01-07-2014, at 11:00 AM, Room IB09, ARTOV
10 years of Cassini-VIMS at Saturn
Dr. Gianrico Filacchione (IAPS)
Abstract: On July 1st 2004, after a 90 minutes-long orbital insertion manoeuvre, the Cassini-Huygens mission has started the exploration of the Saturn system. After ten years from that event, an overview of the Cassini mission, including the more relevant results obtained by VIMS, the Visual and Infrared Mapping Spectrometer, is given. VIMS is an imaging spectrometer covering the 0.35-5.1 µm spectral range, whose VIS channel was realized in our institute under Angioletta Coradini’s guide. VIMS scientific objectives are mainly focused on Saturn and Titan atmospheres, Titan surface composition through narrowband spectral windows in the infrared range, identification of compositional units and surface properties of satellites and ring particles. The principal results obtained by the IAPS VIMS team on these arguments shall be discussed. Scheduled to terminate in 2017, Cassini will complete its mission by flying above Saturn’s poles and through the D ring, allowing us to achieve the most comprehensive view of the gaseous giant planet and surrounding environment.
6-6-2014, at 11:00 AM, Room IB09, ARTOV
Three Unresolved Problems in Studies of the Circumgalactic Medium
Dr. Joseph F. Hennawi (Max-Planck-Institut für Astronomie, Heidelberg Germany)
Abstract: I will argue that observations of the diffuse gas in the outskirts of galaxies, the so called circumgalactic medium, are essential for understanding the gas supply fueling star-formation in galaxies. Such observations provide a fruitful comparison to theoretical models, because hydrodynamics at moderate overdensities is much easier to simulate than molecule or star-formation. Three different observations will be discussed suggesting that the observed properties of the circumgalactic medium are in conflict with the predictions of galaxy formation models. Absorption line modeling techniques will be reviewed, and I’ll also discuss a sensitive search for emission from the circumgalacitc medium, which represents the next frontier given the new capability of the MUSE instrument on the VLT.
16-04-2014, 11.00 AM, ARTOV Room IB09
Gravity and thermodynamics: a new point of view in the analysis of equilibrium and dynamical evolution of globular clusters.
Prof. Marco Merafina (Dip. Fisica Università La Sapienza – Roma)
Abstract: In the analysis of the evolution of globular clusters, stellar encounters strongly contribute in phase space mixing of stellar orbits. In this scenario, thermodynamics plays a central role in the gravitational equilibrium and stability of the clusters, being binary relaxation time shorter than the age of such systems.
On the other hand, the observations of luminosity profiles of globular clusters, at different values of the central gravitational potential, show self similar curves that suggest a unique distribution function (King DF) with changing thermodynamical parameters during the dynamical evolution, according to the numerical simulations existing in literature. This means that the evolution of globular clusters can be studied by considering small thermodynamic transformations which keep constant the functional form of the velocity distribution of stars like in the framework of Boltzmann statistical mechanics.
We then construct King models with a different approach by applying thermodynamic principles to a Boltzmann distribution function with an Hamiltonian function which contains an effective potential depending on the kinetic energy of the stars. In this way, we obtain new relations for the thermodynamical equilibrium in presence of a gravitational potential, a different form of the virial theorem and introduce the concept of thermodynamical and kinetic temperature and pressure. We can also demonstrate that a globular cluster can be described as a Lynden-Bell model containing regions with positive and negative specific heat producing thermodynamic instabilities which drive the systems towards the so called gravothermal catastrophe, first described by Lynden-Bell and Wood in the well known paper in 1968. The results, applied to the new Harris Catalogue for globular clusters, give an important agreement between theory and observations.
18-03-2014, 11.00 AM, ARTOV Room IB09
CO and CO2 in Comets: A Far-Ultraviolet Perspective
Prof. Paul D. Feldman (Department of Physics and Astronomy, University Baltimora)
Abstract: This talk will present an overview of space-based far-ultraviolet spectroscopy of comets over the past 40 years with an emphasis on the measurement of two of the basic molecular constituents of the cometary nucleus, CO and CO2, and the most abundant elemental atoms and ions.
A large number of comets have been observed by successive generations of orbiting spacecraft including the International Ultraviolet Explorer, the Hubble Space Telescope, and the Far Ultraviolet Spectroscopic Explorer. The Alice far-ultraviolet spectrograph on Rosetta brings this capability to the close-in investigation of comet 67P and provides for synergistic comparisons with near-simultaneous infrared, sub-millimeter, and in situ measurements of the same species.
o3-03-2014, 11.00 AM, ARTOV, Room IB09
Thermal measurements of dark and bright surface features on Vesta as derived from Dawn/VIR
Dr. Federico Tosi (INAF-IAPS)
Abstract: Remote sensing data acquired during Dawn’s orbital mission at Vesta showed several local concentrations of high-albedo (bright) and low-albedo (dark) material units, in addition to spectrally distinct meteorite impact ejecta. The thermal behavior of such areas seen at local scale (1-10 km) is related to physical properties that can provide information about the origin of those materials. We used Dawn’s Visible and InfraRed (VIR) mapping spectrometer hyperspectral data to retrieve surface temperatures and spectral emissivities, with high accuracy as long as temperatures are greater than 220 K. Some of the dark and bright features were observed multiple times by VIR in the various mission phases at variable spatial resolution, illumination and observation angles, local solar time, and heliocentric distance. This work presents the first temperature maps and spectral emissivities of several kilometer-scale dark and bright material units on Vesta. Results retrieved from the infrared data acquired by VIR show that bright regions generally correspond to regions with lower temperature, while dark regions correspond to areas with higher temperature. During maximum daily insolation and in the range of heliocentric distances explored by Dawn, i.e. 2.23-2.54 AU, the warmest dark unit found on Vesta rises to a temperature of 273 K, while bright units observed under comparable conditions do not exceed 266 K. Similarly, dark units appear to have higher emissivity on average compared to bright units. Dark-material units show a weak anticorrelation between temperature and albedo, whereas the relation is stronger for bright material units observed under the same conditions. Individual features may show either evanescent or distinct margins in the thermal images, as a consequence of the cohesion of the surface material. For the two categories of dark and bright materials, we were able to highlight the influenc e of heliocentric distance on surface temperatures, and estimate an average temperature rate change of 1% following a variation of 0.04 AU in the solar distance. Finally, we will give a short overview of Vesta’s pitted terrains from a thermal perspective.
19th of December 2013, at 11:00, ARTOV, Room IB09
SIMULATIONS OF THE EXO-PLANETS’ ATMOSPHERE TRANSMITTANCE DURING A PRIMARY TRANSIT
Dr.ssa Gabriella Gilli (IAPS-INAF)
Abstract: The number of identified extrasolar planets has increased considerably in the last decade and thousands of candidates are waiting to be confirmed. Most of them are hot-Jupiters, gaseous giant planets close-in orbit to their parent star, easier to detect via transit or by radial velocity techniques. However, they are far to be representative of the incredible variety of exotic worlds expected to be discovered.
