The Ep,i - Eiso correlation and Fermi Gamma-Ray Bursts

The correlation between the spectral peak photon energy, Ep, and the radiated energy or luminosity (i.e., the "Amati relation" and other correlations derived from it) is one of the central and most debated topics in GRB astrophysics, with relevant implications for the the physics and geometry of the prompt emission, the indentification and understanding of different classes of GRBs (short/long, XRFs, sub-energetic), GRB cosmology. Fermi is exceptionally suited to provide, also in conjunction with Swift observations, a significant step forward in this field of research. Indeed, one of the main goals of the Fermi/GBM is the accurate measurement of Ep, by exploiting its unprecedented broad energy band from ~8 keV to ~30 MeV; in addition, for a small fraction of GRBs the LAT can extend the spectral measurements up to the GeV energy range, thus allowing a reliable estimate of the bolometric radiated energy / luminosity. I provide a review, update and discussion of the impact of Fermi observations in the investigation, understanding and testing of the Ep-Eiso ("Amati")relation and of the other spectrum-energy correlations.

Kerr rotation as solitonic whirl around the Schwarzschild black hole

We propose the new derivation of the Kerr solution by adding to the Schwarzchild black hole the solitonic vortex made from the pure gravitational field. With this method, we can figure out how rotational energy can contribute to the mass of the resulting Kerr black hole. The interpretation of the extremal black hole as a whirl of pure gravity is proposed. Also we suggest a new point of view on the relation between the mass and angular momentum of a Kerr black hole.

Equatorial and circular geodesics in the Hartle-Thorne space-time

The Hartle-Thorne metric is an approximate solution of vacuum Einstein field equations that describes the exterior region of any slowly and rigidly rotating, stationary and axially symmetric body. The metric is given with accuracy up to the second order terms in the body’s angular momentum, and first order in its quadrupole moment. We investigate equatorial and circular geodesics and give, with the same accuracy, analytic formulae for circular geodesics in the Hartle-Thorne metrics. They describe angular velocity, angular momentum, energy, epicyclic frequencies, shear, vorticity and Fermi-Walker precession. These quantities are relevant to several astrophysical phenomena, in particular to the observed high frequency, kilohertz Quasi Periodic Oscillations (kHz QPOs) in the X-ray luminosity from black hole and neutron star sources. It is believed that kHz QPO data may be used to test the strong field regime of Einsteins general relativity, and the physics of super-dense matter of which neutron stars are made of. 

The classification of Gamma-Ray Bursts: long, short and "disguised" GRBs

Observations of Gamma-ray Bursts (GRBs) in the recent years have revealed, with increasing evidence, that the historical classification between long and short bursts has to be revised. Within the Fireshell scenario, both short and long bursts are canonical bursts, consisting of two different phases. First, a Proper-GRB (P-GRB), that is the emission of photons at the tranparency of the fireshell. Then, the Extended Afterglow, multiwavelenght emission due to the interacion of the baryonic remnants of the fireshell with the CircumBurst Medium (CBM). We discriminate between long and short bursts by the amount of energy stored in the first phase with respect to the second one. This is given by the baryon loading parameter, that quantifies the barionic remnants engulfed by the fireshell. When 10E-4<B<10E-2 we will have a long burst, where the afterglow phase is energetically predominant. When B<10E-5 the P-GRB phase is predominant, and we will observe a short burst. Within the Fireshell scenario, we have introduced a third intermediate class: the "disguised" GRBs. They appear like short bursts, because their morphology is characterized by a first, short, hard episode and a following deflated tail, but this last part - coincident with the peak of the afterglow - is energetically predominant. The origin of this peculiar kind of sources is inferred to a very low average density of the environment (of the order of 10E-3, compatible with galactic halos) We have found the prototype of these class of bursts in GRB970228. Many analysis have been performed and have been identified as other examples of disguised bursts (GRB060614, GRB071227 and GRB050509b). The study of these bursts within the Amati relation, empirical correlation fulfilled only by long bursts, seems to confirm our hipothesys.

