Extremal energy shifts of radiation from a ring near a rotating black hole

Radiation from a narrow circular ring shows a characteristic double-horn profile dominated by photons having energy around the maximum or minimum of the allowed range, i.e. near the extremal values of the energy shift. The energy span of a spectral line is a function of the ring radius, black hole spin, and observer's view angle. We describe a useful approach to calculate the extremal energy shifts in the regime of strong gravity. Then we consider an accretion disk consisting of a number of separate nested annuli in the equatorial plane of Kerr black hole, above the innermost stable circular orbit (ISCO). We suggest that the radial structure of the disk emission could be reconstructed using the extremal energy shifts of the individual rings deduced from the broad wings of a relativistic spectral line.Comment: 9 pages, 5 figures, ApJ accepte

Gravitational microlenses with small Einstein radii

Ústav teoretické fyzikyInstitute of Theoretical PhysicsFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Astrofyzikální procesy v blízkosti kompaktních objektů

Title: Astrophysical processes near compact objects: studying extremal en- ergy shifts from accretion rings Author: Vjačeslav Sochora Department: Academy of Sciences of the Czech Republic, Astronomical In- stitute Supervisor: doc. RNDr. Vladimír Karas, DrSc.; Academy of Sciences of the Czech Republic, Astronomical Institute Abstract: The X-ray emission from inner regions of an accretion disk around black holes provides wealth of information about matter in extreme con- ditions. A spectral profile of radiation from a narrow circular ring has a characteristic double-horn profile. Red and blue peaks of the profile are close to the extremal values of the energy shift. We describe a useful approach to calculate the extremal energy shifts in the regime of strong gravity. We dis- cuss if the radial structure of the disk emission could be reconstructed using extremal energy shifts of the individual rings. For this purpose, we simulate artificial data from a bright active galactic nucleus and show that the re- quired sensitivity and energy resolution can be reached with the proposed LOFT mission. Keywords: black hole physics, accretion disks, galactic nucle

Astrofyzikální procesy v blízkosti kompaktních objektů: studium extremálních posuvů energie z akrečních prstenců

Název práce: Astrofyzikální procesy v blízkosti kompaktních objektů: studium extremálních posuvů energie z akrečních prstenců Autor: Vjačeslav Sochora Pracoviště: Astronomický ústav AV ČR Vedoucí disertační práce: doc. RNDr. Vladimír Karas, DrSc., Astronomický ústav AV ČR Abstrakt: Rentgenové záření z vnitřních oblastí akrečního disku okolo černých děr poskytuje velké množství informací o hmotě v extrémních podmínkách. Spektrální profil záření z úzkého, kruhového prstence má charakteristický tvar s dvěma maximy. Červený a modrý vrchol profilu leží blízko extremálních hodnot energetického posuvu čáry. Popisujeme užitečný postup výpočtu ex- tremálních energetických posuvů v režimu silné gravitace. Diskutujeme, zda radiální struktura emise disku může být rekonstruována užitím extrémních energetických posuvů jednotlivých prstenců. Za tímto účelem simulujeme umělá data z jasného galaktického jádra a ukazujeme, že požadované citlivosti a energetického rozlišení může být dosaženo s navrženou misí LOFT. Klíčová slova: fyzika černých děr, akreční disky, galaktická jádraTitle: Astrophysical processes near compact objects: studying extremal en- ergy shifts from accretion rings Author: Vjačeslav Sochora Department: Academy of Sciences of the Czech Republic, Astronomical In- stitute Supervisor: doc. RNDr. Vladimír Karas, DrSc.; Academy of Sciences of the Czech Republic, Astronomical Institute Abstract: The X-ray emission from inner regions of an accretion disk around black holes provides wealth of information about matter in extreme con- ditions. A spectral profile of radiation from a narrow circular ring has a characteristic double-horn profile. Red and blue peaks of the profile are close to the extremal values of the energy shift. We describe a useful approach to calculate the extremal energy shifts in the regime of strong gravity. We dis- cuss if the radial structure of the disk emission could be reconstructed using extremal energy shifts of the individual rings. For this purpose, we simulate artificial data from a bright active galactic nucleus and show that the re- quired sensitivity and energy resolution can be reached with the proposed LOFT mission. Keywords: black hole physics, accretion disks, galactic nucleiMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

Vliv silného gravitačního pole kompaktních objektů na jejich záření

In the present work we describe different cosmic systems that contain the compact objects (neutron stars or black holes). The accretion of the matter on the compact object is a main source of the radiation and that is why we consider several models of accretion. The energy of emitted radiation is different from the observed energy due to the gravitational redshift and the Doppler shift. We are interested in the minimum and maximum values of this change of emitted radiation. We show how to calculate these extremes in Kerr metric by the help of the elliptic integrals assuming that the emission radius, the angular momentum of black hole, and the inclination angle of the observer are given

An Assessment of the Bactericidal and Virucidal Properties of ZrN-Cu Nanostructured Coatings Deposited by an Industrial PVD System

Pathogenic microbes, such as bacteria and viruses, can spread quickly via contaminated surfaces. Most of these pathogenic microorganisms can survive on surfaces for a long time. Touching these surfaces can lead to the transmission of the microorganisms to the human body and cause serious illnesses. ZrN-Cu coatings containing different amounts of Cu were deposited using an industrial PVD system, and their ability to inhibit bacteria and inactivate the SARS-CoV-2 virus was tested. Microstructural studies showed the formation of two distinct ZrN and Cu phases when Cu content was sufficiently high. Hardness and elastic modulus were inversely proportional to the Cu content. The coatings showed outstanding bactericidal properties against Escherichia coli and Pseudomonas aeruginosa, especially when Cu content was more than 12 at.% and exposure time was longer than 40 min. The coatings, however, did not exhibit any significant virucidal properties. Good mechanical properties, along with excellent antibacterial effects, make these coatings suitable for use as self-sanitizing surfaces on objects that people regularly touch and that are prone to bacterial contamination. Their use would thus allow for only minimal transmission or multiplication of bacteria, and the treated surface would not serve as another source of infection