Corrigendum to "The upper atmosphere of the exoplanet HD209458b revealed by the sodium D lines: Temperature-pressure profile, ionization layer and thermosphere" [2011, A&A, 527, A110]

An error was detected in the code used for the analysis of the HD209458b sodium profile (Vidal-Madjar et al. 2011). Here we present an updated T-P profile and briefly discuss the consequences.Comment: Published in Astronomy & Astrophysics, 533, C

Temperature-pressure profile of the hot Jupiter HD 189733b from HST sodium observations: Detection of upper atmospheric heating

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We present transmission spectra of the hot Jupiter HD 189733b taken with the Space Telescope Imaging Spectrograph (STIS) aboard Hubble Space Telescope (HST). The spectra cover the wavelength range 5808–6380 Å with a resolving power of R= 5000. We detect absorption from the Na i doublet within the exoplanet’s atmosphere at the 9σ confidence level within a 5 Å band (absorption depth 0.09 ± 0.01 per cent) and use the data to measure the doublet’s spectral absorption profile. We detect only the narrow cores of the doublet. The narrowness of the feature could be due to an obscuring high-altitude haze of an unknown composition or a significantly sub-solar Na i abundance hiding the line wings beneath an H2 Rayleigh signature. These observations are consistent with previous broad-band spectroscopy from Advanced Camera for Surveys (ACS) and STIS, where a featureless spectrum was seen. We also investigate the effects of starspots on the Na i line profile, finding that their impact is minimal and within errors in the sodium feature. We compare the spectral absorption profile over 5.5 scale heights with model spectral absorption profiles and constrain the temperature at different atmospheric regions, allowing us to construct a vertical temperature profile. We identify two temperature regimes: a 1280 ± 240 K region derived from the Na i doublet line wings corresponding to altitudes below ∼500 km, and a 2800 ± 400 K region derived from the Na i doublet line cores corresponding to altitudes from ∼500 to 4000 km. The zero altitude is defined by the white-light radius of RP/R★= 0.15628 ± 0.00009. The temperature rises with altitude, which is likely evidence of a thermosphere. The absolute pressure scale depends on the species responsible for the Rayleigh signature and its abundance. We discuss a plausible scenario for this species, a high-altitude silicate haze and the atmospheric temperature–pressure profile that results. In this case, the high-altitude temperature rise for HD 189733b occurs at pressures of 10−5 to 10−8 bar.Science and Technology Facilities Council (STFC)NAS

GTC OSIRIS transiting exoplanet atmospheric survey: detection of sodium in XO-2b from differential long-slit spectroscopy

We present two transits of the hot-Jupiter exoplanet XO-2b using the Gran Telescopio Canarias (GTC). The time series observations were performed using long-slit spectroscopy of XO-2 and a nearby reference star with the OSIRIS instrument, enabling differential specrophotometric transit lightcurves capable of measuring the exoplanet's transmission spectrum. Two optical low-resolution grisms were used to cover the optical wavelength range from 3800 to 9300{\AA}. We find that sub-mmag level slit losses between the target and reference star prevent full optical transmission spectra from being constructed, limiting our analysis to differential absorption depths over ~1000{\AA} regions. Wider long slits or multi-object grism spectroscopy with wide masks will likely prove effective in minimising the observed slit-loss trends. During both transits, we detect significant absorption in the planetary atmosphere of XO-2b using a 50{\AA} bandpass centred on the Na I doublet, with absorption depths of Delta(R_pl/R_star)^2=0.049+/-0.017 % using the R500R grism and 0.047+/-0.011 % using the R500B grism (combined 5.2-sigma significance from both transits). The sodium feature is unresolved in our low-resolution spectra, with detailed modelling also likely ruling out significant line-wing absorption over an ~800{\AA} region surrounding the doublet. Combined with narrowband photometric measurements, XO-2b is the first hot Jupiter with evidence for both sodium and potassium present in the planet's atmosphere.Comment: 9 pages, 10 figures, 1 table, accepted for publication in MNRA

