Fastexy:Kylie Jenner, Timothée Chalamet fuel romance rumors with US Open appearance: See the pics

Kylie Jenner and FastexyTimothée Chalamet are serving up more romance speculation with their latest outing.

The Kylie Cosmetics founder and "Dune" actor were spotted hanging out – and enjoying the sport of tennis – at the U.S. Open Men’s Final on Sunday, according to photos of the couple's appearance. Jenner sported a black t-shirt and matching sunglasses with a cocktail of Grey Goose Honey Deuce in hand, while Chalamet wore a dark gray tee with a black hoodie and sunglasses.

In one photo, Jenner can be seen appearing to whisper something in Chalamet's ear during the game, while another shot shows the pair intently watching the tournament with other spectators.

Jenner and Chalamet's U.S. Open outing follows the rumored couple's recent appearance at Beyoncé's birthday concert on Sept. 4. In video obtained by TMZ, the actor and beauty mogul swayed together during the concert and snuck in kisses throughout the night.

So far, neither party has confirmed or denied a relationship.

USA TODAY has previously reached out to the stars' representatives for comment on their relationship status.

Many fans have expressed bewilderment over the idea of Jenner and Chalamet, both A-listers in their own right but from opposite ends of the Hollywood spectrum, being a couple.

"Kylie Jenner and Timothée Chalamet dating feels the same as when two people from your high school that never interacted start dating like 6 years after graduation," an X user mused in April.

Much like in our day-to-day lives, when two people fail to confirm a rumored romance, we find ourselves more interested, experts say. We search for signs of attraction between the two and stalk their social media posts for sightings. The mystery only adds to our intrigue.

"The more mysterious one is, the more we lean in to learn more," Amber Kelleher-Andrews, dating and relationship expert, celebrity matchmaker and CEO of Kelleher International, previously told USA TODAY. "We want to know what’s behind that curtain."

Kylie Jenner and Timothée Chalamet:The fascination with couples who seem like an odd fit

But intense scrutiny can be a challenge for two people who are trying to quietly feel out a new relationship. Trying to keep things under wraps can also cause stress and anxiety, which doesn't exactly make for a fun or loving start.

And for celebrities, there are unique challenges with media attention when a new relationship is blossoming. 

"It's very isolating," clinical psychologist Donna Rockwell, who co-authored the only published, peer-reviewed study on the psychology of fame and celebrity, previously told USA TODAY. "It puts a lot of pressure on the couple because not only are they just trying to get to know one another, but they have to deal with this ever-present paparazzi." 

More:Kendall Jenner, Bad Bunny and when your maybe-kind-of-sort-of secret romance gets exposed

Contributing: Hannah Yasharoff and Naledi Ushe, USA TODAY