the cooling dynamics and kinetic energy release distributions for neutrals formed through dissociation, until several seconds after hot ion formation, are consistent with the establishment of a rapid (sub-microsecond) Np+ reversible arrow Az(+) quasi-equilibrium. Consequently, dissociation by C2H2-elimination proceeds predominantly through common Az(+) decomposition pathways. Simulation of the isomerization, dissociation, recurrent fluorescence, and infrared cooling dynamics using a coupled master equation combined with high-level potential energy surface calculations [CCSD(T)/cc-pVTZ], reproduce the trends in the measurements. The data show that radiative cooling via recurrent fluorescence, predominately through the Np+ D-0 <- D-2 transition, efficiently quenches dissociation for vibrational energies up to approximate to 1 eV above dissociation thresholds. Our measurements support the suggestion that small cations, such as naphthalene, may be more abundant in space than previously thought. The strategy presented in this work could be extended to fingerprint the cooling dynamics of other PAH ions for which isomerization is predicted to precede dissociation.
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15.
  • Mallorquin, M., et al. (författare)
  • TOI-1801 b: A temperate mini-Neptune around a young M0.5 dwarf
  • 2023
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 680
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the discovery, mass, and radius determination of TOI-1801 b, a temperate mini-Neptune around a young M dwarf. TOI-1801 b was observed in TESS sectors 22 and 49, and the alert that this was a TESS planet candidate with a period of 21.3 days went out in April 2020. However, ground-based follow-up observations, including seeing-limited photometry in and outside transit together with precise radial velocity (RV) measurements with CARMENES and HIRES revealed that the true period of the planet is 10.6 days. These observations also allowed us to retrieve a mass of 5.74 +/- 1.46 M-circle plus, which together with a radius of 2.08 +/- 0.12 R-circle plus, means that TOI-1801 b is most probably composed of water and rock, with an upper limit of 2% by mass of H-2 in its atmosphere. The stellar rotation period of 16 days is readily detectable in our RV time series and in the ground-based photometry. We derived a likely age of 600-800 Myr for the parent star TOI-1801, which means that TOI-1801 b is the least massive young mini-Neptune with precise mass and radius determinations. Our results suggest that if TOI-1801 b had a larger atmosphere in the past, it must have been removed by some evolutionary mechanism on timescales shorter than 1 Gyr.
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16.
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17.
  • Wright, Gillian, et al. (författare)
  • The Mid-infrared Instrument for JWST and Its In-flight Performance
  • 2023
  • Ingår i: Publications of the Astronomical Society of the Pacific. - 0004-6280 .- 1538-3873. ; 135:1046
  • Tidskriftsartikel (refereegranskat)abstract
    • The Mid-Infrared Instrument (MIRI) extends the reach of the James Webb Space Telescope (JWST) to 28.5 μm. It provides subarcsecond-resolution imaging, high sensitivity coronagraphy, and spectroscopy at resolutions of λ/Δλ ∼ 100-3500, with the high-resolution mode employing an integral field unit to provide spatial data cubes. The resulting broad suite of capabilities will enable huge advances in studies over this wavelength range. This overview describes the history of acquiring this capability for JWST. It discusses the basic attributes of the instrument optics, the detector arrays, and the cryocooler that keeps everything at approximately 7 K. It gives a short description of the data pipeline and of the instrument performance demonstrated during JWST commissioning. The bottom line is that the telescope and MIRI are both operating to the standards set by pre-launch predictions, and all of the MIRI capabilities are operating at, or even a bit better than, the level that had been expected. The paper is also designed to act as a roadmap to more detailed papers on different aspects of MIRI.
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18.
  • Alimena, Juliette, et al. (författare)
  • Searching for long-lived particles beyond the Standard Model at the Large Hadron Collider
  • 2020
  • Ingår i: Journal of Physics G. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 47:9
  • Tidskriftsartikel (refereegranskat)abstract
    • Particles beyond the Standard Model (SM) can generically have lifetimes that are long compared to SM particles at the weak scale. When produced at experiments such as the Large Hadron Collider (LHC) at CERN, these long-lived particles (LLPs) can decay far from the interaction vertex of the primary proton-proton collision. Such LLP signatures are distinct from those of promptly decaying particles that are targeted by the majority of searches for new physics at the LHC, often requiring customized techniques to identify, for example, significantly displaced decay vertices, tracks with atypical properties, and short track segments. Given their non-standard nature, a comprehensive overview of LLP signatures at the LHC is beneficial to ensure that possible avenues of the discovery of new physics are not overlooked. Here we report on the joint work of a community of theorists and experimentalists with the ATLAS, CMS, and LHCb experiments-as well as those working on dedicated experiments such as MoEDAL, milliQan, MATHUSLA, CODEX-b, and FASER-to survey the current state of LLP searches at the LHC, and to chart a path for the development of LLP searches into the future, both in the upcoming Run 3 and at the high-luminosity LHC. The work is organized around the current and future potential capabilities of LHC experiments to generally discover new LLPs, and takes a signature-based approach to surveying classes of models that give rise to LLPs rather than emphasizing any particular theory motivation. We develop a set of simplified models; assess the coverage of current searches; document known, often unexpected backgrounds; explore the capabilities of proposed detector upgrades; provide recommendations for the presentation of search results; and look towards the newest frontiers, namely high-multiplicity 'dark showers', highlighting opportunities for expanding the LHC reach for these signals.
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19.
  • Chaturvedi, P., et al. (författare)
  • TOI-1468: A system of two transiting planets, a super-Earth and a mini-Neptune, on opposite sides of the radius valley
  • 2022
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 666
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the discovery and characterization of two small transiting planets orbiting the bright M3.0V star TOI-1468 (LSPM J0106+1913), whose transit signals were detected in the photometric time series in three sectors of the TESS mission. We confirm the planetary nature of both of them using precise radial velocity measurements from the CARMENES and MAROON-X spectrographs, and supplement them with ground-based transit photometry. A joint analysis of all these data reveals that the shorter-period planet, TOI-1468 b (P-b = 1.88 d), has a planetary mass of M-b = 3.21 +/- 0.24M(circle plus) and a radius of R-b = 1.280(-0.039)(+0.038) R-circle plus, resulting in a density of rho(b) = 8.39(-0.92)(+1.05) g cm(-3), which is consistent with a mostly rocky composition. For the outer planet, TOI-1468 c (P-c = 15.53 d), we derive a mass of M-c = 6.64(-0.68)(+0.67) M-circle plus,aradius of R-c = 2.06 +/- 0.04 R-circle plus, and a bulk density of rho(c) = 2.00(-0.19)(+0.21) g cm(-3), which corresponds to a rocky core composition with a H/He gas envelope. These planets are located on opposite sides of the radius valley, making our system an interesting discovery as there are only a handful of other systems with the same properties. This discovery can further help determine a more precise location of the radius valley for small planets around M dwarfs and, therefore, shed more light on planet formation and evolution scenarios.
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20.
