91福利

I will give a introduction of brown dwarfs, particularly on metal-deficient L subdwarfs. I will then introduce a few of my on-going projects related to L subdwarfs. L subdwarfs represent a mixture of low-mass stars and brown dwarfs many of which appear to belong to the Galactic halo. They are rare and show different optical and infrared spectroscopic characteristics from L dwarfs. They are poorly characterized due to small number (23 in the literature) of known and un-tested metal-poor atmosphere models. I started to search for L subdwarfs in UKIDSS and SDSS since 2010. I am following up candidates with big telescopes (mostly GTC), and have confirmed 34 new L subdwarfs. I started a programme aiming to obtain medium-resolution spectra with VLT/X-shooter for 33 L subdwarfs for detail model comparison and radial velocity measurements. I also started a 3-year programme to measure parallaxes of 20 L subdwarfs with the GTC.