WTS-2 b: a hot Jupiter orbiting near its tidal destruction radius around a K dwarf
Jayne BirkbyM. CappettaP. CruzJ. KoppenhoeferO. IvanyukAlexander J. MustillS. T. HodgkinD. J. PinfieldBrigitta SipőczG. KovácsR. P. SagliaYa. V. PavlenkoD. BarradoA. BayoDavid A. CampbellS. CatalánL. FossatiM. C. Gálvez-OrtizMatthew A. KenworthyJ. Lillo-BoxE. L. Martı́nD. MislisErnst de MooijS. V. NefsI. A. G. SnellenH. StoevJ. ZendejasC. del BurgoJ. R. BarnesN. GouldingC. A. HaswellM. K. KuznetsovN. LodieuF. MurgasΕ. ΠάλληE. SolanoP. R. SteeleR. Tata
76
Citation
130
Reference
10
Related Paper
Citation Trend
Abstract:
We report the discovery of WTS-2 b, an unusually close-in 1.02-day hot Jupiter (Mp=1.12MJ, Rp=1.363RJ) orbiting a K2V star, which has a possible gravitationally-bound M-dwarf companion at 0.6 arcsec separation contributing ~20 percent of the total flux in the observed J-band light curve. The planet is only 1.5 times the separation from its host star at which it would be destroyed by Roche lobe overflow, and has a predicted remaining lifetime of just ~40 Myr, assuming a tidal dissipation quality factor of Q'*=10^6. Q'* is a key factor in determining how frictional processes within a host star affect the orbital evolution of its companion giant planets, but it is currently poorly constrained by observations. We calculate that the orbital decay of WTS-2 b would correspond to a shift in its transit arrival time of T_shift~17 seconds after 15 years assuming Q'*=10^6. A shift less than this would place a direct observational constraint on the lower limit of Q'* in this system. We also report a correction to the previously published expected T_shift for WASP-18 b, finding that T_shift=356 seconds after 10 years for Q'*=10^6, which is much larger than the estimated 28 seconds quoted in WASP-18 b discovery paper. We attempted to constrain Q'* via a study of the entire population of known transiting hot Jupiters, but our results were inconclusive, requiring a more detailed treatment of transit survey sensitivities at long periods. We conclude that the most informative and straight-forward constraints on Q'* will be obtained by direct observational measurements of the shift in transit arrival times in individual hot Jupiter systems. We show that this is achievable across the mass spectrum of exoplanet host stars within a decade, and will directly probe the effects of stellar interior structure on tidal dissipation.Keywords:
Hot Jupiter
Orbital period
Jupiter (rocket family)
Gas giant
Orbital decay
Roche lobe
Eclipse
Radial velocity
Long-orbital-period subdwarf B (sdB) stars with main-sequence companions are believed to be the product of stable Roche Lobe overflow (RLOF), a scenario challenged by recent observations. Here we represent the results of a systematic study of the orbital-period distribution of sdB binaries in this channel using detailed binary evolution calculations. We show that the observed orbital-period distribution of long-period sdB binaries can be well explained by this scenario. Furthermore, we find that, if the progenitors of the sdB stars have initial masses below the helium flash mass, the sdB binaries produced from stable RLOF follow a unique mass -- orbital period relation for a given metallicity $Z$; increasing the orbital period from $\sim 400$ to $\sim 1100$\,d corresponds to increasing the mass of the sdB star from $\sim 0.40$ to $\sim 0.49\,M_\odot$ for $Z=0.02$. We suggest that the longest sdB binaries (with orbital period $> 1100$\,d) could be the result of atmospheric RLOF. The mass -- orbital period relation can be tested observationally if the mass of the sdB star can be determined precisely, e.g.\ from asteroseismology. Using this relation, we revise the orbital period distribution of sdB binaries produced by the first stable RLOF channel for the best fitting model of Han et al (2003), and show that the orbital period has a peak around 830\,d.
Orbital period
Roche lobe
Subdwarf
Orbital inclination
Cite
Citations (65)