Solar and Stellar Astrophysics (astro-ph.SR)
Fri, 08 Sep 2023
1.A study of the stellar photosphere-hydrogen ionization front interaction in $δ$ Scuti stars
Authors:Mami Deka, Shashi M. Kanbur, Sukanta Deb, Susmita Das
Abstract: Pulsating variable $\delta$ Scuti stars are intermediate-mass stars with masses in the range of $1-3$ $M_{\odot}$ and spectral types between $A2$ and $F2$. They can be found at the intersection of the Cepheid instability strip with the main sequence. They can be used as astrophysical laboratories to test theories of stellar evolution and pulsation. In this contribution, we investigate the observed period-colour and amplitude-colour (PCAC) relations at maximum/mean/minimum light of Galactic bulge and Large Magellanic Cloud $\delta$ Scuti stars for the first time and test the hydrogen ionization front (HIF)-photosphere interaction theory using the MESA- RSP code. The PCAC relations, as a function of pulsation phase, are crucial probes of the structure of the outer stellar envelope and provide insight into the physics of stellar pulsation and evolution. The observed behaviour of the $\delta$ Scuti PCAC relations is consistent with the theory of the interaction between the HIF and the stellar photosphere.
2.Prediction of even and odd sunspot cycles
Authors:Timo Asikainen, Jani Mantere
Abstract: Here we study the prediction of even and odd numbered sunspot cycles separately, thereby taking into account the Hale cyclicity of solar magnetism. We first show that the temporal evolution and shape of all sunspot cycles are extremely well described by a simple parameterized mathematical expression. We find that the parameters describing even sunspot cycles can be predicted quite accurately using the sunspot number 41 months prior to sunspot minimum as a precursor. We find that the parameters of the odd cycles can be best predicted with maximum geomagnetic aa index close to fall equinox within a 3-year window preceding the sunspot minimum. We use the found precursors to predict all previous sunspot cycles and evaluate the performance with a cross-validation methodology, which indicates that each past cycle is very accurately predicted. For the coming sunspot cycle 25 we predict an amplitude of 171 +/- 23 and the end of the cycle in September 2029 +/- 1.9 years. We are also able to make a rough prediction for cycle 26 based on the predicted cycle 25. While the uncertainty for the cycle amplitude is large we estimate that the cycle 26 will most likely be stronger than cycle 25. These results suggest an increasing trend in solar activity for the next decades.
3.Heating and cooling in stellar coronae: coronal rain on a young Sun
Authors:Simon Daley-Yates, Moira M. Jardine, Craig D. Johnston
Abstract: Recent observations of rapidly-rotating cool dwarfs have revealed H$\alpha$ line asymmetries indicative of clumps of cool, dense plasma in the stars' coronae. These clumps may be either long-lived (persisting for more than one stellar rotation) or dynamic. The fastest dynamic features show velocities greater than the escape speed, suggesting that they may be centrifugally ejected from the star, contributing to the stellar angular momentum loss. Many however show lower velocities, similar to coronal rain observed on the Sun. We present 2.5D magnetohydrodynamic simulations of the formation and dynamics of these condensations in a rapidly rotating ($P_{\rm rot}~=~ 1 \ \mathrm{day}$) young Sun. Formation is triggered by excess surface heating. This pushes the system out of thermal equilibrium and triggers a thermal instability. The resulting condensations fall back towards the surface. They exhibit quasi-periodic behaviour, with periods longer than typical periods for solar coronal rain. We find line-of-sight velocities for these clumps in the range $50 \ \mathrm{km} \ \mathrm{s}^{-1}$ (blue shifted) to $250 \ \mathrm{km} \ \mathrm{s}^{-1}$ (red shifted). These are typical of those inferred from stellar H$\alpha$ line asymmetries, but the inferred clump masses of $3.6\times 10^{14}\ \mathrm{g}$ are significantly smaller. We find that a maximum of $\simeq~3\%$ of the coronal mass is cool clumps. We conclude that coronal rain may be common in solar like stars, but may appear on much larger scales in rapid rotators.
