This retrospective study reports the results of radial keratotomy surgery on 225 eyes of 135 patients by one surgeon. Fifty-one percent of the eyes had four incisions and 45% had eight as the initial ...procedure. Fifteen percent of the eyes repeated surgery. The mean preoperative spherical equivalent refraction was -5.10 diopters (SD 1.90, range 1.20 to 11.60 D) and at 3 months to 1 year, the mean was -0.60 D (SD 1.00, range -4.80 to +3.40 D). For the entire series, 69% of the eyes achieved an uncorrected visual acuity of 20/40 or better, 73% were corrected to within +/- 1.00 D of emmetropia, and 3% were overcorrected by more than +1.00 D. For eyes with low preoperative myopia (-3.00 D and less), 100% achieved an uncorrected visual acuity of 20/40 or better, 97% were corrected to within +/- 1.00 D of emmetropia, and 3% were overcorrected by more than +1.00 D. For eyes with moderate myopia (-3.1 to -5.9 D), 73% achieved an uncorrected visual acuity of 20/40 or better, 81% were corrected to within +/- 1.00 D of emmetropia, and 3% were overcorrected by more than +1.00 D. For eyes with higher preoperative myopia (-6.0 to -11.60 D), 47% achieved an uncorrected visual acuity of 20/40 or better, 45% were corrected to within +/- 1.00 D of emmetropia and 3% were overcorrected by more than +1.00 D. One hundred eyes with a follow-up of 2 years or greater were studied for stability; 77% changed by less than 1.00 D from the 1 year value; 17% changed by 1.00 D or more in the hyperopic direction; 6% changed by 1.00 D or more in the myopic direction. There were no vision threatening complications and only one eye had a postoperative best spectacle corrected visual acuity of less than 20/40.
HD 209458 is one of the benchmark objects in the study of hot Jupiter atmospheres and their evaporation through planetary winds. The expansion of the planetary atmosphere is thought to be driven by ...high-energy EUV and X-ray irradiation. We obtained new Chandra HRC-I data, which unequivocally show that HD 209458 is an X-ray source. Combining these data with archival XMM-Newton observations, we find that the corona of HD 209458 is characterized by a temperature of about 1 MK and an emission measure of 7e49 cm^-3, yielding an X-ray luminosity of 1.6e27 erg/s in the 0.124-2.48 keV band. HD 209458 is an inactive star with a coronal temperature comparable to that of the inactive Sun but a larger emission measure. At this level of activity, the planetary high-energy emission is sufficient to support mass-loss at a rate of a few times 1e10 g/s.
A&A 629, A110 (2019) Context: Recently, the He I triplet at 10830 \r{A} has been rediscovered as
an excellent probe of the extended and possibly evaporating atmospheres of
close-in transiting ...planets. This has already resulted in detections of this
triplet in the atmospheres of a handful of planets, both from space and from
the ground. However, while a strong signal is expected for the hot Jupiter HD
209458 b, only upper limits have been obtained so far. Aims: Our goal is to
measure the helium excess absorption from HD 209458 b and assess the extended
atmosphere of the planet and possible evaporation. Methods: We obtained new
high-resolution spectral transit time-series of HD 209458 b using CARMENES at
the 3.5 m Calar Alto telescope, targeting the He I triplet at 10830 \r{A} at a
spectral resolving power of 80 400. The observed spectra were corrected for
stellar absorption lines using out of transit data, for telluric absorption
using the molecfit software, and for the sky emission lines using simultaneous
sky measurements through a second fibre. Results: We detect He I absorption at
a level of 0.91 $\pm$ 0.10 % (9 $\sigma$) at mid-transit. The absorption
follows the radial velocity change of the planet during transit, unambiguously
identifying the planet as the source of the absorption. The core of the
absorption exhibits a net blueshift of 1.8 $\pm$ 1.3 km s$^{-1}$. Possible
low-level excess absorption is seen further blueward from the main absorption
near the centre of the transit, which could be caused by an extended tail.
However, this needs to be confirmed. Conclusions: Our results further support a
close relationship between the strength of planetary absorption in the helium
triplet lines and the level of ionising, stellar X-ray and extreme-UV
irradiation.