The Data Analysis and Final Results for the Gravity Probe B Experiment

The Gravity Probe B (GP-B) experiment, sponsored by NASA and launched on 20 April 2004, tested two fundamental predictions of general relativity, the geodetic effect and the frame-dragging effect. The GP-B spacecraft measured the non-Newtonian drift rates of four ultra-precise cryogenic gyroscopes placed in a circular polar Low Earth Orbit. Science data was collected from 28 August 2004 until cryogen depletion on 29 September 2005. The final results were announced on 4 May 2011 at NASA Headquarters in Washington DC. The data analysis was complicated by two unexpected phenomena, a) a continually damping gyroscope polhode affecting the calibration of the gyro readout and b) two larger than expected Newtonian torques acting on the gyroscopes, comparable in magnitude to the relativistic effects. Experimental evidence strongly indicates that both effects are caused by non-uniform electric potentials (i.e. the patch effect) on the surfaces of the gyroscope rotor and its housing. The five-year long data analysis effort involved first determining the root cause for these classical effects, then developing mathematical models for them, and finally building an optimal filter to estimate them simultaneously with the relativistic drift rates. The data analysis resulted in estimates of the geodetic and frame-dragging effects consistent with General Relativity with accuracies of 0.28% and 19% respectively.

Upscattering spectral formation model for the prompt emission of Gamma Ray Bursts

We propose a model for the spectral formation of Gamma Ray Burst (GRB) prompt emission. The framework in which we derive the emergent spectrum is the explosion of a very massive star due to core pair instability, but other scenarios could be considered such as a jet propagating in the stellar interiors with sub-relativistic velocity as a result of torus accretion onto a massive black hole. We show that the phenomenological Band's function used to describe the GRB prompt emission can be derived by a two-phase inverse Compton process, the first one with saturated Comptonization of a blackbody-like seed photon spectrum off a hot plasma moving outward with sub-relativistic velocity, while the high-energy power-law component above the peak in the EF(E) diagram is obtained qualitatively by the convolution of the resulting bulk-Comptonized spectrum of the earlier phase with a broken-power-law Green's function. We also propose a possible explanation of the GRB temporal variability using basic photon diffusion processes inside an inhomogeneous medium.

Boltzmann equation in curved space time: formulation and applications in general relativity

We write and solve the Boltzmann equation in an arbitrary space time; then we evaluate the statistical moments of the solution to describe the thermodinamic of a gas of massive particles exploiting a manifestly covariant method. We present also the covariant description of photon gas in a curved space. Then we study the Poynting-Robertson effect in the Schwarzschild metric comparing our results with the one in litterature.

Fermi and the 4/3 problem in the classical theory of the electron

The classical theory of the electron with its troublesome coefficient of 4/3 in the inertial mass of the electron due to its electric field alone, though a somewhat academic problem, has fascinated people for over a century, yet a simple resolution by Fermi 90 years ago remains largely unfamiliar even to those who have invested a lot of work in understanding the general problem. His corrected condition of the total force constraint for the prolem.  

Features in the spectrum of primordial perturbations: new constraints from WMAP7+ACT data and prospects for Planck

We update the constraints on possible steps in the inflationary potential by using the latest data from the WMAP7 and ACT Cosmic Microwave Background experiments. We show that the inclusion of new data improves the constraints with respect to older work, especially to smaller angular scales thanks to the ACT data. While we report no evidence in the data for extensions to the simplest, featurless, inflationary model, models with a step in the potential are preferred over simple featureless power-law spectra. We show that the issue can be clarified by the forthcoming CMB data from Planck. 

High energy emission in GRBs : the case of GRB 090902B

In this work we present recent results within the analysis of GRB 090902B. The new value of E_iso = 5.29*10^54 erg for the isotropic energy has been obtained, using Fermi GBM and LAT data. Then a time-resolved spectral analysis has been performed and, with the new isotropic energy, the main parameters in the fireshell scenario have been evaluated, providing the fit of light curve and spectrum in the energy range 8-1000 keV. Finally, according to the dissipative photosphere model of Ryde, a new interpretation has been proposed for the P-GRB episode in GRB 090902B, namely the contaminated P-GRB, still in progress.

