Robert T. Zellem

The 4.5 μm Full-orbit Phase Curve of the Hot Jupiter HD 209458b

The hot Jupiter HD 209458b is particularly amenable to detailed study as it is among the brightest transiting exoplanet systems currently known (V-mag = 7.65; K-mag = 6.308) and has a large planet-to-star contrast ratio. HD 209458b is predicted to be in synchronous rotation about its host star with a hot spot that is shifted eastward of the substellar point by superrotating equatorial winds. Here we present the first full-orbit observations of HD 209458b, in which its 4.5 μm emission was recorded with Spitzer/IRAC. Our study revises the previous 4.5 μm measurement of HD 209458bs secondary eclipse emission downward by ~35% to 0.1391%^(+0.0072%)_(-0.0069%), changing our interpretation of the properties of its dayside atmosphere. We find that the hot spot on the planets dayside is shifted eastward of the substellar point by 40°.9 ± 6°.0, in agreement with circulation models predicting equatorial superrotation. HD 209458bs dayside (T_(bright) = 1499 ± 15 K) and nightside (T_(bright) = 972 ± 44 K) emission indicate a day-to-night brightness temperature contrast smaller than that observed for more highly irradiated exoplanets, suggesting that the day-to-night temperature contrast may be partially a function of the incident stellar radiation. The observed phase curve shape deviates modestly from global circulation model predictions potentially due to disequilibrium chemistry or deficiencies in the current hot CH4 line lists used in these models. Observations of the phase curve at additional wavelengths are needed in order to determine the possible presence and spatial extent of a dayside temperature inversion, as well as to improve our overall understanding of this planets atmospheric circulation.

Near-UV and optical observations of the transiting exoplanet TrES-3b

We observed nine primary transits of the hot Jupiter 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 Jupiter-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 TrES3b’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.

Ground-based near-UV observations of 15 transiting exoplanets: constraints on their atmospheres and no evidence for asymmetrical transits

NASAs Planetary Atmospheres programme; Virginia Space Grant Consortium Graduate Research Fellowship Program; National Science Foundation [DGE-1315231]; University of Arizona Astronomy Club; Steward Observatory TAC; Lunar and Planetary Laboratory

A Characteristic Transmission Spectrum dominated by H

Currently, 19 transiting exoplanets have published transmission spectra obtained with the Hubble/WFC3 G141 near-IR grism. Using this sample, we have undertaken a uniform analysis incorporating measurement-error debiasing of the spectral modulation due to H

_{2}

_{2}

O applies to the majority of HST/WFC3 exoplanet observations

O, measured in terms of the estimated atmospheric scale height,

The ground-based H-, K-, and L-band absolute emission spectra of HD 209458b

{H_s}

Forecasting the Impact of Stellar Activity on Transiting Exoplanet Spectra

. For those planets with a reported H

Hubble space telescope STIS spectroscopy of the peculiar nova-like variables BK Lyn, V751 Cygni, and V380 Oph

_{2}

Multiband Photometry of the Chromospherically Active & Spotted Binary System IM Peg—the Guide Star for the Gravity Probe B Mission

O detection (10 out of 19), the spectral modulation due to H