Conveners
White Dwarfs, Magnetic Compact Stars, and Nuclear Astrophysics: Block 1
- Jaziel Goulart Coelho (UTFPR)
- Manuel Malheiro (Instituto Tecnológico de Aeronáutica)
Description
Theoretical and observational progress in White Dwarfs (WD), considering their constitution and recent observation of very Fast and massive WD, as well the importance and possible identification of strong magnetic fields in Compact Stars together with the relevance of nuclear processes to explain the stability of these sources and even explosive events as bursts, FRBs are the main topics of this parallel session.
Static and uniformly rotating, cold and hot white dwarfs are investigated both in Newtonian gravity and general theory of relativity, employing the well-known Chandrasekhar equation of state. The mass-radius, mass-central density, radius-central density etc relations of stable white dwarfs with $\mu=A/Z=2$ and $\mu=56/26$ (where $A$ is the average atomic weight and $Z$ is the atomic charge)...
Since last 10 years or so, we have been developing the possible existence of highly magnetized white dwarfs. While the primary aim was to explain peculiar overluminous type Ia supernovae, later on, they have been found to have multiple implications including soft gamma-ray repeaters and anomalous X-ray pulsars, and gravitational radiation. Recently, we have successfully simulated their...
The equilibrium configuration of white dwarfs composed of anisotropic fluid distribution in the presence of a strong magnetic field is investigated in this work. By considering a functional form of the anisotropic stress and magnetic field profile, some physical properties of magnetized white dwarfs, such as mass, radius, density, radial and tangential pressures, were derived; their...
In this talk, we present the recent determination of the spin period of CTCV J2056-3014, a magnetic white dwarf in a cataclymisc binary system. Its X-ray and optical emission is clearly modulated with a 29.6 s period and points to an accretion origin. We briefly discuss this object in the context of other fast-spinning white dwarfs.
In this presentation the white dwarf close binaries AE Aquarii and AR Sco are investigated to search for signatures of particle acceleration and associated non-thermal emission. A detailed investigation of the total Fermi-LAT data base reveal signatures of pulsed gamma-ray emission in AE Aquarii, which mimics earlier reports of transient burst-like pulsed TeV gamma-ray emission reported from...
Electron captures by atomic nuclei in dense matter are among the most important processes governing the late evolution of stars. Although these reactions have been known for a long time, most studies have focused on nonmagnetized matter. However, some white dwarfs are endowed with magnetic fields of the order of $10^9$~G. Even more extreme magnetic fields might exist in super Chandrasekhar...
Soft Gamma-Ray Repeaters and Anomalous X-ray Pulsars (SGR/AXPs) are isolated compact stars identified due to a characteristic quiescent soft X-ray emission as well as bursts events. They can also emit in other energy ranges, from radio up to hard X-rays. Their nature is still a question for debate, and several emission mechanisms have been proposed, such as neutron star (NS) with a...
Two mechanisms of gravitational waves (GWs) emission in fast-spinning white dwarfs (WDs) are investigated: accretion of matter and magnetic deformation. In both cases, the GW emission is generated by an asymmetry around the rotation axis of the star. However, in the first case, the asymmetry is due to the amount of accreted matter on the magnetic poles, while in the second case it is due to...
Mass and radius constraints of compact stars (CS), i.e. Neutron stars (NS) and White Dwarfs (WD), based on electromagnetic data are challenging. Radius measurements are mainly based on observation of thermal emission and comparison with theoretical models. Modeling, however, due to the complex and relativistic nature of compact objects, suffers from a number of complications such as parameter...
In this work, we investigate the structure, the radial stability, pycnonuclear reaction and inverse $\beta$-decay in white dwarfs with a finite temperature. Regarding the matter within hot white dwarfs, we consider that it is composed of nucleons and electrons confined in a Wigner-Seitz cell surrounded by free photons. Since photons are being considered, in order to connect smoothly the...
