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Sökning: WFRF:(Henning O.)

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1.
  • Kanai, M, et al. (författare)
  • 2023
  • swepub:Mat__t
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2.
  • Bouchet, P., et al. (författare)
  • JWST MIRI Imager Observations of Supernova SN 1987A
  • 2024
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 965:1
  • Tidskriftsartikel (refereegranskat)abstract
    • There exist very few mid-infrared (IR) observations of supernovae (SNe) in general. Therefore, SN 1987A, the closest visible SN in 400 yr, gives us the opportunity to explore the mid-IR properties of SNe, the dust in their ejecta, and the surrounding medium and to witness the birth of an SN remnant (SNR). The James Webb Space Telescope, with its high spatial resolution and extreme sensitivity, gives a new view on these issues. We report on the first imaging observations obtained with the Mid-InfraRed Instrument (MIRI). We build temperature maps and discuss the morphology of the nascent SNR. Our results show that the temperatures in the equatorial ring (ER) are quite nonuniform. This could be due to dust destruction in some parts of the ring, as had been assumed in some previous works. We show that the IR emission extends beyond the ER, illustrating the fact that the shock wave has now passed through this ring to affect the circumstellar medium on a larger scale. Finally, while submillimeter Atacama Large Millimeter Array observations have hinted at the location of the compact remnant of SN 1987A, we note that our MIRI data have found no such evidence.
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3.
  • Fransson, Claes, 1951-, et al. (författare)
  • Emission lines due to ionizing radiation from a compact object in the remnant of Supernova 1987A
  • 2024
  • Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 383:6685, s. 898-903
  • Tidskriftsartikel (refereegranskat)abstract
    • The nearby Supernova 1987A was accompanied by a burst of neutrino emission, which indicates that a compact object (a neutron star or black hole) was formed in the explosion. There has been no direct observation of this compact object. In this work, we observe the supernova remnant with JWST spectroscopy, finding narrow infrared emission lines of argon and sulfur. The line emission is spatially unresolved and blueshifted in velocity relative to the supernova rest frame. We interpret the lines as gas illuminated by a source of ionizing photons located close to the center of the expanding ejecta. Photoionization models show that the line ratios are consistent with ionization by a cooling neutron star or a pulsar wind nebula. The velocity shift could be evidence for a neutron star natal kick.
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4.
  • Jones, O. C., et al. (författare)
  • Ejecta, Rings, and Dust in SN 1987A with JWST MIRI/MRS
  • 2023
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 958:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Supernova (SN) 1987A is the nearest supernova in ∼400 yr. Using the JWST MIRI Medium Resolution Spectrograph, we spatially resolved the ejecta, equatorial ring (ER), and outer rings in the mid-infrared 12,927 days (35.4 yr) after the explosion. The spectra are rich in line and dust continuum emission, both in the ejecta and the ring. The broad emission lines (280–380 km s−1 FWHM) that are seen from all singly-ionized species originate from the expanding ER, with properties consistent with dense post-shock cooling gas. Narrower emission lines (100–170 km s−1 FWHM) are seen from species originating from a more extended lower-density component whose high ionization may have been produced by shocks progressing through the ER or by the UV radiation pulse associated with the original supernova event. The asymmetric east–west dust emission in the ER has continued to fade, with constant temperature, signifying a reduction in dust mass. Small grains in the ER are preferentially destroyed, with larger grains from the progenitor surviving the transition from SN into SNR. The ER dust is fit with a single set of optical constants, eliminating the need for a secondary featureless hot dust component. We find several broad ejecta emission lines from [Ne ii], [Ar ii], [Fe ii], and [Ni ii]. With the exception of [Fe ii] 25.99 μm, these all originate from the ejecta close to the ring and are likely to be excited by X-rays from the interaction. The [Fe ii] 5.34 to 25.99 μm line ratio indicates a temperature of only a few hundred K in the inner core, which is consistent with being powered by 44 Ti decay.
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5.
  • 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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6.
  • 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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7.
  • Garcia-Lopez, R., et al. (författare)
  • A measure of the size of the magnetospheric accretion region in TW Hydrae
  • 2020
  • Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 584:7822, s. 547-550
  • Tidskriftsartikel (refereegranskat)abstract
    • Stars form by accreting material from their surrounding disks. There is a consensus that matter flowing through the disk is channelled onto the stellar surface by the stellar magnetic field. This is thought to be strong enough to truncate the disk close to the corotation radius, at which the disk rotates at the same rate as the star. Spectro-interferometric studies in young stellar objects show that hydrogen emission (a well known tracer of accretion activity) mostly comes from a region a few milliarcseconds across, usually located within the dust sublimation radius1–3. The origin of the hydrogen emission could be the stellar magnetosphere, a rotating wind or a disk. In the case of intermediate-mass Herbig AeBe stars, the fact that Brackett γ (Brγ) emission is spatially resolved rules out the possibility that most of the emission comes from the magnetosphere4–6 because the weak magnetic fields (some tenths of a gauss) detected in these sources7,8 result in very compact magnetospheres. In the case of T Tauri sources, their larger magnetospheres should make them easier to resolve. The small angular size of the magnetosphere (a few tenths of a milliarcsecond), however, along with the presence of winds9,10 make the interpretation of the observations challenging. Here we report optical long-baseline interferometric observations that spatially resolve the inner disk of the T Tauri star TW Hydrae. We find that the near-infrared hydrogen emission comes from a region approximately 3.5 stellar radii across. This region is within the continuum dusty disk emitting region (7 stellar radii across) and also within the corotation radius, which is twice as big. This indicates that the hydrogen emission originates in the accretion columns (funnel flows of matter accreting onto the star), as expected in magnetospheric accretion models, rather than in a wind emitted at much larger distance (more than one astronomical unit).
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8.
  • Grant, Sierra L., et al. (författare)
  • MINDS. The Detection of 13 CO 2 with JWST-MIRI Indicates Abundant CO 2 in a Protoplanetary Disk
  • 2023
  • Ingår i: Astrophysical Journal Letters. - 2041-8213 .- 2041-8205. ; 947:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We present JWST-MIRI Medium Resolution Spectrometer (MRS) spectra of the protoplanetary disk around the low-mass T Tauri star GW Lup from the MIRI mid-INfrared Disk Survey Guaranteed Time Observations program. Emission from 12CO213CO2, H2O, HCN, C2H2, and OH is identified with 13CO2 being detected for the first time in a protoplanetary disk. We characterize the chemical and physical conditions in the inner few astronomical units of the GW Lup disk using these molecules as probes. The spectral resolution of JWST-MIRI MRS paired with high signal-to-noise data is essential to identify these species and determine their column densities and temperatures. The Q branches of these molecules, including those of hot bands, are particularly sensitive to temperature and column density. We find that the 12CO2 emission in the GW Lup disk is coming from optically thick emission at a temperature of ∼400 K. 13CO2 is optically thinner and based on a lower temperature of ∼325 K, and thus may be tracing deeper into the disk and/or a larger emitting radius than 12CO2. The derived N CO 2 / N H 2 O ratio is orders of magnitude higher than previously derived for GW Lup and other targets based on Spitzer-InfraRed-Spectrograph data. This high column density ratio may be due to an inner cavity with a radius in between the H2O and CO2 snowlines and/or an overall lower disk temperature. This paper demonstrates the unique ability of JWST to probe inner disk structures and chemistry through weak, previously unseen molecular features.
