Now showing items 1-20 of 939

    • Deconvolving the complex structure of the asteroid belt

      Department of Astronomy, University of Florida, Gainesville, FL, 32611, US; NSF's National Optical-Infrared Astronomy Research Laboratory, Tucson, AZ, 85719, US; Armagh Observatory and Planetarium, College Hill, Armagh, BT61 9DG; Dermott, Stanley F.; Li, Dan; Christou, Apostolos A. (IAU Symposium, 2024-01-01)
      The asteroid belt is a unique source of information on some of the most important questions facing solar system science. These questions include the sizes, numbers, types and orbital distributions of the planetesimals that formed the planets, and the identification of those asteroids that are the sources of meteorites and near-Earth asteroids. Answering these questions requires an understanding of the dynamical evolution of the asteroid belt, but this evolution is governed by a complex interplay of mechanisms that include catastrophic disruption, orbital evolution driven by Yarkovsky radiation forces, and chaotic orbital evolution driven by gravitational forces. While the timescales of these loss mechanisms have been calculated using estimates of some critical parameters that include the thermal properties, strengths and mean densities of the asteroids, we argue here that the uncertainties in these parameters are so large that deconvolution of the structure of the asteroid belt must be guided primarily by observational constraints. We argue that observations of the inner asteroid belt indicate that the size-frequency distribution is not close to the equilibrium distribution postulated by Dohnanyi (<xref rid=ref10 ref-type=bibr>1969</xref>). We also discuss the correlations observed between the sizes and the orbital elements of the asteroids. While some of these correlations are significant and informative, others are spurious and may arise from the limitations of the Hierarchical Clustering Method that is currently used to define family membership.
    • GERry: A code to optimise the hunt for the electromagnetic counter-parts to gravitational wave events

      The Univ. of Warwick (United Kingdom); Monash Univ. (Australia); Univ. of Sheffield (United Kingdom); Univ. of Leicester (United Kingdom); Armagh Observatory and Planetarium (United Kingdom); National Astronomical Research Institute of Thailand (Thailand); Univ. of Turku (Finland); The Univ. of Manchester (United Kingdom); Univ. of Portsmouth (United Kingdom); Instituto de Astrofísica de Canarias (Spain); et al. (Observatory Operations: Strategies, Processes, and Systems X, 2024-07-01)
      The search for the electromagnetic counterparts to Gravitational Wave (GW) events has been rapidly gathering pace in recent years thanks to the increasing number and capabilities of both gravitational wave detectors and wide field survey telescopes. Difficulties remain, however, in detecting these counterparts due to their inherent scarcity, faintness and rapidly evolving nature. To find these counterparts, it is important that one optimizes the observing strategy for their recovery. This can be difficult due to the large number of potential variables at play. Such follow-up campaigns are also capable of detecting hundreds or potentially thousands of unrelated transients, particularly for GW events with poor localization. Even if the observations are capable of detecting a counterpart, finding it among the numerous contaminants can prove challenging. Here we present the Gravitational wave Electromagnetic RecovRY code (GERRY) to perform detailed analysis and survey-agnostic quantification of observing campaigns attempting to recover electromagnetic counterparts. GERRY considers the campaign's spatial, temporal and wavelength coverage, in addition to Galactic extinction and the expected counterpart light curve evolution from the GW 3D localization volume. It returns quantified statistics that can be used to: determine the probability of having detected the counterpart, identified the most promising sources, and assessed and refine strategy. Here we demonstrate the code to look at the performance and parameter space probed by current and upcoming wide-field surveys such as GOTO and VRO.
    • Evidence of Cosmic Impact at Abu Hureyra, Syria at the Younger Dryas Onset ( 12.8 ka): High-temperature melting at >2200 °C

      College of Liberal Arts, Rochester Institute of Technology, 14623, Rochester, NY, USA; Department of Earth Science and Marine Science Institute, University of California Santa Barbara, 93106, Santa Barbara, CA, USA; Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DG, Northern Ireland, UK; Geology Division, School of Earth and Sustainability, Northern Arizona University, 86011, Flagstaff, AZ, USA; Wyss Institute for Biologically Inspired Engineering, Harvard University, 02138, Cambridge, MA, USA; Elizabeth City State University, Center of Excellence in Remote Sensing Education and Research, 27909, Elizabeth City, NC, USA; Department of Natural Sciences, Elizabeth City State University, 27909, Elizabeth City, NC, USA; U.S. Geological Survey (USGS), 12201 Sunrise Valley Drive, Reston, VA, 20192, USA; Institute of Geology, Czech Academy of Science of the Czech Republic and, Charles University, Faculty of Science, Czech Republic, CZE; and University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, Alaska, 99775, USA; Los Alamos National Laboratory (retired), 87547, White Rock, NM, USA; et al. (Scientific Reports, 2020-03-01)
      At Abu Hureyra (AH), Syria, the 12,800-year-old Younger Dryas boundary layer (YDB) contains peak abundances in meltglass, nanodiamonds, microspherules, and charcoal. AH meltglass comprises 1.6 wt.% of bulk sediment, and crossed polarizers indicate that the meltglass is isotropic. High YDB concentrations of iridium, platinum, nickel, and cobalt suggest mixing of melted local sediment with small quantities of meteoritic material. Approximately 40% of AH glass display carbon-infused, siliceous plant imprints that laboratory experiments show formed at a minimum of 1200°-1300 °C; however, reflectance-inferred temperatures for the encapsulated carbon were lower by up to 1000 °C. Alternately, melted grains of quartz, chromferide, and magnetite in AH glass suggest exposure to minimum temperatures of 1720 °C ranging to &gt;2200 °C. This argues against formation of AH meltglass in thatched hut fires at 1100°-1200 °C, and low values of remanent magnetism indicate the meltglass was not created by lightning. Low meltglass water content (0.02-0.05% H<SUB>2</SUB>O) is consistent with a formation process similar to that of tektites and inconsistent with volcanism and anthropogenesis. The wide range of evidence supports the hypothesis that a cosmic event occurred at Abu Hureyra ~12,800 years ago, coeval with impacts that deposited high-temperature meltglass, melted microspherules, and/or platinum at other YDB sites on four continents.
    • GERry: A code to optimise the hunt for the electromagnetic counter-parts to gravitational wave events