  • Chen, Deliang, 1961, et al. (författare)
  • Summary of a workshop on extreme weather events in a warming world organized by the Royal Swedish Academy of Sciences
  • 2020
  • Ingår i: Tellus Series B-Chemical and Physical Meteorology. - : Stockholm University Press. - 1600-0889 .- 0280-6509. ; 72:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Climate change is not only about changes in means of climatic variables such as temperature, precipitation and wind, but also their extreme values which are of critical importance to human society and ecosystems. To inspire the Swedish climate research community and to promote assessments of international research on past and future changes in extreme weather events against the global climate change background, the Earth Science Class of the Royal Swedish Academy of Sciences organized a workshop entitled 'Extreme weather events in a warming world' in 2019. This article summarizes and synthesizes the key points from the presentations and discussions of the workshop on changes in floods, droughts, heat waves, as well as on tropical cyclones and extratropical storms. In addition to reviewing past achievements in these research fields and identifying research gaps with a focus on Sweden, future challenges and opportunities for the Swedish climate research community are highlighted.
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21.
  • Christiansen, Morten K, et al. (författare)
  • Incidence, Predictors, and Success of Ventricular Tachycardia Catheter Ablation in Arrhythmogenic Right Ventricular Cardiomyopathy (from the Nordic ARVC Registry).
  • 2020
  • Ingår i: The American journal of cardiology. - : Elsevier BV. - 1879-1913 .- 0002-9149. ; 125:5, s. 803-811
  • Tidskriftsartikel (refereegranskat)abstract
    • Catheter ablation may reduce ventricular tachycardia (VT) burden in arrhythmogenic right ventricular cardiomyopathy (ARVC) patients. However, little is known about factors predicting need for ablation. Therefore, we sought to investigate predictors and use of VT ablation and to evaluate the postprocedural outcome in ARVC patients. We studied 435 patients from the Nordic ARVC registry including 220 probands with definite ARVC according to the 2010 task force criteria and 215 mutation-carrying relatives identified through cascade screening. Patients were followed until first-time VT ablation, death, heart transplantation, or January 1st 2018. Additionally, patients undergoing VT ablation were further followed from the time of ablation for recurrent ventricular arrhythmias. The cumulative use of VT ablation was 4% (95% confidence interval [CI] 3% to 6%) and 11% (95% CI 8% to 15%) after 1 and 10 years. All procedures were performed in probands in whom cumulative use was 8% (95% CI 5% to 12%) and 20% (95% CI 15% to 26%). In adjusted analyses among probands, only young age predicted ablation. In patients undergoing ablation, risk of recurrent arrhythmias was 59% (95% CI 44% to 71%) and 74% (95% CI 59% to 84%) 1 and 5 years after the procedure. Despite high recurrence rates, the burden of ventricular arrhythmias was reduced after ablation (p=0.0042). Young age, use of several antiarrhythmic drugs and inducibility to VT after ablation were associated with an unfavorable outcome. In conclusion, twenty percent of ARVC probands developed a clinical indication for VT ablation within 10 years whereas mutation-carrying relatives were without such need. Although the burden of ventricular arrhythmias decreased after ablation, risk of recurrence was substantial.
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22.
  • Duarte-Cabral, A., et al. (författare)
  • The SEDIGISM survey: Molecular clouds in the inner Galaxy
  • 2021
  • Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 500:3, s. 3027-3049
  • Forskningsöversikt (refereegranskat)abstract
    • We use the 13CO(2-1) emission from the SEDIGISM (Structure, Excitation, and Dynamics of the Inner Galactic InterStellar Medium) high-resolution spectral-line survey of the inner Galaxy, to extract the molecular cloud population with a large dynamic range in spatial scales, using the Spectral Clustering for Interstellar Molecular Emission Segmentation (SCIMES) algorithm. This work compiles a cloud catalogue with a total of 10 663 molecular clouds, 10 300 of which we were able to assign distances and compute physical properties. We study some of the global properties of clouds using a science sample, consisting of 6664 well-resolved sources and for which the distance estimates are reliable. In particular, we compare the scaling relations retrieved from SEDIGISM to those of other surveys, and we explore the properties of clouds with and without high-mass star formation. Our results suggest that there is no single global property of a cloud that determines its ability to form massive stars, although we find combined trends of increasing mass, size, surface density, and velocity dispersion for the sub-sample of clouds with ongoing high-mass star formation. We then isolate the most extreme clouds in the SEDIGISM sample (i.e. clouds in the tails of the distributions) to look at their overall Galactic distribution, in search for hints of environmental effects. We find that, for most properties, the Galactic distribution of the most extreme clouds is only marginally different to that of the global cloud population. The Galactic distribution of the largest clouds, the turbulent clouds and the high-mass star-forming clouds are those that deviate most significantly from the global cloud population. We also find that the least dynamically active clouds (with low velocity dispersion or low virial parameter) are situated further afield, mostly in the least populated areas. However, we suspect that part of these trends may be affected by some observational biases (such as completeness and survey limitations), and thus require further follow up work in order to be confirmed.
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23.
  • Kristiansson, Moa K., et al. (författare)
  • Experimental and theoretical studies of excited states in Ir
  • 2021
  • Ingår i: Physical Review A. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 103:6
  • Tidskriftsartikel (refereegranskat)abstract
    • The properties of atomic negative ions are to a large extent determined by electron-electron correlation which makes them an ideal testing ground for atomic many-body physics. In this paper, we present a detailed experimental and theoretical study of excited states in the negative ion of iridium. The ions were stored at cryogenic temperatures using the double electrostatic ion ring experiment facility at Stockholm University. Laser photodetachment was used to monitor the relaxation of three bound excited states belonging to the [Xe] 4f(14)5d(8)6s(2) ionic ground configuration. Our measurements show that the first excited state has a lifetime much longer than the ion-beam storage time of 1230 +/- 100 s. The binding energy of this state was measured to be 1.045 +/- 0.002 eV. The lifetimes of the second and third excited states were experimentally determined to be 133 +/- 10 and 172 +/- 35 ms, respectively. Multiconfiguration Dirac-Hartree-Fock calculations were performed in order to extract binding energies and lifetimes. These calculations predict the existence of the third excited bound state that was detected experimentally. The computed lifetimes for the three excited bound states agree well with the experimental results and allow for a clear identification of the detected levels.
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24.
  • Kristiansson, Moa K., 1989-, et al. (författare)
  • High-precision electron affinity of oxygen
  • 2022
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Negative ions are important in many areas of science and technology, e.g., in interstellar chemistry, for accelerator-based radionuclide dating, and in anti-matter research. They are unique quantum systems where electron-correlation effects govern their properties. Atomic anions are loosely bound systems, which with very few exceptions lack optically allowed transitions. This limits prospects for high-resolution spectroscopy, and related negative-ion detection methods. Here, we present a method to measure negative ion binding energies with an order of magnitude higher precision than what has been possible before. By laser-manipulation of quantum-state populations, we are able to strongly reduce the background from photodetachment of excited states using a cryogenic electrostatic ion-beam storage ring where keV ion beams can circulate for up to hours. The method is applicable to negative ions in general and here we report an electron affinity of 1.461 112 972(87) eV for O-16. High-precision measurements are useful to find isotopic shifts and electron correlation. Here the authors measure electron affinity and hyperfine splitting of atomic oxygen with higher precision than previous studies.
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25.
