The HAT-P-23 system consists of a G0 dwarf star and a 2 Jupiter-mass planet on a 1.2 d orbit. The orbital eccentricity of about 0.1 was reported. Our analysis of mid-transit times collected so far indicates that a linear ephemeris does not reproduce observations. A long-term trend is visible in the transit time residuals that could be a sign of orbital period shortening (and orbital decay). This could also be a fragment of periodic variation caused by apsidal precession. Numerical calculations show that precession can be induced by tidal interactions of the host star and planet. They would produce variations in transit times with a period of 50 yr and amplitude up to a few tens of minutes (if the orbital eccentricity of 0.1 is assumed).
We propose to acquire new high-quality transit light curves and determine new precise mid-transit times. They will allow us to investigate a hypothesis of the inconstant period of the HAT-P-23 b planet. The system may become a great laboratory to study star-planet tidal interactions, similar to WASP-12.
No conclusive results so far.
The campaign is ongoing.
| No. | Date | Instrument | Comment |
| 1 | 2016 Jul 01 | OSN 1.5 m | R |
| 2 | 2016 Aug 21 | OSN 0.9 m | R, partial with 1.5 m |
| 3 | 2016 Aug 26 | Toruń 0.6 m | clear |
| 4 | 2016 Sep 01 | OSN 1.5 m | R |
| 5 | 2016 Sep 01 | Trebur 1.2 m | clear |
| 6 | 2016 Sep 01 | Toruń 0.6 m | clear |
| 7 | 2016 Sep 07 | Trebur 1.2 m | clear |
PI: Gracjan Maciejewski gmac@umk.pl