      The Univ. of Warwick (United Kingdom); Monash Univ. (Australia); Univ. of Sheffield (United Kingdom); Univ. of Leicester (United Kingdom); Armagh Observatory and Planetarium (United Kingdom); National Astronomical Research Institute of Thailand (Thailand); Univ. of Turku (Finland); The Univ. of Manchester (United Kingdom); Univ. of Portsmouth (United Kingdom); Instituto de Astrofísica de Canarias (Spain); et al. (Observatory Operations: Strategies, Processes, and Systems X, 2024-07-01)
      The search for the electromagnetic counterparts to Gravitational Wave (GW) events has been rapidly gathering pace in recent years thanks to the increasing number and capabilities of both gravitational wave detectors and wide field survey telescopes. Difficulties remain, however, in detecting these counterparts due to their inherent scarcity, faintness and rapidly evolving nature. To find these counterparts, it is important that one optimizes the observing strategy for their recovery. This can be difficult due to the large number of potential variables at play. Such follow-up campaigns are also capable of detecting hundreds or potentially thousands of unrelated transients, particularly for GW events with poor localization. Even if the observations are capable of detecting a counterpart, finding it among the numerous contaminants can prove challenging. Here we present the Gravitational wave Electromagnetic RecovRY code (GERRY) to perform detailed analysis and survey-agnostic quantification of observing campaigns attempting to recover electromagnetic counterparts. GERRY considers the campaign's spatial, temporal and wavelength coverage, in addition to Galactic extinction and the expected counterpart light curve evolution from the GW 3D localization volume. It returns quantified statistics that can be used to: determine the probability of having detected the counterpart, identified the most promising sources, and assessed and refine strategy. Here we demonstrate the code to look at the performance and parameter space probed by current and upcoming wide-field surveys such as GOTO and VRO.
    • The Gravitational-wave Optical Transient Observer (GOTO)

      The Univ. of Sheffield (United Kingdom); The Univ. of Warwick (United Kingdom); Monash Univ. (Australia); Univ. of Leicester (United Kingdom); Armagh Observatory and Planetarium (United Kingdom); National Astronomical Research Institute of Thailand (Thailand); Univ. of Turku (Finland); The Univ. of Manchester (United Kingdom); Univ. of Portsmouth (United Kingdom); Instituto de Astrofísica de Canarias (Spain); et al. (Ground-based and Airborne Telescopes X, 2024-08-01)
      The Gravitational-wave Optical Transient Observer (GOTO) is a project dedicated to identifying optical counterparts to gravitational-wave detections using a network of dedicated, wide-field telescopes. After almost a decade of design, construction, and commissioning work, the GOTO network is now fully operational with two antipodal sites: La Palma in the Canary Islands and Siding Spring in Australia. Both sites host two independent robotic mounts, each with a field-of-view of 44 square degrees formed by an array of eight 40cm telescopes, resulting in an instantaneous 88 square degree field-of-view per site. All four telescopes operate as a single integrated network, with the ultimate aim of surveying the entire sky every 2-3 days and allowing near-24-hour response to transient events within a minute of their detection. In the modern era of transient astronomy, automated telescopes like GOTO form a vital link between multi-messenger discovery facilities and in-depth follow-up by larger telescopes. GOTO is already producing a wide range of scientific results, assisted by an efficient discovery pipeline and a successful citizen science project: Kilonova Seekers.
    • Prospects for a survey of the galactic plane with the Cherenkov Telescope Array

      Institute for Cosmic Ray Research, University of Tokyo, 5-1-5, Kashiwa-no-ha, Kashiwa, Chiba 277-8582, Japan; ETH Zürich, Institute for Particle Physics and Astrophysics, Otto-Stern-Weg 5, 8093 Zürich, Switzerland; INFN and Università degli Studi di Siena, Dipartimento di Scienze Fisiche, della Terra e dell'Ambiente (DSFTA), Sezione di Fisica, Via Roma 56, 53100 Siena, Italy; Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, F-91191 Gif-sur-Yvette Cedex, France; FSLAC IRL 2009, CNRS/IAC, La Laguna, Tenerife, Spain; University of Alabama, Tuscaloosa, Department of Physics and Astronomy, Gallalee Hall, Box 870324 Tuscaloosa, AL 35487-0324, U.S.A.; Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, France; Laboratoire Leprince-Ringuet, CNRS/IN2P3, École polytechnique, Institut Polytechnique de Paris, 91120 Palaiseau, France; Departament de Física Quàntica i Astrofísica, Institut de Ciències del Cosmos, Universitat de Barcelona, IEEC-UB, Martí i Franquès, 1, 08028, Barcelona, Spain; Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, 18008, Granada, Spain; Institute for Computational Cosmology and Department of Physics, Durham University, South Road, Durham DH1 3LE, United Kingdom; Instituto de Física Teórica UAM/CSIC and Departamento de Física Teórica, Universidad Autónoma de Madrid, c/ Nicolás Cabrera 13-15, Campus de Cantoblanco UAM, 28049 Madrid, Spain; Pontificia Universidad Católica de Chile, Av. Libertador Bernardo O'Higgins 340, Santiago, Chile; et al. (Journal of Cosmology and Astroparticle Physics, 2024-10-01)
      Approximately one hundred sources of very-high-energy (VHE) gamma rays are known in the Milky Way, detected with a combination of targeted observations and surveys. A survey of the entire Galactic Plane in the energy range from a few tens of GeV to a few hundred TeV has been proposed as a Key Science Project for the upcoming Cherenkov Telescope Array Observatory (CTAO). This article presents the status of the studies towards the Galactic Plane Survey (GPS). We build and make publicly available a sky model that combines data from recent observations of known gamma-ray emitters with state-of-the-art physically-driven models of synthetic populations of the three main classes of established Galactic VHE sources (pulsar wind nebulae, young and interacting supernova remnants, and compact binary systems), as well as of interstellar emission from cosmic-ray interactions in the Milky Way. We also perform an optimisation of the observation strategy (pointing pattern and scheduling) based on recent estimations of the instrument performance. We use the improved sky model and observation strategy to simulate GPS data corresponding to a total observation time of 1620 hours spread over ten years. Data are then analysed using the methods and software tools under development for real data. Under our model assumptions and for the realisation considered, we show that the GPS has the potential to increase the number of known Galactic VHE emitters by almost a factor of five. This corresponds to the detection of more than two hundred pulsar wind nebulae and a few tens of supernova remnants at average integral fluxes one order of magnitude lower than in the existing sample above 1 TeV, therefore opening the possibility to perform unprecedented population studies. The GPS also has the potential to provide new VHE detections of binary systems and pulsars, to confirm the existence of a hypothetical population of gamma-ray pulsars with an additional TeV emission component, and to detect bright sources capable of accelerating particles to PeV energies (PeVatrons). Furthermore, the GPS will constitute a pathfinder for deeper follow-up observations of these source classes. Finally, we show that we can extract from GPS data an estimate of the contribution to diffuse emission from unresolved sources, and that there are good prospects of detecting interstellar emission and statistically distinguishing different scenarios. Thus, a survey of the entire Galactic plane carried out from both hemispheres with CTAO will ensure a transformational advance in our knowledge of Galactic VHE source populations and interstellar emission.
    • Disruption of a massive molecular cloud by a supernova in the Galactic Centre: Initial results from the ACES project