  • Lacour, S., et al. (författare)
  • The mass of β Pictoris c from β Pictoris b orbital motion
  • 2021
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 654
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims. We aim to demonstrate that the presence and mass of an exoplanet can now be effectively derived from the astrometry of another exoplanet.Methods. We combined previous astrometry of β Pictoris b with a new set of observations from the GRAVITY interferometer. The orbital motion of β Pictoris b is fit using Markov chain Monte Carlo simulations in Jacobi coordinates. The inner planet, β Pictoris c, was also reobserved at a separation of 96 mas, confirming the previous orbital estimations.Results. From the astrometry of planet b only, we can (i) detect the presence of β Pictoris c and (ii) constrain its mass to 10.04(-3.10)(+4.53) M-Jup. If one adds the astrometry of β Pictoris c, the mass is narrowed down to 9.15(-1.06)(+1.08) M-Jup. The inclusion of radial velocity measurements does not affect the orbital parameters significantly, but it does slightly decrease the mass estimate to 8.89(-0.75)(+0.75) M-Jup. With a semimajor axis of 2.68 +/- 0.02 au, a period of 1221 +/- 15 days, and an eccentricity of 0.32 +/- 0.02, the orbital parameters of β Pictoris c are now constrained as precisely as those of β Pictoris b. The orbital configuration is compatible with a high-order mean-motion resonance (7:1). The impact of the resonance on the planets' dynamics would then be negligible with respect to the secular perturbations, which might have played an important role in the eccentricity excitation of the outer planet.
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26.
  • Luque, R., et al. (författare)
  • Precise mass determination for the keystone sub-Neptune planet transiting the mid-type M dwarf G 9-40
  • 2022
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 666
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. Despite being a prominent subset of the exoplanet population discovered in the past three decades, the nature and provenance of sub-Neptune-sized planets is still one of the open questions in exoplanet science. Aims. For planets orbiting bright stars, precisely measuring the orbital and planet parameters of the system is the best approach to distinguish between competing theories regarding their formation and evolution. Methods. We obtained 69 new radial velocity observations of the mid-M dwarf G 9-40 with the CARMENES instrument to measure for the first time the mass of its transiting sub-Neptune planet, G 9-40 b, discovered in data from the K2 mission. Results. Combined with new observations from the TESS mission during Sectors 44, 45, and 46, we are able to measure the radius of the planet to an uncertainty of 3.4% (R-b = 1.900 +/- 0.065 R-circle plus) and determine its mass with a precision of 16% (M-b = 4.00 +/- 0.63 M-circle plus). The resulting bulk density of the planet is inconsistent with a terrestrial composition and suggests the presence of either a water-rich core or a significant hydrogen-rich envelope. Conclusions. G 9-40 b is referred to as a keystone planet due to its location in period-radius space within the radius valley. Several theories offer explanations for the origin and properties of this population and this planet is a valuable target for testing the dependence of those models on stellar host mass. By virtue of its brightness and small size of the host, it joins L 98-59 d as one of the two best warm (T-eq similar to 400 K) sub-Neptunes for atmospheric characterization with JWST, which will probe cloud formation in sub-Neptune-sized planets and break the degeneracies of internal composition models.
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27.
  • Makitie, R. E., et al. (författare)
  • An ARHGAP25 variant links aberrant Rac1 function to early-onset skeletal fragility
  • 2021
  • Ingår i: JBMR Plus. - : Wiley. - 2473-4039. ; 5:7
  • Tidskriftsartikel (refereegranskat)abstract
    • Ras homologous guanosine triphosphatases (RhoGTPases) control several cellular functions, including cytoskeletal actin remodeling and cell migration. Their activities are downregulated by GTPase-activating proteins (GAPs). Although RhoGTPases are implicated in bone remodeling and osteoclast and osteoblast function, their significance in human bone health and disease remains elusive. Here, we report defective RhoGTPase regulation as a cause of severe, early-onset, autosomal-dominant skeletal fragility in a three-generation Finnish family. Affected individuals (n = 13) presented with multiple low-energy peripheral and vertebral fractures despite normal bone mineral density (BMD). Bone histomorphometry suggested reduced bone volume, low surface area covered by osteoblasts and osteoclasts, and low bone turnover. Exome sequencing identified a novel heterozygous missense variant c.652G>A (p.G218R) in ARHGAP25, encoding a GAP for Rho-family GTPase Rac1. Variants in the ARHGAP25 5 ' untranslated region (UTR) also associated with BMD and fracture risk in the general population, across multiple genomewide association study (GWAS) meta-analyses (lead variant rs10048745). ARHGAP25 messenger RNA (mRNA) was expressed in macrophage colony-stimulating factor (M-CSF)-stimulated human monocytes and mouse osteoblasts, indicating a possible role for ARHGAP25 in osteoclast and osteoblast differentiation and activity. Studies on subject-derived osteoclasts from peripheral blood mononuclear cells did not reveal robust defects in mature osteoclast formation or resorptive activity. However, analysis of osteosarcoma cells overexpressing the ARHGAP25 G218R-mutant, combined with structural modeling, confirmed that the mutant protein had decreased GAP-activity against Rac1, resulting in elevated Rac1 activity, increased cell spreading, and membrane ruffling. Our findings indicate that mutated ARHGAP25 causes aberrant Rac1 function and consequently abnormal bone metabolism, highlighting the importance of RhoGAP signaling in bone metabolism in familial forms of skeletal fragility and in the general population, and expanding our understanding of the molecular pathways underlying skeletal fragility. (c) 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.
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28.
  • Platonov, Pyotr G., et al. (författare)
  • Pregnancies, ventricular arrhythmias, and substrate progression in women with arrhythmogenic right ventricular cardiomyopathy in the Nordic ARVC Registry
  • 2020
  • Ingår i: Europace. - : Oxford University Press. - 1099-5129 .- 1532-2092. ; 23:12, s. 1873-1879
  • Tidskriftsartikel (refereegranskat)abstract
    • AIMS: Women with arrhythmogenic right ventricular cardiomyopathy (ARVC) are at relatively lower risk of ventricular arrhythmias (VAs) than men, but the physical burden associated with pregnancy on VA risk remains insufficiently studied. We aimed to assess the risk of VA in relation to pregnancies in women with ARVC.METHODS AND RESULTS: We included 199 females with definite ARVC (n = 121) and mutation-positive family members without ascertained ARVC diagnosis (n = 78), of whom 120 had at least one childbirth. Ventricular arrhythmia-free survival after the latest childbirth was compared between women with one (n = 20), two (n = 67), and three or more (n = 37) childbirths. Cumulative probability of VA for each pregnancy (n = 261) was assessed from conception through 2 years after childbirth and compared between those pregnancies that occurred before (n = 191) or after (n = 19) ARVC diagnosis and in mutation-positive family members (n = 51). The nulliparous women had lower median age at ARVC diagnosis (38 vs. 42 years, P < 0.001) and first VA (22 vs. 41 years, P < 0.001). Ventricular arrhythmia-free survival after the latest childbirth was not related to the number of pregnancies. No pregnancy-related VA was reported among the family members. Women who gave birth after ARVC diagnosis had elevated risk of VA postpartum (hazard ratio 13.74, 95% confidence interval 2.9-63, P = 0.001), though only two events occurred during pregnancies.CONCLUSION: In women with ARVC, pregnancy was uneventful for the overwhelming majority and the number of prior completed pregnancies was not associated with VA risk. Pregnancy-related VA was primarily related to the phenotypical severity rather than pregnancy itself.
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29.
