Context. During primary transits, the spectral signatures of exoplanet atmospheres can be measured using transmission spectroscopy. We can obtain information on the upper atmosphere of these planets by investigating the exoplanets' excess sodium absorption in the optical region. However, a number of factors can affect the observed sodium absorption signature. We present a detailed model correcting for systematic biases to yield an accurate depth for the sodium absorption in HD 189733b. Aims. The goal of this work is to accurately measure the atomspheric sodium absorption light curve in HD 189733b, correcting for the effects of stellar differential limb-darkening, stellar activity, and a "bump" caused by the changing radial velocity of the exoplanet. In fact, owing to the high cadence and quality of our data, it is the first time that the last feature can be detected even by visual inspection. Methods. We use 244 high-resolution optical spectra taken by the UVES instrument mounted at the VLT. Our observations cover a full transit of HD 189733b, with a cadence of 45 s. To probe the transmission spectrum of sodium we produce excess light curves integrating the stellar flux in passbands of 1 Å, 1.5 Å, and 3 Å inside the core of each sodium D-line. We model the effects of external sources on the excess light curves, which correspond to an observed stellar flare beginning close to mid-transit time and the wavelength dependent limb-darkening effects. In addition, by characterizing the effect of the changing radial velocity and Doppler shifts of the planetary sodium lines inside the stellar sodium lines, we estimate the depth and width of the exoplanetary sodium feature. Results. We estimate the shape of the planetary sodium line by a Gaussian profile with an equivalent width of ∼0.0023 ± 0.0010 Å, thereby confirming the presence of sodium in the atmosphere of HD 189733b with excess absorption levels of 0.72 ± 0.25%, 0.34 ± 0.11%, and 0.20 ± 0.06% for the integration bands of 1 Å, 1.5 Å, and 3 Å, respectively. Using the equivalent width of the planetary sodium line, we produce a first order estimate of the number density of sodium in the exoplanet atmosphere.

We report the discovery by the HATSouth survey of HATS-4b, an extrasolar planet transiting a V=13.46 mag G star. HATS-4b has a period of P ≈ 2.5167 d, mass of M p ≈ 1.32 M Jup , radius of R p ≈ 1.02 R Jup and density of ρ p = 1.55 ± 0.16 g cm −3 ≈ 1.24ρ Jup . The host star has a mass of 1.00 M ⊙ , a radius of 0.92 R ⊙ and a very high metallicity [Fe/H]= 0.43 ± 0.08. HATS-4b is among the densest known planets with masses between 1-2 M J and is thus likely to have a significant content of heavy elements of the order of 75 M ⊕ . In this paper we present the data reduction, radial velocity measurement and stellar classification techniques adopted by the HATSouth survey for the CORALIE spectrograph. We also detail a technique to estimate simultaneously v sin i and macroturbulence using high resolution spectra.

We present the detection of sodium absorption in the atmosphere of the extrasolar planet WASP-17b, an inflated 'hot-Jupiter' in a tight orbit around an F6 dwarf. In-transit observations of WASP-17 made with the MIKE spectrograph on the 6.5-m Magellan Telescope were analysed for excess planetary atmospheric absorption in the sodium I 'D' doublet spectral region. Using the interstellar sodium absorption lines as reference, we detect an excess 0.58 \pm 0.13 per cent transit signal, with 4.5{\sigma} confidence, at 1.5 {\AA} bandwidth around the stellar sodium absorption feature. This result is consistent with the previous VLT detection of sodium in WASP-17b, confirming that the planet has a highly inflated atmosphere.Comment: 6 pages, 4 figures and 2 tables, accepted by MNRA

We report the discovery of ten transiting extrasolar planets by the HATSouth survey. The planets range in mass from the Super-Neptune HATS-62b, with M p < 0.179 M J , to the Super-Jupiter HATS-66b, with M p = 5.33 M J , and in size from the Saturn HATS-69b, with R p = 0.94 R J , to the inflated Jupiter HATS-67b, with R p = 1.69 R J . The planets have orbital periods between 1.6092 days (HATS-67b) and 7.8180 days (HATS-61b). The hosts are dwarf stars with masses ranging from 0.89 M ⊙ (HATS-69) to 1.56 M ⊙ (HATS-64), and have apparent magnitudes between V = 12.276 ± 0.020 mag (HATS-68) and V = 14.095 ± 0.030 mag (HATS-66). The Super-Neptune HATS-62b is the least massive planet discovered to date with a radius larger than Jupiter. Based largely on the Gaia DR2 distances and broad-band photometry, we identify three systems as having possible unresolved binary star companions. We discuss in detail our methods for incorporating the Gaia DR2 observations into our modeling of the system parameters, and into our blend analysis procedures.

We report the discovery of HAT-P-67b, which is a hot-Saturn transiting a rapidly rotating F-subgiant. HAT-P-67b has a radius of = host star in a ∼4.81 day period orbit. We place an upper limit on the mass of the planet via radial velocity measurements to be < M M 0.59 p J , and a lower limit of > M 0.056 J by limitations on Roche lobe overflow. Despite being a subgiant, the host star still exhibits relatively rapid rotation, with a projected rotational velocity of35.8 1.1 km s 1 , which makes it difficult to precisely determine the mass of the planet using radial velocities. We validated HAT-P-67b via two Doppler tomographic detections of the planetary transit, which eliminate potential eclipsing binary blend scenarios. The Doppler tomographic observations also confirm that HAT-P-67b has an orbit that is aligned to within 12°, in projection, with the spin of its host star. HAT-P-67b receives strong UV irradiation and is among one of the lowest density planets known, which makes it a good candidate for future UV transit observations in the search for an extended hydrogen exosphere.