      European Southern Observatory (ESO), Karl-Schwarzschild-Straße 2, 85748, Garching, Germany; SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS, UK; European Southern Observatory (ESO), Karl-Schwarzschild-Straße 2, 85748, Garching, Germany; School of Physics and Astronomy, Cardiff University, The Parade, Cardiff, CF24 3AA, UK; Observatorio Astronómico de Quito, Escuela Politécnica Nacional, Interior del Parque La Alameda, 170136, Quito, Ecuador; Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO, 80389, USA; University of Connecticut, Department of Physics, 196A Hillside Road, Unit 3046, Storrs, CT, 06269-3046, USA; Armagh Observatory and Planetarium, College Hill, Armagh, BT61 9DB, Northern Ireland; National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA, 22903, USA; Centro de Astrobiología (CAB), CSIC-INTA, Carretera de Ajalvir km 4, Torrejón de Ardoz, 28850, Madrid, Spain; Instituto de Astronomía, Universidad Católica del Norte, Av. Angamos 0610, Antofagasta, Chile; Chinese Academy of Sciences South America Center for Astronomy, National Astronomical Observatories, CAS, Beijing, 100101, China; Department of Astronomy, University of Florida, PO Box 112055, Gainesville, FL, 32611, USA; et al. (Astronomy and Astrophysics, 2024-11-01)
      The Milky Way's Central Molecular Zone (CMZ) differs dramatically from our local solar neighbourhood, both in the extreme interstellar medium conditions it exhibits (e.g. high gas, stellar, and feedback density) and in the strong dynamics at play (e.g. due to shear and gas influx along the bar). Consequently, it is likely that there are large-scale physical structures within the CMZ that cannot form elsewhere in the Milky Way. In this paper, we present new results from the Atacama Large Millimeter/submillimeter Array (ALMA) large programme ACES (ALMA CMZ Exploration Survey) and conduct a multi-wavelength and kinematic analysis to determine the origin of the M0.8–0.2 ring, a molecular cloud with a distinct ring-like morphology. We estimate the projected inner and outer radii of the M0.8–0.2 ring to be 79″ and 154″, respectively (3.1 pc and 6.1 pc at an assumed Galactic Centre distance of 8.2 kpc) and calculate a mean gas density &gt;10<SUP>4</SUP> cm<SUP>‑3</SUP>, a mass of ~10<SUP>6</SUP> M<SUB>⊙</SUB>, and an expansion speed of ~20 km s<SUP>‑1</SUP>, resulting in a high estimated kinetic energy (&gt;10<SUP>51</SUP> erg) and momentum (&gt;10<SUP>7</SUP> M<SUB>⊙</SUB> km s<SUP>‑1</SUP>). We discuss several possible causes for the existence and expansion of the structure, including stellar feedback and large-scale dynamics. We propose that the most likely cause of the M0.8–0.2 ring is a single high-energy hypernova explosion. To viably explain the observed morphology and kinematics, such an explosion would need to have taken place inside a dense, very massive molecular cloud, the remnants of which we now see as the M0.8–0.2 ring. In this case, the structure provides an extreme example of how supernovae can affect molecular clouds.
    • JCMT 850 μm Continuum Observations of Density Structures in the G35 Molecular Complex

      School of Physics and Astronomy, Yunnan University, Kunming, 650091, People's Republic of China; National Astronomical Observatories, Chinese Academy of Sciences, Datun Road A20, Beijing, People's Republic of China; CAS Key Laboratory of FAST, NAOC, Chinese Academy of Sciences, Beijing, People's Republic of China; University of Chinese Academy of Sciences, Beijing, People's Republic of China; Indian Institute of Space Science and Technology, Thiruvananthapuram, Kerala 695 547, India; National Astronomical Observatories, Chinese Academy of Sciences, Datun Road A20, Beijing, People's Republic of China; Department of Astronomy, Tsinghua University, Beijing 100084, People's Republic of China; Zhejiang Lab, Hangzhou, Zhejiang 311121, People's Republic of China; Department of Physics, National Sun Yat-Sen University, No. 70, Lien-Hai Road, Kaohsiung City 80424, Taiwan; Center of Astronomy and Gravitation, National Taiwan Normal University, Taipei 116, Taiwan; Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK; Physikalisches Institut, University of Cologne, Zülpicher Str. 77, D-50937 Köln, Germany; National Astronomical Observatories, Chinese Academy of Sciences, Datun Road A20, Beijing, People's Republic of China; CAS Key Laboratory of FAST, NAOC, Chinese Academy of Sciences, Beijing, People's Republic of China; University of Chinese Academy of Sciences, Beijing, People's Republic of China; National Astronomical Observatories, Chinese Academy of Sciences, Datun Road A20, Beijing, People's Republic of China; Key Laboratory of Radio Astronomy and Technology, Chinese Academy of Sciences, A20 Datun Road, Datun Road A20, Beijing, People's Republic of China; Max-Plank-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany; Academia Sinica Institute of Astronomy and Astrophysics, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan; et al. (The Astrophysical Journal, 2024-10-01)
      Filaments are believed to play a key role in high-mass star formation. We present a systematic study of the filaments and their hosting clumps in the G35 molecular complex using James Clerk Maxwell Telescope SCUBA-2 850 μm continuum data. We identified five clouds in the complex and 91 filaments within them, some of which form 10 hub–filament systems (HFSs), each with at least three hub-composing filaments. We also compiled a catalog of 350 dense clumps, 183 of which are associated with the filaments. We investigated the physical properties of the filaments and clumps, such as mass, density, and size, and their relation to star formation. We find that the global mass–length trend of the filaments is consistent with a turbulent origin, while the hub-composing filaments of high line masses (m <SUB>l</SUB> &gt; 230 M <SUB>⊙</SUB> pc<SUP>‑1</SUP>) in HFSs deviate from this relation, possibly due to feedback from massive star formation. We also find that the most massive and densest clumps (R &gt; 0.2 pc, M &gt; 35 M <SUB>⊙</SUB>, Σ &gt; 0.05 g cm<SUP>‑2</SUP>) are located in the filaments and in the hubs of HFSs, with the latter bearing a higher probability of the occurrence of high-mass star-forming signatures, highlighting the preferential sites of HFSs for high-mass star formation. We do not find significant variation in the clump mass surface density across different evolutionary environments of the clouds, which may reflect the balance between mass accretion and stellar feedback.
    • Atacama Large Aperture Submillimeter Telescope (AtLAST) science: Our Galaxy