  • Stockett, Mark H., et al. (författare)
  • Radiative cooling of carbon cluster anions C-2n+1(-) (n=3-5)
  • 2020
  • Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 74:7
  • Tidskriftsartikel (refereegranskat)abstract
    • Radiative cooling of carbon cluster anions C-2n+1(-)(n = 3-5) is investigated using the cryogenic electrostatic ion storage ring DESIREE. Two different strategies are applied to infer infrared emission on slow (milliseconds to seconds) and ultraslow (seconds to minutes) timescales. Initial cooling of the ions over the millisecond timescale is probed indirectly by monitoring the decay in the yield of spontaneous neutralization by thermionic emission. The observed cooling rates are consistent with a statistical model of thermionic electron emission in competition with infrared photon emission due to vibrational de-excitation. Slower cooling over the seconds to minutes timescale associated with infrared emission from low-frequency vibrational modes is probed using time-dependent action spectroscopy. For C(9)(-)and C-11(-), cooling is evidenced by the time-evolution of the yield of photo-induced neutralization following resonant excitation of electronic transitions near the detachment threshold. The cross-section for resonant photo-excitation is at least two orders of magnitude greater than for direct photodetachment. In contrast, C(7)(-)lacks electronic transitions near the detachment threshold.
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30.
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31.
  • Vigan, A., et al. (författare)
  • The SPHERE infrared survey for exoplanets (SHINE) : III. The demographics of young giant exoplanets below 300 au with SPHERE
  • 2021
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 651
  • Tidskriftsartikel (refereegranskat)abstract
    • The SpHere INfrared Exoplanet (SHINE) project is a 500-star survey performed with SPHERE on the Very Large Telescope for the purpose of directly detecting new substellar companions and understanding their formation and early evolution. Here we present an initial statistical analysis for a subsample of 150 stars spanning spectral types from B to M that are representative of the full SHINE sample. Our goal is to constrain the frequency of substellar companions with masses between 1 and 75 MJup and semimajor axes between 5 and 300 au. For this purpose, we adopt detection limits as a function of angular separation from the survey data for all stars converted into mass and projected orbital separation using the BEX-COND-hot evolutionary tracks and known distance to each system. Based on the results obtained for each star and on the 13 detections in the sample, we use a Markov chain Monte Carlo tool to compare our observations to two different types of models. The first is a parametric model based on observational constraints, and the second type are numerical models that combine advanced core accretion and gravitational instability planet population synthesis. Using the parametric model, we show that the frequencies of systems with at least one substellar companion are 23.0−9.7+13.5, 5.8−2.8+4.7, and 12.6−7.1+12.9% for BA, FGK, and M stars, respectively. We also demonstrate that a planet-like formation pathway probably dominates the mass range from 1–75 MJup for companions around BA stars, while for M dwarfs, brown dwarf binaries dominate detections. In contrast, a combination of binary star-like and planet-like formation is required to best fit the observations for FGK stars. Using our population model and restricting our sample to FGK stars, we derive a frequency of 5.7−2.8+3.8%, consistent with predictions from the parametric model. More generally, the frequency values that we derive are in excellent agreement with values obtained in previous studies.
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32.
  • Wang, Y., et al. (författare)
  • Cloud formation in the atomic and molecular phase: H I self absorption (HISA) towards a giant molecular filament
  • 2020
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 634
  • Tidskriftsartikel (refereegranskat)abstract
    • Molecular clouds form from the atomic phase of the interstellar medium. However, characterizing the transition between the atomic and the molecular interstellar medium (ISM) is a complex observational task. Here we address cloud formation processes by combining HI self absorption (HISA) with molecular line data. Column density probability density functions (N-PDFs) are a common tool for examining molecular clouds. One scenario proposed by numerical simulations is that the N-PDF evolves from a log-normal shape at early times to a power-law-like shape at later times. To date, investigations of N-PDFs have been mostly limited to the molecular component of the cloud. In this paper, we study the cold atomic component of the giant molecular filament GMF38.1-32.4a (GMF38a, distance = 3.4 kpc, length similar to 230 pc), calculate its N-PDFs, and study its kinematics. We identify an extended HISA feature, which is partly correlated with the (CO)-C-13 emission. The peak velocities of the HISA and (CO)-C-13 observations agree well on the eastern side of the filament, whereas a velocity offset of approximately 4 km s(-1) is found on the western side. The sonic Mach number we derive from the linewidth measurements shows that a large fraction of the HISA, which is ascribed to the cold neutral medium (CNM), is at subsonic and transonic velocities. The column density of the CNM part is on the order of 10(20) to 10(21) cm(-2). The column density of molecular hydrogen, traced by (CO)-C-13, is an order of magnitude higher. The N-PDFs from HISA (CNM), HI emission (the warm and cold neutral medium), and (CO)-C-13 (molecular component) are well described by log-normal functions, which is in agreement with turbulent motions being the main driver of cloud dynamics. The N-PDF of the molecular component also shows a power law in the high column-density region, indicating self-gravity. We suggest that we are witnessing two different evolutionary stages within the filament. The eastern subregion seems to be forming a molecular cloud out of the atomic gas, whereas the western subregion already shows high column density peaks, active star formation, and evidence of related feedback processes.
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33.
  • Zettergren, Henning, et al. (författare)
  • Roadmap on dynamics of molecules and clusters in the gas phase
  • 2021
  • Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 75:5
  • Tidskriftsartikel (refereegranskat)abstract
    • This roadmap article highlights recent advances, challenges and future prospects in studies of the dynamics of molecules and clusters in the gas phase. It comprises nineteen contributions by scientists with leading expertise in complementary experimental and theoretical techniques to probe the dynamics on timescales spanning twenty order of magnitudes, from attoseconds to minutes and beyond, and for systems ranging in complexity from the smallest (diatomic) molecules to clusters and nanoparticles. Combining some of these techniques opens up new avenues to unravel hitherto unexplored reaction pathways and mechanisms, and to establish their significance in, e.g. radiotherapy and radiation damage on the nanoscale, astrophysics, astrochemistry and atmospheric science.
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34.
  • Abou Ghayda, Ramy, et al. (författare)
  • The global case fatality rate of coronavirus disease 2019 by continents and national income: A meta-analysis
  • 2022
  • Ingår i: Journal of Medical Virology. - : WILEY. - 0146-6615 .- 1096-9071. ; 94:6, s. 2402-2413
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this study is to provide a more accurate representation of COVID-19s case fatality rate (CFR) by performing meta-analyses by continents and income, and by comparing the result with pooled estimates. We used multiple worldwide data sources on COVID-19 for every country reporting COVID-19 cases. On the basis of data, we performed random and fixed meta-analyses for CFR of COVID-19 by continents and income according to each individual calendar date. CFR was estimated based on the different geographical regions and levels of income using three models: pooled estimates, fixed- and random-model. In Asia, all three types of CFR initially remained approximately between 2.0% and 3.0%. In the case of pooled estimates and the fixed model results, CFR increased to 4.0%, by then gradually decreasing, while in the case of random-model, CFR remained under 2.0%. Similarly, in Europe, initially, the two types of CFR peaked at 9.0% and 10.0%, respectively. The random-model results showed an increase near 5.0%. In high-income countries, pooled estimates and fixed-model showed gradually increasing trends with a final pooled estimates and random-model reached about 8.0% and 4.0%, respectively. In middle-income, the pooled estimates and fixed-model have gradually increased reaching up to 4.5%. in low-income countries, CFRs remained similar between 1.5% and 3.0%. Our study emphasizes that COVID-19 CFR is not a fixed or static value. Rather, it is a dynamic estimate that changes with time, population, socioeconomic factors, and the mitigatory efforts of individual countries.
