Luigi Foschini - INAF Brera

Luigi Foschini
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Luigi Foschini
INAF Brera

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Astrophysics (16)
High Energy Astrophysical Phenomena (14)
Astrophysics of Galaxies (10)
Physics - History of Physics (6)
Quantum Physics (4)
Physics - Space Physics (3)
General Relativity and Quantum Cosmology (3)
Physics - Popular Physics (2)
Cosmology and Nongalactic Astrophysics (2)
Instrumentation and Methods for Astrophysics (1)
Physics - Geophysics (1)

Publications Authored By Luigi Foschini

Late Winter Lecture Notes, Short Course (10 hours) of Relativistic Astrophysics held at the Department of Physics and Astronomy of the University of Padova, March 13-17, 2017. Read More

Narrow-line Seyfert 1 galaxies (NLS1s) are an interesting subclass of active galactic nuclei (AGN), which tipically does not exhibit any strong radio emission. Seven percent of them, though, are radio-loud and often show a flat radio-spectrum (F-NLS1s). This, along to the detection of $\gamma$-ray emission coming from them, is usually interpreted as a sign of a relativistic beamed jet oriented along the line of sight. Read More

There is no mysterious link between mathematics and physics, because both of them are human inventions designed to study the world. Read More

Affiliations: 1Università di Padova, 2INAF Brera, 3Università di Padova, 4Università di Padova, 5Università di Padova, 6Purdue University, 7Ohio State University, 8Ohio State University, 9Purdue University, 10Università di Padova

Flat-spectrum radio-loud Narrow-Line Seyfert 1 galaxies (NLS1s) are a recently discovered class of $\gamma$-ray emitting Active Galactic Nuclei (AGN), that exhibit some blazar-like properties which are explained with the presence of a relativistic jet viewed at small angles. When blazars are observed at larger angles they appear as radio-galaxies, and we expect to observe an analogue parent population for beamed NLS1s. However, the number of known NLS1s with the jet viewed at large angles is not enough. Read More

The source CGRaBS~J0211$+$1051 (MG1 J021114+1051, z=0.20) flared up on 2011 January 23 in high-energy $\gamma$-rays as reported by {\it Fermi}/LAT. This event was followed by the increased activity at the UV, optical and radio frequencies as detected by the observing facilities worldwide. Read More

I report about the unification of relativistic jets from compact objects. The mass range is between 1.4 and 10 billion solar masses (i. Read More

Narrow-Line Seyfert 1 galaxies have been established as a new class of gamma-ray emitting AGN with relatively low black hole masses, but near-Eddington accretion rates. Other extragalactic gamma-ray sources observed so far such as Flat Spectrum Radio Quasars, Radio Galaxies, and BL Lacertae Objects generally exhibit much higher black hole masses and, in the case of BL Lac objects and FRI Radio Galaxies, much lower accretions rates. The multifrequency campaign of 2013 centered on the bright source 1H 0323+342 will provide further insights into the nature of the jets and their gamma ray production mechanisms in a largely unexplored corner of AGN parameter space. Read More

In his 1989 essay, John Archibald Wheeler has tried to answer the eternal question of existence. He did it by searching for links between information, physics, and quanta. The main concept emerging from his essay is that "every physical quantity, every it, derives its ultimate significance from bits, binary yes-or-no indications". Read More

The recent detection of high-energy gamma rays from Narrow-Line Seyfert 1 Galaxies has confirmed that also this type of active galactic nuclei can generate powerful relativistic jets. I outline the evolution of the knowledge in this research field and the implications on the unification of relativistic jets at all scales. Read More

The recent discovery by Fermi/LAT of high-energy (E>100 MeV) gamma rays from Narrow-Line Seyfert 1 Galaxies (NLS1s) made evident the existence of a third class of gamma-ray emitting Active Galactic Nuclei (AGN), after blazars and radio galaxies. It is now possible to study a rather unexplored range of low masses (10^6-8 Msun) and high accretion rates (up to the Eddington limit) of AGN with relativistic jets. A comparison with the jet emission from Galactic compact objects shows some striking similarities, indicating that NLS1s are the low-mass counterpart of blazars as neutron stars are the low-mass jet systems analogue of stellar mass black holes. Read More

The Blandford-Znajek theory (1977) is generally studied to understand the generation of powerful relativistic jets. However, it could also give important insights about the feedback between a rotating black hole, its ergosphere, and a surrounding accretion disk. The energy flow between these systems could be understood by studying the BZ power as a function of a slip factor, which in turn is defined as a function of the angular velocity of the black hole and the angular velocity of the magnetic field lines (generally anchored to the disk). Read More