      UK Astronomy Technology Centre, Royal Observatory Edinburgh, Edinburgh, EH9 3HJ, UK; IAPS-INAF, Rome, I-00133, Italy; Osservatorio Astrofisico di Arcetri, INAF, Firenze, 50125, Italy; Department of Physics and Astronomy, University College London, London, England, WC1E 6BT, UK; Center for Astrophysics, Harvard &amp; Smithsonian, Cambridge, MA, 02138-1516, USA; Academia Sinica Institute of Astronomy and Astrophysics, Taipei, 10617, Taiwan; Department of Astrophysics, University of Vienna, Vienna, 1180, Austria; Leiden Observatory, Leiden University, Leiden, South Holland, 2300-RA, The Netherlands; Department of Space, Earth and Environment, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden; Observatoire Astronomique de Strasbourg, Universite de Strasbourg, Strasbourg, Grand Est, F-67000, France; School of Physics and Astronomy, Cardiff University, Cardiff, Wales, CF24 3AA, UK; et al. (Open Research Europe, 2024-06-01)
      As we learn more about the multi-scale interstellar medium (ISM) of our Galaxy, we develop a greater understanding for the complex relationships between the large-scale diffuse gas and dust in Giant Molecular Clouds (GMCs), how it moves, how it is affected by the nearby massive stars, and which portions of those GMCs eventually collapse into star forming regions. The complex interactions of those gas, dust and stellar populations form what has come to be known as the ecology of our Galaxy. Because we are deeply embedded in the plane of our Galaxy, it takes up a significant fraction of the sky, with complex dust lanes scattered throughout the optically recognizable bands of the Milky Way. These bands become bright at (sub-)millimetre wavelengths, where we can study dust thermal emission and the chemical and kinematic signatures of the gas. To properly study such large-scale environments, requires deep, large area surveys that are not possible with current facilities. Moreover, where stars form, so too do planetary systems, growing from the dust and gas in circumstellar discs, to planets and planetesimal belts. Understanding the evolution of these belts requires deep imaging capable of studying belts around young stellar objects to Kuiper belt analogues around the nearest stars. Here we present a plan for observing the Galactic Plane and circumstellar environments to quantify the physical structure, the magnetic fields, the dynamics, chemistry, star formation, and planetary system evolution of the galaxy in which we live with AtLAST; a concept for a new, 50m single-dish sub-mm telescope with a large field of view which is the only type of facility that will allow us to observe our Galaxy deeply and widely enough to make a leap forward in our understanding of our local ecology.
    • Atacama Large Aperture Submillimeter Telescope (AtLAST) science: Our Galaxy

      UK Astronomy Technology Centre, Royal Observatory Edinburgh, Edinburgh, EH9 3HJ, UK; IAPS-INAF, Rome, I-00133, Italy; Osservatorio Astrofisico di Arcetri, INAF, Firenze, 50125, Italy; Department of Physics and Astronomy, University College London, London, England, WC1E 6BT, UK; Center for Astrophysics, Harvard &amp; Smithsonian, Cambridge, MA, 02138-1516, USA; Academia Sinica Institute of Astronomy and Astrophysics, Taipei, 10617, Taiwan; Department of Astrophysics, University of Vienna, Vienna, 1180, Austria; Leiden Observatory, Leiden University, Leiden, South Holland, 2300-RA, The Netherlands; Department of Space, Earth and Environment, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden; Observatoire Astronomique de Strasbourg, Universite de Strasbourg, Strasbourg, Grand Est, F-67000, France; School of Physics and Astronomy, Cardiff University, Cardiff, Wales, CF24 3AA, UK; et al. (Open Research Europe, 2024-06-01)
      As we learn more about the multi-scale interstellar medium (ISM) of our Galaxy, we develop a greater understanding for the complex relationships between the large-scale diffuse gas and dust in Giant Molecular Clouds (GMCs), how it moves, how it is affected by the nearby massive stars, and which portions of those GMCs eventually collapse into star forming regions. The complex interactions of those gas, dust and stellar populations form what has come to be known as the ecology of our Galaxy. Because we are deeply embedded in the plane of our Galaxy, it takes up a significant fraction of the sky, with complex dust lanes scattered throughout the optically recognizable bands of the Milky Way. These bands become bright at (sub-)millimetre wavelengths, where we can study dust thermal emission and the chemical and kinematic signatures of the gas. To properly study such large-scale environments, requires deep, large area surveys that are not possible with current facilities. Moreover, where stars form, so too do planetary systems, growing from the dust and gas in circumstellar discs, to planets and planetesimal belts. Understanding the evolution of these belts requires deep imaging capable of studying belts around young stellar objects to Kuiper belt analogues around the nearest stars. Here we present a plan for observing the Galactic Plane and circumstellar environments to quantify the physical structure, the magnetic fields, the dynamics, chemistry, star formation, and planetary system evolution of the galaxy in which we live with AtLAST; a concept for a new, 50m single-dish sub-mm telescope with a large field of view which is the only type of facility that will allow us to observe our Galaxy deeply and widely enough to make a leap forward in our understanding of our local ecology.
    • Atacama Large Aperture Submillimeter Telescope (AtLAST) science: Our Galaxy