Evidences for a double component in the emission of GRB 101023

We present the results of the analysis of GRB 101023 in the fireshell scenario. Its redshift is not known, so we attempted to infer it from the Amati Relation, obtaining z=0.9. Its light curve presents a double emission, which makes it very similar to the already studied GRB 090618. We performed a time-resolved spectral analysis with RMFIT using different spectral models, and fitted the light curve with a numerical code reproducing the fireshell equations of motion. We used Fermi GBM data to build the light curve, in particular the second NaI detector, in the range (8.5-1000 keV). We found that the first emission does not match the requirements for a GRB, while the second part perfectly agrees with being a canonical GRB, with a P-GRB lasting 4s. 

Einstein is still right: new tests of gravitational dynamics in the field of the Earth

General relativity theory by Albert Einstein is still the best and most effective available description of gravitational phenomena, supported by an impressive series of experimental tests on a very wide range of scales. Nevertheless, evidences and hints of various nature (particle physics, cosmology) have placed many times and still place questions on its validity and overall coherence; alternative theories of gravitation have been in fact proposed along the years. In this context, the experimental tests in the Solar System remain an important tool and, perhaps not surprisingly, continue to be among the strongholds of knowledge in this field. In particular, LAGEOS satellites turned out to be among the most powerful probes for the fine characteristics of the gravitation phenomenon, and continue to provide extremely interesting results. Their particular orbits and the extremely precise tracking technique (Satellite Laser Ranging) led along the years to a series of important discoveries. It will be presented and discussed here a recent analysis, which led to the first direct verification of the Schwarzschild relativistic precession in the field of the Earth, and to the simultaneous measurement of the so-called Lense-Thirring and de Sitter effects; emphasis will be given on the analysis strategy, the modelization issues and the related error estimates. It will be also shown a further result, consisting in a new limit, much more stringent than the previous ones, on a possible non Newtonian (Yukawa) interaction, acting at the scale of Earth radius 

A new approach for the heliometric optics

(V. d'Avila, E. Reis Neto, A. Coletti, L. C. Oliveira, V. B. Matias, A. H. Andrei, J. L. Penna, S. Calderari Boscardin, C. Sigismondi) 

Recent research on global climate changes points to three distinct sources of climate disturbance: anthropogenic; natural changes in the oceans and atmosphere; and irregularities in the solar cycles. One of the most direct way to survey the last origin of climatic variability is through the measurement of variations in the diameter and the shape of the solar disk. The heliometric method is one of the most successfull techniques to measure small angles, which has been used with great success in the past for the first determinations of the eccentricity of the Earth´s orbit, as well as the first measurements of stellar parallax. The classic heliometer is a refractor in which the lens is split into two halves to which is applied a linear displacement along the cut. The success of this method is in the fact that it minimizes the dependence of angular measurements to the thermal and mechanical stability of the instrument. However, this classical configuration leaves still room for a small residual dependence with the focus due to non-concentricity of the beams of the two images. A new heliometer has been designed and is being built as a reflector in which the mirror was cut to form two concentric rings. Between the two rings angular displacement is applied in order to generate two solar images. With this new instrument it is possible to achieve the ideal conditions of heliometric technique, in the sense that, for the first time, angular measurements became totally independent of the stability of the instrumental focus. This instrument is suitable for space applications. 

The measurement of solar diameter and limb darkening function with the eclipse observations

(Raponi Andrea andr.raponi@gmail.com)

Is the Sun's diameter variable over time? We have some clues about the solar variability thanks to the recent discovery of the variation of so-called Total Solar Irradiance over a solar cycle of 11 years. The goal of this study is the introduction of a new method to perform astrometry of high resolution on the solar diameter from the ground, through the observation of eclipses. This question first requires the definition of a solar edge. This is why a discussion of the solar diameter and its variations must be linked to the discussion of the so-called Limb Darkening Function (LDF) i.e. the luminosity profile at the solar limb. The difficulties to obtain reliable profiles are discussed. A new method of solar limb darkening function recognition during eclipse is presented. Thanks to the improved accuracy of lunar profiles obtained with the Kaguya Japanese probe,the light curves of Baily's beads recorded during total and annular eclipses provide a powerful tool for diameter's measurements. Accuracy down to a few milliarcseconds are under study. The method proposed is applied for the video of the eclipse in January, 15, 2010 recorded by R. Nugent in Uganda. The results show the profile of the solar atmosphere, outside the photosphere, more luminous than expected. This result permits to reconsider the results of the historical eclipse that show surprisingly high value of the solar diameter. Obtaining the luminosity profile with high resolution, we have also obtained a good opportunity to get information on the solar atmosphere. This issue is discussed as well. 

