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1.
Aspects of micro black hole evaporation
Saeede Nafooshe, 2015, doktorska disertacija

Najdeno v: ključnih besedah
Povzetek najdenega: ...micro black holes, evaporation, gravitons, grey-body factors, large dimensions, quasi-normal mode...
Ključne besede: micro black holes, evaporation, gravitons, grey-body factors, large dimensions, quasi-normal modes, Vaidya metric
Objavljeno: 17.11.2015; Ogledov: 4114; Prenosov: 248
.pdf Polno besedilo (3,14 MB)

2.
Horizon Shells and BMS-like soldering transformations
Martin O'Loughlin, Matthias Blau, 2016, izvirni znanstveni članek

Opis: We revisit the theory of null shells in general relativity, with a particular emphasis on null shells placed at horizons of black holes. We study in detail the considerable freedom that is available in the case that one solders two metrics together across null hypersurfaces (such as Killing horizons) for which the induced metric is invariant under translations along the null generators. In this case the group of soldering transformations turns out to be infinite dimensional, and these solderings create non-trivial horizon shells containing both massless matter and impulsive gravitational wave components. We also rephrase this result in the language of Carrollian symmetry groups. To illustrate this phenomenon we discuss in detail the example of shells on the horizon of the Schwarzschild black hole (with equal interior and exterior mass), uncovering a rich classical structure at the horizon and deriving an explicit expression for the general horizon shell energy- momentum tensor. In the special case of BMS-like soldering supertranslations we find a conserved shell-energy that is strikingly similar to the standard expression for asymptotic BMS supertranslation charges, suggesting a direct relation between the physical properties of these horizon shells and the recently proposed BMS supertranslation hair of a black hole.
Najdeno v: ključnih besedah
Povzetek najdenega: ...on null shells placed at horizons of black holes. We study in detail the considerable freedom...
Ključne besede: Black Holes, Classical Theories of Gravity, Space-Time Symmetries
Objavljeno: 10.03.2016; Ogledov: 2807; Prenosov: 0
.pdf Polno besedilo (333,17 KB)

3.
New Frontiers in Black Hole Astrophysics
2017, zbornik recenziranih znanstvenih prispevkov na mednarodni ali tuji konferenci

Najdeno v: ključnih besedah
Povzetek najdenega: ...astronomy, black holes, active galactic nuclei, gamma ray bursts, tidal...
Ključne besede: astronomy, black holes, active galactic nuclei, gamma ray bursts, tidal disruption events, gravitational waves
Objavljeno: 17.08.2017; Ogledov: 2089; Prenosov: 0
.pdf Polno besedilo (106,73 KB)

4.
Tidal disruption events from different kinds of astrophysical objects: a preliminary analysis
Aurora Clerici, Andreja Gomboc, 2017, objavljeni povzetek znanstvenega prispevka na konferenci

Najdeno v: ključnih besedah
Povzetek najdenega: ...astronomy, tidal disruption events, black holes...
Ključne besede: astronomy, tidal disruption events, black holes
Objavljeno: 17.08.2017; Ogledov: 2598; Prenosov: 0
.pdf Polno besedilo (221,17 KB)

5.
What can Fermi LAT observation of the Galactic Centre tell us about its active past?
Gabrijela Zaharijas, 2017, objavljeni znanstveni prispevek na konferenci

Najdeno v: ključnih besedah
Povzetek najdenega: ...astronomy, black holes, galactic centre, Fermi LAT...
Ključne besede: astronomy, black holes, galactic centre, Fermi LAT
Objavljeno: 17.08.2017; Ogledov: 1923; Prenosov: 0
.pdf Polno besedilo (348,86 KB)

6.
Simulations of Tidal Disruption Events Observations with the LSST
Katja Bricman, 2017, magistrsko delo

Opis: The Large Synoptic Survey Telescope (LSST) will produce a multi-colour survey of 25000 square deg of the Southern sky during its 10 years of operations. It will observe over 20 billion galaxies and a similar number of stars, map the Solar System and the Milky Way, and probe dark matter and dark energy. In addition, it will discover thousands of transients every night, including new classes of objects, which have not yet been observed. Due to its large coverage of the sky it will be a perfect tool for the search of rare Tidal Disruption Events (TDEs), which occur when a star passes close by a supermassive black hole and gets disrupted by its tidal force. Afterwards the stellar debris fall back to the black hole, initially at a rate exceeding the Eddington rate, producing an outflow, which releases a flare of energy. When the fallback rate subsides below the Eddington rate, the gas accretes onto the black hole via accretion disk. The LSST simulation framework enables us to simulate observations of different types of objects with the LSST. In this work, we include TDEs in the LSST simulation framework, estimate the number of detected TDEs, and simulate their light curves using a theoretical model, which predicts a t^(-2.6) light curve decline with time in the outflow phase and a t^{-0.4} decline in the disk phase. We also take a closer look at the distribution of the detected TDEs over cosmological redshift and black hole mass.
Najdeno v: ključnih besedah
Povzetek najdenega: ...a star passes close by a supermassive black hole and gets disrupted by its tidal... ...Synoptic Survey Telescope, Tidal Disruption Events, Black Holes, simulations...
Ključne besede: Astronomical observations, Large Synoptic Survey Telescope, Tidal Disruption Events, Black Holes, simulations
Objavljeno: 17.10.2017; Ogledov: 2277; Prenosov: 0
.pdf Polno besedilo (8,73 MB)

7.
Black holes, gravitational waves and fundamental physics: a roadmap
Katja Bricman, Andreja Gomboc, Tanja Petrushevska, Leor Barack, Aurora Clerici, Christopher Eckner, Nada Ihanec, Gabrijela Zaharijas, 2019, pregledni znanstveni članek

