More observations are needed to determine conclusively the cause of WASP-4b’s changing orbit and confirm the existence of an outer companion. So stay tuned! 😃🔭 20/20

The discovery of WASP-4c makes the WASP-4 system unique, as it would be the most widely separated companion of a transiting hot Jupiter known to date. We do expect many more of these types of systems to be discovered as more RV datasets will have longer baselines 19/20

We find a decay rate of -7.33±0.71 msec/year & an orbital decay lifetime of 15.77 Myr assuming the system is undergoing orbital decay. We derive a modified tidal quality factor of 5.1x10^4, which is an order of magnitude lower than other hot Jupiter systems. #Exoplanets 18/20

The orbital decay & apsidal precession models exhibit very different timing variations in the mid-2020s (see below). Therefore, we predict that it will be possible to conclusively determine the cause of WASP-4b’s changing orbit by then. #Exoplanets 17/20

We find that the TTVS of all of the WASP-4b transits cannot be explained by the second planet but can be explained with either a decaying orbit or apsidal precession, with a slight preference for orbital decay. #Exoplanets 16/20

More RV measurements (and other types of data) are needed to verify the existence of this second planet around WASP-4. #Exoplanets 15/20

WASP-4c, the possible additional planet, orbits at a distance of 6.82 AU with an orbital period of 7001 days. WASP-4c has a Msin(i) of 5.47 MJup. Assuming WASP-4c is near co-planar with WASP-4b, we find a planetary mass between 5.47-6.50 MJup #Exoplanets 14/20

Instead, we find evidence of a possible additional planet in the WASP-4 system (RV model with two-planets below) #Exoplanets 13/20

Our analysis shows that the full RV data set is consistent with no acceleration towards the Earth. We only find this by modeling all RV data (we reproduce the result from Bouma et al. 2020 using only their data) #Exoplanets 12/20

We confirm using all the @NASA_TESS sectors & ground-based transits that the period of WASP-4b is changing #Exoplanets 11/20

Unfortunately, we do not see an occultation of WASP-4b in the @NASA_TESS data. We find a 3-sigma upper limit on the geometric albedo of 0.017. Our upper limit is consistent with the overall trend that hot Jupiters are very dark (like coal) #Exoplanets 10/20

As in our previous study, we modeled each individual transit (the phase folded light curve is below) These data were modeled with the EXOplanet Modeling Package (EXOMOP) developed in my PhD #Exoplanets 9/20

Motivated by the possible changing period of WASP- 4b, we analyze all sectors from TESS & combine the results with all transit, occultation, & RV measurements Altogether, the transit data span 13 years from 2007-2020 and the RV data span 12 years from 2007-2019. #Exoplanets 8/20

Recently, Baluev et al. 2020 confirmed a period change in WASP-4b’s orbit but do not confirm the RV acceleration found by Bouma et al. (2020). However, Baluev et al. (2020) did not include the new RV HIRES data from Bouma et al. (2020) in their analysis. #Exoplanets 7/20

Bouma et al. (2020) obtained RV data on WASP- 4b using HIRES on Keck & found that the observed orbital period variation could be explained by the system accelerating toward the Sun #Exoplanets 6/20

Bouma et al. (2019) first reported an orbital period variation of WASP-4b using @NASA_TESS Southworth et al. (2019) confirmed that the period was decaying with additional ground-based observations & found a decay rate of -9.2 msec/yr #Exoplanets 5/20

WASP-4b is a typical hot Jupiter (~1700 K) discovered in 2008. It orbits its star in 1.3 days! Its atmosphere was found to be cloudy & highly inefficient at heat redistribution. But what about its orbit? #Exoplanets 4/20

To date, WASP-12b is one of the few hot Jupiters confirmed to have a varying period. Earlier this year, we confirmed its decaying orbit with TESS observations Besides WASP-12b, WASP-4b is a well-studied system with hints of a changing period... xitter.cf/Astro_journey/status/1… 3/20