Delta Scorpii 2011 periastron: worldwide observational campaigns and preliminary photometric analysis

Delta Scorpii is a giant Be star in the forefront of the Scorpio, well visible to the naked eye, being normally of magnitude 2.3 In the year 2000 its luminosity rose up suddendly to magnitude 1.6, and the new aspect of scorpio become known to a wide public. This phenomenon has been associated to the close periastron of the companion, orbiting on a elongate ellipse with a period of about 11 years. The periastron, on basis of very high precision astrometry, is expected to occur around 5 July 2011 with an uncertainty of 4 days, and the second star of the system is approaching the atmosphere of the primary, whose circumstellar disk has a H-alpha diameter of 5 milliarcsec, comparable with the periastron distance. The preliminary results of a photometric campaign, in three colours, here presented in the very days of the periastron, show an irregular behaviour of the star luminosity, which can reflect some shocks between the external atmospheres of the two stars.

The power spectrum of the atmospheric seeing during solar drift-scans

C. Sigismondi, M. Caccia, M. Maspero, L. Negrini, M. Bianda, R. Ramelli, G. De Rosi, A. Raponi

The measurements of the solar diameter using drift-scan methods or solar astrolabes are affected by the atmospheric seeing. In particular the components of frequency below 0.1 Hz and around 0.01 Hz have been identified during measurements made in Locarno at the 45 cm IRSOL gregorian solar telescope with the MIMOTERA acquisition camera. This work has been realized in the framework of the international CLAVIUS project dedicated to the high resolution measurements of the solar diameter from the Earth.

Airborne observation of 2011 Draconid meteor outburst: the Italian mission

The forecast of a remarkable outburst of Draconid meteors, associated to P/21 Giacobini-Zinner comet, for 8 october 2011, has been included in the research programs of ICRANet by fixing the calendar of its international acitivities in China to fit also this astronomical event. The flight Alitalia AZ790 of saturday 8 of october from Rome to Beijing, to attend the Third Galileo-Xu meeting between chinese and italian experts on relativistic, stellar and solar astrophysics will be perfect for this purpose. This flight will go over northern Asia during the night and it is good for a visual observational session during the 5 hours around the predicted peak. Even if the field of view of the observations and the lenght of the astronomical night is reduced with respect to normal Earth-based observations, the limiting magnitude is ideal and the absence of clouds at 12 km of height is guaranteed. This experience of sky watch will be, in the spirit of the science meeting, also a tribute to the ancient chinese astronomers devoted to the accurate observations of the sky with written reports, thanks to which several meteor showers have been studied in their past outbursts.

Christopher Clavius astronomer and mathematician

The Jesuit scientist Christopher Clavius (1538-1612) has been the most influential teacher of the renaissance. His contributions to algebra, geometry, astronomy and cartography are enormous. He paved the way, with his texts and his teaching for 40 years in the the Collegio Romano, to the development of these sciences and their fruitful spread all around the World, along the commercial paths of Portugal, which become also the missionary paths for the Jesuits. The books of Clavius were translated into Chinese, by one of his students Matteo Ricci "Li Madou" (1562-1610), and his influence for the development of science in China was crucial. The Jesuits become skilled astronomers, cartographers and mathematicians thanks to the example and the impulse given by Clavius. This success was possible also thanks to the contribution of Clavius in the definition of the Ratio Studiorum, the program of studies, in the Jesuit colleges, so influential for the whole history of modern Europe and all western World.

A study of neutrino productions in gravitational collapses

In order to catch some sight of neutrino production in gravitational collapsing processes, we try to find a simplified model to calculate neutrino production rate based on equilibrium conditions of microscopic processes, provided microscopic process rates are much larger than macroscopic process ones. The preliminary results are consistent with numerical simulations and observational data.