Near-UV and optical observations of the transiting exoplanet TrES-3b
Abstract
We observed nine primary transits of the hot Jpiter TrES-3b in several optical and near-UV photometric bands from 2009 June to 2012 April in an attempt to detect its magnetic field. Vidotto, Jardine and Helling suggest that the magnetic field of TrES-3b can be constrained if its near-UV light curve shows an early ingress compared to its optical light curve, while its egress remains unaffected. Predicted magnetic field strengths of Jpiter-like planets should range between 8 G and 30 G. Using these magnetic field values and an assumed B* of 100 G, the Vidotto et al. method predicts a timing difference of 5-11 min. We did not detect an early ingress in our three nights of near-UV observations, despite an average cadence of 68 s and an average photometric precision of 3.7 mmag. However, we determined an upper limit of TrES-3b's magnetic field strength to range between 0.013 and 1.3 G (for a 1-100 G magnetic field strength range for the host star, TrES-3) using a timing difference of 138 s derived from the Nyquist-Shannon sampling theorem. To verify our results of an abnormally small magnetic field strength for TrES-3b and to further constrain the techniques of Vidotto et al., we propose future observations of TrES-3b with other platforms capable of achieving a shorter near-UV cadence. We also present a refinement of the physical parameters of TrES-3b, an updated ephemeris and its first published near-UV light curve. We find that the near-UV planetary radius of Rp = 1.386+ 0.248- 0.144 RJup is consistent with the planet's optical radius.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- January 2013
- DOI:
- 10.1093/mnras/sts061
- arXiv:
- arXiv:1211.4895
- Bibcode:
- 2013MNRAS.428..678T
- Keywords:
-
- planets and satellites: individual: TrES-3b - techniques: photometric;
- planets and satellites: magnetic fields;
- planetary systems;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- Accepted for Publication in Monthly Notices of the Royal Astronomical Society (2012 September 21). 13 pages, 5 figures