Gamma-ray astronomy

Abstract:

Is the universe fine-tuned for complexity, life, or something else? This comprehensive overview of fine-tuning arguments in physics, with contributions from leading researchers in their fields, sheds light on this often used but seldom understood topic. Each chapter reviews a specific subject in modern physics, such as dark energy, inflation, or solar system formation, and discusses whether any parameters in our current theories appear to be fine-tuned and, if so, to what degree. Connections and differences between these fine-tuning arguments are made clear, and detailed mathematical derivations of various fine-tuned parameters are given. This accessible yet precise introduction to fine-tuning in physics will aid students and researchers across astrophysics, atomic and particle physics and cosmology, as well as all those working at the intersections of physics and philosophy.

Abstract:

© 2019 The Author(s) We report the discovery of the first transient with MeerKAT, MKT J170456.2−482100, discovered in ThunderKAT images of the low-mass X-ray binary GX339−4. MKT J170456.2−482100 is variable in the radio, reaching a maximum flux density of 0.71 ± 0.11 mJy on 2019 October 12, and is undetected in 15 out of 48 ThunderKAT epochs. MKT J170456.2−482100 is coincident with the chromospherically active K-type sub-giant TYC 8332-2529-1, and ∼ 18 yr of archival optical photometry of the star shows that it varies with a period of 21.25 ± 0.04 d. The shape and phase of the optical light curve changes over time, and we detect both X-ray and UV emission at the position of MKT J170456.2−482100, which may indicate that TYC 8332-2529-1 has large star spots. Spectroscopic analysis shows that TYC 8332-2529-1 is in a binary, and has a line-of-sight radial velocity amplitude of 43 km s−1. We also observe a spectral feature in antiphase with the K-type sub-giant, with a line-of-sight radial velocity amplitude of ∼ 12 ± 10 km s−1, whose origins cannot currently be explained. Further observations and investigation are required to determine the nature of the MKT J170456.2−482100 system.