Analysis of the Most Precise Light Curves of HAT-P-36 Detrended from Spot Signals
S. Yalçınkaya1, Ö.Baştürk1, F. El Helweh2, E.M. Esmer1, O. Yörükoğlu1,
M. Yılmaz1, H.V. Şenavcı1, T.Kılıçoğlu1
and S.O. Selam1
1Ankara University, Faculty of Science, Astronomy & Space Sciences Department, Tandogan, TR-06100, Ankara, Turkey
2Bilkent University, Science Faculty, Physics Department, TR-06800 Ankara, Turkey
Received: July 28, 2021
ABSTRACT
We study the most precise light curves of the planet-host
HAT-P-36 that we obtained from the ground primarily with a brand-new
80 cm telescope (T80) very recently installed at Ankara University
Kreiken Observatory (AUKR), Turkey and also from the space with
Transiting Exoplanet Survey Satellite (TESS). The main objective of
the study is to analyze the Transit Timing Variations (TTV) observed
in the hot-Jupiter type planet HAT-P-36 b, a strong candidate for
orbital decay. Our analysis is based on our own observations as well
as those acquired by professional and amateur observers since its
discovery. HAT-P-36 displays out-of-transit variability as well as
light curve anomalies during the transits of its planet due to
stellar spots. We collected and detrended from these anomalies all
complete transit light curves we had access to. We modeled transits
with EXOFAST and measured the mid-transit times forming a
homogeneous data set for a TTV analysis. We found an increase in the
orbital period of HAT-P-36 b at a rate of 0.014 s per year from the
best fitting quadratic function. This increase is only found in the
TTV constructed from the mid-transit times measured from detrended
light curves. We refined the values of the system parameters by
modeling with EXOFASTv2 the Spectral Energy Distribution of
the host star, its archival radial velocity observations from
multiple instruments, and the most precise transit light curves from
the space and ground covering a wide range of wavelengths. We also
analyzed the out-of-transit variability from TESS observations to
search for potential rotational modulations through a frequency
analysis. We report a statistically significant periodicity in the
TESS light curve at 4.22±0.02 d, which might have been caused by
instrumental systematics but should be tracked in the future
observations of the target.
Key words:
Stars: individual: HAT-P-36 -
planetary systems - Methods: observational - Techniques: photometric
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