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9.
  • Koutoulaki, M., et al. (författare)
  • The GRAVITY young stellar object survey: IV. The CO overtone emission in 51 Oph at sub-au scales
  • 2021
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 645
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. 51 Oph is a Herbig Ae/Be star that exhibits strong near-infrared CO ro-vibrational emission at 2.3 μm, most likely originating in the innermost regions of a circumstellar disc. Aims. We aim to obtain the physical and geometrical properties of the system by spatially resolving the circumstellar environment of the inner gaseous disc. Methods. We used the second-generation Very Large Telescope Interferometer instrument GRAVITY to spatially resolve the continuum and the CO overtone emission. We obtained data over 12 baselines with the auxiliary telescopes and derive visibilities, and the differential and closure phases as a function of wavelength. We used a simple local thermal equilibrium ring model of the CO emission to reproduce the spectrum and CO line displacements. Results. Our interferometric data show that the star is marginally resolved at our spatial resolution, with a radius of ∼10.58 ± 2.65R·. The K-band continuum emission from the disc is inclined by 63° ± 1°, with a position angle of 116° ± 1°, and 4 ± 0.8 mas (0.5 ± 0.1 au) across. The visibilities increase within the CO line emission, indicating that the CO is emitted within the dust-sublimation radius. By modelling the CO bandhead spectrum, we derive that the CO is emitted from a hot (T = 1900-2800 K) and dense (NCO = (0.9-9) × 1021 cm-2) gas. The analysis of the CO line displacement with respect to the continuum allows us to infer that the CO is emitted from a region 0.10 ± 0.02 au across, well within the dust-sublimation radius. The inclination and position angle of the CO line emitting region is consistent with that of the dusty disc. Conclusions. Our spatially resolved interferometric observations confirm the CO ro-vibrational emission within the dust-free region of the inner disc. Conventional disc models exclude the presence of CO in the dust-depleted regions of Herbig AeBe stars. Ad hoc models of the innermost disc regions, that can compute the properties of the dust-free inner disc, are therefore required.
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10.
  • Lagrange, A. M., et al. (författare)
  • Unveiling the beta Pictoris system, coupling high contrast imaging, interferometric, and radial velocity data
  • 2020
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 642
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. The nearby and young beta Pictoris system hosts a well resolved disk, a directly imaged massive giant planet orbiting at similar or equal to 9 au, as well as an inner planet orbiting at similar or equal to 2.7 au, which was recently detected through radial velocity (RV). As such, it offers several unique opportunities for detailed studies of planetary system formation and early evolution.Aims. We aim to further constrain the orbital and physical properties of beta Pictoris b and c using a combination of high contrast imaging, long base-line interferometry, and RV data. We also predict the closest approaches or the transit times of both planets, and we constrain the presence of additional planets in the system.Methods. We obtained six additional epochs of SPHERE data, six additional epochs of GRAVITY data, and five additional epochs of RV data. We combined these various types of data in a single Markov-chain Monte Carlo analysis to constrain the orbital parameters and masses of the two planets simultaneously. The analysis takes into account the gravitational influence of both planets on the star and hence their relative astrometry. Secondly, we used the RV and high contrast imaging data to derive the probabilities of presence of additional planets throughout the disk, and we tested the impact of absolute astrometry.Results. The orbital properties of both planets are constrained with a semi-major axis of 9.8 0.4 au and 2.7 +/- 0.02 au for b and c, respectively, and eccentricities of 0.09 +/- 0.1 and 0.27 +/- 0.07, assuming the HIPPARCOS distance. We note that despite these low fitting error bars, the eccentricity of beta Pictoris c might still be over-estimated. If no prior is provided on the mass of beta Pictoris b, we obtain a very low value that is inconsistent with what is derived from brightness-mass models. When we set an evolutionary model motivated prior to the mass of beta Pictoris b, we find a solution in the 10-11 M-Jup range. Conversely, beta Pictoris c's mass is well constrained, at 7.8 +/- 0.4 M-Jup, assuming both planets are on coplanar orbits. These values depend on the assumptions on the distance of the beta Pictoris system. The absolute astrometry HIPPARCOS-Gaia data are consistent with the solutions presented here at the 2 sigma level, but these solutions are fully driven by the relative astrometry plus RV data. Finally, we derive unprecedented limits on the presence of additional planets in the disk. We can now exclude the presence of planets that are more massive than about 2.5 M-Jup closer than 3 au, and more massive than 3.5 M-Jup between 3 and 7.5 au. Beyond 7.5 au, we exclude the presence of planets that are more massive than 1-2 M-Jup.Conclusions. Combining relative astrometry and RVs allows one to precisely constrain the orbital parameters of both planets and to give lower limits to potential additional planets throughout the disk. The mass of beta Pictoris c is also well constrained, while additional RV data with appropriate observing strategies are required to properly constrain the mass of beta Pictoris b.
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11.
  • Ledoux, X., et al. (författare)
  • The Neutrons for Science Facility at SPIRAL-2
  • 2018
  • Ingår i: Radiation Protection Dosimetry. - : OXFORD UNIV PRESS. - 0144-8420 .- 1742-3406. ; 180:1-4, s. 115-119
  • Tidskriftsartikel (refereegranskat)abstract
    • The neutrons for science (NFS) facility is a component of SPIRAL-2, the new superconducting linear accelerator built at GANIL in Caen (France). The proton and deuteron beams delivered by the accelerator will allow producing intense neutron fields in the 100 keV-40 MeV energy range. Continuous and quasi-mono-kinetic energy spectra, respectively, will be available at NFS, produced by the interaction of a deuteron beam on a thick Be converter and by the Li-7(p, n) reaction on thin converter. The pulsed neutron beam, with a flux up to two orders of magnitude higher than those of other existing time-of-flight facilities, will open new opportunities of experiments in fundamental research as well as in nuclear data measurements. In addition to the neutron beam, irradiation stations for neutron-, proton- and deuteron-induced reactions will be available for cross-sections measurements and for the irradiation of electronic devices or biological cells. NFS, whose first experiment is foreseen in 2018, will be a very powerful tool for physics, fundamental research as well as applications like the transmutation of nuclear waste, design of future fission and fusion reactors, nuclear medicine or test and development of new detectors.
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12.
