Probing the close environment of young stellar objects with interferometry

The study of Young Stellar Objects (YSOs) is one of the most exciting topics that can be undertaken by long baseline optical interferometry. The magnitudes of these objects are at the edge of capabilities of current optical interferometers, limiting the studies to a few dozen, but are well within the capability of coming large aperture interferometers like the VLT Interferometer, the Keck Interferometer, the Large Binocular Telescope or 'OHANA. The milli-arcsecond spatial resolution reached by interferometry probes the very close environment of young stars, down to a tenth of an astronomical unit. In this paper, I review the different aspects of star formation that can be tackled by interferometry: circumstellar disks, multiplicity, jets. I present recent observations performed with operational infrared interferometers, IOTA, PTI and ISI, and I show why in the next future one will extend these studies with large aperture interferometers.Comment: Review to be published in JENAM'2002 proceedings "The Very Large Telescope Interferometer Challenges for the future

Cosmological Birefringence: an Astrophysical test of Fundamental Physics

We review the methods used to test for the existence of cosmological birefringence, i.e. a rotation of the plane of linear polarization for electromagnetic radiation traveling over cosmological distances, which might arise in a number of important contexts involving the violation of fundamental physical principles. The main methods use: (1) the radio polarization of radio galaxies and quasars, (2) the ultraviolet polarization of radio galaxies, and (3) the cosmic microwave background polarization. We discuss the main results obtained so far, the advantages and disadvantages of each method, and future prospects.Comment: To appear in the Proceedings of the JENAM 2010 Symposium "From Varying Couplings to Fundamental Physics", held in Lisbon, 6-10 Sept. 201

Modeling Molecular-Line Emission from Circumstellar Disks

Molecular lines hold valuable information on the physical and chemical composition of disks around young stars, the likely progenitors of planetary systems. This invited contribution discusses techniques to calculate the molecular emission (and absorption) line spectrum based on models for the physical and chemical structure of protoplanetary disks. Four examples of recent research illutrate these techniques in practice: matching resolved molecular-line emission from the disk around LkCa15 with theoertical models for the chemistry; evaluating the two-dimensional transfer of ultraviolet radiation into the disk, and the effect on the HCN/CN ratio; far-infrared CO line emission from a superheated disk surface layer; and inward motions in the disk around L1489 IRS.Comment: 6 pages, no figures. To appear in "The Dense Interstellar Medium in Galaxies", Procs. Fourth Cologne-Bonn-Zermatt-Symposiu

Who's in charge? Discovering the autonomy in an institutional data repository for research data curation and sharing

To facilitate data sharing, more and more research data infrastructures have been built. However, less attention is paid to the needs of researchers as data producers in the context of traditional OAIS-compliant institutional data repositories. Meanwhile, researchers usually complete data management tasks themselves throughout the research data lifecycle and express a desire to control the data ingestion process. The contradictory between design and the reality suggests a potential need for autonomy in terms of data curation along with frictions between researchers and professional data curators. In this study, we explore important features of an ideal institutional data repository through designing the NTUData prototype. It is a researcher-centered system that helps integrate the early phases of the data lifecycle into the process of data curation and thus encourage data sharing. Nine participants in the information science field were recruited for a usability test in which the DCP Toolkit was adopted. The results show that researchers prefer to initiate and perform the whole data submission process themselves. They are also concerned about the interoperability to link NTUData to external resources and the interpretability of text labels within this repository. As for their needs towards autonomy, two per- spectives with regards to curating and sharing data can be observed, respectively

Thermal degradation kinetics of a commercial epoxy resin-Comparative analysis of parameter estimation methods

The thermal degradation behavior of a commercial epoxy resin, EpoFix® (Struers), has been investigated by thermogravimetry (TG), differential thermal gravimetry (DTG), and differential thermal analysis (DTA) under nonisothermal conditions in an argon atmosphere. Different methods (Kissinger, Flynn-Wall–Ozawa (FWO), Friedman isoconversion methods, and nonlinear least‐squares (NLSQ) estimation method) have been used to analyze the thermal degradation process and determine the apparent kinetic parameters. The methods produce similar results in terms of activation energy estimations. Nevertheless, the NLSQ method has several advantages over the other methods in terms of both characterizing the activation energy and modeling the thermal degradation—i.e., including this model in a resin degradation process simulation. However, it is interesting to combine the NLSQ method with other isoconversion methods: they can reflect the dependence and variability of the activation energies during pyrolysis processes, while providing a good starting point for a nonlinear procedure, especially with respect to the activation energy E. This work is the first step (apparent kinetic reaction) of complete simulation of experimental oven of degradation of epoxy resin coating of impregnate nuclear fuel sample

Circumstellar disks and planets. Science cases for next-generation optical/infrared long-baseline interferometers

We present a review of the interplay between the evolution of circumstellar disks and the formation of planets, both from the perspective of theoretical models and dedicated observations. Based on this, we identify and discuss fundamental questions concerning the formation and evolution of circumstellar disks and planets which can be addressed in the near future with optical and infrared long-baseline interferometers. Furthermore, the importance of complementary observations with long-baseline (sub)millimeter interferometers and high-sensitivity infrared observatories is outlined.Comment: 83 pages; Accepted for publication in "Astronomy and Astrophysics Review"; The final publication is available at http://www.springerlink.co

Accreting Black Holes

This chapter provides a general overview of the theory and observations of black holes in the Universe and on their interpretation. We briefly review the black hole classes, accretion disk models, spectral state classification, the AGN classification, and the leading techniques for measuring black hole spins. We also introduce quasi-periodic oscillations, the shadow of black holes, and the observations and the theoretical models of jets.Comment: 41 pages, 18 figures. To appear in "Tutorial Guide to X-ray and Gamma-ray Astronomy: Data Reduction and Analysis" (Ed. C. Bambi, Springer Singapore, 2020). v3: fixed some typos and updated some parts. arXiv admin note: substantial text overlap with arXiv:1711.1025