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March 28th 2007 Juliet Datson, students' workshop Brown dwarfs An introduction.

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Presentation on theme: "March 28th 2007 Juliet Datson, students' workshop Brown dwarfs An introduction."— Presentation transcript:

1 March 28th 2007 Juliet Datson, students' workshop Brown dwarfs An introduction

2 March 28th 2007Juliet Datson, students' workshop What are brown dwarfs? No hydrogen burning, only deuterium No hydrogen burning, only deuterium Defined by mass – problem of exact mass measurements Defined by mass – problem of exact mass measurements One test: Lithium test One test: Lithium test Stars soon deplete their lithium, it burns at little lower temperatures than hydrogen Stars soon deplete their lithium, it burns at little lower temperatures than hydrogen If lithium is still there after a certain amount of time – no hydrogen burning If lithium is still there after a certain amount of time – no hydrogen burning M < M(solar) M < M(solar)

3 March 28th 2007Juliet Datson, students' workshop What are brown dwarfs? Boundary between planet and brown dwarf: Boundary between planet and brown dwarf: No free floating planet No free floating planet M(solar) is deuterium burning limit M(solar) is deuterium burning limit Pressure through electron degeneracy Pressure through electron degeneracy Baryonic dark matter candidates Baryonic dark matter candidates

4 March 28th 2007Juliet Datson, students' workshop Size comparison

5 March 28th 2007Juliet Datson, students' workshop Classification of brown dwarfs Spectral classes OBAFGKM Spectral classes OBAFGKM Class M: low mass stars Class M: low mass stars New spectral characteristics New spectral characteristics Need for new classes Need for new classes Class L: Disappearance of TiO and VO Class L: Disappearance of TiO and VO Class T: Methane lines Class T: Methane lines Other classes predicted Other classes predicted

6 March 28th 2007Juliet Datson, students' workshop Spectra

7 March 28th 2007Juliet Datson, students' workshop Spectra Complicated “coming and going” of spectral lines due to condensing of materials at lower temperatures Complicated “coming and going” of spectral lines due to condensing of materials at lower temperatures

8 March 28th 2007Juliet Datson, students' workshop Other interesting features

9 March 28th 2007Juliet Datson, students' workshop How do brown dwarfs form? Turbulent fragmentation Turbulent fragmentation Very low mass prestellar cores Very low mass prestellar cores Disc fragmentation Disc fragmentation Forming in the disc of another star Forming in the disc of another star Ejection Ejection Recently: binary disruption (paper by Goodwin and Whitworth 2007) Recently: binary disruption (paper by Goodwin and Whitworth 2007)

10 March 28th 2007Juliet Datson, students' workshop Why do we want to find them? To fill the gap between planets and stars To fill the gap between planets and stars To fully understand evolution of the universe To fully understand evolution of the universe To prove their mass-range To prove their mass-range To someday be able to define the terms: planet, brown dwarf, star in all variations To someday be able to define the terms: planet, brown dwarf, star in all variations

11 March 28th 2007Juliet Datson, students' workshop How do we find them? Young, hot dwarfs in IR Young, hot dwarfs in IR Companions: Companions: Radial velocity surveys Radial velocity surveys Transits Transits basically the same way, as planets, only easier, because they are usually bigger basically the same way, as planets, only easier, because they are usually bigger Remnants of planet searches Remnants of planet searches Confirmation in spectra Confirmation in spectra

12 March 28th 2007Juliet Datson, students' workshop Image

13 March 28th 2007Juliet Datson, students' workshop My work – brown dwarfs in taurus

14 March 28th 2007Juliet Datson, students' workshop My work Imaging fields in Taurus – Calar Alto? Imaging fields in Taurus – Calar Alto? No, CFHT from the internet No, CFHT from the internet Choose possible brown dwarf candidates Choose possible brown dwarf candidates Collect spectra for confirmation (Calar Alto) Collect spectra for confirmation (Calar Alto) A lot of data reduction with IDL and IRAF A lot of data reduction with IDL and IRAF Great new finding!!! Great new finding!!!

15 March 28th 2007Juliet Datson, students' workshop Calar Alto

16 March 28th 2007Juliet Datson, students' workshop Thank you for your attention.


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