Article
Astronomy & Astrophysics
Marie Cassing, Alexander Brisebois, Muhammad Azeem, Juergen Schaffner-Bielich
Summary: The generic properties of compact objects made of two different fluids of dark matter are studied. Compact objects with a core-shell structure and mixed dark matter components are investigated. The results show novel features in the mass-radius relations for combined dark matter compact objects, distinguishing them from compact objects with a single dark matter fluid and compact stars made of ordinary baryonic matter.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Vania Vellucci, Edgardo Franzin, Stefano Liberati
Summary: The detection of echoes in late gravitational wave signals provides a promising way to test horizonless alternatives to black holes and study the physics of ultracompact objects. Previous searches for these signals have considered periodic waveforms and ignored backreaction effects. This study examines scalar perturbations in exotic compact object scenarios that account for backreaction phenomena and identifies new features that should be considered in future searches.
Article
Physics, Multidisciplinary
Pedro V. P. Cunha, Carlos Herdeiro, Eugen Radu, Nicolas Sanchis-Gual
Summary: Ultracompact objects with light rings but without an event horizon can mimic black holes in their strong gravity phenomenology. Through numerical simulations and the introduction of a novel technique, we confirm the instability triggered by the light rings and identify two possible outcomes: migration to nonultracompact configurations or collapse to black holes.
PHYSICAL REVIEW LETTERS
(2023)
Article
Astronomy & Astrophysics
Artur Alho, Jose Natario, Paolo Pani, Guilherme Raposo
Summary: This paper introduces a rigorous and general framework to study self-gravitating elastic materials within general relativity, and applies it to investigate the existence and viability of spherically symmetric elastic stars. The results show that elasticity contributes to increasing the maximum mass and compactness of the models, supporting the existence of compact stars with mass well above two solar masses.
Article
Astronomy & Astrophysics
Abdusattar Kurban, Yong-Feng Huang, Jin-Jun Geng, Hong-Shi Zong
Summary: According to the strange quark matter hypothesis, there may exist a sequence of strange quark matter objects, including strange quark stars, strange quark dwarfs, and strange quark planets. This study identifies seven candidates of strange dwarfs among observed white dwarfs, which have different mass-radius relations compared to white dwarfs of similar mass.
Article
Astronomy & Astrophysics
Jim Fuller, Wenbin Lu
Summary: The angular momentum content of massive stellar cores is important for determining the rotation rates of neutron stars and black holes. Prior work has shown that low-mass stars rotate slower than predicted, necessitating revised models. This study applies an updated angular momentum transport model to massive helium stars in close binaries and explores its implications for various astrophysical phenomena. The models are consistent with observed rates and energetics, except for broad-lined Ic supernovae.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Physics, Particles & Fields
Robert S. Bogadi, Megandhren Govender, Sibusiso Moyo
Summary: This study investigates the forces involved during the collapse of a compact stellar object and emphasizes the connection between fundamental quantities (forces) and the spacetime geometry in the gravitational formalism.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Physics, Particles & Fields
Robert S. Bogadi, Megandhren Govender
Summary: This study investigates the dynamics of the gravitational collapse of a compact object using a complexity factor scalar derived from the orthogonal splitting of the Riemann tensor. The scalar vanishes for isotropic pressure and homogeneous energy density systems, providing further details on the progression of inhomogeneity during the collapse. The complexity factor can also be used to compare models and justify their physical viability.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
Surajit Kalita, Tushar Mondal, Christopher A. Tout, Tomasz Bulik, Banibrata Mukhopadhyay
Summary: More than two dozen soft gamma-ray repeaters and anomalous X-ray pulsars have been detected, which could be neutron stars or white dwarfs. The existence of highly magnetized white dwarfs and super-Chandrasekhar white dwarfs remains a puzzle. Gravitational wave detectors can estimate the time required for the detection of these objects based on different magnetic field configurations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Hannah Banks, Dorota M. Grabowska, Matthew Mccullough
Summary: Long-baseline atom interferometers provide an exciting opportunity for exploring midband gravitational waves. Observing the contribution of merging binary systems to the total gravitational wave background in this frequency range can reveal more information about the universe. Known stellar-mass compact binary systems can be detected by existing experiments, and hypothetical populations of dark sector exotic compact objects may generate unique signals in subhertz frequencies.
Article
Astronomy & Astrophysics
Alexandre Toubiana, Stanislav Babak, Enrico Barausse, Luis Lehner
Summary: Exotic compact objects can be difficult to distinguish from black holes in the inspiral phase of binaries observed by gravitational-wave detectors, but significant differences may be present in the merger and post-merger signal. A toy model capturing the key features of binaries of exotic compact objects with low compactness was introduced to assess their detectability and distinguishability from black hole binaries. The study showed that current detectors like LISA could potentially observe exotic binaries and differentiate them from black hole binaries.
