The Fate of Binary Stars Hosting Planets upon Interaction with Sgr A* Black hole

Our Galaxy hosts a very massive object at its centre, often referred to as the supermassive black hole Sgr A*. Its gravitational tidal field is so intense that can strip apart a binary star passing its vicinity and accelerate one of the components of the binary as hypervelocity star (HVS) and grab the other star as S-star. Taken into consideration that many binary star systems are known to host planets, in this paper we aim to broaden the study of the close interaction of binary stars and their planetary systems with Sgr A* massive object. Results are obtained via a high precision $N-$body code including post-Newtonian approximation. We quantify the likelihood of capture and ejection of stars and planets after interaction with Sgr A*, finding that the fraction of stars captured around it is about three times that of the planets (~ 49.4% versus ~14.5%) and the fraction of hypervelocity planet (HVP) ejection is about twice HVSs (~21.7% versus ~9.0%). The actual possibility of observational counterparts deserves further investigation.Comment: 10 pages, 5 figures, 4 tables. Accepted for publication in MNRA

Dynamical properties of binary stars hosting planets in the Galactic Center

We present some preliminary results of our work about the close encounter of binary stars hosting planets on S-type orbits with the Sgr A* supermassive black hole in the center of our Galaxy.Comment: Presented at the parallel session chaired by R. Capuzzo-Dolcetta and M. Arca-Sedda, to publish in the Proceedings of the Fifteenth Marcel Grossman Meeting on General Relativity Edited by Elia Battistelli, Robert T. Jantzen, and Remo Ruffini. 6 pages, 4 figures, to be published in Open access e-book proceedings World Scientific, Singapore, 201

Infective Endocarditis as a complication of COVID-19 infection; A case report and review of literature

COVID-19 has been known to induce systemic inflammation and hyper coagulate state leading to different complications. Cardiovascular complications are one of the most important among complications following COVID-19 infection. A 57 years old woman with past medical history of COVID-19 infection about two months ago came to our hospital with presentation of fever and dyspnea. During workup, tricuspid valve infection associated with pulmonary septic emboli was diagnosed without any obvious risk factor for infective endocarditis. It seems that COVID-19 infection may increase the rate of endocarditis in patients with or without risk factors of endocarditis

Characterizing the Sardinia candidate site for the Einstein Telescope

Due to its unique geophysical features and to the low density population of the area, Sos Enattos is a promising candidate site to host the Einstein Telescope (ET), the third-generation Gravitational Wave Observatory. The geophysical characterization of the Sos Enattos former mine, close to one of the proposed ET corners, started in 2010 with the deployment of seismic and environmental sensors underground. Since 2019 a new extensive array of seismometers, magnetometers and acoustic sensors have been installed in three stations along the underground tunnels, with one additional station at the surface. Beside a new geological survey over a wider area, two boreholes about 270 m deep each were excavated at the other two corners, determining the good quality of the drilled granite and orthogneiss rocks and the absence of significant thoroughgoing fault zones. These boreholes are instrumented with broadband seismometers that revealed an outstanding low level of vibrational noise in the low-frequency band of ET-LF (2-10Hz), significantly lower than the Peterson's NLNM and resulting among the quietest seismic stations in the world in that frequency band. The low seismic background and the reduced number of seismic glitches ensure that just a moderated Newtonian noise subtraction would be needed to achieve the ET target sensitivity. Geoelectrical and active seismic campaigns have been carried out to reveal the features of the subsurface, revealing the presence of small-sized fractured areas with limited water circulation. Finally, temporary arrays of seismometers, magnetometers and acoustic sensors are deployed in the area to study the local sources of environmental noise

Array analysis of seismic noise at the Sos Enattos mine, the Italian candidate site for the Einstein Telescope

The area surrounding the dismissed mine of Sos Enattos (Sardinia, Italy) is the Italian candidate site for hosting Einstein Telescope (ET), the third-generation gravitational wave (GW) observatory. One of the goals of ET is to extend the sensitivity down to frequencies well below those currently achieved by GW detectors, i.e. down to 2 Hz. In the bandwidth [1,10] Hz, the seismic noise of anthropogenic origin is expected to represent the major perturbation to the operation of the infrastructure, and the site that will host the future detector must fulfill stringent requirements on seismic disturbances. In this paper we describe the operation of a temporary, 15-element, seismic array deployed in close proximity to the mine. Signals of anthropogenic origin have a transient nature, and their spectra are characterized by a wide spectral lobe spanning the [3,20] Hz frequency interval. Superimposed to this wide lobe are narrow spectral peaks within the [3,8] Hz frequency range. Results from slowness analyses suggest that the origin of these peaks is related to vehicle traffic along the main road running east of the mine. Exploiting the correlation properties of seismic noise, we derive a dispersion curve for Rayleigh waves, which is then inverted for a shallow velocity structure down to depths of ≈≈ 150 m. This data, which is consistent with that derived from analysis of a quarry blast, provide a first assessment of the elastic properties of the rock materials at the site candidate to hosting ET