In this talk I will give a brief overview of the most recent studies of the atmosphere of exo-planets focusing on the transit spectroscopy, nowadays among the most powerful technique to be used to sound the composition of exoplanets’ atmosphere and to interpret their diversity.
I will describe the work activities done at IAPS-INAF in support of the Echo mission and the tools implemented to build a set of simulated radiances (in the Visible and IR) from a parent star through the atmosphere of an orbiting planet. A 1D line-by-line radiative transfer code (TAU-code) has been used to model the transmission spectra of the exo-planets, while the required inputs (pressure-temperature-mixing ratio profiles, absorption cross-sections, H2-H2 CIA coefficients) are taken from the literature. As a starting point, the physical parameters of “typical” hot-Jupiters (HD209458b and HD189733b) have been used and I assumed as bulk components of the atmosphere H2 (85 %) and He (15%). Due to the limited and still incomplete spectral database for extreme temperature conditions, only the most abundant predicted molecules in exo-atmosphere (H2O, CH4, CO, CO2) have been currently included as absorbers in our simulations. Laboratory activity devoted to measure the optical properties of gases and possibly aerosols at extreme conditions can provide the essential support to the models.
13th of December 2013, at 11:00, ARTOV, Room IB09
LOFT – the Large Observatory For x-ray Timing
Dr.ssa Imma Donnarumma e Dr. Yuri Evangelista (IAPS-INAF)
Abstract:The Large Observatory For x-ray Timing (LOFT) mission concept is one of the 5 candidates for the third launch opportunity (M3, 2022-2024) as Medium Size mission of the ESA Cosmic Vision programme and it has just completed a 3-year long phase A study.
LOFT is designed to exploit the diagnostics of very rapid X-ray flux and spectral variability that directly probe the motion of matter down to distances very close to black holes and neutron stars, as well as the physical state of ultradense matter. These prime science goals will be addressed by a payload composed of a Large Area Detector (LAD) and a Wide Field Monitor (WFM). The LAD is a collimated ( < 1 degree field of view) experiment operating in the energy range 2-50 keV, with a 10 m^2 peak effective area and an energy resolution of 200-260 eV at 6 keV. The WFM will operate in the same energy range as the LAD, enabling a simultaneous monitoring of a 4-steradian wide field of view, with an angular resolution of < 5 arcmin and energy resolution of < 350 eV (6 keV). For short transient events (e.g., GRBs) arcmin-localization is computed onboard and transmitted to the ground within 30 seconds after the trigger time. The LAD and WFM experiments will allow to investigate variability from submillisecond QPO’s to years long transient outbursts. In this seminar we will report on the main scientific topics of LOFT, the current status of the project and the baseline mission design.
10th of December 2013, at 11:00, ARTOV, Aula Convegni
Carbon and sulfur cycles in the Jovian moons: the role of energetic processing
Prof. Giovanni Strazzulla (INAF – Osservatorio Astrofisico Catania)
Abstract: The surfaces of the icy moons of Jupiter are continuously modified by ion implantation of energetic ions and electrons from the magnetosphere. The study of the induced effects is based on laboratory simulations aimed e.g. at investigating the induced non-thermal chemical reactions that lead to the formation of a large number of molecules, not present in the original target. In a typical experiment frozen molecules, pure (e.g. H2O, NH3, CO2, SO2 and many others) or mixtures are deposited at low temperature (10-150 K) and irradiated with the chosen ion beam.
When the thickness of the target is greater than the ion penetration depth, ions are implanted in the target and if they are reactive (e.g., H+, Cn+, Nn+, On+, Sn+) induce all of the effects of any other ion, but in addition have a chance, being stopped in the target, to form new species containing the projectile. These experiments are of fundamental relevance to clarify the formation history of the molecular species in particular to reveal their endogenic or exogenic origin.
Some of the results obtained so far will be presented, in particular: (1) H2O2 is formed by ion bombardment of pure water ice and such a process is believed to be responsible for its presence in the ices of Europa and other satellites. (2) The experimental results relative to implantation of reactive ions indicate that some molecular species observed on icy planetary surfaces (e.g. CO2 and hydrated sulfuric acid) could have been formed by implantation of reactive ions that populate the Jovian (and others) magnetosphere and continuously bombard the surfaces of the embedded satellites. In some instances implantation of magnetospheric ions is the main mechanism to initiate the so called sulfur and carbon cycles on the icy surfaces. (3) Specific predictions can be done on the relationship between the fluxes of reactive ions and the formation of species on spatially resolved regions on the surface of Europa. This is of the greatest relevance to understand existing data from space missions and to program the future observations by the programmed space missions, particularly JUICE (ESA).
27th of November 2013, at 11:00, ARTOV, Room IB09
Experimental set-up to study the optical properties of gases at typically planetary conditions
Dr.ssa Stefania Stefani (IAPS-INAF)
Abstract: The measurements in the lab are of major importance to implement the input parameters of the radiative transfer models. In particular we study the optical properties of gases at typically planetary conditions to better interpreted the data coming from VIRTIS instrument on board VENUS-EXPRESS and JIRAM on JUNO. On the other hand, the experimental data, will support the study of our solar system bodies and will also contribute significantly to the understanding of the exoplanets which, in great part of the cases explored until now, present conditions very different from those terrestrial.
We build up three different experimental setup: High Pressure High Temperature (HP-HT), Cavity Ring Down (CRD) and Multi-Pass (MP).
The HP-HT allow us to recreate the same chemical and physical conditions found in the deep atmosphere of Venus and to understand the behavior from 50 down to 16 km of altitude. This facility is not sufficient to study the so called atmospheric windows which allow to observe from an orbiting spacecraft the planet Venus down to its surface, where the pressure reaches 92 bars and the temperature 450°C. For this reason we realized a CRD system able to work with an effective optical path of 5Km. Finally, to study in more details small absorptions and important phenomena such as Collision-Induced-Absorption (CIA), particularly relevant for Jupiter, line mixing and far wings, we realize an additional tool which uses a Multi-Pass (MP) gas cell characterized by a variable optical path from 2.5 up to 30m.
In this seminar we report the obtained results and discuss also the advantages/disadvantages of each individual setup.
19th of November 2013, at 11:00, ARTOV, Room IB09
The Giant Magellan Telescope on las Campanas observatory
Dr. Miguel Roth (Las Campanas Observatory – Chile)
Abstract: The current infrastructure at Las Campanas Observatory (Chile) will be described, and in particular the design,progress and scientific goals of the new Giant Magellan telescope will be presented.
30th of October 2013, at 11.00, ARTOV, Room IB09
Neutral environment of the Galilean moons as a result of their interactions with Jupiter’s magnetosphere.
Dr.ssa Anna Milillo (IAPS-INAF)
Abstract: The exospheres of Jupiter’s icy satellites Europa and Ganymede are mixtures of H2O, O2 and H2 and some minor constituents, released from the surface mainly after the impact of energetic ions of Jupiter’s magnetosphere.
