Contact

Laboratoire Lagrange
UMR 7293
Observatoire de la Cote d'Azur
Université de Nice Sophia-Antipolis
Bd de l'Observatoire
CS 34229 - 06304 Nice Cedex 4
France
andrea.chiavassa@oca.eu

Logo Lagrange



Ph.D. subject available in Nice and in collaboration with Uppsala (Sweden) and ESO (Munich): Click here

Andrea Chiavassa, Dr. in Astrophysics


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"Everything you can imaging is real" Pablo Picasso



Research





Computation of 3D simulations of cool stars with CO5BOLD (Freytag et al. 2012, Journal of Computational Physics, 231) for star-in-a-box model (global model) and with Stagger-code (Nordlund, Stein et Asplund, Living Reviews in Solar Physics 2009, vol. 6, no. 2) for box-in-a-star (local model).

New generation of Red Supergiant simualtions to unveil the mass-loss mechanism

High numerical resolution / non-grey / grid of new stellar paramters



Click on the image to see a movie of the bolometric emerging intensity of the highest resolution simulation. Chiavassa, Freytag, Masseron & Plez 2011, A&A (ADS link)


Voyage over the surface of a supergiant. Click on the images to start the videos !!!!!!




3D Radiative Transfer code OPTIM3D (Chiavassa et al. 2009, A&A, ADS link) using three dimensional simulations in the star-in-a-box configuration (CO5BOLD) as input:

1) spectral synthesis --> to constrain the atmospheric dynamics, photometry, stellar parameters, abundances
2) intensity maps --> to constrain the granulation structure size, the limb darkening, the characterization of the hosted planets


Click on the image to see the convetion in the Hband. The Images have been computed with OPTIM3D for the IONIC - filter mountend at IOTA telescope
Click on the image to see the convetion in the Kband. The Images have been computed with OPTIM3D for the K222-continuum FLUOR filter wavelength 2.2 micron


Click on the image to see the convetion in TiO band at 6100-6600 A. The Images have been computed with OPTIM3D
Click on the image to see the convetion in CaI-H line. The Images have been computed with OPTIM3D


Click on the image to see the convetion with an instrumental convolution to the PSF of a 42 meters telescope in the optical region (GAIA G-band). These images can be qualitatively compared to the observations (image reconstruction). Done with OPTIM3D The simulation scaled to a distance of about 174.3 pc and an apparent diameter of 44.5 mas
Click on the image to see the convetion with an instrumental convolution to the PSF of a 42 meters telescope in the H band (IONIC filter). These images can be qualitatively compared to the observations (image reconstruction). Done with OPTIM3D The simulation scaled to a distance of about 174.3 pc and an apparent diameter of 44.5 mas


Click on the image to see the convetion at different wavelengths. Importance of the high spectral resolution in interferometry (H band) -> different features with respect to wavelength (computed with OPTIM3D)
Click on the image to see the velocity field in the red supergiants'atmospheres at 1.6 micron (computed with OPTIM3D)


Creating observables (visibility, closure phases, image reconstruction as a function of wavelengths and filters) to compare with interferometric observations at different wavelengths (VLTI-Amber/Midi/MATISSE/PIONIER, CHARA, IOTA,...).

Data redution with VLTI-AMBER

Measurement and characterization of the convective pattern (granule size, surface contrast, timescales) of red supergiant stars, K giants, sub-giants and solar type stars.

Image reconstruction

Determination of the 1D - 3D models corrections on abundances, stellar parameters and velocity field at high resolution (top). Large spectral range computation for flux distributions, colors filters (red curves) and comparison to the observations (bottom)


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3D Radiative Transfer code OPTIM3D (Chiavassa et al. 2009, A&A, ADS link) using three dimensional simulations in the box-in-a-star configuration (Stagger-code, Nordlund, Stein et Asplund, Living Reviews in Solar Physics 2009, vol. 6, no. 2) as input:

Intensity maps computed at disk center and µ = 0.8, 0.6, 0.4 for a metal-poor K Giant simulation and integrated over the range 3500-9800 ˚A. The panels have individual scaling. 
Determinations on the interferometric observables, limb darkening, characterization of the granulation pattern, and impact on hosted planet detection (Chiavassa et al. 2010, A&A, ADS link )