4.VLTI/GRAVITY Observations and Characterization of the Brown Dwarf Companion HD 72946 B
Authors:William O. Balmer Department of Physics \& Astronomy, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA Space Telescope Science Institute, Baltimore, MD 21218, USA, Laurent Pueyo Department of Physics \& Astronomy, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA, Tomas Stolker Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands, Sylvestre Lacour LESIA, Observatoire de Paris, PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Janssen, 92195 Meudon, France European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany, Anne-Lise Maire Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France, Paul Mollière Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany, Mathias Nowak Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, United Kingdom, David Sing Department of Physics \& Astronomy, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA Department of Earth \& Planetary Sciences, Johns Hopkins University, Baltimore, MD, USA, Nicolas Pourré European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany, Sarah Blunt Department of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA, Jason J. Wang Center for Interdisciplinary Exploration and Research in Astrophysics, Emily Rickman European Space Agency, Thomas Henning Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France, Kim Ward-Duong Department of Astronomy, Smith College, Northampton MA 01063 USA, R. Abuter LESIA, Observatoire de Paris, PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Janssen, 92195 Meudon, France, A. Amorim Universidade de Lisboa - Faculdade de Ciências, Campo Grande, 1749-016 Lisboa, Portugal CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, R. Asensio-Torres Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France, M. Benisty European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany, J. -P. Berger European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany, H. Beust European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany, A. Boccaletti Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands, A. Bohn Space Telescope Science Institute, Baltimore, MD 21218, USA, M. Bonnefoy European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany, H. Bonnet LESIA, Observatoire de Paris, PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Janssen, 92195 Meudon, France, G. Bourdarot Max Planck Institute for extraterrestrial Physics, Giessenbachstraße~1, 85748 Garching, Germany European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany, W. Brandner Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France, F. Cantalloube Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France, P. Caselli CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, B. Charnay Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands, G. Chauvin European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany, A. Chavez Department of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA, E. Choquet Max Planck Institute for extraterrestrial Physics, Giessenbachstraße~1, 85748 Garching, Germany, V. Christiaens School of Physics and Astronomy, Monash University, Clayton, VIC 3800, Melbourne, Australia, Y. Clénet Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands, V. Coudé du Foresto Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands, A. Cridland Space Telescope Science Institute, Baltimore, MD 21218, USA, R. Dembet Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands, A. Drescher CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, G. Duvert European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany, A. Eckart 1. Institute of Physics, University of Cologne, Zülpicher Straße 77, 50937 Cologne, Germany Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, 53121 Bonn, Germany, F. Eisenhauer CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, H. Feuchtgruber CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, P. Garcia Universidade de Lisboa - Faculdade de Ciências, Campo Grande, 1749-016 Lisboa, Portugal Universidade do Porto, Faculdade de Engenharia, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal, R. Garcia Lopez School of Physics, University College Dublin, Belfield, Dublin 4, Ireland Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France, T. Gardner Astronomy Department, University of Michigan, Ann Arbor, MI 48109 USA, E. Gendron Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands, R. Genzel CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, S. Gillessen CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, J. H. Girard Department of Physics \& Astronomy, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA, X. Haubois European Southern Observatory, Casilla 19001, Santiago 19, Chile, G. Heißel Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands, S. Hinkley University of Exeter, Physics Building, Stocker Road, Exeter EX4 4QL, United Kingdom, S. Hippler Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France, M. Horrobin School of Physics and Astronomy, Monash University, Clayton, VIC 3800, Melbourne, Australia, M. Houllé Max Planck Institute for extraterrestrial Physics, Giessenbachstraße~1, 85748 Garching, Germany, Z. Hubert European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany, L. Jocou European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany, J. Kammerer Department of Physics \& Astronomy, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA, M. Keppler Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France, P. Kervella Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands, L. Kreidberg Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France, A. -M. Lagrange European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands, V. Lapeyrère Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands, J. -B. Le Bouquin European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany, P. Léna Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands, D. Lutz CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, F. Mang CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, G. -D. Marleau Fakult"at f"ur Physik, Universit"at Duisburg-Essen, Lotharstraße 1, 47057 Duisburg, Germany Instit"ut f"ur Astronomie und Astrophysik, Universit"at T"ubingen, Auf der Morgenstelle 10, 72076 T"ubingen, Germany Center for Space and Habitability, Universit"at Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France, A. Mérand LESIA, Observatoire de Paris, PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Janssen, 92195 Meudon, France, J. D. Monnier School of Physics, University College Dublin, Belfield, Dublin 4, Ireland, C. Mordasini Instit"ut f"ur Astronomie und Astrophysik, Universit"at T"ubingen, Auf der Morgenstelle 10, 72076 T"ubingen, Germany, D. Mouillet