We present the simulated exosphere of Europa and Ganymede for different configurations between the positions of the moon, Jupiter and the Sun. We show that the distributions of the major components (H2O, O2) modulate along the orbit around Jupiter. The Ganymede’s case is particularly complex due to its internal magnetic field embedded in the Jupiter’s magnetosphere. We also show that the modeled O2 densities are in good agreement with the analysis results from two HST observations of Europa and Ganymede.
28th of October 2013, at 11.00, ARTOV, Room IB09
Extending polarimetry to Stellar and Solar Hard X-Rays
Dr. Sergio Fabiani (INAF-IAPS Roma)
Abstract: Since the beginning of X-ray astronomy the polarimetry has been recognized as an essential tool for a complete understanding of the physics and geometry of many celestial sources. I will show the main results of my PhD activity at INAF-IAPS that was largely devoted to design and test new instrumentation for X-ray polarimetry, particularly aimed to extend the field of interest to Hard X-rays and solar physics.
I explored the possibility to perform Solar flare X-ray polarimetry to study particle acceleration and magnetic field properties in solar atmosphere by means of polarimeters exploiting the photoelectric effect and Compton scattering. Two mission proposals (XIPE and ADAHELI Plus) to the ESA call of 2012 for a small mission included a solar flare polarimeter whose design was the core activity of my PhD at INAF-IAPS.
New collaborations are in progress to propose a solar flare polarimeter on board future missions, including also a Cubesat.
25th of October 2013, at 11:00, ARTOV; Room IB09
“Modeling the Lyman-alpha backscatter observed by Voyager 1 and 2 in the outer heliosphere and the structure of the heliospheric bow shock, the Voyager 1 crossing of the heliopause, and sundry other topics TBD”
Prof. Gary P. Zank (Department of Space Sciences and Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville)
1) Observations made by ultraviolet (UV) detectors on board Pioneer 10 , Voyager 1 , and Voyager 2 can be used to analyze the distribution of neutral hydrogen throughout the heliosphere, including the interaction regions of the solar wind and local interstellar medium. We use state-of-the art three-dimensional (3D) magnetohydrodynamic (MHD) – kinetic neutral H models to simulate Lyman-alpha backscatter as would be seen by the three spacecraft, exploiting a new 3D Monte Carlo radiative transfer code under solar minimum conditions (Fayock et al., 2013) . Both observations and simulations of the UV backscatter intensity are normalized for each spacecraft flight path at 15 AU, and we compare simulations with Voyager 1 and 2 and Pioneer 10 Lyman-alpha data results, finding a very close match with the Voyager data. Our results predict a large increase in the Lyman-alpha intensity as the hydrogen wall is approached.
2) Recent IBEX observations indicate that the local interstellar medium (LISM) flow speed is less than previously thought (23.2 km/s rather than 26 km/s), indicating that the LISM flow may be either marginally super-fast magnetosonic or sub-fast magnetosonic. This raises two questions: (A) Can a LISM model that is barely super-fast or sub-fast magnetosonic account for Ly-alpha observations that rely critically on the additional absorption provided by the hydrogen wall (H-wall)? and (B) If the LISM flow is weakly super-fast magnetosonic, does the transition assume the form of a traditional shock or does neutral hydrogen (H) mediate shock dissipation and hence structure through charge exchange? Both questions are addressed using three-dimensional self-consistently coupled magnetohydrodynamic plasma – kinetic neutral H models with different LISM magnetic field strengths (2, 3, and 4mG) as well as plasma and neutral H number densities. The 2 and 3mG models are fast magnetosonic far upwind of the heliopause whereas the 4μ G model is fully subsonic. The 2mG model admits a broad (~50–75 AU) bow-shock-like structure. The 3mG model has a smooth super-fast–sub-fast magnetosonic transition that resembles a very broad, ~200 AU thick, bow wave. A theoretical analysis shows that the transition from a super-fast to a sub-fast magnetosonic downstream state is due to the charge exchange of fast neutral H and hot neutral H created in the supersonic solar wind and hot inner heliosheath, respectively. For both the 2mG and the 3mG models, the super-fast magnetosonic LISM flow passes through a critical point. Because the Mach number is only barely super-fast magnetosonic in the 3mG case, the hot and fast neutral H can completely mediate the transition and impose a charge exchange length scale on the structure, making the solar-wind–LISM interaction effectively bow-shock-free. The charge exchange of fast and hot heliospheric neutral H therefore provides a primary dissipation mechanism at the weak heliospheric bow shock. Both super-fast magnetosonic models produce a sizeable H-wall. We find that (1) a sub-fast magnetosonic LISM flow cannot model the observed Ly-alpha absorption profiles along four sightlines corresponding to upwind, sidewind, and downwind; and (2) both the super-fast magnetosonic models can account for the Ly-alpha observations, with possibly the bow-shock-free 3μ G model being slightly favored.
3) With the announcement that Voyager 1 crossed the heliopause, the boundary separating solar material from interstellar material, Voyager 1 now finds itself in the interstellar medium. We will briefly review the observations and the accompanying complications that the observations bring.
4) If time permits, we may discuss some recent developments related to solar energetic particle acceleration and transport in the inner heliosphere.
24th of October 2013, at 11:00, ARTOV, Room IB09
The ODINUS mission concept
Dr. D. Turrini (INAF-IAPS)
Abstract: The ODINUS white paper, submitted in response to ESA’s Call for White Papers for the scientific themes of the next two L-class missions, proposes a mission to the two ice giant planets Uranus and Neptune and to their satellites to explore the birth and the evolution of the Solar System. The ODINUS mission concept is based on the use of a fleet of two twin spacecraft to be put in orbit around Uranus and Neptune respectively. The orbital tour of the two systems takes advantage of highly eccentric orbits to allow a detailed exploration of the major satellites and their interaction with the environment, the planetary atmospheres, exospheres and magnetosphere dynamics, and the ring systems. To fit such a challenging task in the budgets (in terms of costs, mass and power) of an L-class mission, ODINUS proposes the use of two slender, New Horizons-class spacecraft with a scientific payload optimized to perform all the core measurements in these mostly unknown systems. The possibility to gather the same set of measurements for the two planets and their satellites allows for a comparative planetology approach that would be otherwise difficult to achieve. In turn, the comparative study of the two planets will provide a fundamental ground-truth for the study of the most abundant class of extrasolar planets. Finally, the long cruise phase needed to reach the two targets will offer a unique opportunity to explore gravitation, relativity, the interplanetary medium and the solar wind behaviour at large heliocentric distances and, concerning the latter, simultaneously at different angular positions.
17th of October 2013,. at 11:00, ARTOV, Room IB09
Numerical Modelling: Geophysical and Thermal Histories of Asteroids 4 Vesta and 21 Lutetia.