  • Ledoux, X., et al. (författare)
  • The neutrons for science facility at SPIRAL-2
  • 2017
  • Ingår i: ND 2016. - Les Ulis : EDP Sciences.
  • Konferensbidrag (refereegranskat)abstract
    • Numerous domains, in fundamental research as well as in applications, require the study of reactions induced by neutrons with energies from few MeV up to few tens of MeV. Reliable measurements also are necessary to improve the evaluated databases used by nuclear transport codes. This energy range covers a large number of topics like transmutation of nuclear waste, design of future fission and fusion reactors, nuclear medicine or test and development of new detectors. A new facility called Neutrons For Science (NFS) is being built for this purpose on the GANIL site at Caen (France). NFS is composed of a pulsed neutron beam for time-of-flight facility as well as irradiation stations for cross-section measurements. Neutrons will be produced by the interaction of deuteron and proton beams, delivered by the SPIRAL-2 linear accelerator, with thick or thin converters made of beryllium or lithium. Continuous and quasi-mono-energetic spectra will be available at NFS up to 40 MeV. In this fast energy region, the neutron flux is expected to be up to 2 orders of magnitude higher than at other existing time-of-flight facilities. In addition, irradiation stations for neutron-, proton- and deuteron-induced reactions will allow performing cross-section measurements by the activation technique. After a description of the facility and its characteristics, the experiments to be performed in the short and medium term will be presented.
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13.
  • Lestinsky, M., et al. (författare)
  • Physics book: CRYRING@ESR
  • 2016
  • Ingår i: European Physical Journal: Special Topics. - : Springer Science and Business Media LLC. - 1951-6401 .- 1951-6355. ; 225:5, s. 797-882
  • Forskningsöversikt (refereegranskat)abstract
    • The exploration of the unique properties of stored and cooled beams of highly-charged ions as provided by heavy-ion storage rings has opened novel and fascinating research opportunities in the realm of atomic and nuclear physics research. Since the late 1980s, pioneering work has been performed at the CRYRING at Stockholm (Abrahamsson et al. 1993) and at the Test Storage Ring (TSR) at Heidelberg (Baumann et al. 1988). For the heaviest ions in the highest charge-states, a real quantum jump was achieved in the early 1990s by the commissioning of the Experimental Storage Ring (ESR) at GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt (Franzke 1987) where challenging experiments on the electron dynamics in the strong field regime as well as nuclear physics studies on exotic nuclei and at the borderline to atomic physics were performed. Meanwhile also at Lanzhou a heavy-ion storage ring has been taken in operation, exploiting the unique research opportunities in particular for medium-heavy ions and exotic nuclei (Xia et al. 2002).
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14.
  • Middeldorp, Christel M., et al. (författare)
  • The Early Growth Genetics (EGG) and EArly Genetics and Lifecourse Epidemiology (EAGLE) consortia : design, results and future prospects
  • 2019
  • Ingår i: European Journal of Epidemiology. - : Springer Science and Business Media LLC. - 0393-2990 .- 1573-7284. ; 34:3, s. 279-300
  • Tidskriftsartikel (refereegranskat)abstract
    • The impact of many unfavorable childhood traits or diseases, such as low birth weight and mental disorders, is not limited to childhood and adolescence, as they are also associated with poor outcomes in adulthood, such as cardiovascular disease. Insight into the genetic etiology of childhood and adolescent traits and disorders may therefore provide new perspectives, not only on how to improve wellbeing during childhood, but also how to prevent later adverse outcomes. To achieve the sample sizes required for genetic research, the Early Growth Genetics (EGG) and EArly Genetics and Lifecourse Epidemiology (EAGLE) consortia were established. The majority of the participating cohorts are longitudinal population-based samples, but other cohorts with data on early childhood phenotypes are also involved. Cohorts often have a broad focus and collect(ed) data on various somatic and psychiatric traits as well as environmental factors. Genetic variants have been successfully identified for multiple traits, for example, birth weight, atopic dermatitis, childhood BMI, allergic sensitization, and pubertal growth. Furthermore, the results have shown that genetic factors also partly underlie the association with adult traits. As sample sizes are still increasing, it is expected that future analyses will identify additional variants. This, in combination with the development of innovative statistical methods, will provide detailed insight on the mechanisms underlying the transition from childhood to adult disorders. Both consortia welcome new collaborations. Policies and contact details are available from the corresponding authors of this manuscript and/or the consortium websites.
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15.
  • Perotti, G., et al. (författare)
  • Water in the terrestrial planet-forming zone of the PDS 70 disk
  • 2023
  • Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 620:7974, s. 516-520
  • Tidskriftsartikel (refereegranskat)abstract
    • Terrestrial and sub-Neptune planets are expected to form in the inner (less than 10 AU) regions of protoplanetary disks1. Water plays a key role in their formation2,3,4, although it is yet unclear whether water molecules are formed in situ or transported from the outer disk5,6. So far Spitzer Space Telescope observations have only provided water luminosity upper limits for dust-depleted inner disks7, similar to PDS 70, the first system with direct confirmation of protoplanet presence8,9. Here we report JWST observations of PDS 70, a benchmark target to search for water in a disk hosting a large (approximately 54 AU) planet-carved gap separating an inner and outer disk10,11. Our findings show water in the inner disk of PDS 70. This implies that potential terrestrial planets forming therein have access to a water reservoir. The column densities of water vapour suggest in-situ formation via a reaction sequence involving O, H2 and/or OH, and survival through water self-shielding5. This is also supported by the presence of CO2 emission, another molecule sensitive to ultraviolet photodissociation. Dust shielding, and replenishment of both gas and small dust from the outer disk, may also play a role in sustaining the water reservoir12. Our observations also reveal a strong variability of the mid-infrared spectral energy distribution, pointing to a change of inner disk geometry.
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16.
  • Rinaldi, P., et al. (författare)
  • MIDIS : Strong (H beta plus [OIII]) and Ha Emitters at Redshift z similar or equal to 7-8 Unveiled with JWST NIRCam and MIRI Imaging in the Hubble eXtreme Deep Field
  • 2023
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 952:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We make use of JWST medium-band and broadband NIRCam imaging, along with ultradeep MIRI 5.6 mu m imaging, in the Hubble eXtreme Deep Field to identify prominent line emitters at z similar or equal to 7-8. Out of a total of 58 galaxies at z similar or equal to 7-8, we find 18 robust candidates ( similar or equal to 31%) for (H beta + [O III]) emitters, based on their enhanced fluxes in the F430M and F444W filters, with EW0(H beta +[O III]) similar or equal to 87-2100 angstrom. Among these emitters, 16 lie in the MIRI coverage area and 12 exhibit a clear flux excess at 5.6 mu m, indicating the simultaneous presence of a prominent Ha emission line with EW0(H alpha) similar or equal to 200-3000 angstrom. This is the first time that H alpha emission can be detected in individual galaxies at z > 7. The Ha line, when present, allows us to separate the contributions of H beta and [O III] to the (H beta +[O III]) complex and derive Ha-based star formation rates (SFRs). We find that in most cases [O III]/ H beta > 1. Instead, two galaxies have [O III]/H beta < 1, indicating that the NIRCam flux excess is mainly driven by H beta. Most prominent line emitters are very young starbursts or galaxies on their way to/from the starburst cloud. They make for a cosmic SFR density log(10)( rho(SFRH alpha) (M-circle dot yr(-1) Mpc))similar or equal to - 2.351 3 which is about a quarter of the total value (log(10)( SFR (M-circle dot yr(-1) Mpc))similar or equal to - 1.761 3 ) at z similar or equal to 7-8. Therefore, the strong Ha emitters likely had a significant role in reionization.
