PTFO 8-8695 (CVSO 30) is a star in the 7-10 million year old Orion-OB1a
cluster that shows brightness dips that resemble planetary transits.
Although strong evidence against the planet hypothesis for this system
has been presented, the possibility remains debated in the literature.
To obtain further clues, we inspected data from the NASA TESS and the
ESA Gaia missions. The Gaia data suggest that PTFO 8-8695 is a binary:
the photometric data show it to be over-luminous with respect to members
of its kinematic group, and the astrometric data are inconsistent with a
single star. The TESS light curve shows two different photometric
periods. The variability is dominated by a sinusoidal signal with a
period of 11.98 hr, probably caused by stellar rotation. Also present is
a 10.76 hr signal consisting of a not-quite sinusoid interrupted by
hour-long dips, the type of signal previously interpreted as planetary
transits. The phase of the dips is nearly 180° away from the phase of
the originally reported dips. This makes the dips difficult to explain
as planetary transits. Instead, we believe that PTFO 8-8695 is a pair of
young and rapidly rotating M dwarfs, one of which shows the same
“transient-dip” behavior that has been seen in at least 5 other cases.
The origin of these transient dips is still unknown but likely involves
circumstellar material. Combined with recent counter-arguments against
the planetary nature of CI Tau b and V830 Tau b, the rejection of the
planetary hypothesis for PTFO 8-8695b suggests that the number of known
hot Jupiters younger than 100 Myr is approximately zero.