What do the researchers in Antarctica wear if they must go outside during winter?
The US Antarctica Program publishes information about the required extreme cold weather gear. It's provided by the government and has to be returned after your deployment ends. The list is here along with other information. Here's another document that discuses clothing. I've extracted the list below. 

Jackets 
1 each GOR-TEX® wind jacket 
1 each Helly Hansen® rain jacket 
1 each polar fleece jacket 
1 each Carhartt® jacket optional 
1 each Carhartt vest optional 
1 each red down parka optional 

Pants 
1 each GOR-TEX bib coveralls for grantees only 
1 each Helly Hansen rain pants 
1 each polar fleece pants 
1 each Carhartt bib coveralls optional 
1 each Carhartt pants 

Thermal 
2 each thermal top 
2 each thermal bottoms 

Hat and Neck 
1 each Balaklava 
1 each neck gaiter 
1 each polar fleece cap 

Gloves 
1 pair leather work gloves (unlined) 
1 pair leather work gloves (insulated) 
1 pair rubber gloves (with liners) 
1 pair GOR-TEX mitts 
1 pair polypropylene gloves 
1 pair wool gloves 

Footwear 
2 pair tube socks 
1 pair snow boots (Sorel™ or LaCrosse®) 
1 each fisherman boots (rubber or steel-toed) optional 

Miscellaneous 
1 pair goggles 
1 each duffle bag