Hans Sydney

Danish 1.54m
Danish 1.54m telescope at La Silla, ESO, Chile


Fundamental parameters of stars

The ESA/CoRoT satellite was launched in December 2006 and the NASA/Kepler mission in March 2009. There are two main goals of these two missions: (1) Detection of the properties of small extra-solar planets and (2) detailed studies of the interiors of stars by studying their pulsation. I am involved in this work due to my expertise in the determination of the fundamental parameters of stars (effective temperature, surface gravity, and metallicity). I use the software package VWA to make these detailed analyses.

Abundance analysis of binary stars

In collaboration with Jens Viggo Clausen (DEN) and Guillermo Torres (USA) we have completed the abundance analysis of both entangled and disentangled spectra of three solar-like SB2 binary systems (WZ Oph, AD Boo, VZ Hya). Our analysis shows that the best results are obtained with the disentangled spectra. It requires several (at least 10) spectra taken at different points in the orbit to be able to disentangle the spectra properly.

Observations from Dome C

In collaboration with the Small-IRAIT team from Italy, I am analysing photometric data from Dome C on the Antarctic plateau. We will ascess the quality of the data from the 25cm telescope. An immediate advantage of the data from Dome C is that the night is over three months long in the middle of winter. Runa Biguglio collected observations of the eclipsing binary Psi Cen in three filters and I am now processing the data.   

Asteroseismology with WIRE

In 1999 the NASA satellite WIRE was launched. The main experiment failed, but the 52mm star tracker has been used to monotor bright "naked-eye stars", covering most of the Hertzsprung-Russell diagram. My work is done in collaboration with a number of people, e.g. Derek L. Buzasi (USAFA, USA), John Southworth (Warwick, UK), Jens Viggo Clausen (Copenhagen, DK), Conny Aerts (Leuven, BEL), & Tim Bedding (Univ. of Sydney, AUS).

A part of my work is focused on the main sequence stars: from solar-like stars and Delta Scuti stars to Beta Cepheid stars. A number of papers have been published and more are in preparation. At the moment I am collaborating with the astrophysics group in Grenada (Suarez, Garrido) to combine WIRE data with ground-based multi-colour data on Delta Scuti Stars: Epsilon Cephei, 29 Cygni and Delta Ser.

Eclipsing binaries with WIRE

A few new eclipsing binaries have been discovered with WIRE. We find that in all systems at least one of the components is variable. We have initiated an ambitious project to study known detached EBs systems that are difficult to study with photometry from the ground. In collaboration with John Southworth (UK) I have completed papers on Psi Centauri and Beta Aurigae.


Curriculum Vitae



Ph. D. disseration

Master Thesis




Work in progess