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17.
  • Tabone, B., et al. (författare)
  • A rich hydrocarbon chemistry and high C to O ratio in the inner disk around a very low-mass star
  • 2023
  • Ingår i: Nature Astronomy. - 2397-3366. ; 7:7, s. 805-814
  • Tidskriftsartikel (refereegranskat)abstract
    • Carbon is an essential element for life but how much can be delivered to young planets is still an open question. The chemical characterization of planet-forming disks is a crucial step in our understanding of the diversity and habitability of exoplanets. Very low-mass stars (less than 0.2 M⊙) are interesting targets because they host a rich population of terrestrial planets. Here we present the James Webb Space Telescope detection of abundant hydrocarbons in the disk of a very low-mass star obtained as part of the Mid-InfraRed Instrument mid-INfrared Disk Survey (MINDS). In addition to very strong and broad emission from C2H2 and its 13C12CH2 isotopologue, C4H2, benzene and possibly CH4 are identified, but water, polycyclic aromatic hydrocarbons and silicate features are weak or absent. The lack of small silicate grains indicates that we can look deep down into this disk. These detections testify to an active warm hydrocarbon chemistry with a high C/O ratio larger than unity in the inner 0.1 astronomical units (AU) of this disk, perhaps due to destruction of carbonaceous grains. The exceptionally high C2H2/CO2 and C2H2/H2O column density ratios indicate that oxygen is locked up in icy pebbles and planetesimals outside the water iceline. This, in turn, will have important consequences for the composition of forming exoplanets.
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18.
  • Wright, G. S., et al. (författare)
  • The Mid-Infrared Instrument for the James Webb Space Telescope, II: Design and Build
  • 2015
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 127:953, s. 595-611
  • Tidskriftsartikel (refereegranskat)abstract
    • The Mid-InfraRed Instrument (MIRI) on the James Webb Space Telescope (JWST) provides measurements over the wavelength range 5 to 28: 5 mu m. MIRI has, within a single "package," four key scientific functions: photometric imaging, coronagraphy, single-source low-spectral resolving power (R similar to 100) spectroscopy, and medium-resolving power (R similar to 1500 to 3500) integral field spectroscopy. An associated cooler system maintains MIRI at its operating temperature of
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19.
  • 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.
  •  
20.
  • Chauvin, G., et al. (författare)
  • Discovery of a warm, dusty giant planet around HIP 65426
  • 2017
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 605
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims. The SHINE program is a high-contrast near-infrared survey of 600 young, nearby stars aimed at searching for and characterizing new planetary systems using VLT/SPHERE's unprecedented high-contrast and high-angular-resolution imaging capabilities. It is also intended to place statistical constraints on the rate, mass and orbital distributions of the giant planet population at large orbits as a function of the stellar host mass and age to test planet-formation theories.Methods. We used the IRDIS dual-band imager and the IFS integral field spectrograph of SPHERE to acquire high-contrast coronagraphic differential near-infrared images and spectra of the young A2 star HIP 65426. It is a member of the similar to 17 Myr old Lower Centaurus-Crux association. Results. At a separation of 830 mas (92 au projected) from the star, we detect a faint red companion. Multi-epoch observations confirm that it shares common proper motion with HIP 65426. Spectro-photometric measurements extracted with IFS and IRDIS between 0.95 and 2.2 mu m indicate a warm, dusty atmosphere characteristic of young low-surface-gravity L5-L7 dwarfs. Hot-start evolutionary models predict a luminosity consistent with a 6-12 M-Jup, T-eff = 1300-1600K and R = 1.5 +/- 0.1 R-Jup giant planet. Finally, the comparison with Exo-REM and PHOENIX BT-Settl synthetic atmosphere models gives consistent effective temperatures but with slightly higher surface gravity solutions of log(g) = 4.0-5.0 with smaller radii (1.0-1.3 R-Jup).Conclusions. Given its physical and spectral properties, HIP 65426 b occupies a rather unique placement in terms of age, mass, and spectral-type among the currently known imaged planets. It represents a particularly interesting case to study the presence of clouds as a function of particle size, composition, and location in the atmosphere, to search for signatures of non-equilibrium chemistry, and finally to test the theory of planet formation and evolution.
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21.
  • Cockell, C.S., et al. (författare)
  • Darwin - an experimental astronomy mission to search for extrasolar planets
  • 2009
  • Ingår i: Experimental Astronomy. - 0922-6435 .- 1572-9508. ; 23:1, s. 435-461
  • Tidskriftsartikel (refereegranskat)abstract
    • As a response to ESA call for mission concepts for its Cosmic Vision 2015–2025 plan, we propose a mission called Darwin. Its primary goal is the study of terrestrial extrasolar planets and the search for life on them. In this paper, we describe different characteristics of the instrument.
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22.
  • 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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23.
  • 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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24.
  • Fridlund, M., et al. (författare)
  • The Search for Worlds Like Our Own
  • 2010
  • Ingår i: Astrobiology. - : Mary Ann Liebert Inc. - 1531-1074 .- 1557-8070. ; 10:1, s. 5-17
  • Tidskriftsartikel (refereegranskat)abstract
    • The direct detection of Earth-like exoplanets orbiting nearby stars and the characterization of such planets particularly, their evolution, their atmospheres, and their ability to host life-constitute a significant problem. The quest for other worlds as abodes of life has been one of mankind's great questions for several millennia. For instance, as stated by Epicurus similar to 300 BC: "Other worlds, with plants and other living things, some of them similar and some of them different from ours, must exist.'' Demokritos from Abdera (460-370 BC), the man who invented the concept of indivisible small parts-atoms-also held the belief that other worlds exist around the stars and that some of these worlds may be inhabited by life-forms. The idea of the plurality of worlds and of life on them has since been held by scientists like Johannes Kepler and William Herschel, among many others. Here, one must also mention Giordano Bruno. Born in 1548, Bruno studied in France and came into contact with the teachings of Nicolas Copernicus. He wrote the book De l'Infinito, Universo e Mondi in 1584, in which he claimed that the Universe was infinite, that it contained an infinite amount of worlds like Earth, and that these worlds were inhabited by intelligent beings. At the time, this was extremely controversial, and eventually Bruno was arrested by the church and burned at the stake in Rome in 1600, as a heretic, for promoting this and other equally confrontational issues (though it is unclear exactly which idea was the one that ultimately brought him to his end). In all the aforementioned cases, the opinions and results were arrived at through reasoning-not by experiment. We have only recently acquired the technological capability to observe planets orbiting stars other than our Sun; acquisition of this capability has been a remarkable feat of our time. We show in this introduction to the Habitability Primer that mankind is at the dawning of an age when, by way of the scientific method and 21(st)-century technology, we will be able to answer this fascinating controversial issue that has persisted for at least 2500 years.