Dr. Michelangelo Formisano (IAPS-INAF)
Abstract: 4 Vesta and 21 Lutetia, two asteroids of the Main Belt, represent two important case study to investigate the primordial phases of the evolution of terrestrial planets and the Solar System in general. 4 Vesta is one of the large asteroid of the Main Belt and probably it is the parent body of HED meteorites: as a consequence we know it was one of the first bodies to have formed and differentiated in the Solar System. Lutetia is a border-line object: it belongs to those objects that survived to the collisional evolution of the Main Belt and possibly differentiated. Moreover it could be used as a case study to investigate the minimal conditions to obtain a differentiated object. To study the geophysical histories of these two asteroids we developed a numerical 1D model for the contemporary solution of the heat equation with radiogenic heat source and the advection equation, which controls the percolation of the metals inside the asteroid. The numerical solution is obtained using a finite-difference method in radial direction (FTCS scheme). We investigate the link between the evolution of 26Al and 60Fe and long-lived radionuclides (e.g. 238U and 235U), taking into account the chemical differentiation of the body and the affinity of 26Al with silicates: our simulation covered a timespan of 5 Ma starting from the condensation of CAIs. ————————————-
2nd of October 2013, at 11:00, ARTOV, Room IB09
Airglow emissions in the terrestrial planets
Dr.ssa Alessandra Migliorini (INAF-IAPS)
Abstract: Airglow emissions are important features to be studied in order to investigate the chemistry and dynamics in planetary atmospheres. The most important emissions in the terrestrial atmospheres are due to O2 and OH, both on the day and night sides of the planets.
Remote sensing observations using a multi channel spectrometer, like the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS), currently flying on board the ESA Venus Express and Rosetta missions, make possible the simultaneous investigation of the visible and IR properties of these emissions.
Here we focus on the airglow emissions in Venus, Earth and Mars atmospheres, which are controlled by chemical reactions common to the three terrestrial planets. We analyse the O2 and OH emissions detected at the Earth by Rosetta, the night and day O2 emissions in the Mars atmosphere, and we review the O2 and OH nightglow emissions in the Venus atmosphere, observed with VIRTIS/Venus Express.
A comparison of the properties of these emissions in the three planets allow inferring information on the photochemistry and physical conditions of the atmospheres, but also constraining the dynamics responsible for the transport of atomic oxygen, ozone and other minor species. Finally, we address a model for the OH IR emissions in the Earth atmosphere, observed during the Rosetta flyby with our planet on November 2009.
26th of September 2013, at 15.00, ARTOV, Room Gratton
“Martian atmospheric particulate spectral end-members recovery from PFS and IRIS data”
Dr. Mario D’Amore (Institute of Planetary Research del DLR di Berlino)
Abstract: We present an application of a multivariate analyses technique on data returned by the Planetary Fourier Spectrometer (PFS) instrument on board the ESA’s Mars Express (MEX) spacecraft in order to separate the atmospheric contribution from the observed radiation. We observe that Thermal/Far Infrared spectra returned from Mars, covering almost a whole martian year, can be represented by a linear model using a limited set of end-member spectra. We identify the end-members as the suspended mineral dust and water ice clouds, but no surface signature was found. We improve previous studies performed with data from the Thermal Emission Spectrometer (TES) thanks to the higher spectral resolution of PFS. This allows for distinguishing narrow gaseous bands
present in the martian atmosphere. Furthermore, the compar- ison of results from PFS and TES with data collected in 1971 by the Mariner 9 Infrared Interferometer Spectrometer (IRIS) shows an atmospheric dust component with similar spectral behavior. This might indicate homogeneity of the dust source regions over a time period of more than 30 years.
25th of September 2013, at 11.00 Room IB09, ARTOV
“Does X-ray astronomy helps understanding supermassive astrophysical Black Holes? The quest for the BH spin”
Dr. Matteo Guainazzi (ESA)
Abstract: Black holes are simple astrophysical objects. Two quantities, mass and spin, are sufficient to characterize them completely. Spin measurements are particularly important to constrain models of black hole cosmological evolution. In this talk, I will review recent X-ray measurements of black hole spin in Active Galactic Nuclei hosting super-massive (million to billions solar masses) black holes. They have potentially far-reaching implications as a probe of the concurrent evolution of accreting black holes and galaxies, as well as of the innermost regions of the accretion flow, where General Relativity effects (may) have a direct impact on X-ray spectroscopic observables. I will discuss the level of observational maturity of this field, by reviewing the sources of systematic uncertainties affecting these measurements. Finally, I will review the requirements that future X-ray observatories should fulfil for progress in this field to be possible.
1st of August 2013, at 11:00 Room IB09, ARTOV
Energy transport in flares: sunquakes and acoustic wave generation
Prof. Valentina Zharkova (University of Bradford, West Yorkshire, UK)
Abstract: Sunquakes were discovered by Kosovichev and Zharkova (1998, Nature) as ripples travelling from the flare site observed in SOHO/MDI data on the 9th July 1996. In the past decades there were more than 30 other sunquakes are discovered and now actively investigated by a few research groups worldwide as they uncover the mechanisms of energy transport from the solar corona to the photosphere and solar interior. Recently Living with Star NASA programme made this research a strategic one for the next 3-5 years. In this talk I will give a historic overview of the problem and its current status.
31st of July 2013, at 11:00 Room IB09, ARTOV
HXR polarisation in solar flares: theory versus observation
Prof. Valentina Zharkova (University of Bradford, West Yorkshire, UK)
Abstract: In the talk I will speak initially about solar flares in general, the processes of the initial energy release onset via magnetic reconnection and the further development of flares with particle precipitation into flare loop legs. Then I will briefly explain the physical processes leading to HXR emission in flares confined to a magnetic flux tube, the effect of the magnetic field on HXR polarisation. I will also describe how these processes can be obscured in the measurements from different position angles in the solar disk (from centre to the limb). I will explain how the theory of HXR polarisation combined with HXR emission in solar flares can decode the real processes in these events and what physical parameters can be derived from the simultaneous observations of HXR emission, polarisation and directivity. I will also briefly highlight how radio observations in microwave range, in addition to HXR, can be helpful in decoding the real processes.
18th of July 2013, at 11:00, ARTOV, Room IB09
“Inverse cascades and emergence of helicity in anisotropic turbulence”
Dr. Raffaele Marino (NCAR-CISL, BOULDER, USA)
Abstract: We examine the inverse cascade of kinetic energy to large scales in rotating stratified turbulence, while varying the relative frequency of gravity to inertial waves, N/f. Using direct numerical simulations with grid resolutions up to 1024^3 points, we find that the transfer of energy from three-dimensional to two-dimensional modes is most efficient in the range 1/2 < N/f < 2, in which resonances disappear. In this range, the cascade is faster than in the purely rotating case, and thus the interplay between rotation and stratification helps creating large scale structures. The ensuing inverse cascade follows a -5/3 spectral law with an approximately constant flux. This inverse cascade becomes negligible when stratification is dominant.