Article
Astronomy & Astrophysics
L. Mahy, H. Sana, T. Shenar, K. Sen, N. Langer, P. Marchant, M. Abdul-Masih, G. Banyard, J. Bodensteiner, D. M. Bowman, K. Dsilva, M. Fabry, C. Hawcroft, S. Janssens, T. Van Reeth, C. Eldridge
Summary: This study aims to search for dormant stellar-mass black holes by studying 32 Galactic O-type stars and known stellar-mass black hole systems. Multiple methods were used to determine the presence of companions. The results show that out of the 32 single-lined spectroscopic binary systems, 17 have weak secondary companion signatures, 17 newly detected double-lined spectroscopic binaries were identified, and 9 systems possibly have neutron star or low-mass main sequence star companions.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Yotam Sherf
Summary: The study investigates the effect of energy absorption during the binary evolution of ECOs and the role of viscosity in tidal friction. By comparing and contrasting with black holes, the importance of viscosity in quantifying ECO absorption is demonstrated. Additionally, the possibility of measuring ECO absorption in future precision gravitational-wave observations is highlighted.
Article
Physics, Nuclear
G. Lugones, A. G. Grunfeld
Summary: This study investigates the surface tension and curvature coefficient of charged strangelets in relation to factors such as baryon number density, temperature, and neutrino chemical potential. It is found that positively charged strangelets result in significantly decreased surface tension, while extreme astrophysical scenarios with higher temperatures and neutrino chemical potentials also impact these parameters. Gamma is mainly influenced by the density of light quarks and is independent of other factors such as charge-per-baryon ratio and temperature.
Article
Physics, Particles & Fields
A. Zahra, S. A. Mardan, Muhammad Bilal Riaz
Summary: In this study, a new framework for five-dimensional spherical symmetry anisotropic stars that allows for conformal motion is presented. The behavior of model characteristic pressure, stress, density profile, and surface tension are investigated by considering a specific density distribution for the higher dimensional Einstein's field equations. All physical parameters exhibit well-behaved properties in higher dimensions. The analysis predicts the potential existence of compact stars in five dimensions, most likely being strange quark stars.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Lien Rodriguez-Lopez, Rolando Cardenas, Lisdelys Gonzalez-Rodriguez, Mayrene Guimarais, Jorge Horvath
Summary: The study examines the potential lethality of Gamma Ray Bursts on aquatic primary producers on Earth, suggesting that UV flash could significantly reduce phytoplankton biomass in the upper mixed layer of the world's oceans.
ASTRONOMISCHE NACHRICHTEN
(2021)
Article
Astronomy & Astrophysics
Jorge Ernesto Horvath, Livia S. Rocha, Antonio Bernardo, Rodolfo Valientim, Marcio Guilherme Bronzato de Avellar
Summary: In this presentation, an overview of neutron star origin events and masses was presented. It was shown that the distribution of neutron star masses requires multiple mass scales, with the highest value inferred from the sample being compatible with 2.5 solar masses. The talk discussed the possibility of very heavy neutron stars in nature and reviewed the connection between supernovae compact remnants and observed masses.
ASTRONOMISCHE NACHRICHTEN
(2021)
Article
Astronomy & Astrophysics
Milton Rojas Gamarra, Steven R. Gullberg, Monica Estrazulas, Jorge Horvath, Cesar A. Zen Vasconcellos
Summary: This contribution explores the connections between the conceptions about space, time, and Cosmos in history and the cosmogonic view of the Inka culture, emphasizing the importance of understanding and interpreting the Inka legacy within the context of Inka culture and its worldview.
ASTRONOMISCHE NACHRICHTEN
(2021)
Article
Astronomy & Astrophysics
M. G. B. de Avellar, P. P. B. Beaklini, S. P. Nunes, P. H. R. S. Moraes, M. Malheiro
Summary: This study proposes a new model for Fast Radio Bursts (FRBs) based on the sudden discharge of a charged young magnetar. By modeling the magnetar and calculating relevant physical parameters, the results suggest that this model can explain the FRB phenomenon.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
J. E. Horvath, P. H. R. S. Moraes, M. G. B. de Avellar, L. S. Rocha
Summary: This work revisits a model for repeating Fast Radio Bursts based on the release of energy provoked by the magnetic field dynamics affecting a magnetar's crust. The basics of the model are addressed by solving the propagation of perturbations approximately, quantifying the energetics and radiation, and suggesting more detailed studies of nonlinear soliton solutions. The emission of X-rays from SGR 1935+2154 is tentatively associated with a reconnection behind the propagation, and the strength of f-mode gravitational radiation excited by the event is quantified.
RESEARCH IN ASTRONOMY AND ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
J. E. Horvath
Summary: This study focuses on the Crab supernova in 1054 A.D. and suggests that the observed event can be explained by a precursor phenomenon emerging from large supernova sampling and low-mass progenitors. The explosion itself is likely a low-luminosity supernova from small iron core type, rather than an electron-capture event.