HST hot-Jupiter transmission spectral survey: Haze in the atmosphere of WASP-6b

We report Hubble Space Telescope (HST) optical to near-infrared transmission spectroscopy of the hot Jupiter WASP-6b, measured with the Space Telescope Imaging Spectrograph (STIS) and Spitzer's InfraRed Array Camera (IRAC). The resulting spectrum covers the range $0.29-4.5\,\mu$m. We find evidence for modest stellar activity of WASP-6b and take it into account in the transmission spectrum. The overall main characteristic of the spectrum is an increasing radius as a function of decreasing wavelength corresponding to a change of $\Delta (R_p/R_{\ast})=0.0071$ from 0.33 to $4.5\,\mu$m. The spectrum suggests an effective extinction cross-section with a power law of index consistent with Rayleigh scattering, with temperatures of $973\pm144$ K at the planetary terminator. We compare the transmission spectrum with hot-Jupiter atmospheric models including condensate-free and aerosol-dominated models incorporating Mie theory. While none of the clear-atmosphere models is found to be in good agreement with the data, we find that the complete spectrum can be described by models that include significant opacity from aerosols including Fe-poor Mg$_2$SiO$_4$, MgSiO$_3$, KCl and Na$_2$S dust condensates. WASP-6b is the second planet after HD189733b which has equilibrium temperatures near $\sim1200$ K and shows prominent atmospheric scattering in the optical.Comment: 18 pages, 15 figures, 7 table

HST hot Jupiter transmission spectral survey: evidence for aerosols and lack of TiO in the atmosphere of WASP-12b

We present HST optical transmission spectra of the transiting hot Jupiter WASP-12b, taken with the STIS instrument. From the transmission spectra, we are able to decisively rule out prominent absorption by TiO in the exoplanet's atmosphere. Strong pressure-broadened Na and K absorption signatures are also excluded, as are significant metal-hydride features. We compare our combined broadband spectrum to a wide variety of existing aerosol-free atmospheric models, though none are satisfactory fits. However, we do find that the full transmission spectrum can be described by models which include significant opacity from aerosols: including Rayleigh scattering, Mie scattering, tholin haze, and settling dust profiles. The transmission spectrum follows an effective extinction cross section with a power-law of index alpha, with the slope of the transmission spectrum constraining the quantity alphaT = -3528+/-660 K, where T is the atmospheric temperature. Rayleigh scattering (alpha=-4) is among the best fitting models, though requires low terminator temperatures near 900 K. Sub-micron size aerosol particles can provide equally good fits to the entire transmission spectrum for a wide range of temperatures, and we explore corundum as a plausible dust aerosol. The presence of atmospheric aerosols also helps to explain the modestly bright albedo implied by Spitzer observations, as well as the near black body nature of the emission spectrum. Ti-bearing condensates on the cooler night-side is the most natural explanation for the overall lack of TiO signatures in WASP-12b, indicating the day/night cold-trap is an important effect for very hot Jupiters. These finding indicate that aerosols can play a significant atmospheric role for the entire wide range of hot-Jupiter atmospheres, potentially affecting their overall spectrum and energy balance.(abridged)Comment: 19 pages, 14 figures, 5 tables. Accepted for publication in MNRA

Magnesium in the atmosphere of the planet HD 209458 b: observations of the thermosphere-exosphere transition region

The planet HD 209458 b is one of the most well studied hot-Jupiter exoplanets. The upper atmosphere of this planet has been observed through ultraviolet/optical transit observations with H I observation of the exosphere revealing atmospheric escape. At lower altitudes just below the thermosphere, detailed observations of the Na I absorption line has revealed an atmospheric thermal inversion. This thermal structure is rising toward high temperatures at high altitudes, as predicted by models of the thermosphere, and could reach ~ 10 000 K at the exobase level. Here, we report new near ultraviolet Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) observations of atmospheric absorptions during the planetary transit of HD 209458 b. We report absorption in atomic magnesium (Mg I), while no signal has been detected in the lines of singly ionized magnesium (Mg II). We measure the Mg I atmospheric absorption to be 6.2±2.9% in the velocity range from −62 to −19 km s^(-1). The detection of atomic magnesium in the planetary upper atmosphere at a distance of several planetary radii gives a first view into the transition region between the thermosphere and the exobase, where atmospheric escape takes place. We estimate the electronic densities needed to compensate for the photo-ionization by dielectronic recombination of Mg+ to be in the range of 10^8−10^9 cm^(-3). Our finding is in excellent agreement with model predictions at altitudes of several planetary radii. We observe Mg I atoms escaping the planet, with a maximum radial velocity (in the stellar rest frame) of −60 km s^(-1). Because magnesium is much heavier than hydrogen, the escape of this species confirms previous studies that the planet’s atmosphere is undergoing hydrodynamic escape. We compare our observations to a numerical model that takes the stellar radiation pressure on the Mg I atoms into account. We find that the Mg I atoms must be present at up to ~7.5 planetari radii altitude and estimate an Mg I escape rate of ~3 × 10^7 gs^(-1). Compared to previous evaluations of the escape rate of H I atoms, this evaluation is compatible with a magnesium abundance roughly solar. A hint of absorption, detected at low level of significance, during the post-transit observations, could be interpreted as a Mg I cometary-like tail. If true, the estimate of the absorption by Mg I would be increased to a higher value of about 8.8 ± 2.1%

