Mining the RATS archive for compact blue stars
Başlık çevirisi mevcut değil.
- Tez No: 508737
- Danışmanlar: Dr. GAVIN RAMSAI
- Tez Türü: Doktora
- Konular: Fizik ve Fizik Mühendisliği, Matematik, Physics and Physics Engineering, Mathematics
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2016
- Dil: İngilizce
- Üniversite: Queen's University Belfast
- Enstitü: Yurtdışı Enstitü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 226
Özet
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Özet (Çeviri)
In the age of big surveys where torrents of data accumulate with a speed ever increasing, astronomers need to utilise data science and data mining techniques more and more to find their“needles”in these enormous“haystacks”. In this study, I set out to find the“needles”that we are interested in, compact blue objects, in our“haystack”, RATS (RApid Temporal Survey). Here, the word“compact”is used in the manner both“very dense”and“very close”as the binaries in discussion have very short periods, therefore very tight orbits, and are composed of very dense objects. Discovering, identifying and studying compact blue objects (especially Ultra-Compact Binaries - UCBs), will help theoreticians to address some of the key outstanding questions in stellar evolution models, such as the common-envelope phase, which occurs in close binaries, and other last steps of the binary evolution. Although the overall model of stellar evolution is reasonably understood, there are still many uncertainties and questions which remain. This study is initiated to exploit the RATS dataset, which has light-curves and colour information of more than 3 million stars (Ramsay and Hakala, 2005). Although the main motivation of the RATS project was to discover rare AM CVn systems, possible progenitors of type Ia supernovae, which are very short-period (less than 65 minutes) double degenerate binary systems with helium dominated spectra (Solheim, 2010), one can find all kinds of objects with a wide range of characteristics in the dataset. I have searched for compact blue objects in the data through their colour. This search has yielded 2826 blue objects, containing 384 UCB candidates. We obtained spectra for 17 of these objects using GTC (Grand Telescopio Canarias). The spectral identification resulted in 3 extremely He-rich O-type subdwarfs (He-sdO), 3 B-type subdwarfs (sdB) and 2 B-type (sub)dwarfs, 2 sdOs, 2 H-atmosphere (DA) white dwarfs, 2 QSOs and 3 possible subdwarf and cool dwarf binary systems. As the extremely He-rich sdOs are as rare as AM CVns, we obtained high resolution UVES spectra of two of them (i.e. RATJ1754+0137 and RATJ1759+0119) and analysed these objects in detail. Finally, I have identified blue variable objects in the RATS archive, and revealed their nature using their colours, light-curves and spectra.
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