Determination of the 1D - 3D models corrections. Large spectral range computation for flux distributions, colors filters (red curves) and comparison to the observations for all the cool stellar types (Evolved giants, K-Dwarf, Sun, Main sequence stars) and with different metallicity
Determinations on the interferometric observables, limb darkening, characterization of the granulation pattern, and impact on hosted planet detection for main sequence stars (Chiavassa et al. 2012, A&A, link ; Chiavassa et al. 2014, A&A, link )
Determnation of the impact of granulation in planetary transit detection and characterisation (Chiavassa et al. 2015, A&A, link )


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Visualisaztion




Visualizaiton of 3D data with VAPOR(Visualization and Analysis Platform for Ocean, Atmosphere, and Solar Researchers). Volume rendering of Temperature, Mach number, ratio of turbulent pressure/gaz pressure (movie done for one snapshot of a simulation)

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Download three-dimensional spectra

From this page you can download the 3D spectra computed with the 3D Radiative Transfer code OPTIM3D (Chiavassa et al. 2009, A&A, ADS link) for the STAGGER grid (Magic et al. 2013, A&A, ADS link) computed using the Stagger-code (Nordlund, Stein et Asplund, Living Reviews in Solar Physics 2009, ADS link).

Please, before downloading the files, fill and submit this form. I will keep your updated on new data and/or new 3D spectra computed.
Your Name:

Your Institute:

Your Email:





The data can be downloaded here:


Note that the files are in IDL (http://www.exelisvis.com/ProductsServices/IDL.aspx) and the README files with the directions can be downloaded here:


3D spectra acknowledgement and citation

If data extracted from this website are used in your research work, please include citations to the relevant research articles from which the original data were taken:

Chiavassa, Plez, Josselin, Freytag 2009 - ADS link

Magic, Collet, Asplund, Trampedach, Hayek, Chiavassa, Stein, Nordlund 2013 - ADS link

Magic, Chiavassa, Collet, Asplund 2015 - ADS link




For any questions or bugs, please do not hesitate to contact me at:

andrea.chiavassa@oca.eu


Publications

My list of publications (25 May 2017)

36 Referred papers (13 as first author), 40 proceedings, a Chapter for a book, Gaia Techinical notes, Matisse Science note and E-ELT HIRES science case
1119 citations, H index 17
5 press releases + 2 television documentaries
7 invited conferences
ADS link to referred publications
ADS link to not referred publications


Refereed articles

2017

2016

2015


2014


2013


2012


2011


2010


2009


2005



Ph.D. Thesis - Atmospheric Dynamics of red supergiant stars


Curriculum Vitae

                       


Download my Full Curriculum Vitae in English here Download my 1 page Curriculum Vitae in English here

Name : Andrea
Surname : Chiavassa
Birthday : 08 January 1979
Birthplace : Savigliano, Italy




Professional Address : Laboratoire Lagrange
UMR 7293
Observatoire de la Cote d'Azur
Université de Nice Sophia-Antipolis
Bd de l'Observatoire
B.P. 4229 - 06304 Nice Cedex 4
France
Tel : (+33) (0)492 00 3027


Professional E-mail : andrea.chiavassa@oca.eu
Private E-mail : andreew@alice.it


Languages :
Italian - native speaker
French - excellent
English - excellent
German - basic
Spanish - some notions


Current Position : Permanent position at CNRS (Centre national de la recherche scientifique)

Scientific interests : Multidimensional Radiative Transfer, Multidimensional Radiative Hydrodynamics, Surface convection, Spectroscopy, Interferometry, astrometry, planets, interstellar medium




Academic experiences :

October 2010 - Agoust 2012: Fellowship at Institut d'Astronomie et d'Astrophysique de Bruxelles with Prof. Alain Jorissen. Research topic: 3D Chemical abundances in peculiar stars and Gaia predictions for cool stars.

September 2008 - September 2010: Fellowship at Max Planck Institut for Astrophysics, Garching with Prof. Martin Asplund. Research topic: 3D modelling of convection in stellar atmosphere of cool stars. Interferometric and spectroscopic observables for red supergiant, K-giant and AGB stars.

PhD student (october 2004 - june 2008) at GRAAL, Montpellier, France. Development of a 3D radiative transfer code for radiation hydrodynamics simulations of red supergiants. Comparison of theoretical results with spectroscopic and interferometric observations. Determination of the convection pattern on red supergiant stars.

