Revisiting KELT-19Ab, WASP-156b and WASP-121b in the TESS Era. (arXiv:2012.08744v2 [astro-ph.EP] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Yang_F/0/1/0/all/0/1">Fan Yang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chary_R/0/1/0/all/0/1">Ranga-Ram Chary</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_J/0/1/0/all/0/1">Ji-Feng Liu</a>
We present a re-analysis of transit depths of KELT-19Ab, WASP-156b, and
WASP-121b, including data from the Transiting Exoplanet Survey Satellite
(TESS). The large $sim21”$ TESS pixels and point spread function results in
significant contamination of the stellar flux by nearby objects. We use Gaia
data to fit for and remove this contribution, providing general-purpose
software for this correction. We find all the three sources have a larger
inclination, compared to earlier work. For WASP-121b, we find significantly
smaller values (13.5 degrees) of the inclination when using the 30 minutes
cadence data compared to the 2 minutes cadence data. We demonstrate using a
simulation that 30-minute binning data in general, yields a smaller inclination
than the true input value at 25$sigma$. Also, we find that inclination and
semi-major axis are biased small when applying a larger sampling time interval
which is particularly important for deriving sub-percent transit differences
between bands. If we constrain the inclination to previous work, we find the
radius ratio of exoplanet to star ($R_{p}/R_{ast}$) in the broad TESS band is
3.5$sigma$ smaller than previous work for KELT-19Ab, and consistent to within
$sim$2$sigma$ for WASP-156b and WASP-121b. The result for KELT-19Ab favors a
haze-dominated atmosphere. We do not find statistically significant evidence
for the $sim$0.95,$mu$m water feature contaminating the transit depths in
the TESS band for these stars but show that with photometric precision of
500ppm and with a sampling of about 200 observations across the entire transit,
this feature could be detectable in a more narrow $z-$band. Furthermore, we
find that with the inclusion of the TESS photometry, WASP-121b can be fitted
just as well with a cloud-free atmosphere with water vapor as with an opaque
featureless model.
We present a re-analysis of transit depths of KELT-19Ab, WASP-156b, and
WASP-121b, including data from the Transiting Exoplanet Survey Satellite
(TESS). The large $sim21”$ TESS pixels and point spread function results in
significant contamination of the stellar flux by nearby objects. We use Gaia
data to fit for and remove this contribution, providing general-purpose
software for this correction. We find all the three sources have a larger
inclination, compared to earlier work. For WASP-121b, we find significantly
smaller values (13.5 degrees) of the inclination when using the 30 minutes
cadence data compared to the 2 minutes cadence data. We demonstrate using a
simulation that 30-minute binning data in general, yields a smaller inclination
than the true input value at 25$sigma$. Also, we find that inclination and
semi-major axis are biased small when applying a larger sampling time interval
which is particularly important for deriving sub-percent transit differences
between bands. If we constrain the inclination to previous work, we find the
radius ratio of exoplanet to star ($R_{p}/R_{ast}$) in the broad TESS band is
3.5$sigma$ smaller than previous work for KELT-19Ab, and consistent to within
$sim$2$sigma$ for WASP-156b and WASP-121b. The result for KELT-19Ab favors a
haze-dominated atmosphere. We do not find statistically significant evidence
for the $sim$0.95,$mu$m water feature contaminating the transit depths in
the TESS band for these stars but show that with photometric precision of
500ppm and with a sampling of about 200 observations across the entire transit,
this feature could be detectable in a more narrow $z-$band. Furthermore, we
find that with the inclusion of the TESS photometry, WASP-121b can be fitted
just as well with a cloud-free atmosphere with water vapor as with an opaque
featureless model.
http://arxiv.org/icons/sfx.gif