ASTROPHYSICS AND SPACE SCIENCE
(2022)
Article
Astronomy & Astrophysics
Ximena C. Abrevaya, Douglas Galante, Paula M. Tribelli, Oscar J. Oppezzo, Felipe Nobrega, Gabriel G. Araujo, Fabio Rodrigues, Petra Odert, Martin Leitzinger, Martiniano M. Ricardi, Maria Eugenia Varela, Tamires Gallo, Jorge Sanz-Forcada, Ignasi Ribas, Gustavo F. Porto de Mello, Florian Rodler, Maria Fernanda Cerini, Arnold Hanslmeier, Jorge E. Horvath
Summary: This study investigated the potential of halite crystals to protect microorganisms under vacuum and vacuum-ultraviolet radiation conditions. The results showed that halite can effectively protect microorganisms from harm, and the protective effect of halite is higher than that of crystals made from mixtures of salts. These findings suggest that halite crystals may serve as preservation structures on airless bodies or as vehicles for interplanetary transfer of microorganisms.
Article
Astronomy & Astrophysics
Lucas M. de Sa, Antonio Bernardo, Riis R. A. Bachega, Livia S. Rocha, Jorge E. Horvath
Summary: Binary population synthesis provides a way to study the effects of binary evolution models and initial parameter distributions on compact binary merger populations, and compare them to observed properties such as merger rates.
ASTRONOMISCHE NACHRICHTEN
(2023)
Article
Astronomy & Astrophysics
Antonio L. C. Bernardo, Laura Paulucci, Lucas M. M. de Sa, Jorge E. E. Horvath
Summary: The Strange Quark Matter (SQM) hypothesis suggests the existence of a new state of matter, where half of the down quarks become strange quarks under extreme pressure and density conditions. This study aims to characterize the fragmentation of SQM and track the quark configuration of the fragmented matter, utilizing a methodology to estimate the energy of each fragment based on the summed energy of constituent quarks, Coulomb interaction among quarks, and fragments' momenta.
ASTRONOMISCHE NACHRICHTEN
(2023)
Article
Astronomy & Astrophysics
Jorge E. Horvath, Antonio L. C. Bernardo, Riis R. A. Bachega, Lucas M. de Sa, Livia S. Rocha, Pedro H. R. S. Moraes
Summary: The lack of objects between 2 and 5 M-& ODOT; in the joint mass distribution, known as the mass gap, is believed to be the result of the characteristics of the supernova mechanism during their birth. However, recent observations suggest that the reported candidates within the gap may fill it, and the scarcity may be due to small sample statistics. In this study, we quantify the individual candidates and evaluate the joint probability of a mass gap. Our results confidently show that there is no mass gap. The existence of a relatively scarce population of objects and its relation to the formation processes, such as neutron star mergers and collapse of neutron stars to black holes, remains to be explored.
ASTRONOMISCHE NACHRICHTEN
(2023)
Article
Astronomy & Astrophysics
Jorge E. E. Horvath
Summary: In this article, we provide concluding remarks for the 10th edition of the IWARA Workshop, including highlights and comments meant to enrich and provide context to the oral scientific presentations.
ASTRONOMISCHE NACHRICHTEN
(2023)
Article
Astronomy & Astrophysics
Jorge E. Horvath, Rodrigo Rosas Fernandes, Thais E. Idiart
Summary: In this work, we examine the contradictory nature of the coexistence of microphysical quantum reality and macrophysical classical reality in modern Physics. After discussing fundamental concepts in Philosophy, we analyze the implications of the results in Quantum Mechanics, particularly the violations of Bell's theorem, and the fundamental and unsolved tension it creates between the micro and macro world.
ASTRONOMISCHE NACHRICHTEN
(2023)
Article
Astronomy & Astrophysics
L. M. de Sa, A. Bernardo, R. R. A. Bachega, J. E. Horvath, L. S. Rocha, P. H. R. S. Moraes
Summary: The lack of objects between 2 and £5 M in the joint mass distribution of compact objects, known as the mass gap, has been attributed to the supernova mechanism. Recent observations suggest that some candidates within the gap may fill it, indicating a possible scarcity that could be real or a result of small sample statistics. This study quantifies individual candidates and evaluates the joint probability of a mass gap, finding that an absolute mass gap does not exist to a very high confidence level. It remains uncertain if there will be a relative scarcity of objects in the future and how this population can be linked to formation processes.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Lucas M. de Sa, Antonio Bernardo, Riis R. A. Bachega, Livia S. Rocha, Pedro H. R. S. Moraes, Jorge E. Horvath
Summary: The study of compact object populations has made significant progress, with the determination of mass and merger detection. We now have a better understanding of the variety of systems hosting these objects and can evaluate their statistical nature and long-standing problems. This article provides an overview of the field, focuses on Galactic black holes, and offers an updated catalog of their masses and orbital parameters.