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Register a new userHubble PanCET: An isothermal day-side atmosphere for the bloated gas-giant HAT-P-32Ab
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We present a thermal emission spectrum of the bloated hot Jupiter HAT-P-32Ab from a single eclipse observation made in spatial scan mode with the Wide Field Camera 3 (WFC3) aboard the Hubble Space Telescope (HST). The spectrum covers the wavelength regime from 1.123 to 1.644 microns which is binned into 14 eclipse depths measured to an averaged precision of 104 parts-per million. The spectrum is unaffected by a dilution from the close M-dwarf companion HAT-P-32B, which was fully resolved. We complemented our spectrum with literature results and performed a comparative forward and retrieval analysis with the 1D radiative-convective ATMO model. Assuming solar abundance of the planet atmosphere, we find that the measured spectrum can best be explained by the spectrum of a blackbody isothermal atmosphere with Tp = 1995 +/- 17K, but can equally-well be described by a spectrum with modest thermal inversion. The retrieved spectrum suggests emission from VO at the WFC3 wavelengths and no evidence of the 1.4 micron water feature. The emission models with temperature profiles decreasing with height are rejected at a high confidence. An isothermal or inverted spectrum can imply a clear atmosphere with an absorber, a dusty cloud deck or a combination of both. We find that the planet can have continuum of values for the albedo and recirculation, ranging from high albedo and poor recirculation to low albedo and efficient recirculation. Optical spectroscopy of the planets day-side or thermal emission phase curves can potentially resolve the current albedo with recirculation degeneracy.
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We present a 0.3-5 micron transmission spectrum of the hot Jupiter HAT-P-32Ab observed with the Space Telescope Imaging Spectrograph (STIS) and Wide Field Camera 3 (WFC3) instruments mounted on the Hubble Space Telescope, combined with Spitzer Infrared Array Camera (IRAC) photometry. The spectrum is composed of 51 spectrophotometric bins with widths ranging between 150 and 400 AA, measured to a median precision of 215 ppm. Comparisons of the observed transmission spectrum to a grid of 1D radiative-convective equilibrium models indicate the presence of clouds/hazes, consistent with previous transit observations and secondary eclipse measurements. To provide more robust constraints on the planets atmospheric properties, we perform the first full optical to infrared retrieval analysis for this planet. The retrieved spectrum is consistent with a limb temperature of 1248$pm$92 K, a thick cloud deck, enhanced Rayleigh scattering, and $sim$10x solar H2O abundance. We find log($Z/Z_{odot}$) = 2.41$_{-0.07}^{+0.06}$, in agreement with the mass-metallicity relation derived for the Solar System.
We present a comprehensive analysis of the 0.3--5,$mu$m transit spectrum for the inflated hot Jupiter HAT-P-41b. The planet was observed in transit with Hubble STIS and WFC3 as part of the Hubble Panchromatic Comparative Exoplanet Treasury (PanCET) program, and we combine those data with warm textit{Spitzer} transit observations. We extract transit depths from each of the data sets, presenting the STIS transit spectrum (0.29--0.93,$mu$m) for the first time. We retrieve the transit spectrum both with a free-chemistry retrieval suite (AURA) and a complementary chemical equilibrium retrieval suite (PLATON) to constrain the atmospheric properties at the day-night terminator. Both methods provide an excellent fit to the observed spectrum. Both AURA and PLATON retrieve a metal-rich atmosphere for almost all model assumptions (most likely O/H ratio of $log_{10}{Z/Z_{odot}} = 1.46^{+0.53}_{-0.68}$ and $log_{10}{Z/Z_{odot}} = 2.33^{+0.23}_{-0.25}$, respectively); this is driven by a 4.9-$sigma$ detection of H$_2$O as well as evidence of gas absorption in the optical ($>$2.7-$sigma$ detection) due to Na, AlO and/or VO/TiO, though no individual species is strongly detected. Both retrievals determine the transit spectrum to be consistent with a clear atmosphere, with no evidence of haze or high-altitude clouds. Interior modeling constraints on the maximum atmospheric metallicity ($log_{10}{Z/Z_{odot}} < 1.7$) favor the AURA results. The inferred elemental oxygen abundance suggests that HAT-P-41b has one of the most metal-rich atmospheres of any hot Jupiters known to date. Overall, the inferred high metallicity and high inflation make HAT-P-41b an interesting test case for planet formation theories.
