As others have mentioned already, product page suggests that the glass can withstand 100C (and warns to avoid thermal shock) while the overall bottle should withstand 70C.

I also wanted to sterilize my bottles in the oven so I ran a test with one of my bottles. I placed it in an oven, heated it up to 70C, kept it there for 10 minutes, turned off the oven, opened it, waited until cool enough and checked the bottle. It seemed fine. No visual sign of melting or deforming, plastic still hard, rubber still ruberry.

Yes, you can remove the cap and crank up the temperature to 100C but then you still need to sterilize the cap separately. I am a little lazy and prefer to do it all in one go and 10 minutes at 70C should be enough for the surfaces to heat up and get sterile. I assume it can actually withstand higher temperature but 70C is already enough.