# ASTROPHYSICAL MEASUREMENTS

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- Versione italiana
- Academic year
- 2017/2018
- Teacher
- ENRICO VIRGILLI
- Credits
- 6
- Didactic period
- Secondo Semestre
- SSD
- FIS/05

#### Training objectives

- The goal of the course is to describe the problems related to the astrophysical measurements. The astrophysical quantities will be introduced and the basic methods that allow mass estimations (solar mass, stars, star masses, galaxies) length (parsec definition, stars distance, galaxy size, distances between Galaxies) time (age of the Universe, of the Sun, of other celestial objects of interest) will be presented.

Some of the topics covered during the course (as the recent proof of the existence of Gravitational Waves and the continuous discovery of new extrasolar planets) are extremely relevant and therefore are fundamental elements for the student who is approaching Astrophysics. In addition, the student will acquire basic technological/experimental skills through the description of the most sophisticated instrumentation used in particular for X and Gamma-rays detection. Finally, in the section dedicated to the analysis of real data of celestial objects acquired with space observatories, the student will also mature skills to critically fit existing physical models to experimental data. #### Prerequisites

- Students must have a good knowledge of fundamental physics (kinematics, dynamics of point mass particles and of systems of particles), fluidodynamics, waves, thermodynamics. Electromagnetism. Infinitesimal calculus. Basic knowledge of the english language is also required for the recommended bibliography.
#### Course programme

- PART I (6 lectures - 12 hours)

Experimental requirements and fundamental physical quantites

Astronomy with naked eye. Human eye resolving power, spectral band, visual limit.

Requirements for astrophysical observation: sensitivity, spectral resolution, field of view, bandwidth, polarization. Angular resolution. The point spread function (PSF). Interferometry.

Measurements of astrophysical distances. The Astronomical Unit. Direct methods: trigonometric and secular parallax, moving cluster parallaxes. Standard candles and indirect methods: Cepheids and RR Lyrae, type Ia supernovae.

Temperatures evaluation, mass, radius and stellar velocity.

PART II (7 lectures - 14 hours)

Binary Systems - Exoplanets

Kepler's Laws. Kepler equation. Mass measurement from sbinary stars orbits. Escape velocity.

Binary Stars. Tidals and lobes of Roche. Visual, astrometric, spectroscopic, photometric binaries.

Binary systems with neutron stars and black holes. Evolution of binary systems. Binaries X. Eddington's Limit.

Gravitational Waves (GW). GW measurements through LIGO / VIRGO interferometers. Description of the experimental apparatus. Future perspectives of Gravitational Astrophysics. VISIT to the VIRGO Interferometer - Cascina (PI).

Extrasolar planets: research and detection methods. Direct methods. Indirect Methods: Radial velocity, astrometry, transit, Microlensing. Exoplanet properties. Atmospheric composition, temperature. Exoplanets habitability.

PART III (6 lezioni - 12 ore)

Detection Techniques, Telescopes.

Features of Space Telescope (Effective area, angular resolution). Direct-view telescopes and focusing telescopes.

Main detector properties (Efficiency, spectral resolution, temporal resolution, spatial resolution, polarization). Techniques

for X and Gamma X-ray detection.

Crystal scintillators, gas detectors, solid state detectors. X/Gamma-ray optic: Total reflection, Bragg and Laue

Diffraction. Coded masks. Adaptive optics in high energy astrophysics.

PART IV (5 lezioni - 10 ore)

Experimental activity

Experiments at LARIX laboratory - calibration of a solid state detector, study of X-/Gamma-ray diffraction lines of crystalline materials for X / Gamma optics.

Spectroscopy. Basics of satellite data analysis for X-/Gamma ray astronomy. Basics of XSPEC, the main X-ray fitting package. The main physical/mathematical models that can be adopted. Examples of spectral fit of astrophysical sources. #### Didactic methods

- The lectures are delivered with slides, and partly at the blackboard to solve exercises, develop calculations or illustrate demonstrations. It Is also planned a visit to the gravitational waves interferometer VIRGO (Cascina, Pisa) approximately in april.
#### Learning assessment procedures

- During the Astrophysical measurement course, the interaction between students and teacher is encouraged.

The goal of the final exam is to test the student's knowledge level with respect to the course program.

The final exam consists of a unique oral session. The duration of the exam is about 30 minutes

and consists of 3-4 questions. Alternatively to one of the questions, the student can present

a topic discussed during the course (it can be agreed with the teacher). The discussion can be

presented orally or in form of presentation/slides (duration 10-15 minutes).

Alternatively to a theoretical question, students can be asked to solve a problem/exercise related to one of

the discussed arguments. The final score is out of thirties and the exam is supposed to be passed if the score

is >= 18/30. #### Reference texts

- The teacher will provide notes and educational material.

Bibliography:

1. "Astronomy: Principle and Practice", E. Roy and D. Clarke, Institute of Physics Publishing Bristol and Philadelphia. 4th edition.

2. R.W. Hilditch, "An Introduction to Close Binary Stars", Cambridge

3. H. Karttunen et al., "Fundamental Astronomy", Springer

4. "Exoplanet Handbook" by Michael Perryman, Cambridge.