The metastable helium line at 1083 nm can be used to probe the extended upper atmospheres of close-in exoplanets and thus provide insight into their atmospheric mass loss, which is likely to be significant in sculpting their population. We used an ultranarrowband filter centered on this line to observe two transits of the low-density gas giant HAT-P-18b, using the 200 Hale Telescope at Palomar Observatory, and report the detection of its extended upper atmosphere. We constrain the excess absorption to be $0.46pm0.12%$ in our 0.635 nm bandpass, exceeding the transit depth from the Transiting Exoplanet Survey Satellite (TESS) by $3.9sigma$. If we fit this signal with a 1D Parker wind model, we find that it corresponds to an atmospheric mass loss rate between $8.3^{+2.8}_{-1.9} times 10^{-5}$ $M_mathrm{J}$/Gyr and $2.63^{+0.46}_{-0.64} times 10^{-3}$ $M_mathrm{J}$/Gyr for thermosphere temperatures ranging from 4000 K to 13000 K, respectively. With a J magnitude of 10.8, this is the faintest system for which such a measurement has been made to date, demonstrating the effectiveness of this approach for surveying mass loss on a diverse sample of close-in gas giant planets.
We report secondary eclipse photometry of the hot Jupiter HAT-P-32Ab, taken with Hale/WIRC in H and Ks bands and with Spitzer/IRAC at 3.6 and 4.5 micron. We carried out adaptive optics imaging of the planet host star HAT-P-32A and its companion HAT-P-32B in the near-IR and the visible. We clearly resolve the two stars from each other and find a separation of 2.923 +/- 0. 004 and a position angle 110.64 deg +/- 0.12 deg. We measure the flux ratios of the binary in g r i z and H & Ks bands, and determine Teff = 3565 +/- 82 K for the companion star, corresponding to an M1.5 dwarf. We use PHOENIX stellar atmosphere models to correct the dilution of the secondary eclipse depths of the hot Jupiter due to the presence of the M1.5 companion. We also improve the secondary eclipse photometry by accounting for the non-classical, flux-dependent nonlinearity of the WIRC IR detector in the H band. We measure planet-to-star flux ratios of 0.090 +/- 0.033%, 0.178 +/- 0.057%, 0.364 +/- 0.016%, and 0.438 +/- 0.020% in the H, Ks, 3.6 and 4.5 micron bands, respectively. We compare these with planetary atmospheric models, and find they prefer an atmosphere with a temperature inversion and inefficient heat redistribution. However, we also find that the data are equally well-described by a blackbody model for the planet with Tp = 2042 +/- 50 K. Finally, we measure a secondary eclipse timing offset of 0.3 +/- 1.3 min from the predicted mid-eclipse time, which constrains e = 0.0072 +0.0700/-0.0064 when combined with RV data and is more consistent with a circular orbit.
We present the first comprehensive look at the $0.35-5$ $mu$m transmission spectrum of the warm ($sim 800$ K) Neptune HAT-P-11b derived from thirteen individual transits observed using the Hubble and Spitzer Space Telescopes. Along with the previously published molecular absorption feature in the $1.1-1.7$ $mu$m bandpass, we detect a distinct absorption feature at 1.15 $mu$m and a weak feature at 0.95 $mu$m, indicating the presence of water and/or methane with a combined significance of 4.4 $sigma$. We find that this planets nearly flat optical transmission spectrum and attenuated near-infrared molecular absorption features are best-matched by models incorporating a high-altitude cloud layer. Atmospheric retrievals using the combined $0.35-1.7$ $mu$m HST transmission spectrum yield strong constraints on atmospheric cloud-top pressure and metallicity, but we are unable to match the relatively shallow Spitzer transit depths without under-predicting the strength of the near-infrared molecular absorption bands. HAT-P-11bs HST transmission spectrum is well-matched by predictions from our microphysical cloud models. Both forward models and retrievals indicate that HAT-P-11b most likely has a relatively low atmospheric metallicity ($<4.6 ; Z_{odot}$ and $<86 ; Z_{odot}$ at the $2 sigma$ and $3 sigma$ levels respectively), in contrast to the expected trend based on the solar system planets. Our work also demonstrates that the wide wavelength coverage provided by the addition of the HST STIS data is critical for making these inferences.
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