      UK Astronomy Technology Centre, Royal Observatory Edinburgh, Edinburgh, EH9 3HJ, UK; IAPS-INAF, Rome, I-00133, Italy; Osservatorio Astrofisico di Arcetri, INAF, Firenze, 50125, Italy; Department of Physics and Astronomy, University College London, London, England, WC1E 6BT, UK; Center for Astrophysics, Harvard &amp; Smithsonian, Cambridge, MA, 02138-1516, USA; Academia Sinica Institute of Astronomy and Astrophysics, Taipei, 10617, Taiwan; Department of Astrophysics, University of Vienna, Vienna, 1180, Austria; Leiden Observatory, Leiden University, Leiden, South Holland, 2300-RA, The Netherlands; Department of Space, Earth and Environment, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden; Observatoire Astronomique de Strasbourg, Universite de Strasbourg, Strasbourg, Grand Est, F-67000, France; School of Physics and Astronomy, Cardiff University, Cardiff, Wales, CF24 3AA, UK; et al. (Open Research Europe, 2024-06-01)
      As we learn more about the multi-scale interstellar medium (ISM) of our Galaxy, we develop a greater understanding for the complex relationships between the large-scale diffuse gas and dust in Giant Molecular Clouds (GMCs), how it moves, how it is affected by the nearby massive stars, and which portions of those GMCs eventually collapse into star forming regions. The complex interactions of those gas, dust and stellar populations form what has come to be known as the ecology of our Galaxy. Because we are deeply embedded in the plane of our Galaxy, it takes up a significant fraction of the sky, with complex dust lanes scattered throughout the optically recognizable bands of the Milky Way. These bands become bright at (sub-)millimetre wavelengths, where we can study dust thermal emission and the chemical and kinematic signatures of the gas. To properly study such large-scale environments, requires deep, large area surveys that are not possible with current facilities. Moreover, where stars form, so too do planetary systems, growing from the dust and gas in circumstellar discs, to planets and planetesimal belts. Understanding the evolution of these belts requires deep imaging capable of studying belts around young stellar objects to Kuiper belt analogues around the nearest stars. Here we present a plan for observing the Galactic Plane and circumstellar environments to quantify the physical structure, the magnetic fields, the dynamics, chemistry, star formation, and planetary system evolution of the galaxy in which we live with AtLAST; a concept for a new, 50m single-dish sub-mm telescope with a large field of view which is the only type of facility that will allow us to observe our Galaxy deeply and widely enough to make a leap forward in our understanding of our local ecology.
    • Atacama Large Aperture Submillimeter Telescope (AtLAST) science: Our Galaxy

      UK Astronomy Technology Centre, Royal Observatory Edinburgh, Edinburgh, EH9 3HJ, UK; IAPS-INAF, Rome, I-00133, Italy; Osservatorio Astrofisico di Arcetri, INAF, Firenze, 50125, Italy; Department of Physics and Astronomy, University College London, London, England, WC1E 6BT, UK; Center for Astrophysics, Harvard &amp; Smithsonian, Cambridge, MA, 02138-1516, USA; Academia Sinica Institute of Astronomy and Astrophysics, Taipei, 10617, Taiwan; Department of Astrophysics, University of Vienna, Vienna, 1180, Austria; Leiden Observatory, Leiden University, Leiden, South Holland, 2300-RA, The Netherlands; Department of Space, Earth and Environment, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden; Observatoire Astronomique de Strasbourg, Universite de Strasbourg, Strasbourg, Grand Est, F-67000, France; School of Physics and Astronomy, Cardiff University, Cardiff, Wales, CF24 3AA, UK; et al. (Open Research Europe, 2024-06-01)
      As we learn more about the multi-scale interstellar medium (ISM) of our Galaxy, we develop a greater understanding for the complex relationships between the large-scale diffuse gas and dust in Giant Molecular Clouds (GMCs), how it moves, how it is affected by the nearby massive stars, and which portions of those GMCs eventually collapse into star forming regions. The complex interactions of those gas, dust and stellar populations form what has come to be known as the ecology of our Galaxy. Because we are deeply embedded in the plane of our Galaxy, it takes up a significant fraction of the sky, with complex dust lanes scattered throughout the optically recognizable bands of the Milky Way. These bands become bright at (sub-)millimetre wavelengths, where we can study dust thermal emission and the chemical and kinematic signatures of the gas. To properly study such large-scale environments, requires deep, large area surveys that are not possible with current facilities. Moreover, where stars form, so too do planetary systems, growing from the dust and gas in circumstellar discs, to planets and planetesimal belts. Understanding the evolution of these belts requires deep imaging capable of studying belts around young stellar objects to Kuiper belt analogues around the nearest stars. Here we present a plan for observing the Galactic Plane and circumstellar environments to quantify the physical structure, the magnetic fields, the dynamics, chemistry, star formation, and planetary system evolution of the galaxy in which we live with AtLAST; a concept for a new, 50m single-dish sub-mm telescope with a large field of view which is the only type of facility that will allow us to observe our Galaxy deeply and widely enough to make a leap forward in our understanding of our local ecology.
    • A numerical study of near-Earth asteroid family orbital dispersion

      Department of Physics and Astronomy, Queen's University Belfast, University Road, Belfast BT7 1NN, UK; Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DG, UK; Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DG, UK; Humpage, A.; Christou, A. A. (Monthly Notices of the Royal Astronomical Society, 2024-09-01)
      We have studied the evolution of near-Earth asteroid (NEA) families and pairs to inform future searches. To do so, we integrated clusters of simulated NEAs with different initial conditions, namely the orbital inclination, ejection speed, and the effects of mean-motion resonances on the parent body prior to breakup while also varying the orbit, mass, and number of perturbing planetary bodies. We studied the orbital element dispersion rates of NEA family members and found a power-law increase in those families whose orbits brought them close to a planet. This allowed us to conclude that family dispersion is significantly affected by the Kozai-Lidov effect due to oscillations in the eccentricity, and that the rate of dispersion is slowest at high inclination relatively far from the nearest planet. In most cases, the ejection speed of the initial breakup does not affect the dispersion, except within weaker mean-motion resonances where more violent breakups will result in the ejection of a fraction of the asteroids, causing a large increase in dispersion. Within mean-motion resonances, where Kozai-Lidov oscillations are slowed, increases in the dispersion of a family are delayed, leading them to be identifiable for longer.
    • Prospects for γ-ray observations of the Perseus galaxy cluster with the Cherenkov Telescope Array