Master Degree final project ("Laurea in Astrofisica e Fisica Cosmica") at the Laboratoire d'Astrophysique de Grenoble (LAOG), France, under the supervision of Cecilia Ceccarelli (2004, 8 months ERASMUS exchange project) - The 90-110 micron dust feature in low to intermediate mass protostars

Bachelor final project ("Laurea in Fisica") at the University of Turin under the supervision of Gianni Navarra (Mars to June 2002) - Study of the high voltage circuit of photomultipliers of the Pierre Auger Observatory



Teaching and Diffusion of Scientific Knowledge :

Physics : Mechanics and Thermodynamics (univerisity level 2011, Belgium) - 36h

Informatics : Word, Excel and Power Point (univerisity level 2006, France) - 20h

Astrophysics : univerisity level (France, 2005) - 3h

Participation to the animations for the Year of Physics 2005 (Montpellier, France), (high school and primary school) - 60 hours

Several participations to public animations of astronomy (about 2-3 conferences per year)






Computer and Programming Skills :

MacOsX, Linux, Unix, Windows operating systems administration

Programming in Fortran95 e Fortran 77, IDL, Shell Scripts, Yorick Astronomical software : Supermongo, synthetic spectrum calculation, CO5BOLD photosphere models calculations

Others : LaTeX2e, Word, Excel, Power Point

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Red Supergiant Workshop: 28-29 september 2015


RSG-ESO

Workshop objectives:

Red supergiant stars contribute extensively to the chemical and dust enrichment of the Galaxies, and ultimately the Universe. These stars combine violent convective motions, low surface gravity, magnetic field, and high luminosities to trigger strong stellar winds. However, the mass loss mechanism is still poorly known. New observations combining monitoring interferometry/spectro-polarimetry as well as imagery brought new insights on the regions very close to the photosphere where the mass loss ejection take place.

Workshop format:

The idea is to enhance the discussion, we require informal presentations of maximum 30 minutes with room for questions and exchanges. Adequate time for round table discussions are also in program.

Where:

SALLE NEF - Batiment CION
Observatoire de la Cote d'Azur
Bd de l'Observatoire
06304 Nice
France
Click here to access to Google Maps for the address.

Preliminary program:


Monday 28 September:
11.00 - 12.00: The point on the observations. Interferometry (Miguel Montargès), Radio (Alizee Duthu)
12.00 - 13.30: Lunch at the observatory
13.30 - 15.00: The point on the observations. Imagery with VLT (Eric Lagadec), Spectropolarimetrie (Philippe Mathias and Arturo Lopez Ariste), spectroscopy (Eric Josselin)
15.00 - 17.00: Discussion on future observations

Tuesday 29 September:
9.00 - 12.00: The point on the modelisation. The observables provided with 3D models (Andrea Chiavassa, Kateryna Kravchenko, and Bernd Freytag), stellar evolution (Jose Groh)
12.00 - 13.30: Lunch at the observatory
13.30 - 17.00: Discussion on link theory/observations and future collaborations/fundibg applications
N.B. Coffee will be provided in the room at anytime during the workshop

Participants:


Andrea Chiavassa - Observatore de la Cote d'Azur
Eric Lagadec - Observatore de la Cote d'Azur
Pierre Cruzalèbes - Observatore de la Cote d'Azur
Pierre Kervella - LESIA Paris (video conference)
Guy Perrin - LESIA Paris
Miguel Montargès - IRAM Grenoble
Eric Josselin - LUPM Montpellier
Agnès Lebre - LUPM Montpellier
Julien Morin - LUPM Montpellier (video conference)
Benjamin Tessore - LUPM Montpellier
Alizee Duthu - Observatoire de Bordeaux
José Groh - Observatoire de Geneve
Arturo Lopez Ariste - IRAP Toulouse
Michel Auriere - IRAP Toulouse (video conference)
Philippe Mathias - IRAP Toulouse
Pascal Petit - IRAP Toulouse (video conference)
Bernd Freytag - Uppsala (to be confirmed)
Kateryna Kravchenko - ULB Bruxelles
Sophie Van Eck - ULB Bruxelles

How to contact Me



Andrea Chiavassa


Andrea Chiavassa

Where:

Laboratoire Lagrange
UMR 7293
Observatoire de la Cote d'Azur
Batiment CION
Bd de l'Observatoire
B.P. 4229 - 06304 Nice Cedex 4
France

Obs map
Click on the image to access to Google Maps.