Aims: We aim at detecting H\(_2\)O in the atmosphere of the hot Jupiter HD 209458 b and perform a multi-band study in the near infrared with CARMENES. Methods: The H\(_2\)O absorption lines from the ...planet's atmosphere are Doppler-shifted due to the large change in its radial velocity during transit. This shift is of the order of tens of km s\(^{-1}\), whilst the Earth's telluric and the stellar lines can be considered quasi-static. We took advantage of this to remove the telluric and stellar lines using SYSREM, a principal component analysis algorithm. The residual spectra contain the signal from thousands of planetary molecular lines well below the noise level. We retrieve this information by cross-correlating the spectra with models of the atmospheric absorption. Results: We find evidence of H\(_2\)O in HD 209458 b with a signal-to-noise ratio (S/N) of 6.4. The signal is blueshifted by --5.2 \(^{+2.6}_{-1.3}\) km s\(^{-1}\), which, despite the error bars, is a firm indication of day-to-night winds at the terminator of this hot Jupiter. Additionally, we performed a multi-band study for the detection of H\(_2\)O individually from the three NIR bands covered by CARMENES. We detect H\(_2\)O from its 1.0 \(\mu\)m band with a S/N of 5.8, and also find hints from the 1.15 \(\mu\)m band, with a low S/N of 2.8. No clear planetary signal is found from the 1.4 \(\mu\)m band. Conclusions: Our significant signal from the 1.0 \(\mu\)m band in HD 209458 b represents the first detection of H\(_2\)O from this band, the bluest one to date. The unfavorable observational conditions might be the reason for the inconclusive detection from the stronger 1.15 and 1.4 \(\mu\)m bands. H\(_2\)O is detected from the 1.0 \(\mu\)m band in HD 209458 b, but hardly in HD 189733 b, which supports a stronger aerosol extinction in the latter.
Gas planets in close proximity to their host stars experience photoevaporative mass loss. The energy-limited escape concept is generally used to derive estimates for the planetary mass-loss rates. ...Our photoionization hydrodynamics simulations of the thermospheres of hot gas planets show that the energy-limited escape concept is valid only for planets with a gravitational potential lower than \(\log_\mathrm{10}\left( -\Phi_{\mathrm{G}}\right) < 13.11~\)erg\(\,\)g\(^{-1}\) because in these planets the radiative energy input is efficiently used to drive the planetary wind. Massive and compact planets with \(\log_\mathrm{10}\left( -\Phi_{\mathrm{G}}\right) \gtrsim 13.6~\)erg\(\,\)g\(^{-1}\) exhibit more tightly bound atmospheres in which the complete radiative energy input is re-emitted through hydrogen Ly\(\alpha\) and free-free emission. These planets therefore host hydrodynamically stable thermospheres. Between these two extremes the strength of the planetary winds rapidly declines as a result of a decreasing heating efficiency. Small planets undergo enhanced evaporation because they host expanded atmospheres that expose a larger surface to the stellar irradiation. We present scaling laws for the heating efficiency and the expansion radius that depend on the gravitational potential and irradiation level of the planet. The resulting revised energy-limited escape concept can be used to derive estimates for the mass-loss rates of super-Earth-sized planets as well as massive hot Jupiters with hydrogen-dominated atmospheres.
Absorption of high-energy radiation in planetary thermospheres is believed to lead to the formation of planetary winds. The resulting mass-loss rates can affect the evolution, particularly of small ...gas planets. We present 1D, spherically symmetric hydrodynamic simulations of the escaping atmospheres of 18 hot gas planets in the solar neighborhood. Our sample only includes strongly irradiated planets, whose expanded atmospheres may be detectable via transit spectroscopy. The simulations were performed with the PLUTO-CLOUDY interface, which couples a detailed photoionization and plasma simulation code with a general MHD code. We study the thermospheric escape and derive improved estimates for the planetary mass-loss rates. Our simulations reproduce the temperature-pressure profile measured via sodium D absorption in HD 189733 b, but show unexplained differences in the case of HD 209458 b. In contrast to general assumptions, we find that the gravitationally more tightly bound thermospheres of massive and compact planets, such as HAT-P-2 b are hydrodynamically stable. Compact planets dispose of the radiative energy input through hydrogen Ly\(\alpha\) and free-free emission. Radiative cooling is also important in HD 189733 b, but it decreases toward smaller planets like GJ 436 b. The simulations show that the strong and cool winds of smaller planets mainly cause strong Ly\(\alpha\) absorption but little emission. Compact and massive planets with hot, stable thermospheres cause small absorption signals but are strong Ly\(\alpha\) emitters, possibly detectable with the current instrumentation. The absorption and emission signals provide a possible distinction between these two classes of thermospheres in hot gas planets. According to our results, WASP-80 and GJ 3470 are currently the most promising targets for observational follow-up aimed at detecting atmospheric Ly\(\alpha\) absorption signals.
We present three transit observations of HD 189733 b obtained with the
high-resolution spectrograph CARMENES at Calar Alto. A strong absorption signal
is detected in the near-infrared He I triplet at ...10830 \AA{} in all three
transits. During mid-transit, the mean absorption level is $0.88\pm0.04$ %
measured in a $\pm$10 km s$^{-1}$ range at a net blueshift of $-3.5\pm0.4$ km
s$^{-1}$ (10829.84--10830.57 \AA{}). The absorption signal exhibits radial
velocities of $+6.5\pm3.1$ km s$^{-1}$ and $-12.6\pm1.0$ km s$^{-1}$ during
ingress and egress, respectively; measured in the planetary rest frame. We show
that stellar activity related pseudo-signals interfere with the planetary
atmospheric absorption signal. They could contribute as much as 80% of the
observed signal and might also affect the radial velocity signature, but
pseudo-signals are very unlikely to explain the entire signal. The observed
line ratio between the two unresolved and the third line of the He I triplet is
$2.8\pm0.2$, which strongly deviates from the value expected for an optically
thin atmospheres. When interpreted in terms of absorption in the planetary
atmosphere, this favors a compact helium atmosphere with an extent of only 0.2
planetary radii and a substantial column density on the order of $4\times
10^{12}$ cm$^{-2}$. The observed radial velocities can be understood either in
terms of atmospheric circulation with equatorial superrotation or as a sign of
an asymmetric atmospheric component of evaporating material. We detect no clear
signature of ongoing evaporation, like pre- or post-transit absorption, which
could indicate material beyond the planetary Roche lobe, or radial velocities
in excess of the escape velocity. These findings do not contradict planetary
evaporation, but only show that the detected helium absorption in HD 189733 b
does not trace the atmospheric layers that show pronounced escape signatures.
