Astronomy & Astrophysics

Journal Information
ISSN / EISSN: 00046361 / 14320746
Published by: EDP Sciences
Total articles ≅ 43,453

Latest articles in this journal

M. Brauner, T. Masseron, D. A. García Hernández, M. Pignatari, K. A. Womack, M. Lugaro, C. R. Hayes
Published: 31 March 2023
Abstract:
Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics
S. Ronchini, G. Stratta, A. Rossi, D. A. Kann, G. Oganesyan, S. Dall'Osso, M. Branchesi, G. De Cesare
Published: 31 March 2023
Abstract:
Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics
L. Gehrig, E. I. Vorobyov
Published: 31 March 2023
Abstract:
Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics
K. Wohlfarth, C. Wöhler, H. Hiesinger, J. Helbert
Published: 31 March 2023
Abstract:
Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics
M. Bhatt, C. Wöhler, J. Rogall, K. Aravind, S. Ganesh, A. Bhardwaj
Published: 31 March 2023
Abstract:
Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics
O.V. Arkhypov, M. L. Khodachenko
Published: 31 March 2023
Abstract:
Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics
J. Schou, J. Hirzberger, D. Orozco Suárez, Et Al.
Published: 31 March 2023
Abstract:
Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics
Gravity Collaboration, , M. Bauböck, R. Abuter, N. Aimar, P. Amaro Seoane, A. Amorim, J. P. Berger, H. Bonnet, G. Bourdarot, et al.
Published: 31 March 2023
Astronomy & Astrophysics, Volume 672; https://doi.org/10.1051/0004-6361/202245132

Abstract:
Context. In the Milky Way the central massive black hole, Sgr A*, coexists with a compact nuclear star cluster that contains a sub-parsec concentration of fast-moving young stars called S-stars. Their location and age are not easily explained by current star formation models, and in several scenarios the presence of an intermediate-mass black hole (IMBH) has been invoked. Aims. We use GRAVITY astrometric and SINFONI, KECK, and GNIRS spectroscopic data of S2, the best known S-star, to investigate whether a second massive object could be present deep in the Galactic Centre (GC) in the form of an IMBH binary companion to Sgr A*. Methods. To solve the three-body problem, we used a post-Newtonian framework and consider two types of settings: (i) a hierarchical set-up where the star S2 orbits the Sgr A*–IMBH binary and (ii) a non-hierarchical set-up where the IMBH trajectory lies outside the S2 orbit. In both cases we explore the full 20-dimensional parameter space by employing a Bayesian dynamic nested sampling method. Results. For the hierarchical case we find the strongest constraints: IMBH masses > 2000 M on orbits with smaller semi-major axes than S2 are largely excluded. For the non-hierarchical case, the chaotic nature of the problem becomes significant: the parameter space contains several pockets of valid IMBH solutions. However, a closer analysis of their impact on the resident stars reveals that IMBHs on semi-major axes larger than S2 tend to disrupt the S-star cluster in less than a million years. This makes the existence of an IMBH among the S-stars highly unlikely. Conclusions. The current S2 data do not formally require the presence of an IMBH. If an IMBH hides in the GC, it has to be either a low-mass IMBH inside the S2 orbit that moves on a short and significantly inclined trajectory or an IMBH with a semi-major axis > 1″. We provide the parameter maps of valid IMBH solutions in the GC and discuss the general structure of our results and how future observations can help to put even stronger constraints on the properties of IMBHs in the GC.
Umberto Maio, Matteo Viel
Published: 31 March 2023
Astronomy & Astrophysics, Volume 672; https://doi.org/10.1051/0004-6361/202345851

Abstract:
Context. Warm dark matter is a possible alternative to cold dark matter to explain cosmological structure formation. Aims. We study the implications of the latest JWST data on the nature of dark matter. Methods. We compare properties of high-redshift galaxies observed by JWST with hydrodynamical simulations, in the standard cold dark matter model and in warm dark matter models with a suppressed linear matter power spectrum Results. We find that current data are neither in tension with cold dark matter nor with warm dark matter models with mWDM > 2 keV, since they probe bright and rare objects whose physical properties are similar in the different scenarios. Conclusions. We also show how two observables, the galaxy luminosity functions and the galaxy correlation function at small scales of faint objects, can be promising tools for discriminating between the different dark-matter scenarios. Further hints may come from early stellar-mass statistics and galaxy CO emission.
, N. Di Lalla, , S. Silvestri, , , A. F. Tennant, A. Manfreda
Published: 31 March 2023
Astronomy & Astrophysics, Volume 672; https://doi.org/10.1051/0004-6361/202245744

Abstract:
X-ray polarimetry based on gas pixel detectors (GPDs) has reached a high level of maturity thanks to the Imaging X-ray Polarimeter Explorer (IXPE) providing the first-ever spatially resolved polarimetric measurements. However, as this a new technique, a few unexpected effects have emerged in the course of in-flight operations. In particular, it was almost immediately found that, the unpolarized calibration sources on-board were showing radially polarized halos. The origin of these features was recognized in a correlation between the error in reconstructing the absorption point of the X-ray photon and the direction of its electric field vector. Here, we present and discuss this effect in detail, showing that it is possible to provide a simple and robust mathematical formalism to handle it. We further show its role and relevance for the recent IXPE measures as well as for the use of GPD-based techniques in general. We also illustrate how to model it in the context of studying extended sources.
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