      Department of Physics, Tokai University, 4-1-1, Kita-Kaname, Hiratsuka, Kanagawa 259-1292, Japan; Institute for Cosmic Ray Research, University of Tokyo, 5-1-5, Kashiwa-no-ha, Kashiwa, Chiba 277-8582, Japan; Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, F-91191 Gif-sur-Yvette Cedex, France; FSLAC IRL 2009, CNRS/IAC, La Laguna, Tenerife, Spain; University of Alabama, Tuscaloosa, Department of Physics and Astronomy, Gallalee Hall, Box 870324 Tuscaloosa, AL 35487-0324, U.S.A.; Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, France; Laboratoire Leprince-Ringuet, CNRS/IN2P3, École polytechnique, Institut Polytechnique de Paris, 91120 Palaiseau, France; Departament de Física Quàntica i Astrofísica, Institut de Ciències del Cosmos, Universitat de Barcelona, IEEC-UB, Martí i Franquès, 1, 08028, Barcelona, Spain; Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, 18008, Granada, Spain; Instituto de Física Teórica UAM/CSIC and Departamento de Física Teórica, Universidad Autónoma de Madrid, c/ Nicolás Cabrera 13-15, Campus de Cantoblanco UAM, 28049 Madrid, Spain; Pontificia Universidad Católica de Chile, Av. Libertador Bernardo O'Higgins 340, Santiago, Chile; Universidad Nacional Autónoma de México, Delegación Coyoacán, 04510 Ciudad de México, Mexico; et al. (Journal of Cosmology and Astroparticle Physics, 2024-10-01)
      Galaxy clusters are expected to be both dark matter (DM) reservoirs and storage rooms for the cosmic-ray protons (CRp) that accumulate along the cluster's formation history. Accordingly, they are excellent targets to search for signals of DM annihilation and decay at γ-ray energies and are predicted to be sources of large-scale γ-ray emission due to hadronic interactions in the intracluster medium (ICM). In this paper, we estimate the sensitivity of the Cherenkov Telescope Array (CTA) to detect diffuse γ-ray emission from the Perseus galaxy cluster. We first perform a detailed spatial and spectral modelling of the expected signal for both the DM and the CRp components. For each case, we compute the expected CTA sensitivity accounting for the CTA instrument response functions. The CTA observing strategy of the Perseus cluster is also discussed. In the absence of a diffuse signal (non-detection), CTA should constrain the CRp to thermal energy ratio X <SUB>500</SUB> within the characteristic radius R <SUB>500</SUB> down to about X <SUB>500</SUB> &lt; 3 × 10<SUP>-3</SUP>, for a spatial CRp distribution that follows the thermal gas and a CRp spectral index α<SUB>CRp</SUB> = 2.3. Under the optimistic assumption of a pure hadronic origin of the Perseus radio mini-halo and depending on the assumed magnetic field profile, CTA should measure α<SUB>CRp</SUB> down to about Δα<SUB>CRp</SUB> ≃ 0.1 and the CRp spatial distribution with 10% precision, respectively. Regarding DM, CTA should improve the current ground-based γ-ray DM limits from clusters observations on the velocity-averaged annihilation cross-section by a factor of up to ∼ 5, depending on the modelling of DM halo substructure. In the case of decay of DM particles, CTA will explore a new region of the parameter space, reaching models with τ <SUB>χ</SUB> &gt; 10<SUP>27</SUP> s for DM masses above 1 TeV. These constraints will provide unprecedented sensitivity to the physics of both CRp acceleration and transport at cluster scale and to TeV DM particle models, especially in the decay scenario.
    • Prospects for γ-ray observations of the Perseus galaxy cluster with the Cherenkov Telescope Array

      Department of Physics, Tokai University, 4-1-1, Kita-Kaname, Hiratsuka, Kanagawa 259-1292, Japan; Institute for Cosmic Ray Research, University of Tokyo, 5-1-5, Kashiwa-no-ha, Kashiwa, Chiba 277-8582, Japan; Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, F-91191 Gif-sur-Yvette Cedex, France; FSLAC IRL 2009, CNRS/IAC, La Laguna, Tenerife, Spain; University of Alabama, Tuscaloosa, Department of Physics and Astronomy, Gallalee Hall, Box 870324 Tuscaloosa, AL 35487-0324, U.S.A.; Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, France; Laboratoire Leprince-Ringuet, CNRS/IN2P3, École polytechnique, Institut Polytechnique de Paris, 91120 Palaiseau, France; Departament de Física Quàntica i Astrofísica, Institut de Ciències del Cosmos, Universitat de Barcelona, IEEC-UB, Martí i Franquès, 1, 08028, Barcelona, Spain; Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, 18008, Granada, Spain; Instituto de Física Teórica UAM/CSIC and Departamento de Física Teórica, Universidad Autónoma de Madrid, c/ Nicolás Cabrera 13-15, Campus de Cantoblanco UAM, 28049 Madrid, Spain; Pontificia Universidad Católica de Chile, Av. Libertador Bernardo O'Higgins 340, Santiago, Chile; Universidad Nacional Autónoma de México, Delegación Coyoacán, 04510 Ciudad de México, Mexico; et al. (Journal of Cosmology and Astroparticle Physics, 2024-10-01)
      Galaxy clusters are expected to be both dark matter (DM) reservoirs and storage rooms for the cosmic-ray protons (CRp) that accumulate along the cluster's formation history. Accordingly, they are excellent targets to search for signals of DM annihilation and decay at γ-ray energies and are predicted to be sources of large-scale γ-ray emission due to hadronic interactions in the intracluster medium (ICM). In this paper, we estimate the sensitivity of the Cherenkov Telescope Array (CTA) to detect diffuse γ-ray emission from the Perseus galaxy cluster. We first perform a detailed spatial and spectral modelling of the expected signal for both the DM and the CRp components. For each case, we compute the expected CTA sensitivity accounting for the CTA instrument response functions. The CTA observing strategy of the Perseus cluster is also discussed. In the absence of a diffuse signal (non-detection), CTA should constrain the CRp to thermal energy ratio X <SUB>500</SUB> within the characteristic radius R <SUB>500</SUB> down to about X <SUB>500</SUB> &lt; 3 × 10<SUP>-3</SUP>, for a spatial CRp distribution that follows the thermal gas and a CRp spectral index α<SUB>CRp</SUB> = 2.3. Under the optimistic assumption of a pure hadronic origin of the Perseus radio mini-halo and depending on the assumed magnetic field profile, CTA should measure α<SUB>CRp</SUB> down to about Δα<SUB>CRp</SUB> ≃ 0.1 and the CRp spatial distribution with 10% precision, respectively. Regarding DM, CTA should improve the current ground-based γ-ray DM limits from clusters observations on the velocity-averaged annihilation cross-section by a factor of up to ∼ 5, depending on the modelling of DM halo substructure. In the case of decay of DM particles, CTA will explore a new region of the parameter space, reaching models with τ <SUB>χ</SUB> &gt; 10<SUP>27</SUP> s for DM masses above 1 TeV. These constraints will provide unprecedented sensitivity to the physics of both CRp acceleration and transport at cluster scale and to TeV DM particle models, especially in the decay scenario.
    • Binarity at LOw Metallicity (BLOeM): A spectroscopic VLT monitoring survey of massive stars in the SMC