Aims: We explore the capabilities of CARMENES for characterizing hot-Jupiter atmospheres by targeting multiple water bands, in particular, those at 1.15 and 1.4 \(\mu\)m. Hubble Space Telescope ...observations suggest that this wavelength region is relevant for distinguishing between hazy/cloudy and clear atmospheres. Methods: We observed one transit of the hot Jupiter HD 189733 b with CARMENES. Telluric and stellar absorption lines were removed using Sysrem, which performs a principal component analysis including proper error propagation. The residual spectra were analysed for water absorption with cross-correlation techniques using synthetic atmospheric absorption models. Results: We report a cross-correlation peak at a signal-to-noise ratio (SNR) of 6.6, revealing the presence of water in the transmission spectrum of HD 189733 b. The absorption signal appeared slightly blueshifted at -3.9 \(\pm\) 1.3 kms\(^{-1}\). We measured the individual cross-correlation signals of the water bands at 1.15 and 1.4 \(\mu\)m, finding cross-correlation peaks at SNRs of 4.9 and 4.4, respectively. The 1.4 \(\mu\)m feature is consistent with that observed with the Hubble Space Telescope. Conclusions: The water bands studied in this work have been mainly observed in a handful of planets from space. The ability of also detecting them individually from the ground at higher spectral resolution can provide insightful information to constrain the properties of exoplanet atmospheres. Although the current multiband detections can not yet constrain atmospheric haze models for HD 189733 b, future observations at higher signal-to-noise ratio could provide an alternative way to achieve this aim.
We present an interface between the (magneto-) hydrodynamics code PLUTO and the plasma simulation and spectral synthesis code CLOUDY. By combining these codes, we constructed a new photoionization ...hydrodynamics solver: The PLUTO-CLOUDY Interface (TPCI), which is well suited to simulate photoevaporative flows under strong irradiation. The code includes the electromagnetic spectrum from X-rays to the radio range and solves the photoionization and chemical network of the 30 lightest elements. TPCI follows an iterative numerical scheme: First, the equilibrium state of the medium is solved for a given radiation field by CLOUDY, resulting in a net radiative heating or cooling. In the second step, the latter influences the (magneto-) hydrodynamic evolution calculated by PLUTO. Here, we validated the one-dimensional version of the code on the basis of four test problems: Photoevaporation of a cool hydrogen cloud, cooling of coronal plasma, formation of a Stroemgren sphere, and the evaporating atmosphere of a hot Jupiter. This combination of an equilibrium photoionization solver with a general MHD code provides an advanced simulation tool applicable to a variety of astrophysical problems.
Context: Recently, the He I triplet at 10830 Å has been rediscovered as an excellent probe of the extended and possibly evaporating atmospheres of close-in transiting planets. This has already ...resulted in detections of this triplet in the atmospheres of a handful of planets, both from space and from the ground. However, while a strong signal is expected for the hot Jupiter HD 209458 b, only upper limits have been obtained so far. Aims: Our goal is to measure the helium excess absorption from HD 209458 b and assess the extended atmosphere of the planet and possible evaporation. Methods: We obtained new high-resolution spectral transit time-series of HD 209458 b using CARMENES at the 3.5 m Calar Alto telescope, targeting the He I triplet at 10830 Å at a spectral resolving power of 80 400. The observed spectra were corrected for stellar absorption lines using out of transit data, for telluric absorption using the molecfit software, and for the sky emission lines using simultaneous sky measurements through a second fibre. Results: We detect He I absorption at a level of 0.91 \(\pm\) 0.10 % (9 \(\sigma\)) at mid-transit. The absorption follows the radial velocity change of the planet during transit, unambiguously identifying the planet as the source of the absorption. The core of the absorption exhibits a net blueshift of 1.8 \(\pm\) 1.3 km s\(^{-1}\). Possible low-level excess absorption is seen further blueward from the main absorption near the centre of the transit, which could be caused by an extended tail. However, this needs to be confirmed. Conclusions: Our results further support a close relationship between the strength of planetary absorption in the helium triplet lines and the level of ionising, stellar X-ray and extreme-UV irradiation.
