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

New observations of the extended hydrogen exosphere of the extrasolar planet HD209458b

Atomic hydrogen escaping from the planet HD209458b provides the largest observational signature ever detected for an extrasolar planet atmosphere. However, the Space Telescope Imaging Spectrograph (STIS) used in previous observational studies is no longer available, whereas additional observations are still needed to better constrain the mechanisms subtending the evaporation process, and determine the evaporation state of other `hot Jupiters'. Here, we aim to detect the extended hydrogen exosphere of HD209458b with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST) and to find evidence for a hydrogen comet-like tail trailing the planet, which size would depend on the escape rate and the amount of ionizing radiation emitted by the star. These observations also provide a benchmark for other transiting planets, in the frame of a comparative study of the evaporation state of close-in giant planets. Eight HST orbits are used to observe two transits of HD209458b. Transit light curves are obtained by performing photometry of the unresolved stellar Lyman-alpha emission line during both transits. Absorption signatures of exospheric hydrogen during the transit are compared to light curve models predicting a hydrogen tail. Transit depths of (9.6 +/- 7.0)% and (5.3 +/- 10.0)% are measured on the whole Lyman-alpha line in visits 1 and 2, respectively. Averaging data from both visits, we find an absorption depth of (8.0 +/- 5.7)%, in good agreement with previous studies. The extended size of the exosphere confirms that the planet is likely loosing hydrogen to space. Yet, the photometric precision achieved does not allow us to better constrain the hydrogen mass loss rate.Comment: Accepted for publication in Astronomy & Astrophysics. 5 pages, 3 figure

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

Final Calibration of the Berkeley Extreme and Far-Ultraviolet Spectrometer on the ORFEUS-SPAS I and II Missions

The Berkeley Extreme and Far-Ultraviolet Spectrometer (BEFS) flew as part of the ORFEUS telescope on the ORFEUS-SPAS I and II space-shuttle missions in 1993 and 1996, respectively. The data obtained by this instrument have now entered the public domain. To facilitate their use by the astronomical community, we have re-extracted and re-calibrated both data sets, converted them into a standard (FITS) format, and placed them in the Multimission Archive at Space Telescope (MAST). Our final calibration yields improved wavelength scales and effective-area curves for both data sets.Comment: To appear in the January 2002 issue of the PASP. 17 pages with 9 embedded postscript figures; uses emulateapj5.st

Deuterium Toward Two Milky Way Disk Stars: Probing Extended Sight Lines with the Far Ultraviolet Spectroscopic Explorer

We have carried out an investigation of the abundance of deuterium along two extended sight lines through the interstellar medium (ISM) of the Galactic disk. The data include Far Ultraviolet Spectroscopic Explorer (FUSE) observations of HD 195965 (B1Ib) and HD 191877 (B0V), as well as Space Telescope Imaging Spectrograph (STIS) observations of HD 195965. The distances to HD 195965 and HD 191877, derived from spectroscopic parallax, are 794+/-200 pc and 2200+/-550 pc, respectively, making these the longest Galactic disk sight lines in which deuterium has been investigated with FUSE. The higher Lyman lines clearly show the presence of deuterium. We use a combination of curve of growth analyses and line profile fitting to determine the DI abundance toward each object. We also present column densities for OI and NI toward both stars, and HI measured from Ly-alpha absorption in the STIS spectrum of HD 195965. The D/H ratios along these sight lines are lower than the average value found with FUSE for the local interstellar medium (37 to 179 pc from the Sun). These observations lend support to earlier detections of variation in D/H over distances greater than a few hundred pc. The D/H and O/H values measured along these sight lines support the expectation that the ISM is not well mixed on distances of ~1000 pc.Comment: 32 pages, 18 figures. Abridged abstract. Accepted for publication in ApJ. Uses emulateapj5.st

Deuterium Toward WD1634-573: Results from the Far Ultraviolet Spectroscopic Explorer (FUSE) Mission

