Empirijska veza mase i luminoziteta zvijezda u galaktičkom skupu Hijade

master's thesis

• Title (english): The empirical mass-luminosity relation in the galactic cluster Hyades
• Author: Martina Mesarić
• Mentor: Krešimir Pavlovski (mentor)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2014-04-18, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract

Otvoreni galaktički skupovi važni su za proučavanje strukture i razvoja zvijezda. Zvijezde u skupu nastale iz istog molekulskog oblaka, što znači da imaju vrlo sličan kemijski sastav i da su približno iste starosti. Zvijezde unutar skupa razlikuju se po masi, koja je usko vezana uz ostale zvjezdane parametre. Masa je glavno svojstvo koje određuje razvojni put zvijezde, duljinu njezina trajanja na glavnom nizu HR dijagrama, te konačni stadij razvoja.
Mase zvijezda mogu se direktno mjeriti jedino u dvojnim ili višestrukim sustavima. Dvojne zvijezde su gravitacijski vezani sustavi dvije zvijezde koje se gibaju oko zajedničkog centra mase. Najvrjedniji su spektroskopski pomrčinski dvojni sustavi, u čijem su spektru vidljive spektralne linije obje komponente sustava. Iz spektroskopske i foto-metrijske analize takvog sustava moguće je izračunati mase, polumjere i luminozitete zvijezda s velikom točnošću.
U ovome radu analizirana su spektroskopska i fotometrijska mjerenja dvojnog sustava V818 Tau u otvorenom skupu Hijade. U spektroskopskoj analizi korištena je metoda spektralnog raspetljavanja, koja iz niza kompozitnih spektara dvojne zvijezde daje individualne spektre komponenata, istodobno računajući orbitalne elemente sustava. Analiza spektara omogućuje određivanje atmosferskih parametara zvijezda: efektivne temperature, metalicitet i rotacijske brzine. U kombinaciji s analizom svjetlosnih krivulja dolazi se do mase, polumjera i luminoziteta zvijezda dvojnog sustava. Svjetlosna krivulja modelirana je pomoću Wilson-Devinney programa, koji koristi Rocheovu geometriju za opis sustava, zajedno s detaljnom obradom efekta refleksije i ostalih fizikalnih pojava.
V818 Tau jedina je pomrčinska dvojna zvijezda u skupu Hijade, te daje veliku težinu kod postavljanja relacije masa-luminozitet. U ovom radu relacija masa-luminozitet određena je pomoću 10 zvijezda, uz komponente V818 Tau iskorištene su još 4 interfero-metrijske dvojne zvijezde.

Abstract (english)

Galactic open clusters are important for studying structure and evolution of stars. Stars in a cluster were formed from the same molecular cloud; hence they have very similar chemical composition and approximately the same age. Members of a cluster differ by their mass, which is tightly bound with other stellar parameters. Mass is the main property that determines the evolutionary path of a star, its main sequence lifetime and a final stage of the evolution.
Stellar mass can be measured directly only in binary or multiple systems. Binary stars are gravitationally bound systems of two components orbiting around their common center of mass. The most valuable are the eclipsing spectroscopic binaries, for which the spectral lines from both stars are visible in their spectrum. From spectroscopic and photometric analysis of such a system, it is possible to calculate masses, radii and luminosities with great accuracy.
In this work, the spectroscopic and photometric measurements of the binary system V818 Tau in Hyades star cluster are analyzed. The method of spectral disentangling is used in spectroscopic analysis, which enables separation of the individual spectra of the component stars from a time series of composite spectra, simultaneously deriving the system orbital elements. In turn, the spectral analysis gives the atmospheric parameters of both stars: effective temperatures, metallicity and rotational velocities. In combination with the light curve analysis the masses, radii and luminosities can be determined. The Wilson-Devinney code is used for light curve modeling, which implements Roche geometry and a detailed treatment of reflection and other physical effects.
V818 Tau is only eclipsing binary system in Hyades. Therefore is extremely important in anchoring the mass-luminosity relation for Hyades. In this work, the mass-luminosity relation is deduced from 10 stars, besides the components of V818 Tau another 4 interferometric binary stars were used.

• Keywords: zvjezdani skupovi; jednadžbe strukture zvijezda; dvojne zvijezde; Wilson-Devinney metoda; galaktički skup Hijade
• Keywords (english): binary stars; Wilson-Devinney code; eclipsing binary system in Hyades
• Language: croatian
• URN:NBN: urn:nbn:hr:217:699061
• Study programme: Title: Physics; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra fizike (magistar/magistra fizike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2017-08-21 13:04:25