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35.
  • Alsufyani, Maryam, et al. (författare)
  • The effect of aromatic ring size in electron deficient semiconducting polymers for n-type organic thermoelectrics
  • 2020
  • Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 8:43, s. 15150-15157
  • Tidskriftsartikel (refereegranskat)abstract
    • N-type semiconducting polymers have been recently utilized in thermoelectric devices, however they have typically exhibited low electrical conductivities and poor device stability, in contrast to p-type semiconductors, which have been much higher performing. This is due in particular to the n-type semiconductors low doping efficiency, and poor charge carrier mobility. Strategies to enhance the thermoelectric performance of n-type materials include optimizing the electron affinity (EA) with respect to the dopant to improve the doping process and increasing the charge carrier mobility through enhanced molecular packing. Here, we report the design, synthesis and characterization of fused electron-deficient n-type copolymers incorporating the electron withdrawing lactone unit along the backbone. The polymers were synthesized using metal-free aldol condensation conditions to explore the effect of enlarging the central phenyl ring to a naphthalene ring, on the electrical conductivity. When n-doped with N-DMBI, electrical conductivities of up to 0.28 S cm(-1), Seebeck coefficients of -75 mu V K-1 and maximum Power factors of 0.16 mu W m(-1) K-2 were observed from the polymer with the largest electron affinity of -4.68 eV. Extending the aromatic ring reduced the electron affinity, due to reducing the density of electron withdrawing groups and subsequently the electrical conductivity reduced by almost two orders of magnitude.
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36.
  • Álvarez-Márquez, J., et al. (författare)
  • MIRI/JWST observations reveal an extremely obscured starburst in the z = 6.9 system SPT0311-58
  • 2023
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 671
  • Tidskriftsartikel (refereegranskat)abstract
    • Luminous infrared starbursts in the early Universe are thought to be the progenitors of massive quiescent galaxies identified at redshifts 2–4. Using the Mid-IRfrared Instrument (MIRI) on board the James Webb Space Telescope (JWST), we present mid-infrared sub-arcsec imaging and spectroscopy of such a starburst: the slightly lensed hyper-luminous infrared system SPT0311-58 at z = 6.9. The MIRI IMager (MIRIM) and Medium Resolution Spectrometer (MRS) observations target the stellar (rest-frame 1.26 μm emission) structure and ionised (Paα and Hα) medium on kpc scales in the system. The MIRI observations are compared with existing ALMA far-infrared continuum and [C II]158μm imaging at a similar angular resolution. Even though the ALMA observations imply very high star formation rates (SFRs) in the eastern (E) and western (W) galaxies of the system, the Hα line is, strikingly, not detected in our MRS observations. This fact, together with the detection of the ionised gas phase in Paα, implies very high internal nebular extinction with lower limits (AV) of 4.2 (E) and 3.9 mag (W) as well as even larger values (5.6 (E) and 10.0 (W)) by spectral energy distribution (SED) fitting analysis. The extinction-corrected Paα lower limits of the SFRs are 383 and 230 M⊙ yr−1 for the E and W galaxies, respectively. This represents 50% of the SFRs derived from the [C II]158 μm line and infrared light for the E galaxy and as low as 6% for the W galaxy. The MIRIM observations reveal a clumpy stellar structure, with each clump having 3–5×109 M⊙ mass in stars, leading to a total stellar mass of 2.0 and 1.5×1010 M⊙ for the E and W galaxies, respectively. The specific star formation (sSFR) in the stellar clumps ranges from 25 to 59 Gyr−1, assuming a star formation with a 50–100 Myr constant rate. This sSFR is three to ten times larger than the values measured in galaxies of similar stellar mass at redshifts 6–8. Thus, SPT0311-58 clearly stands out as a starburst system when compared with typical massive star-forming galaxies at similar high redshifts. The overall gas mass fraction is Mgas/M∗ ∼ 3, similar to that of z ∼ 4.5–6 star-forming galaxies, suggesting a flattening of the gas mass fraction in massive starbursts up to redshift 7. The kinematics of the ionised gas in the E galaxy agrees with the known [C II] gas kinematics, indicating a physical association between the ionised gas and the cold ionised or neutral gas clumps. The situation in the W galaxy is more complex, as it appears to be a velocity offset by about +700 km s−1 in the Paα relative to the [C II] emitting gas. The nature of this offset and its reality are not fully established and require further investigation. The observed properties of SPT0311-58, such as the clumpy distribution at sub(kpc) scales and the very high average extinction, are similar to those observed in low- and intermediate-z luminous (E galaxy) and ultra-luminous (W galaxy) infrared galaxies, even though SPT0311-58 is observed only ∼800 Myr after the Big Bang. Such massive, heavily obscured clumpy starburst systems as SPT0311-58 likely represent the early phases in the formation of a massive high-redshift bulge, spheroids and/or luminous quasars. This study demonstrates that MIRI and JWST are, for the first time, able to explore the rest-frame near-infrared stellar and ionised gas structure of these galaxies, even during the Epoch of Reionization.
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37.
  • Baturova, Maria A., et al. (författare)
  • Atrial fibrillation as a clinical characteristic of arrhythmogenic right ventricular cardiomyopathy : Experience from the Nordic ARVC Registry
  • 2020
  • Ingår i: International Journal of Cardiology. - : Elsevier BV. - 0167-5273 .- 1874-1754. ; 298, s. 39-43
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Recent studies in arrhythmogenic right ventricular cardiomyopathy (ARVC) patients have drawn attention to atrial fibrillation (AF) as an arrhythmic manifestation of ARVC and as an indicator of atrial involvement in the disease progression. We aimed to assess the prevalence of AF in the Scandinavian cohort of ARVC patients and to evaluate its association with disease clinical manifestations. Methods: Study sample comprised of 293 definite ARVC patients by 2010 Task Force criteria (TFC2010) and 141 genotype-positive family members (total n = 434, 43% females, median age at ARVC diagnosis 41 years [interquartile range (IQR) 28–52 years]). ARVC diagnostic score was calculated as the sum of major (2 points) and minor (1 point) criteria in all categories of the TFC2010. Results: AF was diagnosed in 42 patients (10%): in 41 patients with definite ARVC diagnosis (14%) vs in one genotype-positive family member (1%), p < 0.001. The median age at AF onset was 51 (IQR 38–58) years. The prevalence of AF was related to the ARVC diagnostic score: it significantly increased starting with the diagnostic score 4 (2% in those with score 3 vs 13% in those with score 4, p = 0.023) and increased further with increased diagnostic score (Somer's d value is 0.074, p < 0.001). Conclusion: AF is seen in 14% of definite ARVC patients and is related to the severity of disease phenotype thus suggesting AF being an arrhythmic manifestation of this cardiomyopathy indicating atrial myocardial involvement in the disease progression.
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38.