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25.
  • 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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26.
  • Gieser, C., et al. (författare)
  • JOYS: Disentangling the warm and cold material in the high-mass IRAS 23385+6053 cluster
  • 2023
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 679
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. High-mass star formation occurs in a clustered mode where fragmentation is observed from an early stage onward. Young protostars can now be studied in great detail with the recently launched James Webb Space Telescope (JWST). Aims. We study and compare the warm (>100 K) and cold (<100 K) material toward the high-mass star-forming region (HMSFR) IRAS 23385+6053 (IRAS 23385 hereafter) combining high-angular-resolution observations in the mid-infrared (MIR) with the JWST Observations of Young protoStars (JOYS) project and with the NOrthern Extended Millimeter Array (NOEMA) at millimeter (mm) wavelengths at angular resolutions of 0.a2 1.a0. Methods. We investigated the spatial morphology of atomic and molecular species using line-integrated intensity maps. We estimated the temperature and column density of different gas components using H2 transitions (warm and hot component) and a series of CH3CN transitions as well as 3 mm continuum emission (cold component). Results. Toward the central dense core of IRAS 23385, the material consists of relatively cold gas and dust ( 50 K), while multiple outflows create heated and/or shocked H2 and show enhanced temperatures ( 400 K) along the outflow structures. An energetic outflow with enhanced emission knots of [FeII] and [NiII] suggests J-type shocks, while two other outflows have enhanced emission of only H2 and [SI] caused by C-type shocks. The latter two outflows are also more prominent in molecular line emission at mm wavelengths (e.g., SiO, SO, H2CO, and CH3OH). Data of even higher angular resolution are needed to unambiguously identify the outflow-driving sources given the clustered nature of IRAS 23385. While most of the forbidden fine structure transitions are blueshifted, [NeII] and [NeIII] peak at the source velocity toward the MIR source A/mmA2 suggesting that the emission is originating from closer to the protostar. Conclusions. The warm and cold gas traced by MIR and mm observations, respectively, are strongly linked in IRAS 23385. The outflows traced by MIR H2 lines have molecular counterparts in the mm regime. Despite the presence of multiple powerful outflows that cause dense and hot shocks, a cold dense envelope still allows star formation to further proceed. To study and fully understand the spatially resolved MIR properties, a representative sample of low- and high-mass protostars has to be probed using JWST.
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27.
  • Glauser, A. M., et al. (författare)
  • Characterizing exoplanets in the visible and infrared: A spectrometer concept for the EChO space mission
  • 2013
  • Ingår i: Journal of Astronomical Instrumentation. - 2251-1725 .- 2251-1717. ; 2:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Transit-spectroscopy of exoplanets is one of the key observational techniques used to characterize extrasolar planets and their atmospheres. The observational challenges of these measurements require dedicated instrumentation and only the space environment allows undisturbed access to earth-like atmospheric features such as water or carbon dioxide. Therefore, several exoplanet-specific space missions are currently being studied. One of them is EChO, the Exoplanet Characterization Observatory, which is part of ESA's Cosmic Vision 2015-2025 program, and which is one of four candidates for the M3 launch slot in 2024. In this paper we present the results of our assessment study of the EChO spectrometer, the only science instrument onboard this spacecraft. The instrument is a multi-channel all-reflective dispersive spectrometer, covering the wavelength range from 400 nm to 16μm simultaneously with a moderately low spectral resolution. We illustrate how the key technical challenge of the EChO mission - the high photometric stability - influences the choice of spectrometer concept and fundamentally drives the instrument design. First performance evaluations underline the suitability of the elaborated design solution for the needs of the EChO mission.
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28.
  • 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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29.
  • 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.
  •  
30.
  • 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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31.
  • 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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32.
  • Langlois, M., et al. (författare)
  • The SPHERE infrared survey for exoplanets (SHINE) : II. Observations, data reduction and analysis, detection performances, and initial results
  • 2021
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 651
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. In recent decades, direct imaging has confirmed the existence of substellar companions (exoplanets or brown dwarfs) on wide orbits (>10 au) around their host stars. In striving to understand their formation and evolution mechanisms, in 2015 we initiated the SPHERE infrared survey for exoplanets (SHINE), a systematic direct imaging survey of young, nearby stars that is targeted at exploring their demographics.Aims. We aim to detect and characterize the population of giant planets and brown dwarfs beyond the snow line around young, nearby stars. Combined with the survey completeness, our observations offer the opportunity to constrain the statistical properties (occurrence, mass and orbital distributions, dependency on the stellar mass) of these young giant planets.Methods. In this study, we present the observing and data analysis strategy, the ranking process of the detected candidates, and the survey performances for a subsample of 150 stars that are representative of the full SHINE sample. Observations were conducted in a homogeneous way between February 2015 and February 2017 with the dedicated ground-based VLT/SPHERE instrument equipped with the IFS integral field spectrograph and the IRDIS dual-band imager, covering a spectral range between 0.9 and 2.3 μm. We used coronographic, angular, and spectral differential imaging techniques to achieve the best detection performances for this study, down to the planetary mass regime.Results. We processed, in a uniform manner, more than 300 SHINE observations and datasets to assess the survey typical sensitivity as a function of the host star and of the observing conditions. The median detection performance reached 5σ-contrasts of 13 mag at 200 mas and 14.2 mag at 800 mas with the IFS (YJ and YJH bands), and of 11.8 mag at 200 mas, 13.1 mag at 800 mas, and 15.8 mag at 3 as with IRDIS in H band, delivering one of the deepest sensitivity surveys thus far for young, nearby stars. A total of sixteen substellar companions were imaged in this first part of SHINE: seven brown dwarf companions and ten planetary-mass companions.These include two new discoveries, HIP 65426 b and HIP 64892 B, but not the planets around PDS70 that had not been originally selected for the SHINE core sample. A total of 1483 candidates were detected, mainly in the large field of view that characterizes IRDIS. The color-magnitude diagrams, low-resolution spectrum (when available with IFS), and follow-up observations enabled us to identify the nature (background contaminant or comoving companion) of about 86% of our subsample. The remaining cases are often connected to crowded-field follow-up observations that were missing. Finally, even though SHINE was not initially designed for disk searches, we imaged twelve circumstellar disks, including three new detections around the HIP 73145, HIP 86598, and HD 106906 systems.Conclusions. Nowadays, direct imaging provides a unique opportunity to probe the outer part of exoplanetary systems beyond 10 au to explore planetary architectures, as highlighted by the discoveries of: one new exoplanet, one new brown dwarf companion, and three new debris disks during this early phase of SHINE. It also offers the opportunity to explore and revisit the physical and orbital properties of these young, giant planets and brown dwarf companions (relative position, photometry, and low-resolution spectrum in near-infrared, predicted masses, and contrast in order to search for additional companions). Finally, these results highlight the importance of finalizing the SHINE systematic observation of about 500 young, nearby stars for a full exploration of their outer part to explore the demographics of young giant planets beyond 10 au and to identify the most interesting systems for the next generation of high-contrast imagers on very large and extremely large telescopes.
