Are "The Expanse" and "The Martian" set in the same universe?

Question

There is a passage from Babylon's Ashes, the sixth novel in James S.A. Corey's The Expanse series, which references a ship called "Mark Watney" (bold emphasis mine, italic author's):

In the middle column, the colony ships she and her fleet had taken: the Bedyadat Jadida, out of Luna. The John Galt and the Mark Watney, out of Mars.
_{- Chapter 15: Pa}

Mark Watney is an astronaut from Andy Weir's The Martian, the first astronaut sent to Mars to almost die on it, as well as the first person ever to grow potatoes on another celestial body. In your face, Neil Armstrong!

Does that imply that The Expanse and The Martian take place in the same universe?

Answer 1

They are not, the reference in the Expanse is merely "thrown in for fun"

In a recent AMA for his new book Artemis, Andy Weir was asked:

How did The Expanse end up set in the same timeline as The Martian? Did they just put the Mark Watney ship in and it happened after the fact, or was it something they came to you ahead of time with?
_{Question by /u/ManaByte for Andy Weir}

To which Andy responded:

I love The Expanse - fantastic stories. But no, The Martian and The Expanse are not in the same continuity. They just threw in the reference for fun. I'm honored.
_{Andy Weir (/u/sephalon) stating they are not in the same continuity}

It would appear that James S.A. Corey was either making or joke or lying. I have sent him an e-mail to see if he'd either comment on the tweet or leave a note here. It seems that would be in vain, as Daniel Abraham (1 of the 2 co-authors working under the pen-name James S.A. Corey) has stated on reddit that it was just a joke in response to this comment thread:

It was a friendly joke at SDCC a few years back. Andy’s awesome, and we’re fans. I think we can keep the copyright lawyers in their cages for the time being.
_{Daniel Abraham in response to discussing the copyright infringement of using the name Mark Watney}

Answer 2

According to the authors, they are in the same universe.

There is a tweet by the author of The Expanse series, James S. A. Corey¹, where they, possibly half-jokingly, acknowledges the fact (click to go to Twitter):

@JamesSACorey: At SDCC @andyweirauthor and I did a signing together and agreed our books are in the same continuity. Movie and TV show too. Movie's Awesome

Andy Weir appears to be in cahoots with them on this.

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¹: James S.A. Corey is the pen name of Daniel Abraham and Ty Franck. Our gratitude goes to @ench for pointing this out!