  • Beuther, H., et al. (författare)
  • JWST Observations of Young protoStars (JOYS): Outflows and accretion in the high-mass star-forming region IRAS 23385+6053
  • 2023
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 673
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. Understanding the earliest stages of star formation, and setting it in the context of the general cycle of matter in the interstellar medium, is a central aspect of research with the James Webb Space Telescope (JWST). Aims. The JWST program JOYS (JWST Observations of Young protoStars) aims to characterize the physical and chemical properties of young high- and low-mass star-forming regions, in particular the unique mid-infrared diagnostics of the warmer gas and solid-state components. We present early results from the high-mass star formation region IRAS 23385+6053. Methods. The JOYS program uses the Mid-Infrared Instrument (MIRI) Medium Resolution Spectrometer (MRS) with its integral field unit (IFU) to investigate a sample of high- and low-mass star-forming protostellar systems. Results. The full 5-? 28 μm MIRI MRS spectrum of IRAS 23385+6053 shows a plethora of interesting features. While the general spectrum is typical for an embedded protostar, we see many atomic and molecular gas lines boosted by the higher spectral resolution and sensitivity compared to previous space missions. Furthermore, ice and dust absorption features are also present. Here, we focus on the continuum emission, outflow tracers such as the H2(0-? 0)S(7), [FeII](4F9/2-6D9/2), and [NeII](2P1/2-2P3/2) lines, and the potential accretion tracer Humphreys α H I(7-6). The short-wavelength MIRI data resolve two continuum sources, A and B; mid-infrared source A is associated with the main millimeter continuum peak. The combination of mid-infrared and millimeter data reveals a young cluster in the making. Combining the mid-infrared outflow tracers H2, [FeII], and [NeII] with millimeter SiO data reveals a complex interplay of at least three molecular outflows driven by protostars in the forming cluster. Furthermore, the Humphreys α line is detected at a 3-?4σ? level toward the mid-infrared sources A and B. One can roughly estimate both accretion luminosities and corresponding accretion rates to be between ∼2.6 × 10-6 and ∼0.9 × 10-4 Mo yr-1. This is discussed in the context of the observed outflow rates. Conclusions. The analysis of the MIRI MRS observations for this young high-mass star-forming region reveals connected outflow and accretion signatures, as well as the enormous potential of JWST to boost our understanding of the physical and chemical processes at play during star formation.
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39.
  • Bluhm, P., et al. (författare)
  • Precise mass and radius of a transiting super-Earth planet orbiting the M dwarf TOI-1235: a planet in the radius gap?
  • 2020
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 639
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the confirmation of a transiting planet around the bright weakly active M0.5 V star TOI-1235 (TYC 4384-1735-1, V ≈ 11.5 mag), whose transit signal was detected in the photometric time series of sectors 14, 20, and 21 of the TESS space mission. We confirm the planetary nature of the transit signal, which has a period of 3.44 d, by using precise RV measurements with the CARMENES, HARPS-N, and iSHELL spectrographs, supplemented by high-resolution imaging and ground-based photometry. A comparison of the properties derived for TOI-1235 b with theoretical models reveals that the planet has a rocky composition, with a bulk density slightly higher than that of Earth. In particular, we measure a mass of Mp = 5.9 ± 0.6 M⊕ and a radius of Rp = 1.69 ± 0.08 R⊕, which together result in a density of ρp = 6.7- 1.1+ 1.3 g cm-3. When compared with other well-characterized exoplanetary systems, the particular combination of planetary radius and mass places our discovery in the radius gap, which is a transition region between rocky planets and planets with significant atmospheric envelopes. A few examples of planets occupying the radius gap are known to date. While the exact location of the radius gap for M dwarfs is still a matter of debate, our results constrain it to be located at around 1.7 R⊕ or larger at the insolation levels received by TOI-1235 b (~60 S⊕). This makes it an extremely interesting object for further studies of planet formation and atmospheric evolution.
  •  
40.
  • Breznau, Nate, et al. (författare)
  • Observing many researchers using the same data and hypothesis reveals a hidden universe of uncertainty
  • 2022
  • Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 119:44
  • Tidskriftsartikel (refereegranskat)abstract
    • This study explores how researchers analytical choices affect the reliability of scientific findings. Most discussions of reliability problems in science focus on systematic biases. We broaden the lens to emphasize the idiosyncrasy of conscious and unconscious decisions that researchers make during data analysis. We coordinated 161 researchers in 73 research teams and observed their research decisions as they used the same data to independently test the same prominent social science hypothesis: that greater immigration reduces support for social policies among the public. In this typical case of social science research, research teams reported both widely diverging numerical findings and substantive conclusions despite identical start conditions. Researchers expertise, prior beliefs, and expectations barely predict the wide variation in research outcomes. More than 95% of the total variance in numerical results remains unexplained even after qualitative coding of all identifiable decisions in each teams workflow. This reveals a universe of uncertainty that remains hidden when considering a single study in isolation. The idiosyncratic nature of how researchers results and conclusions varied is a previously underappreciated explanation for why many scientific hypotheses remain contested. These results call for greater epistemic humility and clarity in reporting scientific findings.
  •  
41.
  • Bull, James N., et al. (författare)
  • Autoionization from the plasmon resonance in isolated 1-cyanonaphthalene 
  • 2023
  • Ingår i: Journal of Chemical Physics. - 0021-9606 .- 1089-7690. ; 158:24
  • Tidskriftsartikel (refereegranskat)abstract
    • Polycyclic aromatic hydrocarbons have widely been conjectured to be ubiquitous in space, as supported by the recent discovery of two isomers of cyanonaphthalene, indene, and 2-cyanoindene in the Taurus molecular cloud-1 using radioastronomy. Here, the photoionization dynamics of 1-cyanonaphthalene (1-CNN) are investigated using synchrotron radiation over the hν = 9.0–19.5 eV range, revealing that prompt autoionization from the plasmon resonance dominates the photophysics for hν = 11.5–16.0 eV. Minimal photo-induced dissociation, whether originating from an excited state impulsive bond rupture or through internal conversion followed by a statistical bond cleavage process, occurs over the microsecond timescale (as limited by the experimental setup). The direct photoionization cross section and photoelectron angular distributions are simulated using an ezDyson model combining Dyson orbitals with Coulomb wave photoejection. When considering these data in conjunction with recent radiative cooling measurements on 1-CNN+, which showed that cations formed with up to 5 eV of internal energy efficiently stabilize through recurrent fluorescence, we conclude that the organic backbone of 1-CNN is resilient to photodestruction by VUV and soft XUV radiation. These dynamics may prove to be a common feature for the survival of small polycyclic aromatic hydrocarbons in space, provided that the cations have a suitable electronic structure to support recurrent fluorescence.  
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42.
  • Chen, H.Y., et al. (författare)
  • Dyslipidemia, inflammation, calcification, and adiposity in aortic stenosis: a genome-wide study
  • 2023
  • Ingår i: European Heart Journal. - : Oxford University Press. - 0195-668X .- 1522-9645. ; 44:21, s. 1927-1939
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims Although highly heritable, the genetic etiology of calcific aortic stenosis (AS) remains incompletely understood. The aim of this study was to discover novel genetic contributors to AS and to integrate functional, expression, and cross-phenotype data to identify mechanisms of AS. Methods and results A genome-wide meta-analysis of 11.6 million variants in 10 cohorts involving 653 867 European ancestry participants (13 765 cases) was performed. Seventeen loci were associated with AS at P ≤ 5 × 10−8, of which 15 replicated in an independent cohort of 90 828 participants (7111 cases), including CELSR2–SORT1, NLRP6, and SMC2. A genetic risk score comprised of the index variants was associated with AS [odds ratio (OR) per standard deviation, 1.31; 95% confidence interval (CI), 1.26–1.35; P = 2.7 × 10−51] and aortic valve calcium (OR per standard deviation, 1.22; 95% CI, 1.08–1.37; P = 1.4 × 10−3), after adjustment for known risk factors. A phenome-wide association study indicated multiple associations with coronary artery disease, apolipoprotein B, and triglycerides. Mendelian randomization supported a causal role for apolipoprotein B-containing lipoprotein particles in AS (OR per g/L of apolipoprotein B, 3.85; 95% CI, 2.90–5.12; P = 2.1 × 10−20) and replicated previous findings of causality for lipoprotein(a) (OR per natural logarithm, 1.20; 95% CI, 1.17–1.23; P = 4.8 × 10−73) and body mass index (OR per kg/m2, 1.07; 95% CI, 1.05–1.9; P = 1.9 × 10−12). Colocalization analyses using the GTEx database identified a role for differential expression of the genes LPA, SORT1, ACTR2, NOTCH4, IL6R, and FADS. Conclusion Dyslipidemia, inflammation, calcification, and adiposity play important roles in the etiology of AS, implicating novel treatments and prevention strategies. © The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.
