Brown dwarfs An introduction March 28 th 2007

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

What are brown dwarfs? No hydrogen burning, only deuterium l Defined by mass – problem of exact mass measurements l One test: Lithium test l l Stars soon deplete their lithium, it burns at little lower temperatures than hydrogen l If lithium is still there after a certain amount of time – no hydrogen burning l M < 0. 065 M(solar) March 28 th 2007 Juliet Datson, students' workshop

What are brown dwarfs? l Boundary between planet and brown dwarf: l No free floating planet l 0. 0013 M(solar) is deuterium burning limit l Pressure through electron degeneracy l Baryonic dark matter candidates March 28 th 2007 Juliet Datson, students' workshop

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

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

Spectra March 28 th 2007 Juliet Datson, students' workshop

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

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

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

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

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

Image March 28 th 2007 Juliet Datson, students' workshop

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

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

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

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