      The School of Physics and Astronomy, Tel Aviv University, Tel Aviv, 6997801, Israel; ESO – European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748, Garching bei München, Germany; Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium; Department of Physics &amp; Astronomy, Hounsfield Road, University of Sheffield, Sheffield, S3 7RH, UK; Instituto de Astrofísica de Canarias, C. Vía Láctea, s/n, 38205, La Laguna, Santa Cruz de Tenerife, Spain; Universidad de La Laguna, Dpto. Astrofísica, Av. Astrofśico Francisco Sánchez, 38206, La Laguna, Santa Cruz de Tenerife, Spain; Escola de Ciências e Tecnologia, Universidade Federal do Rio Grande do Norte, Natal, RN, 59072-970, Brazil; Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr. 12–14, 69120, Heidelberg, Germany; School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK; Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium; Heidelberger Institut für Theoretische Studien, Schloss-Wolfsbrunnenweg 35, 69118, Heidelberg, Germany; Universität Heidelberg, Department of Physics and Astronomy, Im Neuenheimer Feld 226, 69120, Heidelberg, Germany; Royal Observatory of Belgium, Avenue Circulaire/Ringlaan 3, 1180, Brussels, Belgium; et al. (Astronomy and Astrophysics, 2024-10-01)
      Surveys in the Milky Way and Large Magellanic Cloud have revealed that the majority of massive stars will interact with companions during their lives. However, knowledge of the binary properties of massive stars at low metallicity, and therefore in conditions approaching those of the Early Universe, remain sparse. We present the Binarity at LOw Metallicity (BLOeM) campaign, an ESO large programme designed to obtain 25 epochs of spectroscopy for 929 massive stars in the Small Magellanic Cloud, allowing us to probe multiplicity in the lowest-metallicity conditions to date (Z = 0.2 Z<SUB>⊙</SUB>). BLOeM will provide (i) the binary fraction, (ii) the orbital configurations of systems with periods of P ≲ 3 yr, (iii) dormant black-hole binary candidates (OB+BH), and (iv) a legacy database of physical parameters of massive stars at low metallicity. Main sequence (OB-type) and evolved (OBAF-type) massive stars are observed with the LR02 setup of the GIRAFFE instrument of the Very Large Telescope (3960–4570 Å resolving power R = 6200; typical signal-to-noise ratio(S/N) ≈70–100). This paper utilises the first nine epochs obtained over a three-month time period. We describe the survey and data reduction, perform a spectral classification of the stacked spectra, and construct a Hertzsprung-Russell diagram of the sample via spectral-type and photometric calibrations. Our detailed classification reveals that the sample covers spectral types from O4 to F5, spanning the effective temperature and luminosity ranges 6.5 ≲ T<SUB>eff</SUB>/kK ≲ 45 and 3.7 &lt; log L/L<SUB>⊙</SUB> &lt; 6.1 and initial masses of 8 ≲ M<SUB>ini</SUB> ≲ 80 M<SUB>⊙</SUB>. The sample comprises 159 O-type stars, 331 early B-type (B0–3) dwarfs and giants (luminosity classes V–III), 303 early B-type supergiants (II–I), and 136 late-type BAF supergiants. At least 82 stars are OBe stars: 20 O-type and 62 B-type (13% and 11% of the respective samples). In addition, the sample includes 4 high-mass X-ray binaries, 3 stars resembling luminous blue variables, 2 bloated stripped-star candidates, 2 candidate magnetic stars, and 74 eclipsing binaries.
    • Binarity at LOw Metallicity (BLOeM): A spectroscopic VLT monitoring survey of massive stars in the SMC