  •  
33.
  • Markhus, R., et al. (författare)
  • EEG in fitness to drive evaluations in people with epilepsy - Considerable variations across Europe
  • 2020
  • Ingår i: Seizure-European Journal of Epilepsy. - : Elsevier BV. - 1059-1311. ; 79, s. 56-60
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: Epilepsy patients consider driving issues to be one of their most serious concerns. Ideally, decisions regarding fitness to drive should be based upon thorough evaluations by specialists in epilepsy care. In 2009, an EU directive was published aiming to harmonize evaluation practices within European countries, but, despite these recommendations, whether all epileptologists use the same criteria is unclear. We therefore conducted this study to investigate routine practices on how epileptologists at European epilepsy centers evaluate fitness to drive. Methods: A questionnaire was sent to 63 contact persons identified through the European Epi-Care and the Epilepsy network. The questionnaire addressed how fitness-to-drive evaluations were conducted, the involvement of different professionals, the use and interpretation of EEG, and opinions on existing regulations and guidelines. Results: The questionnaire was completed by 35 participants (56 % response rate). Results showed considerable variation regarding test routines and the emphasis placed on the occurrence and extent of epileptiform discharges revealed by EEG. 82 % of the responders agreed that there was a need for more research on how to better evaluate fitness-to-drive in people with epilepsy, and 89 % agreed that regulations on fitness to drive evaluations should be internationally coordinated. Conclusion: Our survey showed considerable variations among European epileptologists regarding use of EEG and how findings of EEG pathology should be assessed in fitness-to-drive evaluations. There is a clear need for more research on this issue and international guidelines on how such evaluations should be carried out would be of value.
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34.
  • Morales, J. C., et al. (författare)
  • A giant exoplanet orbiting a very-low-mass star challenges planet formation models
  • 2019
  • Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 365:6460, s. 1441-1445
  • Tidskriftsartikel (refereegranskat)abstract
    • Surveys have shown that super-Earth and Neptune-mass exoplanets are more frequent than gas giants around low-mass stars, as predicted by the core accretion theory of planet formation. We report the discovery of a giant planet around the very-low-mass star GJ 3512, as determined by optical and near-infrared radial-velocity observations. The planet has a minimum mass of 0.46 Jupiter masses, very high for such a small host star, and an eccentric 204-day orbit. Dynamical models show that the high eccentricity is most likely due to planet-planet interactions. We use simulations to demonstrate that the GJ 3512 planetary system challenges generally accepted formation theories, and that it puts constraints on the planet accretion and migration rates. Disk instabilities may be more efficient in forming planets than previously thought.
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35.
  • Ray, T. P., et al. (författare)
  • Outflows from the youngest stars are mostly molecular
  • 2023
  • Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 622, s. 48-52
  • Tidskriftsartikel (refereegranskat)abstract
    • The formation of stars and planets is accompanied not only by the build-up of matter, namely accretion, but also by its expulsion in the form of highly supersonic jets that can stretch for several parsecs1,2. As accretion and jet activity are correlated and because young stars acquire most of their mass rapidly early on, the most powerful jets are associated with the youngest protostars3. This period, however, coincides with the time when the protostar and its surroundings are hidden behind many magnitudes of visual extinction. Millimetre interferometers can probe this stage but only for the coolest components3. No information is provided on the hottest (greater than 1,000 K) constituents of the jet, that is, the atomic, ionized and high-temperature molecular gases that are thought to make up the jet's backbone. Detecting such a spine relies on observing in the infrared that can penetrate through the shroud of dust. Here we report near-infrared observations of Herbig-Haro 211 from the James Webb Space Telescope, an outflow from an analogue of our Sun when it was, at most, a few times 104 years old. These observations reveal copious emission from hot molecules, explaining the origin of the 'green fuzzies'4-7 discovered nearly two decades ago by the Spitzer Space Telescope8. This outflow is found to be propagating slowly in comparison to its more evolved counterparts and, surprisingly, almost no trace of atomic or ionized emission is seen, suggesting its spine is almost purely molecular. Near-infrared imagery and spectroscopy from JWST of the Herbig-Haro 211 system, an analogue of the young Sun, reveals supersonic jets of hot molecules that can explain the origin of the 'green fuzzies' phenomenon.
  •  
36.
  • Webb, Thomas R., et al. (författare)
  • Systematic Evaluation of Pleiotropy Identifies 6 Further Loci Associated With Coronary Artery Disease
  • 2017
  • Ingår i: Journal of the American College of Cardiology. - : Elsevier BV. - 0735-1097 .- 1558-3597. ; 69:7, s. 823-836
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND Genome-wide association studies have so far identified 56 loci associated with risk of coronary artery disease (CAD). Many CAD loci show pleiotropy; that is, they are also associated with other diseases or traits.OBJECTIVES This study sought to systematically test if genetic variants identified for non-CAD diseases/traits also associate with CAD and to undertake a comprehensive analysis of the extent of pleiotropy of all CAD loci.METHODS In discovery analyses involving 42,335 CAD cases and 78,240 control subjects we tested the association of 29,383 common (minor allele frequency >5%) single nucleotide polymorphisms available on the exome array, which included a substantial proportion of known or suspected single nucleotide polymorphisms associated with common diseases or traits as of 2011. Suggestive association signals were replicated in an additional 30,533 cases and 42,530 control subjects. To evaluate pleiotropy, we tested CAD loci for association with cardiovascular risk factors (lipid traits, blood pressure phenotypes, body mass index, diabetes, and smoking behavior), as well as with other diseases/traits through interrogation of currently available genome-wide association study catalogs.RESULTS We identified 6 new loci associated with CAD at genome-wide significance: on 2q37 (KCNJ13-GIGYF2), 6p21 (C2), 11p15 (MRVI1-CTR9), 12q13 (LRP1), 12q24 (SCARB1), and 16q13 (CETP). Risk allele frequencies ranged from 0.15 to 0.86, and odds ratio per copy of the risk allele ranged from 1.04 to 1.09. Of 62 new and known CAD loci, 24 (38.7%) showed statistical association with a traditional cardiovascular risk factor, with some showing multiple associations, and 29 (47%) showed associations at p < 1 x 10(-4) with a range of other diseases/traits.CONCLUSIONS We identified 6 loci associated with CAD at genome-wide significance. Several CAD loci show substantial pleiotropy, which may help us understand the mechanisms by which these loci affect CAD risk.
