ACCESS: An optical transmission spectrum of the high-gravity, hot Jupiter HAT-P-23b. (arXiv:2104.04101v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Weaver_I/0/1/0/all/0/1">Ian C. Weaver</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lopez_Morales_M/0/1/0/all/0/1">Mercedes López-Morales</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Alam_M/0/1/0/all/0/1">Munazza K. Alam</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Espinoza_N/0/1/0/all/0/1">Néstor Espinoza</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rackham_B/0/1/0/all/0/1">Benjamin V. Rackham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Goyal_J/0/1/0/all/0/1">Jayesh M. Goyal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+MacDonald_R/0/1/0/all/0/1">Ryan J. MacDonald</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lewis_N/0/1/0/all/0/1">Nikole K. Lewis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Apai_D/0/1/0/all/0/1">Dániel Apai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bixel_A/0/1/0/all/0/1">Alex Bixel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jordan_A/0/1/0/all/0/1">Andrés Jordán</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kirk_J/0/1/0/all/0/1">James Kirk</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McGruder_C/0/1/0/all/0/1">Chima McGruder</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Osip_D/0/1/0/all/0/1">David J. Osip</a>
We present a new ground-based visible transmission spectrum of the
high-gravity, hot Jupiter HAT-P-23b, obtained as part of the ACCESS project. We
derive the spectrum from five transits observed between 2016 and 2018, with
combined wavelength coverage between 5200 {AA} – 9269 {AA} in 200 {AA} bins,
and with a median precision of 247 ppm per bin. HAT-P-23b’s relatively high
surface gravity (g ~ 30 m/s^2), combined with updated stellar and planetary
parameters from Gaia DR2, gives a 5-scale-height signal of 384 ppm for a
hydrogen-dominated atmosphere. Bayesian models favor a clear atmosphere for the
planet with the tentative presence of TiO, after simultaneously modeling
stellar contamination, using spots parameter constraints from photometry. If
confirmed, HAT-P-23b would be the first example of a high-gravity gas giant
with a clear atmosphere observed in transmission at optical/NIR wavelengths;
therefore, we recommend expanding observations to the UV and IR to confirm our
results and further characterize this planet. This result demonstrates how
combining transmission spectroscopy of exoplanet atmospheres with long-term
photometric monitoring of the host stars can help disentangle the exoplanet and
stellar activity signals.
We present a new ground-based visible transmission spectrum of the
high-gravity, hot Jupiter HAT-P-23b, obtained as part of the ACCESS project. We
derive the spectrum from five transits observed between 2016 and 2018, with
combined wavelength coverage between 5200 {AA} – 9269 {AA} in 200 {AA} bins,
and with a median precision of 247 ppm per bin. HAT-P-23b’s relatively high
surface gravity (g ~ 30 m/s^2), combined with updated stellar and planetary
parameters from Gaia DR2, gives a 5-scale-height signal of 384 ppm for a
hydrogen-dominated atmosphere. Bayesian models favor a clear atmosphere for the
planet with the tentative presence of TiO, after simultaneously modeling
stellar contamination, using spots parameter constraints from photometry. If
confirmed, HAT-P-23b would be the first example of a high-gravity gas giant
with a clear atmosphere observed in transmission at optical/NIR wavelengths;
therefore, we recommend expanding observations to the UV and IR to confirm our
results and further characterize this planet. This result demonstrates how
combining transmission spectroscopy of exoplanet atmospheres with long-term
photometric monitoring of the host stars can help disentangle the exoplanet and
stellar activity signals.
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