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43.
  • Christensen, Alex Hørby, et al. (författare)
  • Complications of implantable cardioverter-defibrillator treatment in arrhythmogenic right ventricular cardiomyopathy
  • 2022
  • Ingår i: Europace. - : Oxford University Press (OUP). - 1099-5129 .- 1532-2092. ; 24:2, s. 306-312
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims: Treatment with implantable cardioverter-defibrillators (ICD) is a cornerstone for prevention of sudden cardiac death in arrhythmogenic right ventricular cardiomyopathy (ARVC). We aimed at describing the complications associated with ICD treatment in a multinational cohort with long-term follow-up. Methods and results: The Nordic ARVC registry was established in 2010 and encompasses a large multinational cohort of ARVC patients, including their clinical characteristics, treatment, and events during follow-up. We included 299 patients (66% males, median age 41 years). During a median follow-up of 10.6 years, 124 (41%) patients experienced appropriate ICD shock therapy, 28 (9%) experienced inappropriate shocks, 82 (27%) had a complication requiring surgery (mainly lead-related, n = 75), and 99 (33%) patients experienced the combined endpoint of either an inappropriate shock or a surgical complication. The crude rate of first inappropriate shock was 3.4% during the first year after implantation but decreased after the first year and plateaued over time. Contrary, the risk of a complication requiring surgery was 5.5% the first year and remained high throughout the study period. The combined risk of any complication was 7.9% the first year. In multivariate cox regression, presence of atrial fibrillation/flutter was a risk factor for inappropriate shock (P < 0.05), whereas sex, age at implant, and device type were not (all P > 0.05). Conclusion: Forty-one percent of ARVC patients treated with ICD experienced potentially life-saving ICD therapy during long-term follow-up. A third of the patients experienced a complication during follow-up with lead-related complications constituting the vast majority.
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44.
  • Christensen, Diana Hedevang, et al. (författare)
  • Type 2 diabetes classification : a data-driven cluster study of the Danish Centre for Strategic Research in Type 2 Diabetes (DD2) cohort
  • 2022
  • Ingår i: BMJ Open Diabetes Research and Care. - : BMJ. - 2052-4897. ; 10:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Introduction A Swedish data-driven cluster study identified four distinct type 2 diabetes (T2D) clusters, based on age at diagnosis, body mass index (BMI), hemoglobin A1c (HbA1c) level, and homeostatic model assessment 2 (HOMA2) estimates of insulin resistance and beta-cell function. A Danish study proposed three T2D phenotypes (insulinopenic, hyperinsulinemic, and classical) based on HOMA2 measures only. We examined these two new T2D classifications using the Danish Centre for Strategic Research in Type 2 Diabetes cohort. Research design and methods In 3529 individuals, we first performed a k-means cluster analysis with a forced k-value of four to replicate the Swedish clusters: severe insulin deficient (SIDD), severe insulin resistant (SIRD), mild age-related (MARD), and mild obesity-related (MOD) diabetes. Next, we did an analysis open to alternative k-values (ie, data determined the optimal number of clusters). Finally, we compared the data-driven clusters with the three Danish phenotypes. Results Compared with the Swedish findings, the replicated Danish SIDD cluster included patients with lower mean HbA1c (86 mmol/mol vs 101 mmol/mol), and the Danish MOD cluster patients were less obese (mean BMI 32 kg/m 2 vs 36 kg/m 2). Our data-driven alternative k-value analysis suggested the optimal number of T2D clusters in our data to be three, rather than four. When comparing the four replicated Swedish clusters with the three proposed Danish phenotypes, 81%, 79%, and 69% of the SIDD, MOD, and MARD patients, respectively, fitted the classical T2D phenotype, whereas 70% of SIRD patients fitted the hyperinsulinemic phenotype. Among the three alternative data-driven clusters, 60% of patients in the most insulin-resistant cluster constituted 76% of patients with a hyperinsulinemic phenotype. Conclusion Different HOMA2-based approaches did not classify patients with T2D in a consistent manner. The T2D classes characterized by high insulin resistance/hyperinsulinemia appeared most distinct.
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45.
  • Colina, L., et al. (författare)
  • Uncovering the stellar structure of the dusty star-forming galaxy GN20 at z=4.055 with MIRI/JWST
  • 2023
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 673
  • Tidskriftsartikel (refereegranskat)abstract
    • Luminous infrared galaxies at high redshifts (z > 4) include extreme starbursts that build their stellar mass over short periods of time, that is, of 100 Myr or less. These galaxies are considered to be the progenitors of massive quiescent galaxies at intermediate redshifts (z similar to 2) but their stellar structure and buildup is unknown. Here, we present the first spatially resolved near-infrared (rest-frame 1.1 mu m) imaging of GN20, one of the most luminous dusty star-forming galaxies known to date, observed at an epoch when the Universe was only 1.5 Gyr old. The 5.6 mu m image taken with the JWST Mid-Infrared Instrument (MIRI/JWST) shows that GN20 is a very luminous galaxy (M-1.1 mu m,M- AB = 25.01, uncorrected for internal extinction), with a stellar structure composed of a conspicuous central source and an extended envelope. The central source is an unresolved nucleus that carries 9% of the total flux. The nucleus is co-aligned with the peak of the cold dust emission, and offset by 3.9 kpc from the ultraviolet stellar emission. The diffuse stellar envelope is similar in size (3.6 kpc effective radius) to the clumpy CO molecular gas distribution. The centroid of the stellar envelope is offset by 1 kpc from the unresolved nucleus, suggesting GN20 is involved in an interaction or merger event supported by its location as the brightest galaxy in a proto-cluster. Additional faint stellar clumps appear to be associated with some of the UV- and CO-clumps. The stellar size of GN20 is larger by a factor of about 3 to 5 than known spheroids, disks, and irregulars at z similar to 4, while its size and low Sersic index are similar to those measured in dusty, infrared luminous galaxies at redshift 2 of the same mass (similar to 10(11) M-circle dot). GN20 has all the ingredients necessary for evolving into a massive spheroidal quiescent galaxy at intermediate redshift: it is a large, luminous galaxy at z = 4.05 involved in a short and massive starburst centred in the stellar nucleus and extended over the entire galaxy, out to radii of 4 kpc, and likely induced by the interaction or merger with a member of the proto-cluster.
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46.