We also show that, in the Boussinesq framework, helicity (velocity-vorticity correlation), is spontaneously created due to an interplay between buoyancy and rotation. Helicity emerges from the joint action of eddies and of inertia-gravity waves (with inertia and gravity with respective associated frequencies f and N), and it occurs when the waves are sufficiently strong. For N/f
3rd of July 2013, at 11:00, ARTOV, Room IB09
“The Hard X-ray Polarimeter X-calibur and X-ray Polarization Observations of Black Holes in X-ray Binaries”
Prof. Henric Krawczynski (Washington University in Saint Luis)
Abstract: The main topic of this talk will be a report on the design, performance, and status of the balloon-borne hard X-ray polarimeter X-Calibur. The polarimeter uses a Compton scattering slab and an assembly of 32 Cadmium Zinc Telluride (CZT) detectors to measure the linear polarization properties of the 20 keV – 70 keV X-ray emission from cosmic sources over. The experiment is scheduled for a one-day balloon flight from Fort Sumner (NM) in Fall 2013. The first flight should allow us to constrain the polarization properties of the X-ray emission from the stellar mass black holes Cyg X-1 and GRS 1915+105, from the Crab Nebula and Pulsar, from the accreting X-ray pulsar Her X-1, and from one Active Galactic Nucleus (e.g. the blazar Mrk 421). For the brighter sources (i.e. the Crab Nebula), the one-day flight will allow us to measure polarization degrees down to a few percent. The talk will include a discussion of the scientific potential of soft and hard X-ray polarimetry with a special emphasis on polarimetric observations of black holes in X-ray binaries.
5th of June 2013, at 11.00, ARTOV, Room IB09
“Blazars: Survey multi-banda e SED risolte temporalmente”
Dr. Paolo Giommi (ASDC Director)
Abstract: Presentero’ alcuni risultati di survey di blazar eseguite in varie bande di energia (radio, microonde, IR, raggi-x e raggi gamma).
Mostrero’ come simulazioni MonteCarlo supportano uno scenario nel quale risultati apparentemente molto diversi possono essere interpetati in modo molto semplice.
Nella seconda parte del seminario presentero’ risultati basati su nuovi tool (sviluppati nell’ambito del VO e di altre collaborazioni internazionali) per l’utilizzo di dati in multi-frequenza e multi-temporali.
Verrano presentate le SED di alcuni blazar che includono decine di migliaia di misure al fine di caratterizzare i blazar sulla base della loro SED e dell’evoluzione temporale in parti diverse dello spettro elettromagnetico. Discutero’ le implicazioni che questi nuovi risultati hanno sui modelli interpretativi.
4th of June 2013, at 11:00, ARTOV, Room IB09
“La struttura geometrica del Pantheon”
Dr. Marcello Ranieri (associato IAPS-INAF Roma)
Abstract: Tecniche CAD condotte su rilievi Laser-Scanner hanno messo in luce le geometrie circolari e Pitagoriche impiegate in pianta nella costruzione del monumento.
22nd of April 2013, at 11.30, ARTOV, Aula convegni
FISICAST: una nuova piattaforma per “spiegare la fisica alla gente”
Dr. Gianluca Li Causi (IAPS-INAF Roma)
Abstract: Inseguendo l’idea ambiziosa di “spiegare la fisica alla gente” é nato “FISICAST, il podcast della fisica”, un modo innovativo di raccontare, spiegandoli, i concetti della fisica, i fenomeni della natura e le tecnologie di uso comune.
Fortemente orientato all’ascoltatore, ne utilizza il linguaggio e ne implementa i commenti, prima della pubblicazione sul web in forma di podcast fatti da brevi brani audio, nel formato di intervista, dialogo, o monologo, successivamente musicati per un piacevole ascolto.
Per questo siamo alla continua ricerca di parole, esempi e analogie per coniugare la semplicità al rigore scientifico e così facendo… stiamo re-imparando la fisica anche noi!.
16th of April 2013, at 10.00, ARTOV, Aula IB09
THE SEVEN YEAR Swift-XRT POINT SOURCE CATALOG (1SWXRT)
Dr. Valerio D’Elia (ASI-Science Data Centre, Frascati/INAF Osservatorio Astronomico di Roma)
Abstract: Swift is a multi-wavelength observatory specifically designed for gamma-ray burst (GRB) astronomy that is operational since 2004. Swift is also a very flexible multi-purpose facility that supports a wide range of scientific fields such as active galactic nuclei, supernovae, cataclysmic variables, Galactic transients, active stars and comets.
The Swift X-ray Telescope (XRT) has collected more than 150 Ms of observations in its first seven years of operations. We present the list of all the X-ray point sources detected in XRT imaging data during the first seven years of Swift operations. All these point-like sources, will be stored in a catalog publicly available (1SWXRT).
Count rates, fluxes and the corresponding uncertainties are computed. We have analyzed more than 35,000 XRT fields, with exposures ranging between 500 s and 100 ks, for a total exposure time of 140 Ms. The catalog includes ~ 89,000 entries, of which almost 85,000 are not affected by pile-up and are not GRBs.
Since many XRT fields were observed several times, we have a total of ~36,000 distinct celestial sources. We computed count rates in three energy bands: 0.3-10 keV (Full, or F), 0.3-3 keV (Soft, or S) and 2-10 keV (Hard, or H). Each entry has a detection in at least one of these bands. In particular, we detect ~ 80,000, ~ 70,000 and ~ 25,500$ in the F, S and H band, respectively. Count rates were converted into fluxes in the 0.5-10, 0.5-2 and 2-10 keV bands. Some possible scientific uses of the catalog are also highlighted.
27th of March 2013, at 11.00, ARTOV, Congress Room
“A MODEL FOR THE CORRELATION OF HARD X-RAY INDEX WITH EDDINGTON RATIO IN BLACK HOLE X-RAY BINARIES”
Dr. Erlin Qiao (National Astronomical Observatories, Chinese Academy of Sciences)
Observations show that there is a positive correlation between the Eddington ratioλ and hard X-ray index Γ for λ >~0.01, and there is an anti-correlation between λ and Γ for λ < ~0.01 in black hole X-ray binaries (with λ = Lbol/LEdd). In this work, we theoretically investigate the correlation between Γ and λ within the framework of a diskcorona model. We improve the model by taking into account all cooling processes, including synchrotron and self-Compton radiations in the corona, Comptonization of the soft photons from the underlying accretion disk, and the bremsstrahlung radiations. Presuming that the coronal flow above the disk can reach up to the 0.1 Eddington rate at the outer region, we calculate the structure of the two-phase accretion flows and the emergent spectra for accretion rates from 0.003 to 0.1. We find that at accretion rates larger than ~ 0.01 Eddington rate, a fraction of coronal gas condenses into the disk and an inner disk can be sustained by condensation. In this case, the X-ray emission is dominated by the scattering of the soft photon from the underlying disk in the corona. The emission from the inner disk and corona can produce the positive correlation between λ and Γ . While at accretion rates lower than ~0.01 Eddington accretion rate, the inner disk vanishes completely by evaporation, and the accretion is dominated by advection-dominated accretion flows (ADAFs), in which the X-ray emission is produced by the Comptonization of the synchrotron and bremsstrahlung photons of ADAF itself. The emission from ADAFs can produce the anti-correlation between λ and Γ . We show that our model can roughly explain the observed evolution of Γ3−25 keV with L0.5−25 keV /LEdd for the black hole X-ray transient H1743 −322 in the decay of 2003 from the thermal-dominated state to low /hard state. The promising applications of our model to AGNs will also be discussed.
