Article
Astronomy & Astrophysics
Shanika Galaudage, Karl Wette, Duncan K. Galloway, Chris Messenger
Summary: In this study, a semi-coherent search for pulsations in two low mass X-ray binaries was performed using X-ray data. No clear evidence for pulsations was found, but upper limits on the fractional pulse amplitude were obtained, improving upon previous work.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Yash Bhargava, Nandini Hazra, A. R. Rao, Ranjeev Misra, Dipankar Bhattacharya, Jayashree Roy, Md Shah Alam
Summary: This study analyses the aperiodic flaring features observed in Cyg X-1, measuring the truncation of the inner accretion disc and studying the movement of the inner edge. The research discusses possible mechanisms causing these phenomena.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Silvia Gasparotto, Evangelos I. Sfakianakis
Summary: In this study, we revisit the evidence for CMB birefringence in a rich Axiverse and analyze its properties. By constraining the shape of input probability density functions, we contribute to the understanding of the statistical distribution of the Axiverse and its implications for cosmic birefringence.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Ying Qin, Xinwen Shu, Shuangxi Yi, Yuan-Zhu Wang
Summary: Recent observations have shown that spin measurements in binary black hole systems are typically small, consistent with classical isolated binary evolution. However, high spin values have been consistently found in high-mass X-ray binaries. In order to explain this discrepancy, it is necessary to consider the angular momentum transport mechanism within the progenitors of these black holes.
RESEARCH IN ASTRONOMY AND ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Basabendu Barman, Debasish Borah, Arnab Dasgupta, Anish Ghoshal
Summary: We propose a novel way to probe high-scale Dirac leptogenesis by introducing heavy singlet Dirac fermions, a singlet scalar, and a discrete Z(2) symmetry. The formation of domain walls in the early Universe, if made unstable by a soft Z(2)-breaking term, can generate gravitational waves (GWs) with a spectrum characterized by the wall tension, the singlet vacuum expectation value (VEV), and the soft symmetry breaking scale. We find that most near-future GW observatories can probe Dirac leptogenesis scales up to 10^11 GeV.
Article
Physics, Multidisciplinary
Kamran Qadir Abbasi, Ibrar Hussain, Asghar Qadir
Summary: The behavior of the Khan-Penrose impulsive plane colliding gravitational wave spacetime was investigated, revealing a rapid build-up of force at the essential singularity after collision, while the singularity did not appear in the force before the waves passed, indicating a topological singularity. By extending the analysis to Szekeres colliding sandwich gravitational waves, it was found that what Szekeres called a coordinate singularity after the collision of waves turns out to be a curvature singularity.
EUROPEAN PHYSICAL JOURNAL PLUS
(2021)
Article
Astronomy & Astrophysics
Yang Jiang, Xi-Long Fan, Qing-Guo Huang
Summary: Cosmology models predict a relic background of gravitational-wave radiation in the early universe. Using a Bayesian framework, we focused on the stochastic background generated by superinflation in string theory and searched for this signal in the observing data of Advanced LIGO and Virgo O1 to O3 runs. Our results put constraints on the GW energy density, ruling out certain parameter space restricted by the model itself due to non-decreasing dilaton and stable cosmology background (0 bound).
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Nicola Bartolo, Daniele Bertacca, Robert Caldwell, Carlo R. Contaldi, Giulia Cusin, Valerio De Luca, Emanuela Dimastrogiovanni, Matteo Fasiello, Daniel G. Figueroa, Gabriele Franciolini, Alexander C. Jenkins, Marco Peloso, Mauro Pieroni, Arianna Renzini, Angelo Ricciardone, Antonio Riotto, Mairi Sakellariadou, Lorenzo Sorbo, Gianmassimo Tasinato, Jesus Torrado, Sebastien Clesse, Sachiko Kuroyanagi
Summary: We investigate the sensitivity of the Laser Interferometer Space Antenna (LISA) to the anisotropies of the Stochastic Gravitational Wave Background (SGWB). By building a Signal-to-Noise estimator and performing a Fisher matrix analysis, we quantify the detectability of different multipoles by LISA. This study provides important information for understanding the origin of the SGWB and discriminating among different superimposed SGWB sources.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Katelyn J. Wagner, John T. Whelan, Jared K. Wofford, Karl Wette
Summary: This study applies lattice covering problem to template placement in the search for continuous gravitational waves from the low-mass xray binary Scorpius X-1. By defining a shearing coordinate transformation, potential correlations are minimized and the lattices constructed have fewer templates with improved sensitivity.
CLASSICAL AND QUANTUM GRAVITY
(2022)
Article
Astronomy & Astrophysics
Pratyusava Baral, Soumendra Kishore Roy, Supratik Pal
Summary: The analysis suggests that it is more effective to probe the null diagnostic, rather than the standard EoS parameters, for any possible signature of dark energy at intermediate redshift measurements like eLISA.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
William Giare, Alessandro Melchiorri
Summary: This paper investigates the robustness of assuming the tensor tilt as scale independent, showing that even a small scale dependence can remarkably affect the shape of the primordial spectrum and significantly change the final constraints when non-linear corrections are considered. The study also examines the scale dependence in two different physical models of inflation, providing examples of negligible scale dependence and non-negligible scale dependence.
Article
Astronomy & Astrophysics
Nikolaos Karnesis, Stanislav Babak, Mauro Pieroni, Neil Cornish, Tyson Littenberg
Summary: This study presents a generic method for characterizing foreground signals from a given astrophysical population and predicts different levels of foreground noise through an iterative procedure.
Article
Astronomy & Astrophysics
Yuanhao Zhang, Maria Alessandra Papa, Badri Krishnan, Anna L. Watts
Summary: Researchers conducted a search for continuous gravitational waves from a neutron star in the low-mass X-ray binary Scorpius X-1 using the LIGO O2 public data, achieving unprecedented sensitivity and excluding certain mass-radius combinations and magnetic field strengths. They corrected an error in the literature and reinterpreted the latest LIGO/Virgo results in light of their findings.
ASTROPHYSICAL JOURNAL LETTERS
(2021)
Article
Astronomy & Astrophysics
Paritosh Verma
Summary: This paper presents the theoretical background for analyzing gravitational waves from spinning neutron stars in Brans-Dicke theory, which aims to modify general relativity by varying gravitational constant G and has three polarization states. The response of a laser interferometric detector to the GW signal in BD theory is derived, and a statistic based on the maximum likelihood principle is obtained to identify the signal in detector's noise. Monte Carlo simulations in Gaussian noise are performed to test the detectability of the signal and the accuracy of estimation of its parameters.
Article
Astronomy & Astrophysics
Christian Adamcewicz, Eric Thrane
Summary: This paper investigates the imprint of formation history on the distribution of masses, spins, and eccentricity of binary black hole systems. The joint distribution of binary black hole parameters in two or more dimensions is explored, and an anticorrelation between the mass ratio and effective inspiral spin chi(eff) is found. The paper addresses a previously overlooked subtlety in 2D population studies using statistical tools, and demonstrates the power of copulas in gravitational-wave astronomy while scrutinizing their astrophysical inferences.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