We use Far Ultraviolet Spectrocopic Explorer (FUSE) observations to study interstellar absorption along the line of sight to the white dwarf WD1634-573 (d=37.1+/-2.6 pc). Combining our measurement of D I with a measurement of H I from Extreme Ultraviolet Explorer data, we find a D/H ratio toward WD1634-573 of D/H=(1.6+/-0.5)e-5. In contrast, multiplying our measurements of D I/O I=0.035+/-0.006 and D I/N I=0.27+/-0.05 with published mean Galactic ISM gas phase O/H and N/H ratios yields D/H(O)=(1.2+/-0.2)e-5 and D/H(N)=(2.0+/-0.4)e-5, respectively. Note that all uncertainties quoted above are 2 sigma. The inconsistency between D/H(O) and D/H(N) suggests that either the O I/H I and/or the N I/H I ratio toward WD1634-573 must be different from the previously measured average ISM O/H and N/H values. The computation of D/H(N) from D I/N I is more suspect, since the relative N and H ionization states could conceivably vary within the LISM, while the O and H ionization states will be more tightly coupled by charge exchange.Comment: 23 pages, 5 figures; AASTEX v5.0 plus EPSF extensions in mkfig.sty; accepted by ApJ Supplemen

Detection of oxygen and carbon in the hydrodynamically escaping atmosphere of the extrasolar planet HD209458b

Four transits of the planet orbiting the star HD209458 were observed with the STIS spectrograph on board HST. The wavelength domain (1180-1710A) includes HI as well as CI, CII, CIV, NV, OI, SI, SiII, SiIII and SiIV lines. During the transits, absorptions are detected in HI, OI and CII (5+/-2%, 13+/-4.5% and 7.5+/-3.5%, respectively). No absorptions are detected for other lines. The 5% mean absorption over the whole HI Lyman alpha line is consistent with the previous detection at higher resolution (Vidal-Madjar et al. 2003). The absorption depths in OI and CII show that oxygen and carbon are present in the extended upper atmosphere of HD209458b. These species must be carried out up to the Roche lobe and beyond, most likely in a state of hydrodynamic escape.Comment: 6 pages, 4 figures, 1 table, submitted to ApJ Letters, revised version with slightly revisited absorption depth estimate

The Low Velocity Wind from the Circumstellar Matter Around the B9V Star sigma Herculis

We have obtained FUSE spectra of sigma Her, a nearby binary system, with a main sequence primary, that has a Vega-like infrared excess. We observe absorption in the excited fine structure lines C II* at 1037 A, N II* at 1085 A, and N II** at 1086 A that are blueshifted by as much as ~30 km/sec with respect to the star. Since these features are considerably narrower than the stellar lines and broader than interstellar features, the C II and N II are circumstellar. We suggest that there is a radiatively driven wind, arising from the circumstellar matter, rather than accretion as occurs around beta Pic, because of sigma Her's high luminosity. Assuming that the gas is liberated by collisions between parent bodies at 20 AU, the approximate distance at which blackbody grains are in radiative equilibrium with the star and at which 3-body orbits become unstable, we infer dM/dt ~ 6 * 10^-12 M_{sun}/yr. This wind depletes the minimum mass of parent bodies in less than the estimated age of the system.Comment: 6 pages, 3 figures, ApJ in pres

HST/STIS Optical Transit Transmission Spectra of the hot-Jupiter HD209458b

We present the transmission spectra of the hot-Jupiter HD209458b taken with the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope. Our analysis combines data at two resolutions and applies a complete pixel-by-pixel limb-darkening correction to fully reveal the spectral line shapes of atmospheric absorption features. Terrestrial-based Na I and H I contamination are identified which mask the strong exoplanetary absorption signature in the Na core, which we find reaches total absorption levels of ~0.11% in a 4.4 Ang band. The Na spectral line profile is characterized by a wide absorption profile at the lowest absorption depths, and a sharp transition to a narrow absorption profile at higher absorption values. The transmission spectra also shows the presence of an additional absorber at ~6,250 Ang, observed at both medium and low resolutions. We performed various limb-darkening tests, including using high precision limb-darkening measurements of the sun to characterize a general trend of Atlas models to slightly overestimate the amount of limb-darkening at all wavelengths, likely due to the limitations of the model's one-dimensional nature. We conclude that, despite these limitations, Atlas models can still successfully model limb-darkening in high signal-to-noise transits of solar-type stars, like HD209458, to a high level of precision over the entire optical regime (3,000-10,000 Ang) at transit phases between 2nd and 3rd contact.Comment: 18 pages, 11 figures, Accepted to Ap