26th of March 2013, at 11:30, ARTOV, Room IB09
“SOFIA: Stratospheric Observatory for Infrared Astronomy”
Dr. William T. Reach (NASA AMES Research Center)
Abstract: SOFIA is a world-class, US-German collaboration, infrared observatory that operates from on-board a 747 aircraft. I will describe the observatory, its purpose and capabilities as well as the scientific results form its first flights
and the opportunities for guest investigators.
22nd of March 2013, at 11:30, ARTOV, Room IB09
“The Massive Black Hole at the Centre of the Galaxy”
Prof. Farhad Yusef-Zadeh Northwestern University (Northwestern University, Evanston, Illinois)
Abstract: The processes occurring in the nuclear disk of our own Galaxy are interesting because this region can potentially provide a template for the study of more distant galactic nuclei. There are several sources of activity that take place in this unique region of the Galaxy.
One is the underluminous supermassive black hole (Sgr A*) at the dynamical centre of the Galaxy. Sgr A* exhibits flares which occur a few times a day, arising from the inner ten Schwarzschild radii of a 4 million solar mass black hole. The other is the nuclear stellar cluster which consists of a population of evolved stars as well as a young population of stars in a disk orbiting within 0.5 pc Sgr A*. On a scale of milli-pc, a three earth mass gas and dust cloud (G2) is on a collision course with Sgr~A*. VLT observations indicate that the G2 cloud approaches pericentre in mid-2013 and it will be disrupted and portions will likely be accreted by the massive black hole residing there.
In this talk, I will describe what we have learned from studying Sgr A*, how stars are formed near Sgr A* and what we expect to learn by monitoring the light from the interaction of the G2 cloud and Sgr A*.
13th of March 2013, at 11:00, ARTOV, Room IB09
“Problems in the standard picture of blazars”
Dr. Luigi Costamante (Dipartimento di Fisica Università di Perugia)
Abstract: In the last years, new observations in the GeV to Tev band together with X-ray data have revealed a new phenomenology, which questions the standard understanding of the blazar phenomenon. In particular, on location of the blazar-zone, the difference between FSRQ and BL Lac jets and extreme acceleration mechanisms, the latter also highlighted by the Crab flares. After a quick review of the observational aspects, I will discuss the main issues in perspective of CTA, LOFT and possible GeV Cherenkov arrays.
5th of March 2013, at 11:00, ARTOV, Room IB09
“The quest for exoplanets”
Dr. Mauro Barbieri (Università di Padova)
Abstract: Mentre sono trascorsi vent’anni dalla scoperta del primo pianeta al di fuori del Sistema Solare, la scienza dei pianeti extrasolari grazie alle sue scoperte rivoluzionarie è divenuta una delle discipline fondamentali dell’astronomia moderna. Ad oggi sono oltre 800 i pianeti extrasolari conosciuti e studiati. In questo seminario verranno esposte le tecniche osservative, le caratteristiche fisiche e chimiche di questi pianeti, e con uno sguardo al futuro verranno presentati alcuni dei prossimi progetti per la ricerca di pianeti abitabili
21st of February 2013, at 15:00, ARTOV, Room IB09
“Star formation rates in LINER host galaxies”
Dr. Silvia Tommasin (The Hebrew University of Jerusalem, Jerusalem, Israel)
Abstract: Low Ionization Nuclear Emission-line Regions (LINERs) are characterized by low ionization AGN optical emission lines from the center of their host galaxies. Through the FAR-IR observations with Herschel/PACS of a sample of optically selected LINERs at z~0.3, we find that their host galaxy have a surprisingly high FAR-IR luminosity. It leads to star formation rates (SFR) up to 3 order of magnitude larger then the SFR inferred by optical (H_alpha) or UV measurements. Is this discrepancy due to high obscuration of these sources or to their star formatin history? These LINERs show also a different relation between star formation luminosity and AGN luminosity in respect with local LINERs, is this due to an evolutionary effect? We will discuss possible causes and consequences of FAR-IR properties of LINERs host galaxies, how they affect the star formation rate estimates, and their connections with the AGN emission.
21st of February 2013, at 11:00, ARTOV, Room IB09
“Warm absorbes in X-ray binaries “
Dr. Antonino D’Aì (Università di Palermo)
Abstract: Low-mass X-ray binaries observed at high inclination angle show periodic dips in their light curves associated with partial screening from a bulge formed by the accretion stream from the companion star. High-resolution spectroscopy of these sources has confirmed the ubiquitous presence of highly ionized absorbers, usually with significant blue-shifts (interpreted as radiatively driven disk winds). These two phenomena, neutral dipping and warm absorption, seem thus to be strictly connected. I will present a preliminary spectroscopic analysis of the bright atoll source GX 13+1, whose characteristics constitute a perfect benchmark for testing this paradigma.
“HAVS: un sistema informatico fault tolerant con tempi di inattività “quasi zero” economico e di uso generale”
Dr. Memmo Federici (INAF-IAPS Roma) e Sig. Bruno Martino (CNR-IASI Roma)
13th of February 2013, at 15.00, ARTOV, Room IB09
“Measurements of galactic cosmic rays and solar energetic particles on board the future interferometers for gravitational wave detection in space”
Prof. Catia Grimani (DiSBeF, Università degli Studi di Urbino “Carlo Bo”)
Abstract: Test-mass charging due to galactic cosmic rays (GCRs) and solar energetic particles (SEPs) represents one of the main sources of noise in missions devoted to gravitational wave detection in space such as eLISA/NGO and ASTROD. Particle detectors on board future space interferometers will help in monitoring the test-mass charging process. Variations and fluctuations of GCRs and evolution of SEP events of different intensities are discussed for the correlation of SEP radiation monitor observations and particle fluxes charging the test masses. The performance of the radiation monitors designed for the LISA Pathfinder mission is considered for the results presented in this work. We point out that in addition to the primary use of test-mass charging monitoring, particle detectors on board space interferometers will naturally provide SEP observations at different intervals in heliolongitude and distances from Earth for space weather applications.
6th of February 2013, at 15:00, ARTOV, Room IB09
Dr.ssa Cecilia Ceccarelli (Institute de Planétologie et d’Astrophysique de Grenoble, Grenoble, France)
“Our chemical origins”
Abstract: The Solar System was born about 4.5 billions years ago from a condensation inside a cold (~10K) molecular cloud. What happened to that initial condensation and how did it evolved up to form the Earth and its environment that permitted life to thrive?
To answer these questions, we need to assemble many pieces of a giant puzzle that covers different fields. The chemical composition of comets and some parts of meteorites provide us with some precious pieces when it is compared to that in sources which will eventually become other Suns and planetary systems. For example, it tell us that Earth inherited water from cold iced bodies, that comets conserved only in part the imprint of interstellar chemistry while some pieces of meteorites have imprinted it forever, that nitrogen in comets is an heritage from different interstellar molecules, that deuterium in meteorites spots is inherited from the material of the primordial condensation. And all this tells us the story of how and from what the Earth and the Solar System bodies formed. In this presentation, I will give an overview of the link between the interstellar chemistry and the Solar System origin.