European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany, E. Nasedkin Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France, T. Ott CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, G. P. P. L. Otten Academia Sinica, Institute of Astronomy and Astrophysics, 11F Astronomy-Mathematics Building, NTU/AS campus, No. 1, Section 4, Roosevelt Rd., Taipei 10617, Taiwan, C. Paladini Astronomy Department, University of Michigan, Ann Arbor, MI 48109 USA, T. Paumard Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands, K. Perraut European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany, G. Perrin Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands, O. Pfuhl LESIA, Observatoire de Paris, PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Janssen, 92195 Meudon, France, J. Rameau European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany, L. Rodet Center for Astrophysics and Planetary Science, Department of Astronomy, Cornell University, Ithaca, NY 14853, USA, Z. Rustamkulov Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, United Kingdom, J. Shangguan CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, T. Shimizu CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, C. Straubmeier School of Physics and Astronomy, Monash University, Clayton, VIC 3800, Melbourne, Australia, E. Sturm CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, L. J. Tacconi CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, E. F. van Dishoeck Space Telescope Science Institute, Baltimore, MD 21218, USA CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, A. Vigan Max Planck Institute for extraterrestrial Physics, Giessenbachstraße~1, 85748 Garching, Germany, F. Vincent Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands, F. Widmann CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, E. Wieprecht CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, E. Wiezorrek CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, T. Winterhalder LESIA, Observatoire de Paris, PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Janssen, 92195 Meudon, France, J. Woillez LESIA, Observatoire de Paris, PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Janssen, 92195 Meudon, France, S. Yazici CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal, A. Young CENTRA - Centro de Astrof\' isica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal
Abstract: Tension remains between the observed and modeled properties of substellar objects, but objects in binary orbits, with known dynamical masses can provide a way forward. HD 72946 B is a recently imaged brown dwarf companion to the nearby, solar type star. We achieve $\sim100~\mu\mathrm{as}$ relative astrometry of HD 72946 B in the K-band using VLTI/GRAVITY, unprecedented for a benchmark brown dwarf. We fit an ensemble of measurements of the orbit using orbitize! and derive a strong dynamical mass constraint $\mathrm{M_B}=69.5\pm0.5~\mathrm{M_{Jup}}$ assuming a strong prior on the host star mass $\mathrm{M_A}=0.97\pm0.01~\mathrm{M_\odot}$ from an updated stellar analysis. We fit the spectrum of the companion to a grid of self-consistent BT-Settl-CIFIST model atmospheres, and perform atmospheric retrievals using petitRADTRANS. A dynamical mass prior only marginally influences the sampled distribution on effective temperature, but has a large influence on the surface gravity and radius, as expected. The dynamical mass alone does not strongly influence retrieved pressure-temperature or cloud parameters within our current retrieval setup. Independent of cloud prescription and prior assumptions, we find agreement within $\pm2\,\sigma$ between the C/O ratio of the host ($0.52\pm0.05)$ and brown dwarf ($0.43$ to $0.63$), as expected from a molecular cloud collapse formation scenario, but our retrieved metallicities are implausibly high ($0.6-0.8$) in light of an excellent agreement of the data with the solar abundance model grid. Future work on our retrieval framework will seek to resolve this tension. Additional study of low surface-gravity objects is necessary to assess the influence of a dynamical mass prior on atmospheric analysis.
5.The evolution and impact of 3000 Msol stars in the early Universe
Authors:D. Nandal, E. Farrell, G. Buldgen, G. Meynet, S. Ekstrom
Abstract: We present evolutionary models of massive, accreting population III stars with constant and variable accretion rates until the end of silicon burning, with final masses of 1000 - 3000 Msol. In all our models, after the core-hydrogen burning phase, the star expands towards the red side of the Hertzsprung-Russell diagram where it spends the rest of its evolution. During core helium burning, the models exhibit an outer convective envelope as well as many large intermediate convective zones. These intermediate zones allow for strong internal mixing to occur which enriches the surface in helium. The effect of increasing metallicity at a constant accretion rate of 1e-3 Msol/yr shows an increase in lifetime, final mass and distribution of helium in the envelope. Our fiducial model with mass of 3000 Msol has a final surface helium abundance of 0.74 with 9% of its total mass or 50% of the core mass below Gamma1 < 4/3 at the end of core silicon burning. If the collapse of the core is accompanied by the ejection of the envelope above the carbon-oxygen core, this could have a significant impact on the chemical evolution of the surroundings and subsequent stellar generations. The model has has a final log(N/O) ~ 0.45, above the lower limit in the recently detected high-redshift galaxy GN-z11. We discuss the impact of a single 3000 Msol on chemical, mechanical and radiative feedback, and present directions for future work.
6.The Local Group Symbiotic Star Population and its Weak Relation with Type Ia Supernovae
Authors:M. Laversveiler, D. R. Gonçalves
Abstract: Here we study the symbiotic stars (SySt) population and its relation with type Ia supernovae (SNe Ia) in the galaxies of the Local Group. SySt are low- and/or intermediate-mass evolved binary systems where a white dwarf (WD) accretes mass from a giant star. A fraction of these WDs can become massive enough to reach the Chandrasekhar mass. Therefore, SySt have been considered as potential SNe Ia progenitors. Taking two approaches, one empirical and another statistical, we estimated the SySt population on the Galaxy as having a minimum value of $1.69\times10^3$ and a expected one of $3.23\times10^4$. For Local Group dwarfs galaxies, the computed SySt population ranges from 2 to 4 orders of magnitudes lower. Concerning the SNe Ia with SySt progenitors, our general result is that SySt are not the main SNe Ia progenitors. On the other hand, we still expect that about 0.5-8% of the SNe Ia have symbiotic progenitors in the Milky Way, while the majority of the - low-mass - dwarfs galaxies did not experience a symbiotic type Ia supernova.