      The School of Physics and Astronomy, Tel Aviv University, Tel Aviv, 6997801, Israel; ESO – European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748, Garching bei München, Germany; Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium; Department of Physics &amp; Astronomy, Hounsfield Road, University of Sheffield, Sheffield, S3 7RH, UK; Instituto de Astrofísica de Canarias, C. Vía Láctea, s/n, 38205, La Laguna, Santa Cruz de Tenerife, Spain; Universidad de La Laguna, Dpto. Astrofísica, Av. Astrofśico Francisco Sánchez, 38206, La Laguna, Santa Cruz de Tenerife, Spain; Escola de Ciências e Tecnologia, Universidade Federal do Rio Grande do Norte, Natal, RN, 59072-970, Brazil; Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr. 12–14, 69120, Heidelberg, Germany; School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK; Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium; Heidelberger Institut für Theoretische Studien, Schloss-Wolfsbrunnenweg 35, 69118, Heidelberg, Germany; Universität Heidelberg, Department of Physics and Astronomy, Im Neuenheimer Feld 226, 69120, Heidelberg, Germany; Royal Observatory of Belgium, Avenue Circulaire/Ringlaan 3, 1180, Brussels, Belgium; et al. (Astronomy and Astrophysics, 2024-10-01)
      Surveys in the Milky Way and Large Magellanic Cloud have revealed that the majority of massive stars will interact with companions during their lives. However, knowledge of the binary properties of massive stars at low metallicity, and therefore in conditions approaching those of the Early Universe, remain sparse. We present the Binarity at LOw Metallicity (BLOeM) campaign, an ESO large programme designed to obtain 25 epochs of spectroscopy for 929 massive stars in the Small Magellanic Cloud, allowing us to probe multiplicity in the lowest-metallicity conditions to date (Z = 0.2 Z<SUB>⊙</SUB>). BLOeM will provide (i) the binary fraction, (ii) the orbital configurations of systems with periods of P ≲ 3 yr, (iii) dormant black-hole binary candidates (OB+BH), and (iv) a legacy database of physical parameters of massive stars at low metallicity. Main sequence (OB-type) and evolved (OBAF-type) massive stars are observed with the LR02 setup of the GIRAFFE instrument of the Very Large Telescope (3960–4570 Å resolving power R = 6200; typical signal-to-noise ratio(S/N) ≈70–100). This paper utilises the first nine epochs obtained over a three-month time period. We describe the survey and data reduction, perform a spectral classification of the stacked spectra, and construct a Hertzsprung-Russell diagram of the sample via spectral-type and photometric calibrations. Our detailed classification reveals that the sample covers spectral types from O4 to F5, spanning the effective temperature and luminosity ranges 6.5 ≲ T<SUB>eff</SUB>/kK ≲ 45 and 3.7 &lt; log L/L<SUB>⊙</SUB> &lt; 6.1 and initial masses of 8 ≲ M<SUB>ini</SUB> ≲ 80 M<SUB>⊙</SUB>. The sample comprises 159 O-type stars, 331 early B-type (B0–3) dwarfs and giants (luminosity classes V–III), 303 early B-type supergiants (II–I), and 136 late-type BAF supergiants. At least 82 stars are OBe stars: 20 O-type and 62 B-type (13% and 11% of the respective samples). In addition, the sample includes 4 high-mass X-ray binaries, 3 stars resembling luminous blue variables, 2 bloated stripped-star candidates, 2 candidate magnetic stars, and 74 eclipsing binaries.
    • The clumped winds of the most massive stars

      Anton Pannekoek Institute for Astronomy, University of Amsterdam, 1090 GE Amsterdam, The Netherlands; Anton Pannekoek Institute for Astronomy, University of Amsterdam, 1090 GE Amsterdam, The Netherlands; Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium; Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, UK; Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium; LMU München, Universitätssternwarte, Scheinerstr. 1, 81679 München, Germany; Department of Aerospace, Physics and Space Sciences, Florida Institute of Technology, 150 W. University Boulevard, Melbourne, FL 32901, USA; Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium; European Southern Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile; Centro de Astrobiología, CSIC-INTA. Crtra. de Torrejón a Ajalvir km 4. 28850 Torrejón de Ardoz (Madrid, ), Spain; Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany; Heidelberger Institut für Theoretische Studien, Schloss-Wolfsbrunnenweg 35, 69118 Heidelberg, Germany; Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, 69120 Heidelberg, Germany; et al. (IAU Symposium, 2024-01-01)
      The core of the cluster R136 in the Large Magellanic Cloud hosts the most massive stars known. The high mass-loss rates of these stars strongly impact their surroundings, as well as the evolution of the stars themselves. To quantify this impact accurate mass-loss rates are needed, however, uncertainty about the degree of inhomogeneity of the winds (`wind clumping'), makes mass-loss measurements uncertain. We combine optical and ultraviolet HST/STIS spectroscopy of 56 stars in the core of R136 in order to put constraints on the wind structure, improving the accuracy of the mass-loss rate measurements. We find that the winds are highly clumped, and use our measured mass-loss rates to test theoretical predictions. Furthermore we find, for the first time, tentative trends in the wind-structure parameters as a function of mass-loss rate, suggesting that the winds of stars with higher mass-loss rates are less clumped than those with lower mass-loss rates.
    • Constraining physical processes in pre-supernovae massive star evolution

      Armagh Observatory, and Planetarium, College Hill, Armagh BT61 9DG, N. Ireland; Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr. 12-14, 69120 Heidelberg, Germany; Astrophysics Group, Keele University, Keele, Staffordshire, ST5 5BG, UK; Kavli Institute for the Physics and Mathematics of the Universe, (WPI), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, 277-8583, Japan; Higgins, Erin R.; Vink, Jorick S.; Sander, Andreas; Hirschi, Raphael (IAU Symposium, 2024-01-01)
      While we have growing numbers of massive star observations, it remains unclear how efficient the key physical processes such as mass loss, convection and rotation are, or indeed how they impact each other. We reconcile this with detailed stellar evolution models, yet these models have their own drawbacks with necessary assumptions for 3-dimensional processes like rotation which need to be adapted into 1-dimensional models. The implementation of empirical mass-loss prescriptions in stellar evolution codes can lead to the extrapolation of base rates to unconstrained evolutionary stages leading to a range of uncertain fates. In short, there remain many free parameters and physical processes which need to be calibrated in order to align our theory better with upcoming observations. We have tested various processes such as mass loss and internal mixing, including rotational mixing and convective overshooting, against multiple observational constraints such as using eclipsing binaries, the Humphreys-Davidson limit, and the final masses of Wolf-Rayet stars, across a range of metallicities. In fact, we developed a method of disentangling the effects of mixing and mass loss in the `Mass-Luminosity Plane' allowing direct calibration of these processes. In all cases, it is important to note that a combined appreciation for both stellar winds and internal mixing are important to reproduce observations.
    • Predictions for the Maximum Masses of Black Holes below the PI Boundary

      Armagh Observatory and Planetarium; Queen's University Belfast; Armagh Observatory and Planetarium; Winch, Ethan; Vink, Jorick; Higgins, Erin; Sabhahit, Gautham (IAU General Assembly, 2024-08-01)
      While the initial discovery of GW150914 resulted in the detection of black holes larger than initially expected, it was the GW190521 event which truly challenged astrophysical assumptions about stellar evolution and black hole progenitors, as the components of GW190521 were firmly within the traditional Pair-Instability (PI) mass-gap – a range of masses where no black holes were expected to be created due to PI supernovae (PISN). We investigate the possibility that this merger involved first generation black holes, and that the unexpectedly heavy 85 solar mass BH could be produced from fundamental stellar physics. We present the results of studies involving the stellar evolution code MESA, as we systematically vary several parameters of stellar physics (in particular mixing and mass loss) to test assumptions and build a population of potential black hole progenitors within the traditional PI gap.