Prof. Jessica Sunshine (Astronomy dep. Maryland Univ.)
“Comets as Viewed by the Deep Impact Spacecraft: Tempel 1, Hartley 2, Garrard, and Beyond”
Abstract: Since the spectacular impact experiment at comet Tempel 1, the Deep Impact (DI) spacecraft has observed several comets and continues to do so. Once thought to be relatively simple bodies, DI has revealed surprising diversity and unexpected behavior among comets.
22th of January 2013, 11:30; Room IB09, ARTOV
Dr.ssa Francesca Scipioni (INAF-IAPS)
“Spectroscopic identification and classification of terrain units on Dione’s and Rhea’s surfaces based on Cassini/VIMS data”
Abstract: Dione and Rhea are two of the largest and densest icy satellites of Saturn. Their surfaces show a clear asymmetry between their leading/trailing hemispheres, the leading side being brighter than the trailing side, which shows regions mantled by a dark veneer, whose origin is mostly exogenic. In order to identify different terrain units on the two satellites’ surface, we applied the Spectral Angle Mapper (SAM) classification technique to Dione’s and Rhea’s hyperspectral cubes acquired by Cassini/VIMS in the infrared range 1-5 µm. SAM is a supervised method which needs some reference spectra, or endmembers, to drive the classification. We identified nine endmembers for Dione and eight for Rhea, corresponding to nine and eight terrain units respectively, which mostly distinguish for water ice abundance and ice grain size. Moreover, we investigated CO2 and the C-H fundamental stretch of the alkens as possible contaminants. The analysis of the spectra returned by VIMS shows that different regions of Dione and Rhea have variations in water ice bands depths, in average ice grain size, and in the concentration of CO2 and CH, which are clearly connected to morphological and geological structures. Generally, the spectral classes that classify optically darker terrains are those showing suppressed water ice bands, a finer ice grain size and a higher concentration of carbon dioxide. On the contrary, spectral units labeling brighter regions have deep water ice absorption bands, high albedo and a small concentration of CO2. In particular, from our analysis, it emerges that ice grain size must be larger than 25 µm for both satellites, and contaminants abundance ranges between 10 and 50% for Dione, and between 0.01 and 15% for Rhea. In order to understand how the different spectral units distribute on the two satellites’ surface, all classified VIMS pixels have been projected on Dione’s and Rhea’s optical mosaics.
10th of January 2013, 15:00; Room IB09, ARTOV
Dr. Mike Nolan (Osservatorio di Arecibo)
“Arecibo radar observatios of Near-Earth Asteroids and Comets”
Abstract: The Arecibo planetary radar is the most sensitive system in the world for studying near-Earth objects. We present a summary of the observations over the last decade of the surprising variety of objects in near-Earth space. Asteroids span a range of shapes: nearly spheroidal, elongated, binary systems, and highly irregular. Spin rates range from minutes to weeks, implying a wide range of internal structures and formation mechanisms.
27th of November 2012, 11:30; Room IB09, ARTOV
Dr. Achille Nucita (Università del Salento)
“IMBHs: is there any missing link?”
Abstract: Black holes in galactic binaries and super-massive black holes in the center of many galaxies seem to be common objects. By extrapolating the fundamental M_BH-M_Bulge relation derived from the study of super-massive black holes in AGNs, one expects to find a new class of medium sized black holes at the center of globular clusters and spheroidal dwarf galaxies. A caution on this statement is necessary: only a few candidates of the so called intermediate mass black holes (IMBHs) are known so far. We review the theoretical scenarios for the IMBH existence and discuss the constraints offered by the observations. We furthermore concentrate on a few good IMBH candidates in the Fornax and Ursa minor dSph galaxies possibly identified when analysing archival XMM-Newton and Chandra data.
22nd of October, 2012, 11:00; Room IB09, ARTOV
Dr. Simone Dall’Osso (The Hebrew University of Jerusalem)
“The decaying magnetic fields of magnetars: evidence and inference”
Abstract: Almost 2 decades ago, the peculiar emission of the Soft Gamma Repeaters and Anomalous X-ray Pulsars was proposed to be produced by the decay of superstrong magnetic fields, in a (very) small population of neutron stars (NSs) with extreme properties. Originally considered an oddity, the model has progressively received strong support from a huge body of observations. Nowadays, the role of such objects in several astrophysical setttings is much debated, and their implications for forthcoming observational windows may be far reaching. I discuss new observational evidence for decay of the dipole magnetic field in magnetar candidates, that has accumulated in recent years thanks to the improved burst detection capabilities of the new generation of high-energy observatories. Making contact with previous studies of field decay in the population of “normal” radio pulsars, I stress the great advantages that magnetars offer in this respect. I further show that, although certainly decaying, the dipole field of these objects cannot power their persistent X-ray emission. The latter indeed requires the dissipation of an additional, stronger field component, presumably hidden in the interior of these neutron stars. Using existing models it is even possible to determine the salient properties of this internal field component, a work that can be much developed in parallel with a better understanding of NSs interior structure. Finally, I sketch preliminary considerations on the possible evolutionary links between magnetars and other classes of neutron stars that have nearly as strong dipole fields but do not show magnetar-like activity.
05th of October 2012, 11:00; Room IB09, ARTOV
Dr. Carlie Peters (Brown University)
EARLY EVOLUTION OF THE LUNAR CRUST
Abstract: The magma ocean hypothesis for the Moon formulates several predictions about the composition and stratigraphy of the early lunar crust. Data from the Moon Mineralogy Mapper (the near-infrared imaging spectrometer flown on Chandrayaan-1) are used to constrain the compositional evolution of the upper and lower lunar crust. Results appear to require an early mantle-overturn
20th of September 2012, 11:00; Room IB09, ARTOV
Dr. Tom Robitaille (Max Planck Institute for Astronomy, Heidelberg)
” A new grid of model spectral energy distributions for young stellar object”
Abstract: In 2006, we made available a grid of model spectral energy distributions (SEDs) for young stellar objects (YSOs) that has since been used by the community to model thousands of sources in nearby and more distant star forming regions in the Milky-Way and Magellanic clouds. In this talk I will present a new and much larger grid of model SEDs that addresses many issues with the original model grid, such as parameter space coverage, the dependence on stellar evolutionary tracks, and is well suited to modeling long-wavelength observations such as Herschel and longer-wavelength data. The new models were computed with HYPERION, a new Monte-Carlo radiative transfer code (Robitaille, 2011). I will present the design of the model grid, initial modeling results, and I will discuss some of the open issues and limitations in using model SEDs to interpret observations of YSOs.