The discovery of high-energy (E>100 MeV) gamma rays from Narrow-Line Seyfert 1 Galaxies (gamma-NLS1s) has confirmed the presence of powerful relativistic jets in this class of active galactic nuclei (AGN). Although the jet emission is similar to that of blazars and radio galaxies, gamma-NLS1s have some striking differences: relatively small masses (10^6-10^8 M_sun), high accretion rates (0.1-1 times the Eddington limit) and are generally hosted by spiral galaxies. Read More

The classical diagrams of radio loudness and jet power as a function of mass and accretion rate of the central spacetime singularity in active galactic nuclei are reanalyzed by including the data of the recently discovered powerful relativistic jets in Narrow-Line Seyfert 1 Galaxies. The results are studied in the light of the known theories on the relativistic jets, indicating that while the Blandford-Znajek mechanism is sufficient to explain the power radiated by BL Lac Objects, it fails to completely account the power from quasars and Narrow-Line Seyfert 1. This favors the scenario outlined by Cavaliere & D'Elia of a composite jet, with a magnetospheric core plus a hydromagnetic component emerging as the accretion power increases and the disc becomes radiation-pressure dominated. Read More

In 2008, the Fermi Gamma-ray Space Telescope has revealed - for the first time - high-energy (E > 100 MeV) gamma rays from a few Narrow-Line Seyfert 1 Galaxies (NLS1s). Later, in 2009 and 2010, two multifrequency campaigns on one of these sources, PMN J0948+0022 (z=0.585), definitely confirmed the presence, in sources of this type, of a relativistic jet very similar and with comparable power to those in blazars. Read More

The effect of the observed continuum emitted from a relativistic jet on the measurement of the full width half maximum (FWHM) of an emission line is analyzed. If the jet contribution is not properly subtracted, the FWHM of the line could seem narrower than what it should be. The cases of emission line detected in BL Lac objects and gamma-ray Narrow-Line Seyfert 1 galaxies (gamma-NLS1s) are addressed. Read More

In this essay, I review the importance of languages in the study of reality, following the well-known aphorisms by Galilei, Bohr and many others. The emphasis on these aspects helps us to understand that it is not meaningful to ask if the reality if "digital" or "analog", but we have to search what is the best language to study some specific aspects of the reality. This problem is particularly felt in the case of frontier science, like quantum gravity, where, in front of several theories (syntaxes) available, there are presently neither observations nor experiments leading to the building of a convincing semantics. Read More

Let's take stock of the situation on one of the most studied astrophysical phenomena during the latest years: the jets escaping from protostars, stellar singularities, GRB and active galactic nuclei. Read More

By using the Fermi satellite, a group of physicists discovers a new type of gamma-ray active nucleus Read More

These notes were originally prepared as additional material for the lessons I have given at the summer school Gamma-ray Astrophysics and Multifrequency: Data analysis and astroparticle problems, organized by the Department of Physics of the University of Perugia (Italy) on July 3-7, 2006. The necessarily limited time of the lessons forced to a drastic selection of the topics and, therefore, I have thought it was useful to complete the slides of the presentation with the notes you find in these few pages. These notes are a kind of ``link'' between the theoretical approach of the University lessons and the practice of the real use. Read More

We review 6 years of INTEGRAL observations of blazars, from Target-Of-Opportunity (TOO) to normal observations to coordinated campaigns, from the new and unexpected discoveries to the improvements in this research field. We also shortly review what is expected from INTEGRAL for the forthcoming years. Read More

We report on an analysis of X- and $\gamma$-ray observations of PKS 1830-211, based on the long-term campaigns carried out by \emph{INTEGRAL} and COMPTEL. The \emph{INTEGRAL} data currently available present a $33\sigma$ significance detection in the 20-100 keV band, while the COMPTEL 6-years data provide a $5.2\sigma$ significance detection in the 1-3 MeV energy band. Read More

Affiliations: 1INAF - Trieste Astronomical Observatory, 2INAF - IASF, Bologna, 3INAF - Brera Astronomical Observatory
Category: Astrophysics

The blazars 3C 454.3, PKS 0537-441 and PKS 2155-304 are traditionally known to be among the most active sources of this class. They emit at all frequencies, up to the gamma-rays, and are good probes of multiwavelength nuclear variability. Read More

Affiliations: 1CASS/UCSD, 2AIM/CEA Saclay, 3AIM/CEA Saclay, 4INAF/IASF - Bologna, 5ISDC, 6Univ. of Iowa
Category: Astrophysics