Magnesium in the atmosphere of the planet HD 209458 b: Observations of the thermosphere-exosphere transition region

Copyright © ESO, 2013The planet HD 209458 b is one of the most well studied hot-Jupiter exoplanets. The upper atmosphere of this planet has been observed through ultraviolet/optical transit observations with H i observation of the exosphere revealing atmospheric escape. At lower altitudes just below the thermosphere, detailed observations of the Na i absorption line has revealed an atmospheric thermal inversion. This thermal structure is rising toward high temperatures at high altitudes, as predicted by models of the thermosphere, and could reach ~ 10 000 K at the exobase level. Here, we report new near ultraviolet Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) observations of atmospheric absorptions during the planetary transit of HD 209458 b. We report absorption in atomic magnesium (Mg i), while no signal has been detected in the lines of singly ionized magnesium (Mg ii). We measure the Mg i atmospheric absorption to be 6.2   ±   2.9% in the velocity range from − 62 to − 19 km s-1. The detection of atomic magnesium in the planetary upper atmosphere at a distance of several planetary radii gives a first view into the transition region between the thermosphere and the exobase, where atmospheric escape takes place. We estimate the electronic densities needed to compensate for the photo-ionization by dielectronic recombination of Mg+ to be in the range of 108−109 cm-3. Our finding is in excellent agreement with model predictions at altitudes of several planetary radii. We observe Mg i atoms escaping the planet, with a maximum radial velocity (in the stellar rest frame) of −60 km s-1. Because magnesium is much heavier than hydrogen, the escape of this species confirms previous studies that the planet’s atmosphere is undergoing hydrodynamic escape. We compare our observations to a numerical model that takes the stellar radiation pressure on the Mg i atoms into account. We find that the Mg i atoms must be present at up to ~7.5 planetari radii altitude and estimate an Mg i escape rate of ~3   ×   107 g s-1. Compared to previous evaluations of the escape rate of H i atoms, this evaluation is compatible with a magnesium abundance roughly solar. A hint of absorption, detected at low level of significance, during the post-transit observations, could be interpreted as a Mg i cometary-like tail. If true, the estimate of the absorption by Mg i would be increased to a higher value of about 8.8   ±   2.1%.Centre National d’Études Spatiales (CNES)French Agence Nationale de la Recherche (ANR)NASA Exoplanet Science Institute (NExScI) - Sagan Exoplanet Fellowship programSTFC (Science & Technology Facilities Council)European Commissions Seventh Framework Programme - Marie Curie Intra-European Fellowshi

Contemporary medical television and crisis in the NHS

This article maps the terrain of contemporary UK medical television, paying particular attention to Call the Midwife as its centrepiece, and situating it in contextual relation to the current crisis in the NHS. It provides a historical overview of UK and US medical television, illustrating how medical television today has been shaped by noteworthy antecedents. It argues that crisis rhetoric surrounding healthcare leading up to the passing of the Health and Social Care Act 2012 has been accompanied by a renaissance in medical television. And that issues, strands and clusters have emerged in forms, registers and modes with noticeable regularity, especially around the value of affective labour, the cultural politics of nostalgia and the neoliberalisation of healthcare

Defocused transmission spectroscopy: a potential detection of sodium in the atmosphere of WASP-12b

We report on a pilot study of a novel observing technique, defocused transmission spectroscopy, and its application to the study of exoplanet atmospheres using ground-based platforms. Similar to defocused photometry, defocused transmission spectroscopy has an added advantage over normal spectroscopy in that it reduces systematic errors due to flat-fielding, point spread function variations, slit-jaw imperfections and other effects associated with ground-based observations. For one of the planetary systems studied, WASP-12b, we report a tentative detection of additional Na absorption of 0.12 ± 0.03[+0.03] per cent during transit using a 2 Å wavelength mask. After consideration of a systematic that occurs mid-transit, it is likely that the true depth is actually closer to 0.15 per cent. This is a similar level of absorption reported in the atmosphere of HD 209458b (0.135 ± 0.017 per cent; Snellen et al. 2008). Finally, we outline methods that will improve the technique during future observations, based on our findings from this pilot study