Population study of single lined spectroscopic binary stars in the RAVE survey

Birko, Danijela (author), Zwitter, Tomaž (mentor)

In the 10 years of observations, \textsc{Rave} survey obtained radial velocities (RV) of 451,788 stars. Most of the stars were observed only once, but in the final \textsc{Rave} data release 6, 37,664 of them (8.3 \%) are classified as normal single stars that have multiple RV measurements. These objects were selected for this study. A probability function for the detection of RV variations is used for identifying 3838 single lined binary (SB1) candidates. From the 3838 SB1, 406 main sequence dwarf candidates with Solar like masses are selected and the estimation of orbital parameters (period, eccentricity, mass ratio and system velocity) is performed by matching the measured RVs with theoretical velocity curves sampling the orbital parameter space. The reliability of this method is verified by studying a mock sample from the The Ninth Catalogue of Spectroscopic Binary Orbits. Stars from this study were originally classified as normal single stars. Studying the boxiness and asymmetry of their calcium triplet spectral lines points out some possible SB2 candidates. Matching their spectra to a synthetic library indicates probable properties of their components. Joining \textsc{Rave} and \textit{Gaia} DR2 yields 450,646 stars with RVs measured by both surveys. Although \textit{Gaia} published only median values of measured RVs, and stars with variable RVs were excluded from DR2, it turns out that 27,716 of them are SB1 candidates. This is an increase by an order of magnitude over study performed with the \textsc{Rave} DR6 data only. It is obvious that larger time span between these two surveys will in the future enable detection of even more binaries, especially those with longer orbital periods. The study of SB1 from joined \textsc{Rave} and \textit{Gaia} surveys is of a great importance for the interpretation of the \textit{Gaia} ongoing measurements, which will be published in the \textit{Gaia} DR3, 1 year from now.

• Language: English
• Keywords: binaries: spectroscopic, surveys, methods: data analysis
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FMF - Faculty of Mathematics and Physics
• Year: 2020
• PID: 20.500.12556/RUL-116152
• COBISS.SI-ID: 16819459
• Publication date in RUL: 19.05.2020

Secondary language

• Language: Slovenian
• Title: Študij populacije spektroskopskih dvojnih zvezd z enojnimi črtami v pregledu neba RAVE

Abstract

V desetih letih opazovanj je pregled neba \textsc{Rave} pridobil vrednosti radialnih hitrosti 451,788 zvezd. Ve\v{c}ina zvezd je bila opazovana le enkrat, vendar zadnja, kon\v{c}na objava podatkov vsebuje 37,664 zvezd (8.3 \%), ki so ozna\v{c}ene kot obi\v{c}ajne enojne zvezde, ter imajo ve\v{c} kot eno meritev radialne hitrosti. V tem delu smo preverili, ali morebitna spremenljivost radialne hitrosti ve\v{c}krat opazovanih zvezd ka\v{z}e na to, da ima zvezda nevidno gravitacijsko vezano spremljevalko. Z uporabo verjetnostne funkcije za zaznavanje spreminjajo\v{c}e radialne hitrosti smo identificirali 3838 takih dvojnih zvezd. Med 3838 zvezdami je 406 pripadnic glavne veje, z masami podobnimi masi Sonca. Te zvezde so bile izbrane za oceno orbitalnih parametrov kot so perioda, ekscentri\v{c}nost tirnice, razmerje mas in sistemska hitrost. Izmerjene vrednosti radialne hitrosti posamezne zvezde so primerjane s teoreti\v{c}nimi, za razli\v{c}ne vrednosti parametrov, ki dolo\v{c}ajo obliko krivulje spremembe radialne hitrosti. Zanesljivost metode je preverjena na testnem vzorcu zvezd, z znanimi orbitalnimi parametri iz kataloga spektroskopskih dvojnic. \v{C}eprav so zvezde iz te \v{s}tudije bile prvotno razvr\v{sc}ene med obi\v{c}ajne enojne zvezde, je podrobna \v{s}tudija \v{c}okatosti in asimetrij v profilih spektralnih \v{c}rt kalcijevega tripleta v nekaj primerih nakazala prispevek svetlobe spremljevalke. Pribli\v{z}ek vrednosti fizikalnih parametrov obeh komponent je pridobljen s primerjavo spektra s teoreti\v{c}nimi sinteti\v{c}nimi spektri. Najdene dvojnice z dvojnimi spektralnimi \v{c}rtami (SB2) imajo kraj\v{s}e orbitalne periode, velikostnega reda nekaj tednov ali mesecev, ter ve\v{c}je razlike radialnih hitrosti, ob tem pa podobne mase, kar pomeni podoben izsev, zaradi \v{c}esa lahko opazimo vpliv sekundarne komponente v spektru. Skupni katalog pregleda neba \textsc{Rave} in \textit{Gaia} vsebuje 450,646 zvezd z vrednostimi radialnih hitrosti izmerjenih v obeh raziskavah. \v{C}eprav je \textit{Gaia} do sedaj objavila samo povpre\v{c}ne vrednosti radialnih hitrosti in so zvezde s spremenljivimi vrednostmi bile izklju\v{c}ene iz objave podatkov, se je izkazalo, da je med njimi 27,716 kandidatov za dvojnice. Ta \v{s}tevilka je za velikostni red ve\v{c}ja od \v{s}tevila dvojnic odkritih le v okviru projekta \textsc{Rave} ali kateregakoli drugega spektroskopskega pregleda neba doslej.

• Keywords: dvojne zvezde: spektroskopske, raziskave, metode: analiza podatkov