Opis: The grand challenges of contemporary fundamental physics—dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem—all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on 'Black holes, Gravitational waves and Fundamental Physics.
Najdeno v: ključnih besedah
Ključne besede: black holes, gwverse
Objavljeno: 24.06.2019; Ogledov: 1651; Prenosov: 0
.pdf Polno besedilo (7,00 MB)

8.
A study of stellar debris dynamics during a tidal disruption event
Aurora Clerici, 2020, doktorska disertacija

Opis: The number of observed tidal disruption events is increasing rapidly with the advent of new surveys. Thus, it is becoming increasingly important to improve TDE models using different stellar and orbital parameters. We study the dynamical behaviour of tidal disruption events produced by a massive black hole like Sgr A* by changing different initial orbital parameters, taking into account the observed orbits of S stars. Investigating different types of orbits and penetration factors is important since their variations lead to different timescales of the tidal disruption event debris dynamics, making mechanisms such as self-crossing and pancaking act strongly or weakly, thus affecting the circularisation and accretion disk formation. We have performed smoothed particle hydrodynamics simulations. Each simulation consists in modelling the star with $10^5$ particles, and the density profile is described by a polytrope with $\gamma$ = 5/3. The massive black hole is modelled with a generalised post-Newtonian potential, which takes into account relativistic effects of the Schwarzschild space-time. Our analyses find that mass return rate distributions of solar-like stars and S-like stars with same eccentricity have similar durations, but S-like stars have higher mass return rate, as expected due to their larger mass. Regarding debris circularisation, we identify four types of evolution, related to the mechanisms and processes involved during circularisation: in type 1 the debris does not circularise efficiently, hence a disk is not formed or is formed after relatively long time; in type 2 the debris slowly circularises and eventually forms a disk with no debris falling back; in type 3 the debris relatively quickly circularises and forms a disk while there is still debris falling back; finally, in type 4 the debris quickly and efficiently circularises, mainly through self-crossings and shocks, and forms a disk with no debris falling back. Finally, we find that the standard relation of circularisation radius $r_{\rm circ} = 2r_{\rm t}$ holds only for $\beta = 1$ and eccentricities close to parabolic.
Najdeno v: ključnih besedah
Povzetek najdenega: ...tidal disruption events produced by a massive black hole like Sgr A* by changing different... ...and bulge, 98.62.Js Galactic nuclei (including black holes), circumnuclear matter, and bulges, 98.62.Mw Infall, accretion,...
Ključne besede: 07.05.Tp Computer modeling and simulation, 95.30.Lz Hydrodynamics, 98.35.Jk Galactic center, bar, circumnuclear matter, and bulge, 98.62.Js Galactic nuclei (including black holes), circumnuclear matter, and bulges, 98.62.Mw Infall, accretion, and accretion disks
Objavljeno: 29.09.2020; Ogledov: 1141; Prenosov: 44
.pdf Polno besedilo (37,55 MB)

9.
TDEs with LSST
Katja Bricman, 2018, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: The Large Synoptic Survey Telescope (LSST) is an upcoming ground-based survey telescope in Chile, which will produce a multi-color survey of 18000 square degrees of the Southern Sky during its 10 years of observations. Due to its large coverage of the sky and its observing strategy it will be a perfect tool in search for transient astrophysical events, including rare Tidal Disruption Events (TDEs). TDEs occur when a star passes close by a supermassive black hole (SMBH) in a center of a galaxy and gets disrupted by its tidal forces. These events emit a bright flare of light, which can be observed to cosmological distances. In the seminar I will provide an overview of the LSST and TDEs, and present the preliminary results on the estimated absolute rates of TDE detection in 10 years of LSST operations, which were obtained by simulations of TDE light curves with an end-to-end LSST simulations framework.
Najdeno v: ključnih besedah
Povzetek najdenega: ...a star passes close by a supermassive black hole (SMBH) in a center of a... ...Tidal Disruption Events, Supermassive Black Holes, Sky Surveys...
Ključne besede: Tidal Disruption Events, Supermassive Black Holes, Sky Surveys
Objavljeno: 04.01.2021; Ogledov: 661; Prenosov: 23
.pdf Polno besedilo (1009,99 KB)

10.
Studying TDEs in the era of LSST
Katja Bricman, Andreja Gomboc, 2019, objavljeni povzetek znanstvenega prispevka na konferenci

Najdeno v: ključnih besedah
Povzetek najdenega: ...disruption of stars by their host supermassive black hole (SMBH) can provide us with important... ...by the Action CA16104 Gravitational waves, black holes and fundamental physics (GWverse), supported by COST...
Ključne besede: The observing strategy with continuous scanning and large sky coverage of the upcoming ground-based Large Synoptic Survey Telescope (LSST) will make it a perfect tool in search of rare transients, such as Tidal Disruption Events (TDEs). Bright optical flares resulting from tidal disruption of stars by their host supermassive black hole (SMBH) can provide us with important information about the mass of the SMBH involved in the disruption and thus enable the study of quiescent SMBHs, which represent a large majority of SMBHs found in centres of galaxies. These types of transients are extremely rare, with only about few tens of candidates discovered so far. It is expected that the LSST will provide a large sample of new TDE light curves. Here we present simulations of TDE observations using an end-to-end LSST simulation framework. Based on the analysis of simulated light curves we estimate the number of TDEs with good quality light curves the LSST is expected to discover in 10 years of observations. In addition, we investigate whether TDEs observed by the LSST could be used to probe the SMBH mass distribution in the universe. The participation at this conference is supported by the Action CA16104 Gravitational waves, black holes and fundamental physics (GWverse), supported by COST (European Cooperation in Science and Technology).
Objavljeno: 04.01.2021; Ogledov: 688; Prenosov: 0

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