Kavli Affiliate: Roland Vanderspek
| First 5 Authors: Christopher R. Mann, David Lafrenière, Diana Dragomir, Samuel N. Quinn, Thiam-Guan Tan
| Summary:
We present a successful validation of the long-period
($91.68278^{+0.00032}_{-0.00041}$ days) transiting sub-Neptune planet TOI-1221
b (TIC 349095149.01) around a Sun-like (m$_{rm V}$=10.5) star. We combine {it
TESS} light curve measurements and ground-based time-series photometry from
PEST (0.3~m) and LCOGT (1.0~m) to analyze the transit light curves and rule out
nearby stars as potential eclipsing binary contaminants. High-contrast imaging
from SOAR and Gemini/Zorro rule out nearby stellar contaminants down to
$Delta$mag = 5 at separation $r = 0.1"$. Reconnaissance spectroscopy from
CHIRON sets a planetary upper limit on the mass of the object (1.1 and 3.5
M$_{rm Jup}$ at 1$sigma$ and 3$sigma$, respectively) and shows no sign of a
spectroscopic binary companion. We fit a planetary radius $R_{rm
p}/R_star=0.02679^{+0.00067}_{-0.00056}$ corresponding to $R_{rm p} =
2.91^{+0.13}_{-0.12} R_{oplus}$, placing it in the sub-Neptune regime. It’s
orbital semi-major axis of $a=0.404^{+0.026}_{-0.023}$ au predicts an
insolation of $S = 5.57^{+0.75}_{-0.68} S_{oplus}$, suggesting a moderate
equilibrium temperature of $T_{rm eq} =$ 400 K given a Neptune-like model. In
analyzing 8 transits, we find significant evidence (> $5sigma$) of sinusoidal
transit timing variations with amplitude of $23.0^{+5.2}_{-4.1}$ minutes, and a
super-period of $485^{+15}_{-19}$ days. We find a false positive probability
from TRICERATOPS of FPP $ = 0.0014 pm 0.0003$ as well as other qualitative and
quantitative evidence to support the statistical validation of TOI-1221 b.
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