Hard X-ray imaging of the Galactic plane by the INTEGRAL satellite is uncovering large numbers of 20-100 keV "IGR" sources. We present results from Chandra, INTEGRAL, optical, and IR observations of 4 IGR sources: 3 sources in the Norma region of the Galaxy (IGR J16195-4945, IGR J16207-5129, and IGR J16167-4957) and one that is closer to the Galactic center (IGR J17195-4100). In all 4 cases, one relatively bright Chandra source is seen in the INTEGRAL error circle, and these are likely to be the soft X-ray counterparts of the IGR sources. Read More

In Spring 2005, the blazar 3C454.3 underwent a dramatic outburst at all wavelengths from mm to X-rays. This prompted INTEGRAL observations, accomplished in 15-18 May 2005. Read More

We report the discovery of a Narrow Line QSO located at about 1.3' from the Broad Line Radio Galaxy 3C445. The source,1WGA J2223. Read More

It is known, from observational data recorded from airbursts, that small asteroids breakup at dynamical pressures lower than their mechanical strength. This means that actual theoretical models are inconsistent with observations. In this paper, we present a detailed discussion about data recorded from airbursts and about several theoretical models. Read More

Recent works, both theoretical and observational, have suggested that turbulence could play a non-negligible role in the broadening of emission lines in active galactic nuclei. The purpose of this note is to show how shock wave-turbulence interaction, under unsteady regime, can affect the broadening of emission lines. Read More

We investigate the conditions under which Leonid meteoroids might generate short duration (burster) electrophonic sounds. A `first order' theory is employed to estimate the approximate electron number density in the meteoroid ablation column as a function of time. Using the threshold conditions discussed in an earlier communication (Beech and Foschini 1999) we find that Leonid meteoroids more massive than about 0. Read More

The existence of large domains of antimatter is still an open question. Some space mission and experiments in the near future are expected to give reasonable answer to that question. Meanwhile, we can try to search for other signatures of the presence of antimatter. Read More

The current philosophy of impact hazard considers the danger from small asteroids negligible. However, several facts claim for a revision of this philosophy. In this paper, some of these facts are reviewed and discussed. Read More

Some notes and questions about the concept of time are exposed. Particular reference is given to the problem in quantum mechanics, in connection with the indeterminacy principle. Read More

This letter presents a new solution for the Tunguska event of June 30th, 1908. The solution has been obtained starting from seismic data, is in fair agreement with the observational evidence, and supports the asteroidal hypothesis for the origin of the Tunguska cosmic body. It is based on an improved model of the hypersonic flow around a small asteroid in the Earth's atmosphere. Read More

The passage of particles through matter is one of the principal ways to investigate nature. In this article, we would like to outline the most important stages in the development of the theory about the stopping power. Read More

During the 80's, some experiments and the repetitions of old ones, lead to the hypothesis of a fifth force. Nevertheless, a more accurate research was not able to confirm this hypothesis. This article wants to go over again the most important steps of the event. Read More

The unexpected discoveries at the beginning of the century, particularly thanks to Heisenberg, Bohr, and Godel, has driven the science to drastic changes, opening new, extraordinary, and infinite research fields. After this, many scientists saw, and still today see, a crisis, with dreadful meaning, in the science. However, this crisis is only present in that type of science, driven by determinism, which is strictly linked to the common sense. Read More

On January 19, 1993, a very bright bolide (peak magnitude -23) crossed the sky of Northern Italy, ending with an explosion approximately over the town of Lugo (Emilia Romagna, Italy). The explosion (14 kton of energy) generated shock waves which were recorded by six local seismic stations. A reanalysis of the available data leads us to the hypothesis that the meteoroid was a porous carbonaceous chondrite, somehow similar in constitution to the asteroid 253 Mathilde. Read More

In this paper, a meteoric plasma is analyzed from a physical viewpoint, with particular emphasis on its interaction with radio waves. The attention is drawn to some macroscopic characteristics of a meteoric plasma and it is shown that the electron-ion collision frequency is not negligible, as commonly thought. Read More

Thanks to post-flight analyses of several artificial satellites carried out during last years, the meteoroids hazard for space navigation and in-orbit satellites permanence is now clear. Even if catastrophic impact is a rare event, high meteoroids fluxes can erode and weaken the satellite or space station main structures. However, the main danger seems to be the impact-generated plasma, which can produce electromagnetic interferences, disturbing the on-board electronics. Read More

It is shown that the plasma, generated during an impact of a meteoroid with an artificial satellite, can produce electromagnetic radiation below the microwave frequency range. This interference is shown to exceed local noise sources and might disturb regular satellite operations. Read More

The logic--linguistic structure of quantum physics is analysed. The role of formal systems and interpretations in the representation of nature is investigated. The problems of decidability, completeness, and consistency can affect quantum physics in different ways. Read More