  • Desidera, S., et al. (författare)
  • The SPHERE infrared survey for exoplanets (SHINE) I. Sample definition and target characterization
  • 2021
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 651
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. Large surveys with new-generation high-contrast imaging instruments are needed to derive the frequency and properties of exoplanet populations with separations from ~5 to 300 au. A careful assessment of the stellar properties is crucial for a proper understanding of when, where, and how frequently planets form, and how they evolve. The sensitivity of detection limits to stellar age makes this a key parameter for direct imaging surveys.Aims. We describe the SpHere INfrared survey for Exoplanets (SHINE), the largest direct imaging planet-search campaign initiated at the VLT in 2015 in the context of the SPHERE Guaranteed Time Observations of the SPHERE consortium. In this first paper we present the selection and the properties of the complete sample of stars surveyed with SHINE, focusing on the targets observed during the first phase of the survey (from February 2015 to February 2017). This early sample composed of 150 stars is used to perform a preliminary statistical analysis of the SHINE data, deferred to two companion papers presenting the survey performance, main discoveries, and the preliminary statistical constraints set by SHINE.Methods. Based on a large database collecting the stellar properties of all young nearby stars in the solar vicinity (including kinematics, membership to moving groups, isochrones, lithium abundance, rotation, and activity), we selected the original sample of 800 stars that were ranked in order of priority according to their sensitivity for planet detection in direct imaging with SPHERE. The properties of the stars that are part of the early statistical sample wererevisited, including for instance measurements from the Gaia Data Release 2. Rotation periods were derived for the vast majority of the late-type objects exploiting TESS light curves and dedicated photometric observations.Results. The properties of individual targets and of the sample as a whole are presented.
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47.
  •  
48.
  • Duffy, J. Emmett, et al. (författare)
  • A Pleistocene legacy structures variation in modern seagrass ecosystems
  • 2022
  • Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 119:32
  • Tidskriftsartikel (refereegranskat)abstract
    • Distribution of Earth's biomes is structured by the match between climate and plant traits, which in turn shape associated communities and ecosystem processes and services. However, that climate-trait match can be disrupted by historical events, with lasting ecosystem impacts. As Earth's environment changes faster than at any time in human history, critical questions are whether and how organismal traits and ecosystems can adjust to altered conditions. We quantified the relative importance of current environmental forcing versus evolutionary history in shaping the growth form (stature and biomass) and associated community of eelgrass (Zostera marina), a widespread foundation plant of marine ecosystems along Northern Hemisphere coastlines, which experienced major shifts in distribution and genetic composition during the Pleistocene. We found that eelgrass stature and biomass retain a legacy of the Pleistocene colonization of the Atlantic from the ancestral Pacific range and of more recent within-basin bottlenecks and genetic differentiation. This evolutionary legacy in turn influences the biomass of associated algae and invertebrates that fuel coastal food webs, with effects comparable to or stronger than effects of current environmental forcing. Such historical lags in phenotypic acclimatization may constrain ecosystem adjustments to rapid anthropogenic climate change, thus altering predictions about the future functioning of ecosystems. 
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49.
  • Francis, L., et al. (författare)
  • JOYS: MIRI/MRS spectroscopy of gas-phase molecules from the high-mass star-forming region IRAS 23385+6053
  • 2024
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 683
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. Space-based mid-infrared (IR) spectroscopy is a powerful tool for the characterization of important star formation tracers of warm gas which are unobservable from the ground. The previous mid-IR spectra of bright high-mass protostars with the Infrared Space Observatory (ISO) in the hot-core phase typically show strong absorption features from molecules such as CO2, C2H2, and HCN. However, little is known about their fainter counterparts at earlier stages. Aims. We aim to characterize the gas-phase molecular features in James Webb Space Telescope Mid-Infrared Instrument Medium Resolution Spectrometer (MIRI/MRS) spectra of the young and clustered high-mass star-forming region IRAS 23385+6053. Methods. Spectra were extracted from several locations in the MIRI/MRS field of view, targeting two mid-IR sources tracing embedded massive protostars as well as three H2 bright outflow knots at distances of >8000 au from the multiple. Molecular features in the spectra were fit with local thermodynamic equilibrium (LTE) slab models, with their caveats discussed in detail. Results. Rich molecular spectra with emission from CO, H2, HD, H2O, C2H2, HCN, CO2, and OH are detected towards the two mid-IR sources. However, only CO and OH are seen towards the brightest H2 knot positions, suggesting that the majority of the observed species are associated with disks or hot core regions rather than outflows or shocks. The LTE model fits to 12CO2, C2H2, HCN emission suggest warm 120a-200 K emission arising from a disk surface around one or both protostars. The abundances of CO2 and C2H2 of ~10âà  à  7 are consistent with previous observations of high-mass protostars. Weak ~500 K H2O emission at ~6a-7 μm is detected towards one mid-IR source, whereas 250a-1050 K H2O absorption is found in the other. The H2O absorption may occur in the disk atmosphere due to strong accretion-heating of the midplane, or in a disk wind viewed at an ideal angle for absorption. CO emission may originate in the hot inner disk or outflow shocks, but NIRSpec data covering the 4.6 μm band head are required to determine the physical conditions of the CO gas, as the high temperatures seen in the MIRI data may be due to optical depth. OH emission is detected towards both mid-IR source positions and one of the shocks, and is likely excited by water photodissociation or chemical formation pumping in a highly non-LTE manner. Conclusions. The observed molecular spectra are consistent with disks having already formed around two protostars in the young IRAS 23385+6054 system. Molecular features mostly appear in emission from a variety of species, in contrast to the more evolved hot core phase protostars which typically show only absorption; however, further observations of young high-mass protostars are needed to disentangle geometry and viewing angle effects from evolution.
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50.
  • Garatti, A. Caratti o., et al. (författare)
  • The GRAVITY young stellar object survey: II. First spatially resolved observations of the CO bandhead emission in a high-mass YSO
  • 2020
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 635
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. The inner regions of the discs of high-mass young stellar objects (HMYSOs) are still poorly known due to the small angular scales and the high visual extinction involved. Aims. We deploy near-infrared spectro-interferometry to probe the inner gaseous disc in HMYSOs and investigate the origin and physical characteristics of the CO bandhead emission (2.3-2.4 m). Methods. We present the first GRAVITY/VLTI observations at high spectral (R = 4000) and spatial (mas) resolution of the CO overtone transitions in NGC2024 IRS 2. Results. The continuum emission is resolved in all baselines and is slightly asymmetric, displaying small closure phases (8). Our best ellipsoid model provides a disc inclination of 34 1, a disc major axis position angle (PA) of 166 1, and a disc diameter of 3:99 0:09 mas (or 1.69 0.04 au, at a distance of 423 pc). The small closure phase signals in the continuum are modelled with a skewed rim, originating from a pure inclination effect. For the first time, our observations spatially and spectrally resolve the first four CO bandheads. Changes in visibility, as well as differential and closure phases across the bandheads are detected. Both the size and geometry of the CO-emitting region are determined by fitting a bidimensional Gaussian to the continuum-compensated CO bandhead visibilities. The CO-emitting region has a diameter of 2.740:08 0:07 mas (1.16 0.03 au), and is located in the inner gaseous disc, well within the dusty rim, with inclination and PA matching the dusty disc geometry, which indicates that both dusty and gaseous discs are coplanar. Physical and dynamical gas conditions are inferred by modelling the CO spectrum. Finally, we derive a direct measurement of the stellar mass of M 14:7 M by combining our interferometric and spectral modelling results.
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