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Justyna Modzelewska

Bio: Justyna Modzelewska is an academic researcher. The author has contributed to research in topics: Luminosity & Quasar. The author has an hindex of 1, co-authored 1 publications receiving 48 citations.

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Journal ArticleDOI
TL;DR: In this article, a simple physical mechanism was proposed for the formation of the Low Ionization Line part of the Broad Line Region in Active Galactic Nuclei, where the local effective temperature of a non-illuminated accretion disk drops below 1000 K and allows for dust formation.

51 citations


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01 Jan 1965
TL;DR: In this article, Maarten Schmidt solved the puzzle by recognizing the Balmer lines of hydrogen, strongly redshifted, in the spectrum of the quasar 3C 273, and reached the "most direct and least objectionable" conclusion, that 3c 273 was no star, but the enormously bright nucleus of a distant galaxy.
Abstract: In the early 1960s, astronomers were puzzled by quasars — sources of intense radio emission that seemed to be stars, but had unintelligible optical spectra. In 1963, Maarten Schmidt solved the puzzle by recognizing the Balmer lines of hydrogen, strongly redshifted, in the spectrum of the quasar 3C 273. Schmidt reached the "most direct and least objectionable" conclusion, that 3C 273 was no star, but the enormously bright nucleus of a distant galaxy.

505 citations

Journal ArticleDOI
TL;DR: A detailed view of the possible detection of a black hole can be found in this article, where the authors show a schematic view of a path leading to this objective from observations of existing type.
Abstract: Since the observational detection of black holes is inherently difficult, it is important to begin with a clear idea of the general possibilities for such detection as they seem practical from observations of existing type. FIGURE 1 shows a schematic view of the paths leading to this objective. The primary attribute by which we hope to recognize a black hole is its gravitational mass, which is discernible through its effect on macroscopic bodies (orbital motions) or microscopic bodies (compressional heating with emission of x-rays). The combination of large mass, small radius, and small luminosity constitutes the unique signature of a massive black hole, and there do exist invisible components to numerous binaries that may fulfill these conditions. Since other small objects (white dwarfs and neutrons stars) cannot have masses exceeding about 1.5 Mo, large mass means M 2 2 Mo. The notions of small radius and small luminosity can be taken in general to mean that these quantities are small compared with the values expected for any conceivable stable astronomical body that could be present. Those binaries for which fairly serious black hole arguments have been made to date are e Aur,\"34,10 p Lyrae,3,\" Cygnus X1 = HDE 226868,',e and BM Ori.\" Space does not permit discussion of the merits of these cases, although counterarguments have been made regarding ,8 Lyrae',* and might well be made against Cyg X-1 and BM Ori. It has been predicted for most of a decade, if not longer, that black holes in binary systems might be x-ray sources. Indeed, Cygnus X-1 may be one such case. However, x-rays are not the only evidence that might uncover collapsed stars, and it is fortunate that this is so because of the intrinsic difficulty of unambiguous identification of a black hole. That is, we would like, if at all possible, to have several independent demonstrations that a black hole is present. A possible path is offered by spectroscopic and photometric observations of certain unusual binaries that have long histories of observational peculiarities and, in addition, have massive invisible secondary components. It would be quite convincing if we could travel both paths of FIGURE 1 for some particular binary system. For example, E Aur might turn on as an x-ray source, or Cyg X-1 might, on detailed examination, show properties similar to those of BM Ori. An appreciation for the left path of FIGURE 1 (optical observations) may be gained through consideration of the eclipsing binary E Aurigae. The most striking peculiarity of e Aur is that the eclipse is apparently total (flat bottom)-yet the spectrum of the eclipsed component remains visible at all times. This, of course, proves that the eclipse really is not total, so we must find another explanation. It can easily be shown' that the eclipse also is not annular and that the disk models by Huang,' by Kopal,5 and by Cameron' are not compatible with the observations.'\" Useful observations of E Aur have been made since 1848, and models for the eclipse mechanism have been offered over the past 40 years. To explain

479 citations

Journal ArticleDOI
TL;DR: In this article, the authors consider the contribution of high-energy neutrino emission from blazar flares, including the recent event IceCube-170922A and the 2014-2015 neutrinos flare that could originate from TXS 0506+056.
Abstract: We consider implications of high-energy neutrino emission from blazar flares, including the recent event IceCube-170922A and the 2014–2015 neutrino flare that could originate from TXS 0506+056. First, we discuss their contribution to the diffuse neutrino intensity taking into account various observational constraints. Blazars are likely to be subdominant in the diffuse neutrino intensity at sub-PeV energies, and we show that blazar flares like those of TXS 0506+056 could make ≲1%–10% of the total neutrino intensity. We also argue that the neutrino output of blazars can be dominated by the flares in the standard leptonic scenario for their γ-ray emission, and energetic flares may still be detected with a rate of . Second, we consider multi-messenger constraints on the source modeling. We show that luminous neutrino flares should be accompanied by luminous broadband cascade emission, emerging also in X-rays and γ-rays. This implies that not only γ-ray telescopes like Fermi but also X-ray sky monitors such as Swift and MAXI are critical to test the canonical picture based on the single-zone modeling. We also suggest a two-zone model that can naturally satisfy the X-ray constraints while explaining the flaring neutrinos via either photomeson or hadronuclear processes.

137 citations

Journal ArticleDOI
TL;DR: In this paper, a physically motivated model was proposed to explain the distribution of quasars in the optical plane, where a hard X-ray power law uniquely tight to the disk at the basis of observational scaling, and the Broad Line Region distance was determined also from observational scaling.
Abstract: The concept of the quasar main sequence is very attractive since it stresses correlations between various parameters and implies the underlying simplicity. In the optical plane defined by the width of the H\\{beta} line and the ratio of the equivalent width of the Fe II to H\\{beta} observed objects form a characteristic pattern. In this paper, we use a physically motivated model to explain the distribution of quasars in the optical plane. Continuum is modelled as an accretion disk with a hard X-ray power law uniquely tight to the disk at the basis of observational scaling, and the Broad Line Region distance is determined also from observational scaling. We perform the computations of the FeII and H\\{beta} line production with the code CLOUDY. We have only six free parameters for an individual source: maximum temperature of the accretion disk, Eddington ratio, cloud density, cloud column density, microturbulence, and iron abundance, and only the last four remain as global parameters in our modelling of the whole sequence. Our theoretically computed points cover well the optical plane part populated with the observed quasars, particularly if we allow for super-Solar abundance of heavy elements. Explanation of the exceptionally strong Fe II emitter requires a stronger contribution from the dark sides of the clouds. Analyzing the way how our model covers the optical plane we conclude that there is no single simple driver behind the sequence, as neither the Eddington ratio nor broad band spectrum shape plays the dominant role. Also, the role of the viewing angle in providing the dispersion of the quasar main sequence is apparently not as strong as expected.

73 citations