Wednesday 18th of April 2012, 15:00; Room IB09
Dr. Dimitris Stamatellos (School of Physics and Astronomy Cardiff University- UK)
“Probing the initial stages of star formation with radiative transfer simulations”
Abstract: Stars form in the cores of dense molecular clouds when gravity dominates over thermal, turbulent, and magnetic support. It is important to constrain the properties of these cores, as they determine the outcome of the star formation process. In the last decade, space (Spitzer, Akari, Herschel) and ground based (JCMT/SCUBA) observatories have observed low-and high- mass cores in the Solar neighbourhood and in the Galactic plane. These observations coupled with radiative transfer modelling have constrained the properties of the initial stages of star formation. I will discuss the methodology of Monte Carlo continuum radiative transfer, present radiative transfer models of prestellar cores, and discuss their implications for star formation.
Monday 2nd of April 2012, 11:00 Room Convegni
Prof. Giuseppe Lodato (Università degli Studi di Milano)
“Modeling the lightcurve of tidal disruption events”
Abstract: Tidal disruptions of stars by a a supermassive black hole are a unique probe into the properties of quiescent black holes, which are not surrounded by a sufficient amount of gas to shine as AGN engines. A number of candidate TDEs have been identified in the last few years, as powerful flares in X-rays and in the UV. However, these lightcurves were generally not well sampled. In the last year, several new candidates with very well sampled lightcurves have been discovered. It has thus become essential to support these observations with detailed theoretical models. In particular, while the general expectation is that the bolometric lightcurve should follow a t^(-5/3) decline, the behaviour of the individual lightcurves in different bands in not straightforward.
Here I will discuss these issues from a theoretical point of view, concentrating mainly in the emission from the resulting accretion disc, and I will then focus on the application of such models to the recently discovered events Swift J1644+57 and Swift J2058+05. Finally, I will also show that the peculiarities of GRB 101225A (the “Christmans burst”) can also be explained as a galactic TDE, where a minor body (an asteroid, or a comet) is disrupted by a neutron star.
Thursday 29th of March 2012 , 11:00; Aula IB09
Lisa Nortmann (Institut für Astrophysik Goettingen – Göttingen, Germany European Southern Observatory, Garching, Germany)
“On the Current State and the Future of Exoplanet Characterization”
Abstract: In the past two decades about 760 exoplanets have been detected with various methods. More than 190 of those exoplanets are known to transit their host star in our line of sight. These transiting extra solar planets provide us with the unique opportunity to further characterize their parameters with ever increasing precision.
Current space missions such as CoRoT and Kepler are beginning to find rocky transiting exoplanets with radii smaller than Earth’s. In response to the quantity of these detections the focus of exoplanet research has shifted from the detection towards the characterization of these planets and, in particular, their atmospheres. Knowledge of the planet atmosphere is of key importance to constrain the planet’s interior composition. Furthermore, it is our only hope of identifying habitable worlds in the future. In order to interpret the results for rocky planet atmospheres, that we will be able to obtain with the upcoming generation of telescopes (E-ELT, James Web Space Telescope, etc. ), these results will have to be set into context with observations of our own Solar System’s planets, which can be studied in much closer detail.
In my talk I will give a brief introduction into the current state of exoplanet science with focus on the transit method and its great potential for the characterization of the planet, its orbit and even its host star’s properties. I will give an outlook on the future of this field and the open questions that will have to be answered in order to pave the way towards the discovery of a truly Earth-like exoplanet.
Wednesday 1st of February 2012; 15:00; Room IB09
Stefano Cristiani – Osservatorio Astronomico di Trieste – INAF
“Il mezzo intergalattico come strumento di indagine cosmologica”
Abstract: The history of the universe during and soon after the Dark Age is recorded in the all-pervading intergalactic medium (IGM), which is believed to contain most of the ordinary baryonic material resulting out of the big bang. Throughout the epoch of structure formation, the IGM became clumpy and acquired peculiar motions under the influence of gravity and acted as a reservoir for the gas that gets accreted, cools and forms stars within galaxies and as a sink for the metal-enriched material, energy and radiation which they eject.
Along the line of sight to a distant source – a quasar, a gamma-ray burst, a galaxy – every parcel of IGM gas selectively absorbs certain wavelengths of light due to the presence of the various chemical elements in it. Through the analysis of these absorption lines we can study the spatial distributions, motions, chemical enrichment, and ionization histories of gaseous structures from redshift seven and beyond until the present. It is an exciting game: from few details of little apparent significance, it is possible to deduce a surprising number of important conclusions about our Universe, especially when we link the information provided by absorption lines with the complementary information derived from the evolutionary properties of luminous galactic structures.
Tuesday 31st of January, 2012; 15:00; Room Aula Convegni
Dr.ssa Saori Konami (RIKEN, Institute of Physical & Chemical Research & Tokyo University of Science Tokyo, Japan)
“A COMPARISON OF METAL ABUNDANCE PATTERNS OF INTER-STELLAR MEDIUM IN STARBURST AND NON-STARBURST GALAXIES WITH X-ray OBSERVATION”
Abstract: Metal abundances of the hot X-ray emitting interstellar medium (ISM) contain a historical record of star formation and evolution in galaxies. O and Mg are synthesized in SNe II, but Fe is main product of SN Ia. Suzaku XIS enables us to measure accurately the ratios of O and Mg to Fe owing to its high sensitivity below 1 keV and low, stable background. We have investigated the metal abundances of O, Ne, Mg, and Fe in the ISM of the starburst galaxies M 82 and NGC 3079, and a non-starburst galaxy, NGC 4258. The derived ratios of O/Fe, Ne/Fe, and Mg/Fe of the outflow regions of M 82 and starburst core of NGC 3079 are about 2–3 times solar.
This abundance pattern indicates that starburst activity enriches the ISM and intergalatic medium with SN II yields.
In contrast, the abundance ratios in the ISM of NGC 4258 is similar to that of our Galaxy. Furthermore, we will briefly introduce abundances in eary type galaxies and simulations for Astro-H
Friday 27th of January, 2012; 11:00; Room Aula Convegni
Dr. Sylvaine Turck-Chièze (SAp/IRFU/CEA, Ce Saclay France)
“From seismology of stars to fundamental physics”
Abstract: The space missions: SoHO, SDO, COROT and KEPLER have produced a revolution in the way we can study the solar and stellar interiors. A large part of the HR diagram could
be covered by seismic observations and already today, more than thousands of stars are scrutinized thanks to the detection of acoustic and gravity modes. In this review, I shall recall their main results for hydrogen burning and helium burning phases. I shall comment also on the new activities like 3D simulations of turbulence and convection interaction near the surface for different stars, which have the objective to go beyond the classical mixing length theory.
Other activities are concentrated to verify and validate the microscopic physic like opacities and nuclear reaction rates. I shall present our program in France for the first of these two: the interaction of photons with matter and the experimental capability of the high energy lasers for this objective. The waited progress for Astrophysics, coming from the astrophysical community, might be an improved way to treat the macroscopic physics. Two main actors are considered, the internal rotation and the internal magnetic field that are mainly ignored or insufficiently described today. This perspective will open a renewal of interest for final stages of stellar evolution and for X—ray line spectroscopy perspective.