Title: The purest brown dwarf & properties of low-mass celestial populations 

Time: 10:30-11:30, July. 19 

Place: middle conference room 

Speaker: 张曾华 (ZengHua Zhang; Observatoire de Paris, PSL fellow)  

Abstract: 

　　The formation of sub-stars (often referred to as brown dwarfs) which are not massive enough to support steady nuclear reaction in their hearts were predicted in 1962. A few thousands of brown dwarfs have been discovered in the Galactic disk since 1995. However, very few halo brown dwarf candidates were reported.  

　　I will present the discovery of an L type ultra subdwarf, SDSS J0104+15. Our analysis shows SDSS J0104+15 to be the most metal-poor and highest mass substellar object known to-date. SDSS J0104+15 is joined by another five L type extreme and ultra subdwarfs in a `halo brown dwarf transition zone’ in the Teff–[Fe/H] plane, which represents a narrow mass range in which unsteady nuclear fusion occurs. This halo brown dwarf transition zone forms a `substellar subdwarf gap’ for mid L to early T types.   

　　In this talk, I will also try to clarify the difference between the following celestial populations: cool stars, brown dwarfs, and planets; red dwarfs, and ultracool dwarfs; low-mass stars, very low-mass stars, and substellar objects; dwarfs, subdwarfs, extreme subdwarfs, and ultra subdwarfs.  

　　Paper: http://adsabs.harvard.edu/abs/2017MNRAS.468..261Z 

　　RAS press:  

　　http://www.ras.org.uk/news-and-press/2967-astronomers-identify-purest-most-massive-brown-dwarf