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37.
  • 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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38.
  • 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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39.
  • Akiyama, E., et al. (författare)
  • DISCOVERY OF A DISK GAP CANDIDATE AT 20 AU IN TW HYDRAE
  • 2015
  • Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 802:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a new Subaru/HiCIAO high-contrast H-band polarized intensity (PI) image of a nearby transitional disk associated with TW Hydrae. The scattered light from the disk was detected from 0 ''.2 to 1 ''.5 (11-81 AU) and the PI image shows a clear axisymmetric depression in PI at similar to 0 ''.4 (similar to 20 AU) from the central star, similar to the similar to 80 AU gap previously reported from Hubble Space Telescope images. The azimuthal PI profile also shows that the disk beyond 0 ''.2 is almost axisymmetric. We discuss two possible scenarios explaining the origin of the PI depression: (1) a gap structure may exist at similar to 20 AU from the central star because of a shallow slope seen in the PI profile, and (2) grain growth may be occurring in the inner region of the disk. Multi-band observations at near-infrared and millimeter/submillimeter wavelengths play a complementary role in investigating dust opacity and may help reveal the origin of the gap more precisely.
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40.
  • Alibert, Y., et al. (författare)
  • Origin and Formation of Planetary Systems
  • 2010
  • Ingår i: Astrobiology. - : Mary Ann Liebert Inc. - 1531-1074 .- 1557-8070. ; 10:1, s. 19-32
  • Tidskriftsartikel (refereegranskat)abstract
    • To estimate the occurrence of terrestrial exoplanets and maximize the chance of finding them, it is crucial to understand the formation of planetary systems in general and that of terrestrial planets in particular. We show that a reliable formation theory should not only explain the formation of the Solar System, with small terrestrial planets within a few AU and gas giants farther out, but also the newly discovered exoplanetary systems with close-in giant planets. Regarding the presently known exoplanets, we stress that our current knowledge is strongly biased by the sensitivity limits of current detection techniques (mainly the radial velocity method). With time and improved detection methods, the diversity of planets and orbits in exoplanetary systems will definitely increase and help to constrain the formation theory further. In this work, we review the latest state of planetary formation in relation to the origin and evolution of habitable terrestrial planets.
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41.
  • Allentoft, Morten E., et al. (författare)
  • Population genomics of post-glacial western Eurasia
  • 2024
  • Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 625:7994, s. 301-311
  • Tidskriftsartikel (refereegranskat)abstract
    • Western Eurasia witnessed several large-scale human migrations during the Holocene1–5. Here, to investigate the cross-continental effects of these migrations, we shotgun-sequenced 317 genomes—mainly from the Mesolithic and Neolithic periods—from across northern and western Eurasia. These were imputed alongside published data to obtain diploid genotypes from more than 1,600 ancient humans. Our analyses revealed a ‘great divide’ genomic boundary extending from the Black Sea to the Baltic. Mesolithic hunter-gatherers were highly genetically differentiated east and west of this zone, and the effect of the neolithization was equally disparate. Large-scale ancestry shifts occurred in the west as farming was introduced, including near-total replacement of hunter-gatherers in many areas, whereas no substantial ancestry shifts happened east of the zone during the same period. Similarly, relatedness decreased in the west from the Neolithic transition onwards, whereas, east of the Urals, relatedness remained high until around 4,000 bp, consistent with the persistence of localized groups of hunter-gatherers. The boundary dissolved when Yamnaya-related ancestry spread across western Eurasia around 5,000 bp, resulting in a second major turnover that reached most parts of Europe within a 1,000-year span. The genetic origin and fate of the Yamnaya have remained elusive, but we show that hunter-gatherers from the Middle Don region contributed ancestry to them. Yamnaya groups later admixed with individuals associated with the Globular Amphora culture before expanding into Europe. Similar turnovers occurred in western Siberia, where we report new genomic data from a ‘Neolithic steppe’ cline spanning the Siberian forest steppe to Lake Baikal. These prehistoric migrations had profound and lasting effects on the genetic diversity of Eurasian populations.
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42.
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43.
  • Asensio-Torres, Ruben, et al. (författare)
  • Polarimetry and flux distribution in the debris disk around HD 32297
  • 2016
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 593
  • Tidskriftsartikel (refereegranskat)abstract
    • We present high-contrast angular differential imaging (ADI) observations of the debris disk around HD32297 in H-band, as well as the first polarimetric images for this system in polarized differential imaging (PDI) mode with Subaru/HICIAO. In ADI, we detect the nearly edge-on disk at > 5 sigma levels from similar to 0.45 '' to similar to 1.7 '' (50-192AU) from the star and recover the spine deviation from the midplane already found in previous works. We also find for the first time imaging and surface brightness (SB) indications for the presence of a gapped structure on both sides of the disk at distances of similar to 0.75 '' (NE side) and similar to 0.65 '' (SW side). Global forward-modelling work delivers a best-fit model disk and well-fitting parameter intervals that essentially match previous results, with high-forward scattering grains and a ring located at 110AU. However, this single ring model cannot account for the gapped structure seen in our SB profiles. We create simple double ring models and achieve a satisfactory fit with two rings located at 60 and 95AU, respectively, low-forward scattering grains and very sharp inner slopes. In polarized light we retrieve the disk extending from similar to 0.25-1.6 '', although the central region is quite noisy and high S/N are only found in the range similar to 0.75-1.2 ''. The disk is polarized in the azimuthal direction, as expected, and the departure from the midplane is also clearly observed. Evidence for a gapped scenario is not found in the PDI data. We obtain a linear polarization degree of the grains that increases from similar to 10% at 0.55 '' to similar to 25% at 1.6 ''. The maximum is found at scattering angles of similar to 90 degrees, either from the main components of the disk or from dust grains blown out to larger radii.
  •  
44.
  • Barlow, M. J., et al. (författare)
  • A Herschel PACS and SPIRE study of the dust content of the Cassiopeia A supernova remnant
  • 2010
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 518, s. L138-
  • Tidskriftsartikel (refereegranskat)abstract
    • Using the 3.5-m Herschel Space Observatory, imaging photometry of Cas A has been obtained in six bands between 70 and 500 mu m with the PACS and SPIRE instruments, with angular resolutions ranging from 6 to 37 ''. In the outer regions of the remnant the 70-mu m PACS image resembles the 24-mu m image Spitzer image, with the emission attributed to the same warm dust component, located in the reverse shock region. At longer wavelengths, the three SPIRE bands are increasingly dominated by emission from cold interstellar dust knots and filaments, particularly across the central, western and southern parts of the remnant. Nonthermal emission from the northern part of the remnant becomes prominent at 500 mu m. We have estimated and subtracted the contributions from the nonthermal, warm dust and cold interstellar dust components. We confirm and resolve for the first time a cool (similar to 35 K) dust component, emitting at 70-160 mu m, that is located interior to the reverse shock region, with an estimated mass of 0.075 M-circle dot.