Dynamics of stars and planets in the super dense Central Galactic Region

There is observational evidence that a compact massive object (CMO) of about four million solar masses cloaks at the heart of the Milky Way (MW), known as Sgr A*. The gravitational tidal field of this CMO (probably a Supermassive black hole, SMBH) is extremely strong so that binary star passing in its vicinity are likely stripped apart. One component of the binary can be hurled swiftly out of the Galactic Centre, or even the MW, as Hypervelocity Star (HVS) and its twin could be seized on an eccentric orbit revolving around the central massive object, similar to the observed S-stars (Hills mechanism). Given that many binary star systems are acknowledged to host planets, we intend in this thesis deepening the study of the violent dynamics of binary stars and their planetary systems with the Sgr A* massive object, highlighting the resulting fraction of HVS hosting planet. In the first part of this thesis, we focus on tight binary stars with one planet for each component of the binary, and investigate the fate of the four-body system after the interaction with the SMBH. Results are achieved by means of a high precision, regularized, numerical integrator suitable for those large mass ratios which are involved in the interaction of SMBH and stars/planets. Furthermore, in order to develop the investigation of dynamics in the proximity of Sgr A*, we model the environment of the Galactic Centre (GC) by applying the local distribution of stars in the form of a regular external potential which also generates dynamical friction on the approaching objects. The Galaxy density profile, is represented in spherical symmetry as the sum of a Dehnen and a Plummer distribution for the galactic background and the nuclear star cluster (NSC) around the GC, respectively. After setting proper initial conditions for our chosen set of binary stars hosting one planet each, we carried out integrations taking into account the gravity field of the massive object in the post-Newtonian approximation up to 2.5 order. This allows us to evaluate the likelihood of ejection and capture of the four-body system in its interaction with Sgr A* emphasizing mainly on the fate of the planets initially bound to the binary star. Our simulations show that after the interplay between four-body system and the SMBH, the result is that of giving rise to lonely hypervelocity stars (HVSs) or S-stars and, also, to HVSs or S-stars that would keep their planets. Furthermore, it is possible to spectate rogue hypervelocity planets (HVP) thrown out of the Galaxy or starless planets (S-planets) revolving around the SMBH in independent eccentric orbits similar to those of S-stars. Stars and/or planets can be, also, devoured by the SMBH. Here, "devoured" means that a star or planet enters inside $3 R_s$ i.e. within the innermost stable circular orbit (ISCO) of the non-rotating SMBH. We show that both starless S-planets and S-stars with planets can exist around the SMBH on high eccentric ($e sim 0.97$) orbits similar to the G2 cloud orbital eccentricity. Eventually, in this thesis we focus on the dynamical evolution and stability of populous planetary systems in the vicinity of Sgr A*. The S-star cluster, which is a dynamically relaxed dense cluster of stars and consists of roughly 40 stars, inhabits in the centre of the Galaxy. Spectroscopic analysis of the S-stars reveals the existence of both a population of early- and late-type stars on tightly eccentric orbits, with different orientations and semi-major axes. These stars are believed to be the captured companions of the HVSs in the binary-SMBH disruption. Accordingly, they might have formed elsewhere and migrated to the GC, probably hosting planetary systems. The existence of planets or planetary systems in the vicinity of Sgr A* is still an open argument. Our aim is to investigate the destiny of their putative planetary systems after close interaction with the central black hole of our Galaxy. We run simulations for the 40 stars of this cluster for which the orbital parameters are known from the literature. For the sake of simplicity, the planetary systems assigned to each of the stars of this cluster are similar to our Solar planetary system in mass, eccentricity and semi-major axis. Our simulations show that the innermost planets are more likely to remain bound to their host stars until the end of the simulation. However, we show that starless Jupiter-like planets can be found in orbits similar to the G1 cloud as semi-major axis and eccentricity. In addition, a small fraction of starless Uranus-like planets can revolve Sgr A* in a way consistent with the G1 cloud as semi-major axis and inclination

Molecular modeling of ionization processes relevant for electrically insulating liquids

Insulating liquids are often used as a dielectric barrier between two electrodes in high-voltage devices and may suffer a breakdown in high electric fields. Breakdown happens when a conductive plasma channel, a streamer, is created in high field regions which propagates through the barrier and bridges the gap between two electrodes. This phenomenon is influenced by the field-dependent molecular properties of the insulating liquid. Among the different properties, the molecular ionization potential (IP) and excitation energies are investigated for molecules relevant for insulating liquids. It is demonstrated how density functional theory (DFT) can be used to propose suitable molecules for the design of new insulating liquids. A model based on constrained DFT is developed for the calculation of field-dependent IP and time-dependent DFT is used to study a few lowest excitation energies in the field. For a dielectric liquid in the electric field, energy is added continuously to the liquid. The liquid releases energy by emitting heat or light in the UV/VIS region. Thus, the excitation energies of molecules in liquids may be important in the streamer experiments. The IP decreases strongly with increasing the field, while the excitation energies are weakly dependent on the field. There is a threshold field for different types of molecules that above it a two-state system consisting of the electronic ground state and the ionized state is obtained. The local electric field is an important parameter in modeling the streamer behavior and is different from the external electric field. A forcefield model is developed to calculate the response of the local field to the external field (local field factor). The local field factors are calculated for liquid benzene by combining the force-field model with the molecular dynamics simulations. The local field factor increases significantly at the absorption frequency for liquid benzene. The force-field model can also be used to calculate different dielectric properties of liquids

Dynamical properties of binary stars hosting planets in the Galactic Center

We present some preliminary results of our work about the close encounter of binary stars hosting planets on S-type orbits with the Sgr A* supermassive black hole in the center of our Galaxy