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45.
  •  
46.
  • Bonnefoy, M., et al. (författare)
  • First light of the VLT planet finder SPHERE IV. Physical and chemical properties of the planets around HR8799
  • 2016
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 587
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. The system of four planets discovered around the intermediate-mass star HR8799 offers a unique opportunity to test planet formation theories at large orbital radii and to probe the physics and chemistry at play in the atmospheres of self-luminous young (similar to 30 Myr) planets. We recently obtained new photometry of the four planets and low-resolution (R similar to 30) spectra of HR8799 d and e with the SPHERE instrument (Paper III).Aims. In this paper (Paper IV), we aim to use these spectra and available photometry to determine how they compare to known objects, what the planet physical properties are, and how their atmospheres work.Methods. We compare the available spectra, photometry, and spectral energy distribution (SED) of the planets to field dwarfs and young companions. In addition, we use the extinction from corundum, silicate (enstatite and forsterite), or iron grains likely to form in the atmosphere of the planets to try to better understand empirically the peculiarity of their spectrophotometric properties. To conclude, we use three sets of atmospheric models (BT-SETTL14, Cloud-AE60, Exo-REM) to determine which ingredients are critically needed in the models to represent the SED of the objects, and to constrain their atmospheric parameters (T-eff, log g, M/H).Results. We find that HR8799d and e properties are well reproduced by those of L6-L8 dusty dwarfs discovered in the field, among which some are candidate members of young nearby associations. No known object reproduces well the properties of planets b and c. Nevertheless, we find that the spectra and WISE photometry of peculiar and/or young early-T dwarfs reddened by submicron grains made of corundum, iron, enstatite, or forsterite successfully reproduce the SED of these planets. Our analysis confirms that only the Exo-REM models with thick clouds fit (within 2 sigma) the whole set of spectrophotometric datapoints available for HR8799 d and e for T-eff = 1200 K, log g in the range 3.0-4.5, and M/H = +0.5. The models still fail to reproduce the SED of HR8799c and b. The determination of the metallicity, log g, and cloud thickness are degenerate.Conclusions. Our empirical analysis and atmospheric modelling show that an enhanced content in dust and decreased CIA of H-2 is certainly responsible for the deviation of the properties of the planet with respect to field dwarfs. The analysis suggests in addition that HR8799c and b have later spectral types than the two other planets, and therefore could both have lower masses.
  •  
47.
  • Boso, A., et al. (författare)
  • Isospin dependence of electromagnetic transition strengths among an isobaric triplet
  • 2019
  • Ingår i: Physics Letters B. - : ELSEVIER. - 0370-2693 .- 1873-2445. ; 797
  • Tidskriftsartikel (refereegranskat)abstract
    • Electric quadrupole matrix elements, M-p, for the J(pi) = 2(+) -> 0(+), Delta T = 0, T = 1 transitions across the A = 46 isobaric multiplet Cr-46-V-46-Ti-46 have been measured at GSI with the FRS-LYCCA-AGATA setup. This allows direct insight into the isospin purity of the states of interest by testing the linearity of M-p with respect to T-z. Pairs of nuclei in the T = 1 triplet were studied using identical reaction mechanisms in order to control systematic errors. The M-p values were obtained with two different methodologies: (i) a relativistic Coulomb excitation experiment was performed for Cr-46 and Ti-46; (ii) a "stretched target" technique was adopted here, for the first time, for lifetime measurements in V-46 and Ti-46. A constant value of M-p across the triplet has been observed. Shell-model calculations performed within the fp shell fail to reproduce this unexpected trend, pointing towards the need of a wider valence space. This result is confirmed by the good agreement with experimental data achieved with an interaction which allows excitations from the underlying sd shell. A test of the linearity rule for all published data on complete T = 1 isospin triplets is presented. (C) 2019 The Author(s). Published by Elsevier B.V.
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48.
  • 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.
  •  
49.
  • Ceccarelli, C., et al. (författare)
  • Herschel spectral surveys of star- forming regions Overview of the 555-636 GHz range
  • 2010
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 521, s. L22-
  • Tidskriftsartikel (refereegranskat)abstract
    • High resolution line spectra of star-forming regions are mines of information: they provide unique clues to reconstruct the chemical, dynamical, and physical structure of the observed source. We present the first results from the Herschel key project " Chemical HErschel Surveys of Star forming regions", CHESS. We report and discuss observations towards five CHESS targets, one outflow shock spot and four protostars with luminosities bewteen 20 and 2 x 105 L similar to : L1157-B1, IRAS 16293-2422, OMC2-FIR4, AFGL 2591, and NGC 6334I. The observations were obtained with the heterodyne spectrometer HIFI on board Herschel, with a spectral resolution of 1 MHz. They cover the frequency range 555-636 GHz, a range largely unexplored before the launch of the Herschel satellite. A comparison of the five spectra highlights spectacular differences in the five sources, for example in the density of methanol lines, or the presence./absence of lines from S-bearing molecules or deuterated species. We discuss how these differences can be attributed to the different star-forming mass or evolutionary status.
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50.
  • Cheetham, A., et al. (författare)
  • Discovery of a brown dwarf companion to the star HIP 64892
  • 2018
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 615
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the discovery of a bright, brown dwarf companion to the star HIP 64892, imaged with VLT/SPHERE during the SHINE exoplanet survey. The host is a B9.5V member of the Lower-Centaurus-Crux subgroup of the Scorpius Centaurus OB association. The measured angular separation of the companion (1.2705 +/- 0.0023) corresponds to a projected distance of 159 +/- 12AU. We observed the target with the dual-band imaging and long-slit spectroscopy modes of the IRDIS imager to obtain its spectral energy distribution (SED) and astrometry. In addition, we reprocessed archival NACO L-band data, from which we also recover the companion. Its SED is consistent with a young (<30 Myr), low surface gravity object with a spectral type of M9 gamma +/- 1. From comparison with the BT-Settl atmospheric models we estimate an effective temperature of T-eff = 2600 +/- 100 K, and comparison of the companion photometry to the COND evolutionary models yields a mass of similar to 29-37 M-J at the estimated age of 16(-7)(+15) Myr for the system. The star HIP 64892 is a rare example of an extreme-mass ratio system (q similar to 0.01) and will be useful for testing models relating to the formation and evolution of such low-mass objects.
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